ENIR11- Unit IV - Biomass Biomass – Definition and potential • Biomass - Biological material derived from living or recently living organisms. • So, in context, the term biomass applies to both animal and plant derived material. • Biomass is the only above ground carbon source. So what ?? • 500 mmt of agro-residue waste is available in India, of which around 120 mmt is fired in field causing severe air pollution and particulate matter emissions. • Other than power and heating applications, biomass also can be used to generate fuels, chemicals, bio-char and activated carbon. Types of biomass with EXAMPLES Wood and woody biomass Coniferous or deciduous; angiospermous or gymnospermous; soft or hard; stems, branches, foliage, bark, chips, lumps, pellets, briquettes, sawdust, sawmill and others from various wood species Herbaceous and agricultural biomass Annual or perennial and field-based or processed-based such as: 2.1. Grasses and flowers (alfalfa, arundo, bamboo, bana, brassica, cane, cynara, miscanthus, switchgrass, timothy, others 2.2. Straws (barley, bean, flax, corn, mint, oat, rape, rice, rye, sesame, sunflower, wheat, others) 2.3. Other residues (fruits, shells, husks, hulls, pits, pips, grains, seeds, coir, stalks, cobs, kernels, bagasse, food, fodder, pulps, cakes, others Marine or freshwater algae; macroalgae (blue, green, blue-green, brown, red) or microalgae; seaweed, kelp, lake weed, water hyacinth, others Bones, meat-bone, meal, chicken litter, various manures, Animal and human biomass wastes others Contaminated biomass and Municipal solid waste, demolition wood, refuse-derived fuel, industrial biomass sewage sludge, hospital waste, paper-pulp sludge, wastes (semi-biomass) waste papers, paperboard waste, chipboard, fibreboard, plywood, wood pallets and boxes, railway sleepers, tannery waste, others Blends from the above varieties Biomass mixtures Aquatic biomass 3 Process of fixation of carbohydrates in plants? • Photosynthesis -Energy derived from the Sun light and carbon source from CO2 CO2+ H2O (CH2O)n+ O2 • These photo reactions leads to generation of glucose, fructose, sucrose, starch, lipids, and cellulose. • Cellulose is a polymer of glucose. Like wise other multiple combinations of these components form hemicellulose, lignin,, protein extractives, oils (lipids) and ash etc. • Animals, unlike plants consume plant base residues and become/emit as a source of hydrocarbons. • So, how do we characterize various types of biomass? Characteristics or compositional analysis of biomass-criteria Proximate analysis • Fixed carbon (FC), • volatile matter (VM), • moisture (M); • Ash content (A),- (Si, Al, Fe, Ca, S, Mg, K, Ti, Na, P, plus occasionally Mn, Cl and trace elements); Ultimate analysis or elemental • C, O, H, S, N Biochemical analysis • Carbohydrate , Protein, lipids 6 • Classifying biomass is very different and done in different ways. One of the major classifications are based on the following, A. Wet biomass and Dry Biomass. 1. Wet biomass (moisture more than 30% by wt… Examples ???) 2. Dry biomass (moisture less than 30% by wt. Examples????) B. Bio-degradable or Non biodegradable? 1. Bio-degradable(One that has less lignin content and wet Examples ???) 2. Non-Biodegradable - This has lignin content and takes time to get spitted into simpler molecules using bio-digestion method. So more suitable for thermochemical conversion. Examples?? Graphical representation of biomass properties Van Krevelan Plot H/C and O/C ratio of biomass C/N ratio Ternary diagram Types of biomass conversion Biomass Dry Biomass Wet Biomass (plant and animal matter ) Bio-chemical conversion Thermo-chemical Physio-chemical Transesterification Combustion Gasification Pyrolysis Application Heat Fuel Power Chemicals Charcoal Bio-Oil Manure Thermo-chemical conversion route - Basics • Stoichiometry ?? Bio-fuels First generation bio-fuels •Uses food crops and feeds •Example: Bio-ethanol production from starch crops, Biodiesel from sunflower oil via transesterification S.No Composition % (w/w) 1 Cellulose (C(H2O)0.83) 28 - 45 2 Hemi cellulose (CH2O) 10 - 29 3 Lignin (CH1.3O0.3) 0 - 40 4 Crude proteins, oil extractions and ash 6 - 15 5 Generic Empirical formula 6 s = (A/F)stoichio (g of air/g of biomass) C H1.6 O0.9 4.5 Second generation bio-fuels •Uses non food crops, agro, forest and industrial wastes •Example: Syngas from Rice husk via gasification, Biogas from kitchen waste via biomethanisation Most of cellulose and hemicellulose form volatile matter (80%) and most of the lignin forms fixed carbon/char (20%) About 60% of s is used for volatile oxidation and the remaining 40% is used for char oxidation. This 60% of s is called as volatile stoichiometry (𝜙v =1) • Now we talk about third generation biofuels also. (Will be explained later) Thermo-chemical Conversion Combustion Biomass + heat Gasification Pyrolysis Biomass + heat Biomass + heat Air ≥ s CO2 + H2O + N2 + (O2) Inert Air ≤ 0.6 s Pyrolytic gas + Oil + Charcoal Volatile oxidation/partial oxidation products CO + H2 + CO2 + HHC + CH4 + H2O + N2 Fixed carbon Reduction reactions C + CO2 C + H 2O CO + H2O Air = 0 2 CO CO + H2 CO2 + H2 CO + H2 + CO2 + HHC + CH4 + H2O + N2 Thermo chemical conversion of Biomass in a packed bed Gasifier CO,H2,CO2, CH4 , N2, HHC, H2O + Steam/CO2,out Syngas Composition Syngas 800 – 1000°C Char layer 1000 – 1500°C Devolatalization 54% 15% 1% 300°C Gasification 10% H2 CO, H2, CH4, HHC, N2 CH4 Reduction CO 20% Char (FC) CO2 N2 + Steam/CO2,in CO, CO2v, H2, H2Ov, CH4,HHC, N2 Air ≤ 0.6 s Volatile Oxidation Biomass + Δ Oxidizer O2 + Steam/CO2,in Air With O2/CO2 /steam as Oxidizer C + CO2 C + H 2O CO + H2O 2 CO CO + H2 CO2 + H2 Types of Gasifiers Fixed Bed Bubbling Fluidized Bed Circulating Fluidized Bed Low and medium scale heating and power applications ( 0.1 – 1 MW) Power Applications ( 5 – 20MW) Power Applications ( > 5 MW) Moving grate boiler Why gasification? • Combustion efficiency of biomass boilers can be as close to 98%. (Very good right? Then why gasification?) Reasons are, 1. Product of gasification is fuel gas which have wide variety of application like heat, power, fuel cells, liquid fuel and chemical synthesis. 2. It can be used for small power levels (a few kWe to a few Mwe) using reciprocating engines. 3. Typical example is 10 to 200 kWe biomass-steam-electricity the efficiency is 3 – 5 % i.e. 4.5 – 7.5 kg/kWh whereas for biomass-gasification-reciprocating engines the effieciency is 20 – 25 % i.e 1 to 1.3 kg/kWh. 4. Biomass gasification is a staging combustion process, hence air required is close to stoichiometry unlike combustion where excess air is used which increases the pollution (Nox, CO, Unburnt hydrocarbons and ash) and air handling energy more. 5. Also, some chemical/metallurgical process requires CO to reduce metal oxides to metal. This CO is generally produced from natural gases. These applications gasification gas can be a good sustainable alternative too. Physio –chemical Conversion • https://www.youtube.com/watch?v=ieuW8GUdTSM 1. Esterification is the reaction between a carboxylic acid and an alcohol to produce an ester with the help of catalyst 1. Transesterification occurs between an ester and an alcohol to produce a different ester (biodiesel) and glycerol as by-product Transesterification is the process of exchanging the organic group R″ of an ester with the organic group R′ of an alcohol with catalysed by an acid or base catalyst. The reaction can also be accomplished with the help of enzymes (biocatalysts) particularly lipases (E.C.3.1.1.3). Biodiesel or fatty acid methyl ester 21 Source: https://www.sciencedirect.com/science/article/pii/S0306261910003946 Source: https://www.sciencedirect.com/science/article/pii/S0306261910003946 Algae based biodiesel production – Third generation biofuel Why third generation? Biodiesel – Pros and cons • Biodiesel will form a small but very important part of global energy supply in the coming decades. • There is a continual issue of land space utilization, oil seeds yield, food crop competition when we talk on transesterification techniques. • Biodiesel from algae seems to be a promising alternate source of biodiesel production (third generation biofuel). • Biodiesel industry itself faces strong competition from non-ester renewable diesel fuels and second generation bioethanol. • Improving efficiency of the production process, using low cost feedstock, developing cost effective catalyst, and managing agricultural land, have to be addressed. • Further development on the use of the by-product will enhance the economic viability of the overall biodiesel production process Biochemical conversion • It is a chemical process in the living organisms or involving the living organisms to produce energy/product. • Simple biochemical process is photosynthesis 1. Anaerobic digestion 2. Fermentation 26 Anaerobic digestion – Bio Methanation • Anaerobic digestion is a series of biological processes in which microorganisms break down biodegradable material in the absence of oxygen. One of the end products is biogas, which is combusted to generate electricity and heat. C6H12O6 → 3CO2 + 3CH4 General Equation for Anerobic digestion is 𝐶𝑥 𝐻𝑦 𝑂𝑧 + 𝑥 − 𝑦 𝑧 − 4 2 𝐻2 𝑂 → 𝑥 𝑦 𝑧 − + 2 8 4 𝐶𝑂2 + 𝑥 𝑦 𝑧 + − 2 8 4 𝐶𝐻4 ***The average gas yield is around 0.2 to 0.4 m3 per kg of dry biomass. 27 Basics of Anaerobic Digestion For production of biogas the three basic steps have been explained as Composition for some food wastes Item TS VS Cellulose (%) Lignin % Food waste 27 96 12-16 4-6 Fruits + Vegetable mix 10 90 15-18 4-6 Pineapple peel 12 95 47 7-9 Apple peel 15 97 44 4-6 Coffee pulp 68 88 40 7-9 Tapioca 87 97 - - Factors Affecting Biogas production • pH (6.5 to 7.5) • Temperature • Total solid content (1:1) • Loading rate (1.2 to 5.3 kg of VS/m3/day • Seeding • Diameter to depth ratio (0.66 to1) • C/N ratio • Retention time • Feedstock type • Acid accumulation *The optimum condition is different and case specific. Effect of temperature on digestion Stages Hydrolysis Acidogenesis Acetogenesis Methanogenesis 30 31 Configuration A single or multiple digesters in sequence may be used. Hydrolysis, acetogenesis, and acidogenesis occur in the first reaction vessel. The organic material is then heated to the required operational temperature prior to being pumped into a methanogenic reactor. Working video: https://www.youtube.com/watch?v=DyZR3rRirxs 32 BIOGAS PLANT: KHADI AND VILLAGE INDUSTRIES COMMISSION (KVIC) 3/22/2022 33 BIOGAS PLANT: JANATA 3/22/2022 34 BIOGAS PLANT: FIBER-GLASS REINFORCED POLYESTER (FRP) 3/22/2022 35 FERMENTATION • It is a biochemical process where chemical breakdown of complex polymers by bacteria, yeasts, or other microorganisms into ethanol or acid production is taken place. One glucose molecule is converted into two ethanol molecules and two carbon dioxide molecule. C6H12O6 (glucose) → 2 C2H5OH (ethanol) + 2 CO2 (carbon dioxide) Click to add text Click to add text 36 Stages in bioethanol production Pretreatment Hydrolysis Fermentation Distillation 37 PRETREATMENT Breaks the rigidity of structure in order to access carbohydrate molecules. Physical - Milling Chemical - Conc. acid treatment, Alkali treatment, Organosolv Biological - Filamentous fungi (white-rot and brown) Pycnoporus cinnarbarinus Pleurotus ostreaus Ceriporiopsis subvermispora 38 Hydrolysis Splitting or breakdown of cellulose and hemicellulose or other carbohydrate molecules into sugars with the help of water. Hydrolysis of starch Cellulose hydrolysis Hemicellulose - α-& ß-amylase, -cellulases - hemicellulase 39 Fermentation Monosaccharides will be converted into ethanol and CO2 by yeast Yeast- Saccharomyces cerevisiae S. cerevisiae will ferment only the hexose sugars present in the hydrolysate but not the pentose sugars C5 sugars fermenting starins - Pichia stipitis, Candida shehatae and Pachysolan tannophilus 40 Distillation -Separates the products of fermentation. - Boiling point Distillation Crude ethanol 41 Biomass Feedstock preparation Chipping Grinding Chopping Palletization or Briquetting Drying Straw Baling ***Remember the energy and efforts for these Common issues with biomass power • Biomass availability is seasonal. • Biomass distribution is not uniform (actually this is advantage to have decentralized biomass based power plants. How?) • The bulk density of biomass (mass occupied by unit volume) is low making it difficult/cost ineffective to transport. • In summary, biomass gasification is technically viable only logistics are a important bottle neck for effective implementation of the technology. Thank You Guys ! All the best !! Ocean thermal energy conversion (OTEC) systems What is OTEC • OTEC systems use the ocean's natural thermal gradient—the fact that the ocean's layers of water have different temperatures—to drive a powerproducing cycle. • In deep tropical waters ocean surface temperature can be as high as 27 ℃; and at depths as close as 1000 ft below the surface, temperature can be as low as 4 ℃. OTEC system • There are three types of electricity conversion systems: closed-cycle, open-cycle, and hybrid. • Closed-cycle systems use the ocean's warm surface water to vaporize a working fluid, which has a lowboiling point, such as ammonia. Introduction • Renewable Ocean Energy: Tides, Currents, and Waves. • Oceans cover more than 70% of Earth's surface, making them the world's largest solar collectors. Closed-loop OTEC cycle An OTEC system application case • Hydrogen can be produced via electrolysis using electricity generated by the OTEC process. • Stored hydrogen can then be transported and used to power fuel cells. Closed-loop OTEC facility Open loop OTEC Scale of Hydropower Projects Large-hydro Medium-hydro 15 - 100 MW usually feeding a grid Small-hydro More than 100 MW feeding into a large electricity grid 1 - 15 MW - usually feeding into a grid Mini-hydro Above 100 kW, but below 1 MW Either stand alone schemes or more often feeding into the grid Micro-hydro From 5kW up to 100 kW Usually provided power for a small community or rural industry in remote areas away from the grid. Pico-hydro From a few hundred watts up to 5kW Remote areas away from the grid. www.itdg.org/docs/technical_information_service/micro_hydro_power.pdf Types of Hydroelectric Installation Boyle, Renewable Energy, 2nd edition, Oxford University Press, 2003 Geothermal power plants can be divided into two main groups, Steam cycles and binary cycles. Typically the steam cycles are used at higher well enthalpies, and binary cycles for lower enthalpies. The steam cycles allow the fluid to boil, and then the steam is separated from the brine and expanded in a turbine. Usually the brine is rejected to the environment (re-injected), or it is flashed again at a lower pressure. Here the Single Flash (SF) and Double Flash (DF) cycles will be presented. A binary cycle uses a secondary working fluid in a closed power generation cycle. A heat exchanger is used to transfer heat from the geothermal fluid to the working fluid, and the cooled brine is then rejected to the environment or re-injected. The Organic Rankine Cycle (ORC) and Kalina cycle will be presented. DRY STEAM POWER PLANTS “Dry” steam extracted from natural reservoir 180-225 ºC ( 356-437 ºF) 4-8 MPa (580-1160 psi) 200+ km/hr (100+ mph) Steam is used to drive a turbo-generator Steam is condensed and pumped back into the ground Can achieve 1 kWh per 6.5 kg of steam A 55 MW plant requires 100 kg/s of steam Boyle, Renewable Energy, 2nd edition, 2004 DRY STEAM SCHEMATIC Boyle, Renewable Energy, 2nd edition, 2004 SINGLE FLASH STEAM POWER PLANTS Steam with water extracted from ground Pressure of mixture drops at surface and more water “flashes” to steam Steam separated from water Steam drives a turbine Turbine drives an electric generator Generate between 5 and 100 MW Use 6 to 9 tonnes of steam per hour SINGLE FLASH STEAM SCHEMATIC Boyle, Renewable Energy, 2nd edition, 2004 BINARY CYCLE POWER PLANTS Low temps – 100o and 150oC Use heat to vaporize organic liquid E.g., iso-butane, iso-pentane Use vapor to drive turbine Causes vapor to condense Recycle continuously Typically 7 to 12 % efficient 0.1 – 40 MW units common http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp BINARY CYCLE SCHEMATIC Boyle, Renewable Energy, 2nd edition, 2004 ADVANTAGES 1) It is a renewable source of energy. 2) By far, it is non-polluting and environment friendly. 3) There is no wastage or generation of by-products. 4) Geothermal energy can be used directly. In ancient times, people used this source of energy for heating homes, cooking, etc. 5) Maintenance cost of geothermal power plants is very less. ) Unlike solar energy, it is not dependent on the weather conditions. DISADVANTAGES 1) Only few sites have the potential of Geothermal Energy. 2) Most of the sites, where geothermal energy is produced, are far from markets or cities, where it needs to be consumed. 3) Total generation potential of this source is too small. 4) There is always a danger of eruption of volcano. 5) Installation cost of steam power plant is very high. 6) There is no guarantee that the amount of energy which is produced will justify the capital expenditure and operations costs. 7) It may release some harmful, poisonous gases that can escape through the holes drilled during construction. 7 TIDAL ENERGY Tidal power or tidal energy is a form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity. Although not yet widely used, tidal energy has potential for future electricity generation. Tides are more predictable than the wind and the sun. Special turbines, and other technologies can capture the power of waves and tides and convert it into clean, pollution-free electricity. Like other renewable resources, both wave and tidal energy are variable in nature. Waves are produced by winds blowing across the surface of the ocean. How does a tidal power plant work? Tidal stream generators are very similar to wind turbines except they are below the water surface instead of above or on land. The turbine and generator converts the movement of water coming from change in tide, the kinetic energy, into electricity. How much energy is produced by tidal power? For wave energy, one estimate is 2,000 terawatthours per year (approximately 10 percent of global electricity production), and tidal stream power— which uses ocean currents to drive underwater blades in a manner similar to wind power generation—in shallow water can generate some 3,800 terawatthours per year MAIN COMPONENTS Barrage or dyke or dam – dams built across the full width of a tidal estuary Sluice ways- gate controlled devices – allow water to enter into basin during high tide and from the basin during low tide. Embankments – made of concrete to prevent water from flowing certain parts of barrage and to help in maintenance work and electrical wiring Power house Modes of operation Ebb Generation Flood Generation Two way Generation Pumping and turbining EBB GENERATION FLOOD GENERATION TWO WAY GENERATION Modes of Generation Single Basin Arrangement Double Basin Arrangement SINGLE BASIN ARRANGEMENT DOUBLE BASIN ARRANGEMENT POLLUTION POLLUTION CONTENTS • Air Pollution - Indoor Air Pollution - Air quality standards - Air Quality Index - Effects of air pollution - Air pollution control - Air pollution measurement • Water Pollution - Water Pollutants - Impacts of Water Pollution • Soil Pollution - Causes of Soil Pollution - Effects of Soil Pollution - Control of Soil Pollution Air Pollution • Air pollution consists of chemicals or particles in the air that can harm the health of humans, animals, and plants. It also damages buildings. • Pollutants in the air take many forms. They can be gases, solid particles, or liquid droplets. • Air pollution is certainly not a new phenomenon. Early references date to the Middle Ages, when smoke from burning coal was already considered such a serious problem that in 1307, King Edward I banned its use in lime kilns in London. • In more recent times, though still decades ago, several serious episodes focused attention on the need to control the quality of the air we breathe. • The worst of these occurred in London, in 1952. A week of intense fog and smoke resulted in over 4,000 excess deaths that were directly attributed to the pollution. • In the United States, the most alarming episode occurred during a 4-day period in 1948 in Donora, Pennsylvania, when 20 deaths and almost 6,000 illnesses were linked to air pollution. • Those air pollution episodes were the results of exceptionally high concentrations of sulphur oxides and particulate matter, the primary constituents of industrial smog or sulphurous smog. • Sulphurous smog is caused almost entirely by combustion of fossil fuels, especially coal, in stationary sources such as power plants and smelters. • In contrast, the air pollution problem in many cities is caused by emissions of carbon monoxide, oxides of nitrogen, and various volatile organic compounds that swirl around in the atmosphere reacting with each other and with sunlight to form photochemical smog. • Although stationary sources also contribute to photochemical smog, the problem is most closely associated with motor vehicles. Sources of emissions • There are many sources of the gases and particulate matter that pollute our atmosphere. • Substances that are emitted directly into the atmosphere are called primary pollutants, whereas others that are created by various physical processes and chemical reactions that take place in the atmosphere are called secondary pollutants. • For example, nitrogen oxides and hydrocarbons emitted when fuels are burned are primary pollutants, but the ozone that is created when those chemicals react with each other in the atmosphere is a secondary pollutant. • The sources of primary pollutant emissions can be conveniently categorized by the processes that create them. Most primary pollutants enter the atmosphere as a result of 1. combustion, 2. evaporation, 3. grinding and abrasion. • Automobile exhaust emissions and power plant stack gases are created during combustion; • volatile substances such as gasoline, paints, and cleaning fluids enter the atmosphere by evaporation; • Whereas, dust kicked up when land is ploughed and asbestos fibers that flake off of pipe insulation are examples of grinding and abrasion. • Of these, combustion accounts for the great majority of emissions, and the gases and particulate matter released when fuels are burned have been the focus of most of the technical and legislative pollution control efforts. • To investigate the origins of primary pollutants resulting from combustion, let’s begin with complete combustion of a pure hydrocarbon fuel such as methane (CH4) : CH4 + 2 O2 → CO2 + 2 H2O (1) • The products of combustion are simple carbon dioxide and water, neither of which had been considered an air pollutant until we realized that the accumulation of it in the atmosphere was enhancing Earth’s natural greenhouse effect. • If the temperature of combustion isn’t high enough, or there isn’t enough oxygen available, or if the fuel isn’t given enough time to burn completely, then the fuel will not be completely oxidized, and some of the carbon will be released as carbon monoxide (CO) instead of CO2 . • Also, some of the fuel will not be completely burned, so there will be emissions of various partially combusted hydrocarbons that we will represent by (HC). • So we can write the following descriptive reaction to represent incomplete combustion of our pure hydrocarbon fuel, methane : CH4 + O2 → mostly (CO2 + 2 H2O) + traces of [CO + (HC)] (2) • Of course, most combustion takes place in air, not in a pure oxygen environment, and air is roughly 78 percent N2 and 21 percent O2. • When the temperature of combustion is high enough, some of that nitrogen reacts with the oxygen in air to form various nitrogen oxides (NOx). • Since this NOx is formed when combustion temperatures are high, it is referred to as thermal NOx. air (N2 + O2) + Heat → Thermal NOx (3) • Most fuels have a number of other elements in them such as nitrogen, sulphur, lead (in gasoline), mercury (in coal), and other unburnable materials called ash. • Burning fuel with these “impurities” in them releases additional NOx (called fuel NOx ), oxides of sulphur (SOx ), lead (Pb), mercury (Hg), more particulate matter, and ash. • Combining the effects of incomplete combustion, combustion in air, and combustion of fuels that are not pure hydrocarbons yields the following qualitative description of combustion : Fuel (H, C, S, N, Pb, Hg, ash) + Air (N2 + O2) → Emissions (CO2, H2O, CO, NOx, SOx, Pb, Hg, particulates) + ash (4) • Now let’s add a simple representation of the photochemical reactions that produce ozone (O3) and other constituents of photochemical smog. • Hydrocarbons and other organic compounds that readily vaporize are called volatile organic compounds (VOCs). VOCs react with NOx in the presence of sunlight to produce photochemical smog: VOCs + NOx + Sunlight → Photochemical smog (O3 + etc.) (5) • To distinguish between the ozone that is formed near the ground by (5) from the ozone that exists in the stratosphere , the designations ground-level ozone and stratospheric ozone are sometimes used. • As we shall see, ground-level ozone is harmful to our health, whereas stratospheric ozone protects our health by shielding us from ultraviolet radiation from the sun. • One way to approach emissions and controls of air pollutants is to categorize the sources as mobile sources or stationary sources • Mobile sources include highway vehicles (automobiles and trucks), and other modes of transportation, including railroads, aircraft, farm vehicles, and boats and ships. • Stationary sources are often categorized as stationary fuel combustion, which includes electric power plants and industrial energy systems; industrial processes, such as metals processing, petroleum refineries, and other chemical and allied product manufacturing; and miscellaneous sources. • Very roughly speaking, mobile sources are responsible for most of the CO and almost half of the NOx, whereas stationary sources are responsible for most of the SOx, Hg, particulates, and VOCs, along with a bit more than half of the NOx . Indoor Air Pollution • Indoor air pollution is the degradation of indoor air quality by harmful chemicals and other materials; it can be up to 10 times worse than outdoor air pollution. • This is because contained areas enable potential pollutants to build up more than open spaces. • Statistics suggest that in developing countries, health impacts of indoor air pollution far outweigh those of outdoor air pollution. • Indoor Air Quality (IAQ) refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. • Understanding and controlling common pollutants indoors can help reduce your risk of indoor health concerns. • Health effects from indoor air pollutants may be experienced soon after exposure or, possibly, years later. Indian Air Quality Index • The Air Quality Index (AQI) is used for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you. • The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air. Indian Air Quality Index contd. Indian Air Quality Index contd. Indian Air Quality Index contd. Indian Air Quality Index contd. • https://app.cpcbccr.com/AQI_India/ • https://www.aqi.in/ • https://aqicn.org/map/india/ Air Pollution Control 1. Automobile Emission Controls • Vehicular emissions are caused by both combustion and evaporation. During the exhaust stroke of an internal combustion engine, combustion gases are pushed through the exhaust manifold and out the tailpipe. In this exhaust system, most of the control of automobile emissions now occurs. • In addition, fuel evaporation from the gas tank itself, from the engine while it is running, and during refueling at the gas station, all contribute significant amounts of hydrocarbon vapors to the atmosphere. (a) Catalytic converters • Catalytic converters use reduction and oxidation (redox) reactions to reduce harmful emissions. • They use a reduction catalyst composed of platinum and rhodium. It helps reduce nitrogen oxides (NOx) by removing nitrogen atoms from nitrogen oxide molecules (NO and NO2). This lets the free oxygen form oxygen gas (O2). Then, the nitrogen atoms attached to the catalyst react with each other. This reaction creates nitrogen gas (N2 ) Reduction Reactions 2NO→ N2+O2 (6) 2NO2→ N2+2O2 (7) • Catalytic converters also use an oxidative catalyst composed of platinum or palladium. It helps reduce hydrocarbons (HC) and carbon monoxide (CO). To start with, carbon monoxide and oxygen combine to form carbon dioxide (CO2). Then, unburnt hydrocarbons and oxygen combine to form carbon dioxide and water. Oxidation Reactions 2CO + O2→ 2CO2 (8) HC + O2 → H2O + CO2 (9) How do catalytic converters work? • On a car, the catalytic converter is attached to the exhaust pipe. A metal casing contains a ceramic honeycomb. The honeycomb is coated with a mix of platinum (Pt), palladium (Pd) and rhodium (Rh). • These noble metals are good at resisting oxidation, corrosion and acid. That means they can stand up to bad weather and all the chemicals released by a car engine. • The noble metals in catalytic converters act as catalysts. Catalysts are compounds that can trigger a chemical reaction without being affected themselves. The honeycomb structure inside a catalytic converter maximizes the surface area where reactions can take place. (b) Alternative Fuels • Ethanol • Methanol • Biodiesel • Compressed Natural Gas (CNG) • Liquefied Petroleum Gas (LPG) (c) Electric-Drive Vehicles • Hybrid Electric Vehicles (HEVs) • Electric Vehicles (EVs) • Fuel-Cell Vehicles (FCVs) 2. Stationary Sources Emission Control • Non transportation fossil-fuel combustion is responsible for 90 percent of the SOx and almost half of the NOx and PM10 emitted in the atmosphere. Most of that is released at electric power plants, and most of the power plant emissions result from the combustion of coal. • Although most stationary source emissions are caused by combustion of fossil fuels, other processes such as evaporation of volatile organic substances, grinding, and forest fires, can be important as well • Since most air pollutants are produced during combustion, one of the most important, but most overlooked, approaches to reducing emissions is simply to reduce the consumption of fossil fuels. • There are three broad approaches that can be taken to reduce fossil fuel consumption: (1) increase the conversion efficiency from fuel to energy, (2) increase the efficiency with which energy is used, and (3) substitute other, less polluting, energy sources for fossil fuels. • To the extent that fossil fuels continue to be used, there are three general approaches that can be used to reduce emissions: 1. Precombustion controls reduce the emission potential of the fuel itself. Examples include switching to fuels with less sulphur or nitrogen content in power plants. In some cases, fossil-fuels can be physically or chemically treated to remove some of the sulphur or nitrogen before combustion. 2. Combustion controls reduce emissions by improving the combustion process itself. Examples include new burners in power plants that reduce NOx emissions, and new fluidized bed boilers that reduce both NOx and SOx . 3. Postcombustion controls capture emissions after they have been formed but before they are released to the air. On power plants, these may be combinations of particulate collection devices and flue-gas desulfurization techniques, used after combustion but before the exhaust stack. Coal-Fired Power Plants 1. Precombustion Controls 2. Fluidized-Bed Combustion (FBC) Fluidized-Bed Combustion (FBC) • Fluidized-bed combustion (FBC) is one of the most promising clean coal technologies. In an FBC boiler, crushed coal mixed with limestone is held in suspension (fluidized) by fastrising air injected from the bottom of the bed. • Sulphur oxides formed during combustion react with the limestone (CaCO3) to form solid calcium sulphate (CaSO4) , which falls to the bottom of the furnace and is removed. Sulphur removal rates can be higher than 90 percent. • In an FBC boiler, the hot, fluidized particles are in direct contact with the boiler tubes. This enables much of the heat to be transferred to the boiler tubes by conduction, which is much more efficient than convection and radiation heat transfer occurring in conventional boilers. • The increase in heat transfer efficiency enables the boilers to operate at around 800°C, which is about half the temperature of conventional boilers and is well below the 1,400°C threshold at which thermal (NOx) is formed. Flue-gas desulfurization (FGD) of flue gas Particulate Control • A number of gas-cleaning devices can be used to remove particulates. The most appropriate device for a given source will depend on such factors as particle size, concentration, corrosivity, toxicity, volumetric flow rate, required collection efficiency, allowable pressure drops, and costs. 1. Cyclone Collectors 2. Electrostatic Precipitators 3. Baghouses Combined Heat and Power Systems Air Pollution Measurement Air pollutants are measured by a variety of techniques, most involving drawing sample air into the analyser and determining the concentration of the pollutant in the air. 1. Ozone – ultraviolet spectroscopy 2. Oxides of nitrogen – chemiluminescence 3. Sulfur dioxide - pulsed fluorescent spectrophotometry 4. Carbon monoxide - infrared spectrometry 5. Fine particles as PM10 and PM2.5 - Tapered Element Oscillating Microbalance (TEOM), High Volume Air Sampler 6. Ammonia – chemiluminescence 7. Visibility - nephelometer High Volume Air Sampler Water Pollution When the well’s dry, we know the worth of water. —Ben Franklin, Poor Richard’s Almanac Water pollution occurs when harmful substances—often chemicals or microorganisms— contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and rendering it toxic to humans or the environment. • Water is uniquely vulnerable to pollution. Known as a “universal solvent,” water is able to dissolve more substances than any other liquid on earth. • It’s also why water is so easily polluted. Toxic substances from farms, towns, and factories readily dissolve into and mix with it, causing water pollution. Major sources of water pollution are : i. Domestic sewage ii. Industrialization iii. Population growth iv. Pesticides and fertilizers v. Plastics and polythene bags vi. Urbanization vii. Weak management system Water Pollutants • Water that has been withdrawn, used for some purpose, and then returned will be polluted in one way or another. • Agricultural return water contains pesticides, fertilizers, and salts; municipal return water carries human sewage, pharmaceuticals, and surfactants; power plants discharge water that is elevated in temperature; and industry contributes a wide range of chemical pollutants and organic wastes. • To aggravate the problem, pollutants also enter water from natural sources and from human sources via nonaqueous routes. • Arsenic, antimony, and fluoride often come from natural mineral deposits through which groundwater flows. • Much of the mercury in water is deposited from the air after being emitted from coal combustion. • The polybrominated biphenyl ethers (PBDEs), are now found in water throughout the world and are believed to be transported largely on dust in the air. • The list of pollutants that contaminate water is lengthy, so it helps to organize the list into a smaller number of major categories : (a) Pathogens (b) Oxygen-Demanding Wastes (c) Nutrients (d) Salts (e) Thermal Pollution Water Pollutants (f) Heavy Metals (g) Pesticides (h) Volatile Organic Chemicals (i) Radioactive Substances (j) Microplastics Pathogens • It has long been known that contaminated water is responsible for the spread of many contagious diseases. • Pathogens are disease-causing organisms that grow and multiply within the host. The resulting growth of microorganisms in a host is called an infection. • Examples of pathogens associated with water include bacteria, responsible for cholera, bacillary dysentery (shigellosis), typhoid, and paratyphoid fever; viruses, responsible for infectious hepatitis. • There are many ways that contaminated water is associated with infectious diseases. Waterborne diseases, such as cholera and typhoid, are spread by ingestion of contaminated water. Oxygen-Demanding Wastes • One of the most important measures of the quality of a water source is the amount of dissolved oxygen (DO) present. • The saturated value of dissolved oxygen in water is modest, on the order of 8 to 15 mg of oxygen per liter of water, depending on temperature and salinity. • The minimum recommended amount of DO for a healthy fish population has often been set at 5 mg/L. • Oxygen-demanding wastes are substances that oxidize in the receiving body of water. As bacteria decompose these wastes, they utilize oxygen dissolved in the water, which reduces the remaining amount of DO. • As DO drops, fish and other aquatic life are threatened and, in the extreme case, killed. In addition, as dissolved oxygen levels fall, undesirable odors, tastes, and colors reduce the acceptability of that water as a domestic supply and reduce its attractiveness for recreational uses. • Oxygen-demanding wastes are usually biodegradable organic substances contained in municipal wastewaters or in effluents from certain industries, such as food processing and paper production. • Even naturally occurring organic matter, such as leaves and animal droppings, that finds its way into surface water contributes to oxygen depletion. • There are several measures of oxygen demand commonly used. The chemical oxygen demand (COD) is the amount of oxygen needed to chemically oxidize the wastes, whereas the biochemical oxygen demand (BOD) is the amount of oxygen required by microorganisms to biologically degrade the wastes. Nutrients • Nutrients are chemicals, such as nitrogen, phosphorus, carbon, sulphur, calcium, potassium, iron, manganese, boron, and cobalt, that are essential to the growth of living things. • In terms of water quality, nutrients can be considered as pollutants when their concentrations are sufficient to allow excessive growth of aquatic plants, particularly algae. • Nutrient enrichment can lead to blooms of algae, which eventually die and decompose. • Their decomposition removes oxygen from the water, potentially leading to levels of DO that are insufficient to sustain normal life forms. • Algae and decaying organic matter add colour, turbidity, odours, and objectionable tastes to water that are difficult to remove and that may greatly reduce its acceptability as a domestic water source. The process of nutrient enrichment, called eutrophication. • Nutrients as well as other pollution may come from either point-sources or nonpointsources. The most common point-sources are the discharge pipes from industries and wastewater treatment plants but may also include discharges from waste disposal sites, mines, animal feedlots, and large construction sites. • Runoff from agricultural lands, pastures and ranges, small construction sites, urban areas, abandoned mines, and logging sites are typical nonpoint-sources of pollution. • Detergent formulations have evolved in response to environmental concerns since their introduction just after World War II to replace soaps. • Despite the decrease in phosphorus in detergents and the implementation of phosphorus removal processes at some wastewater treatment plants, phosphorus induced eutrophication is still the largest water quality problem in lakes, reservoirs. Salts • Water naturally accumulates a variety of dissolved solids, or salts, as it passes through soils and rocks on its way to the sea. These salts typically include such cations as sodium, calcium, magnesium, and potassium, and anions such as chloride, sulfate, and bicarbonate. • As a rough approximation, fresh water can be considered to be water with less than 1,500 mg/L total dissolved solids (TDS); brackish waters may have TDS values up to 5,000 mg/L; and saline waters are those with concentrations above 5,000 mg/L. Seawater contains 30,000 to 34,000 mg/L TDS. • All naturally occurring water has some amount of salt in it. In addition, many industries discharge high concentrations of salts, and urban runoff may contain large amounts in areas where salt is used to keep ice from forming on roads in the winter. • Although such human activities may increase salinity by adding salts to a given volume of water, it is more often the opposite process, the removal of fresh water by evaporation, that causes salinity problems. • When water evaporates, the salts are left behind, and since there is less remaining fresh water to dilute them, their concentration increases. • Irrigated agriculture, especially in arid areas, is always vulnerable to an accumulation of salts due to this evapotranspiration on the cropland itself. • Salt accumulation in soils is often controlled by flushing the salts away with additional amounts of irrigation water. This increases costs; wastes water, which may not be abundantly available in the first place. Thermal Pollution • A large steam-electric power plant requires an enormous amount of cooling water. A typical nuclear plant, for example, warms about 150,000 m3/hr of cooling water by 10°C as it passes through the plant’s condenser. • If that heat is released into a local river or lake, the resulting rise in temperature can adversely affect life in the vicinity of the thermal plume. • As temperatures increase, the demand for oxygen goes up, and the amount of DO available goes down. Heavy Metals • The term heavy metal is less precisely defined. It is often used to refer to metals with specific gravity greater than about 4 or 5. In terms of their environmental impacts, the most important heavy metals are mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As). • Most metals are toxic, including aluminum, arsenic, beryllium, bismuth, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, selenium, strontium, thallium, tin, titanium, and zinc. • Some of these metals, such as chromium and iron, are essential nutrients in our diets, but in higher doses, they can cause a range of adverse impacts on the body, including nervous system and kidney damage, creation of mutations, and induction of tumors. • The most important route for the elimination of metals after they are inside a person is via the kidneys. • The kidneys contain millions of excretory units called nephrons, and chemicals that are toxic to the kidneys are called nephrotoxins. Cadmium, lead, and mercury are examples of nephrotoxic metals. • Metals may be inhaled, as is often the case with lead, for example, and they may be ingested. How well they are absorbed in the body depends somewhat on the particular metal in question and the particular form that it exists in. • For example, liquid mercury is not very toxic and most of what is ingested is excreted from the body. Mercury vapor, on the other hand, is highly toxic. As a vapor, it enters the lungs where it diffuses into the bloodstream. When blood containing mercury reaches the brain, the mercury can pass into the brain, where it causes serious damage to the central nervous system. • By contrast, lead does not pose much of a threat as a vapor since it has such a low vapor pressure, and is most dangerous when it is dissolved into its ionic form, Pb2+ . Lead dissolved in blood is transferred to vital organs, including the kidneys and brain. • Metals differ from other toxic substances in that they are totally non-degradable, which means they are virtually indestructible in the environment. • Thus, it is imperative when metal pollution is remediated that the waste products be disposed of in such a way as to minimize further environmental and human impacts. Pesticides • The term pesticide is used to cover a range of chemicals that kill organisms that humans consider undesirable. Pesticides can be delineated as insecticides, herbicides, rodenticides, and fungicides. • There are three main groups of synthetic organic insecticides: organochlorines (also known as chlorinated hydrocarbons), organophosphates, and carbamates. • The most widely known pesticide is DDT (dichlorodiphenyltrichloroethane), which has been widely used to control insects that carry diseases such as malaria (mosquitoes), typhus (body lice), and plague (fleas). • By contributing to the control of these diseases, DDT is credited with saving literally millions of lives worldwide. • The organophosphates are rapidly absorbed through the skin, lungs, and gastrointestinal tract, so unless proper precautions are taken, they are very hazardous to those who use them. • Humans exposed to excessive amounts have shown a range of symptoms, including tremor, confusion, slurred speech, muscle twitching, and convulsions. • Acute human exposure to carbamates has led to a range of symptoms such as nausea, vomiting, blurred vision, and, in extreme cases, convulsions and death. Volatile Organic Chemicals • Volatile organic chemicals (VOCs) are among the most commonly found contaminants in groundwater. They are often used as solvents in industrial processes and a number of them are either known or suspected carcinogens or mutagens. • Their volatility means they are not often found in concentrations above a few μg/L in surface waters, but in groundwater, their concentrations can be hundreds or thousands of times higher. • Their volatility also suggests the most common method of treatment, which is to aerate the water to encourage them to vaporize and disperse in the atmosphere. • Five VOCs are especially toxic, and their presence in drinking water is cause for special concern: vinyl chloride, tetrachloroethylene, trichloroethylene, 1,2- dichloroethane, and carbon tetrachloride. • The most toxic of the five is vinyl chloride (chloroethylene). It is a known human carcinogen used primarily in the production of polyvinyl chloride resins. • Trichloroethylene (TCE) is a solvent that was quite commonly used to clean everything from electronics parts to jet engines and septic tanks. It is a suspected carcinogen and is among the most frequently found contaminants in groundwater. • Carbon tetrachloride was a common household cleaning agent that is now more often used in grain fumigants, fire extinguishers, and solvents. It is very toxic if ingested; only a few milliliters can produce death. It is relatively insoluble in water, and therefore only occasionally found in contaminated groundwater. Microplastics • A micro-plastic is any piece of plastic smaller than 5mm in diameter. • “If current consumption rates continue, the planet will hold another 33 billion tonnes of plastic by 2050. This would fill 2.75 billion refuse-collection [garbage] trucks, which would wrap around the planet roughly 800 times if placed end to end.” Where do micro-plastics come from? • Microplastics are used in consumer products. These micro-plastics are created purposefully by companies as part of a product offering or the production process. • For example, micro-beads are found in products like facial scrubs or toothpaste, where the micro-beads are embedded in the product. After you use the product the micro-beads will make its way down your sink and then eventually end up in the sea. It was only until recently that people have been made aware of the micro-bead process. • A plastic bottle does not retain its form or shape. Over time, with forces, such as wind, UV radiation in the form of sunlight, or abrasion in water, the plastics break down into smaller and smaller pieces, eventually becoming microplastics. The life cycle of micro-plastics are still uncertain but most scientific experts estimate it to be between 450 years and forever. • Globally, we only recycle about 9% of the plastics we produce. If we measure this in plastic bottles then out of every 10 plastic bottles potentially 9 can end up back in our environment. • The small plastic fibres of a standard polyester T-shirt can lose up to 1gram of fibers on one washing cycle. • Microplastics were found in sea salt several years ago. But how extensively plastic bits are spread throughout the most commonly used seasoning remained unclear. Now, new research shows microplastics in 90 percent of the table salt brands sampled worldwide. Radioactive Substances • Radioactive waste is any pollution that emits radiation beyond what is naturally released by the environment. It’s generated by uranium mining, nuclear power plants, and the production and testing of military weapons, as well as by universities and hospitals that use radioactive materials for research and medicine. • Radioactive waste can persist in the environment for thousands of years, making disposal a major challenge. • Accidentally released or improperly disposed of contaminants threaten groundwater, surface water, and marine resources. Soil pollution Soil pollution is defined as the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease causing agents, which have adverse effects on plant growth and animal health. • Although the majority of pollutants have anthropogenic origins, some contaminants can occur naturally in soils as components of minerals and can be toxic at high concentrations. • Soil pollution often cannot be directly assessed or visually perceived, making it a hidden danger. • Soil is the thin layer of organic and inorganic materials that covers the Earth's rocky surface. • The organic portion, which is derived from the decayed remains of plants and animals, is concentrated in the dark uppermost topsoil. The inorganic portion made up of rock fragments, was formed over thousands of years by physical and chemical weathering of bedrock. • Productive soils are necessary for agriculture to supply the world with sufficient food. There are many different ways that soil can become polluted, such as: • Seepage from a landfill • Discharge of industrial waste into the soil • Percolation of contaminated water into the soil • Rupture of underground storage tanks • Excess application of pesticides, herbicides or fertilizer • Solid waste seepage The most common chemicals involved in causing soil pollution are: • Petroleum hydrocarbons • Heavy metals • Pesticides • Solvents Types of Soil Pollution • Agricultural Soil Pollution i) pollution of surface soil ii) pollution of underground soil • Soil pollution by industrial effluents and solid wastes i) pollution of surface soil ii) disturbances in soil profile • Pollution due to urban activities i) pollution of surface soil ii) pollution of underground soil Causes of Soil Pollution • Soil pollution is caused by the presence of man-made chemicals or other alteration in the natural soil environment. • This type of contamination typically arises from the rupture of underground storage links, application of pesticides, percolation of contaminated surface water to subsurface strata, oil and fuel dumping, leaching of wastes from landfills or direct discharge of industrial wastes to the soil. • The most common chemicals involved are petroleum hydrocarbons, solvents, pesticides, lead and other heavy metals. This occurrence of this phenomenon is correlated with the degree of industrialization and intensities of chemical usage. A soil pollutant is any factor which deteriorates the quality, texture and mineral content of the soil or which disturbs the biological balance of the organisms in the soil. Pollution in soil has adverse effect on plant growth. Pollution in soil is associated with • Indiscriminate use of fertilizers • Indiscriminate use of pesticides, insecticides and herbicides • Dumping of large quantities of solid waste • Deforestation and soil erosion Transport pathway of pesticides in the environment Potential interrelated pathways for soil-subsurface chemical contamination Agricultural sources of soil pollution Systematic categorization of the main pollutants in soils Behaviour of pesticides in environment Chemical and biological processes of Manmade Nanoparticles Principal uptake pathways for the uptake of soil contaminants by plants Possible exposure pathways of soil contamination in a residential scenario Simplified pathway for oral exposure to soil pollutants Effects of Soil Pollution Agricultural • Reduced soil fertility • Reduced nitrogen fixation • Increased erodibility • Larger loss of soil and nutrients • Deposition of silt in tanks and reservoirs • Reduced crop yield • Imbalance in soil fauna and flora Industrial • Dangerous chemicals entering underground water • Ecological imbalance • Release of pollutant gases • Release of radioactive rays causing health problems • Increased salinity • Reduced vegetation Urban • Clogging of drains • Inundation of areas • Public health problems • Pollution of drinking water sources • Foul smell and release of gases • Waste management problems Control of soil pollution Reducing chemical fertilizer and pesticide use • Applying bio-fertilizers and manures can reduce chemical fertilizer and pesticide use. Biological methods of pest control can also reduce the use of pesticides and thereby minimize soil pollution. Reusing of materials • Materials such as glass containers, plastic bags, paper, cloth etc. can be reused at domestic levels rather than being disposed, reducing solid waste pollution. Recycling and recovery of materials • This is a reasonable solution for reducing soil pollution. Materials such as paper, some kinds of plastics and glass can and are being recycled. • This decreases the volume of refuse and helps in the conservation of natural resources. For example, recovery of one tonne of paper can save 17 trees. Reforesting • Control of land loss and soil erosion can be attempted through restoring forest and grass cover to check wastelands, soil erosion and floods. Crop rotation or mixed cropping can improve the fertility of the land. Solid waste treatment • Proper methods should be adopted for management of solid waste disposal. Industrial wastes can be treated physically, chemically and biologically until they are less hazardous. • Acidic and alkaline wastes should be first neutralized; the insoluble material if biodegradable should be allowed to degrade under controlled conditions before being disposed. ENIR11 - ENERGY AND ENVIRONMENTAL ENGINEERING Green house gases and Noise Pollutions Dr. Karthik D Dept. of Energy and Environment National Institute of Technology Tiruchirappalli Greenhouse Gases – Effect 01-02-2022 2 Greenhouse • The greenhouse is a structure or building made of with glass walls and glass roof, in which that need protection from cold weather are grown. • The glass wall and glass roof allowing sunlight to penetrate in freely and warm the air and plant inside. • If the door and ventilation windows are closed, the warm air can't escape. So the temperature of everything in the greenhouse goes up. • Thus greenhouse act as green trap. 01-02-2022 3 Electromagnetic spectrum Short wave and long wave radiation • Electromagnetic spectrum is the collection of wavelengths of light (electromagnetic radiation). • In the electromagnetic spectrum, we see that, when the energy increases the wavelength decreases and vice versa. • That means, Energy is inversely proportional to wavelength 01-02-2022 • Shortwave radiation contains higher amount of energy and longwave contain a smaller amount of energy 4 Electromagnetic spectrum • Radiation from the sun, commonly known as sunlight , is a mixture of electromagnetic waves ranging Infrared (IR) to Ultraviolet rays (UV). Due to visible light, we can see sunlight. • As the sun is reasonable hot (surface temperature of 6000oC) it radiates as a shorter wavelength. • However, since the earth is much cooler than the sun (average temperature of the earth: 15oC), its radiating much weaker infrared energy (longer wavelength). 01-02-2022 5 How greenhouse works? • Solar energy enters our atmosphere as shortwave radiation in the form of ultraviolent (UV) rays and visible light • When the radiation enters the greenhouse, the radiation absorbed by the inside object of the greenhouse. • Theses objects re-emitted the infrared radiations as a longer wavelength, which cannot pass easily through the glass. • Because, shortwave radiation ( higher energy) can easily pass through the glass wall of a greenhouse and go inside it. • But, the longer wavelength radiation( lower energy) does not allow to escape through the glass. So it again reflected inside the greenhouse. • Thereby, this re-emitted longwave radiations warms the soil, plants and so on inside a greenhouse. • Even without an internal supply of heat, the temperature inside a greenhouse becomes higher than that outside. • Thus the glass acts as a heat trap. This is called greenhouse effect. 01-02-2022 6 Greenhouse gases • The earth is surrounded by a blanket of gases including greenhouse gases. • The greenhouse gases are those gases in the atmosphere which by absorbing thermal radiation emitted by the earth’s surface have a blanketing effect over the surface keeping it warmer. • Without naturally occurring greenhouse gases, Earth's average temperature would be near -18°C instead of the much warmer 15°C. • The earth’s atmosphere allows short-wave solar radiation from the sun to pass relatively unimpeded. • The long-wave infrared radiation emitted from the warm earth’s surface is partially trapped and re-emitted downwards by greenhouse gases such as water vapour, carbon dioxide, methane, nitrous oxide, in the upper atmosphere. • In this way an energy balance is set up, which ensures that the Earth is warmer than it would be without it. 01-02-2022 7 Greenhouse Effect Fig. The Green House Effect 01-02-2022 8 Enhanced Greenhouse Effect • The natural greenhouse effect is enhanced by the increase of greenhouse gases in the atmosphere especially carbon dioxide from the burning of fossil fuels, coal, oil and gas together with wide deforestation over the past 200 years and more substantially. • The important GHG’s that are directly influenced by human activities leading to enhanced greenhouse effect are carbon dioxide, methane, nitrous oxide, the chlorofluorocarbons (CFCs). • The earth’s surface temperature has increased by about 0.6°C over the last century, and as a consequence the sea level is estimated to have risen by perhaps 20 cm. 01-02-2022 Rising Global Temperatures due to enhanced greenhouse effect 9 Enhanced Greenhouse Effect contd. • Predictions show that if atmospheric concentrations of greenhouse gases, mainly due to fossil fuel combustion, continue to increase at the present rates, the earth’s temperature may increase by another 2–4°C in the next century. • If this prediction is realized, the sea level could rise by 30–60 cm before the end of this century. • The impacts of such sea level increase can easily be understood and include flooding of coastal settlements, displacement of fertile zones for agriculture to higher latitudes, and decrease in availability of freshwater for irrigation and other essential uses. • Thus, such consequences could put in danger the survival of entire populations. 01-02-2022 10 Composition of the Atmosphere • The atmosphere is concentrated at the earth’s surface and rapidly thins as you move upward, blending with space at roughly 100 miles above sea level. • The atmosphere is actually very thin compared to the size of the earth, equivalent in thickness to a piece of paper laid over a beach ball. • Nitrogen accounts for 78% of the atmosphere, oxygen 21% and argon 0.9%. Gases like carbon dioxide, nitrous oxides, methane, and ozone are trace gases that account for about a tenth of one percent of the atmosphere. • Water vapour is unique in that its concentration varies from 0-4% of the atmosphere depending on where you are and what time of the day it is. 01-02-2022 11 Fig. Composition of the Atmosphere 01-02-2022 Fig. % Share of Greenhouse gases 12 CO2 concentration in the atmosphere over the time period 01-02-2022 13 01-02-2022 14 01-02-2022 15 01-02-2022 16 01-02-2022 17 01-02-2022 18 01-02-2022 19 Global Warming Potential (GWP) • Global warming potential (GWP)is a measure of how much energy the emissions of 1 tonne of a gas will absorb over a given period of time, relative to the emissions of 1 tonne of carbon dioxide (CO2). Global warming potential (GWP) of various green houses gases 01-02-2022 20 Global Temperature Change 01-02-2022 21 What is Acid Rain? • Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulphuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. • This can include rain, snow, fog, hail or even dust that is acidic. Fig. Acid Rain Formation 01-02-2022 22 What Causes Acid Rain? • Acid rain results when sulphur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents. • The SO2 and NOX react with water, oxygen and other chemicals to form sulphuric and nitric acids. These then mix with water and other materials before falling to the ground. • While a small portion of the SO2 and NOX that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels. • Recently, attention also has been given to other substances, such as volatile organic compounds (VOCs), chlorides, ozone, and trace metals that may participate in a complex set of chemical transformations in the atmosphere, resulting in acid precipitation and the formation of other regional air pollutants. • The major sources of SO2 and NOX in the atmosphere are: 1. Burning of fossil fuels to generate electricity. 2. Vehicles and heavy equipment. 3. Manufacturing, oil refineries and other industries. 01-02-2022 23 Measuring Acid Rain • Normal rain has a pH of about 5.6; it is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak carbonic acid. • Acid rain usually has a pH between 4.2 and 4.4. The pH scale 01-02-2022 24 Effects of Acid Rain • Acidification of lakes, streams and soils. • Direct and indirect effect (release of metals, for example: Aluminum which washes away plant nutrients) • Killing of wildlife (trees, crops, aquatic plants and animals) • Decay of building materials and paints, statues, and sculptures • Health problems (respiratory, burning-skin and eyes) 01-02-2022 25 Remedies for Acid Rain • Cleaning up Exhaust Pipes and Smokestacks • Restoring Damaged Environments • Alternative Energy Sources • Individual, National/State, and International Actions 01-02-2022 26 Fig. Effect of Acid Rain on Taj Mahal 01-02-2022 27 Pollution from Power Plants Coal Power plants • Coal is an organic sedimentary rock with terrestrial origin. Because it is derived from lignin, a plant material, it contains sulphur and nitrogen impurities along with metals. • Nitric oxide catalyzes the production of ground level ozone in the presence of sunlight and organic compounds. Smog is a threat to the health of humans and reduces agricultural productivity. Particulate matter or soot • Particulate matter or soot is released when coal is burned. Fine particles, with a diameter of 2.5 micrometers or less, and coarse particles, with a diameter of 10 micrometers or less is produced. • The irregular surfaces of these aerosols provide locations for SO2 and NOx to bind. Their high concentration on the particle surfaces promotes reactions that would have a much lower rate in the atmosphere and many of the surface reactions yield toxic or irritating chemical substances. • Particulate matter or soot is linked with chronic bronchitis, aggravated asthma, cardiovascular effects like heart attacks, and premature death. 01-02-2022 28 Pollution from Power Plants contd. Mercury • Mercury is a metallic pollutant released from coal combustion. Coal-burning power plants are one of the largest human-caused source of mercury emissions. • When the mercury vapour finds its way into bodies of water, it is converted by bacteria into the more toxic compound, methyl mercury. This is a known neurotoxin. It causes mental retardation, seizures, cerebral palsy and death. Fly Ash • Fly ash is a by-product of power and incineration plants operated either on coal and biomass, or municipal solid waste. • Fly ash often contains pollutants such as heavy metals and organic compounds. • The composition of fly ash is very variable, depending on their origins, then also the pollutants can be very different. • There are different types of fly ash such as Coal Fly Ash, Flue Gas Desulphurisation (FGD) Fly Ash, Municipal Solid Waste Incineration (MSWI) Fly Ash and Fly Ash from Biomass Matter Burning. • Fly ash is a valuable resource with potential use in several applications like agriculture, synthesis of zeolite, adsorbent and building materials. 01-02-2022 29 Pollution from Power Plants contd. Water Pollution • In a coal power plant, water is used for washing coal, circulating in the boiler furnace to produce steam and cooling of equipment. The dust from coal-cleaned water contaminates groundwater. Thermal Pollution • Thermal pollution is the degradation of water quality by any process that changes the ambient water temperature. • A common cause of thermal pollution is the use of water as a coolant by coal based power plants. • When water used as a coolant is returned to the natural environment at a higher temperature, the sudden change in temperature decreases oxygen supply and affects the ecosystem. • Fish and other organisms adapted to particular temperature range can be killed by an abrupt change in water temperature (either a rapid increase or decrease in the temperature of the water known as thermal shock). 01-02-2022 30 Fig. Thermal Pollution from Coal based power plant 01-02-2022 31 Fig. Thermal Pollution from Coal based power plant 01-02-2022 32 Pollution from Power Plants contd. Nuclear Power plants • Nuclear energy is a source of clean-air, carbon free electricity that produces no greenhouse gases or air pollutants. While nuclear power plants do not produce greenhouse gases, the process of producing nuclear energy does have some environmental impacts. • Run-off from uranium mining contains traces of radium and other metals which could be harmful to biological systems within both the local environment and downstream of the mine. • Equipment used in the process of mining uranium that becomes too radioactive to be sold has to be buried and covered in clay and soil so that no harmful radiation is emitted. • While nuclear power plants do not emit greenhouse gases the mining of uranium does create greenhouse gas emissions. The process of mining and milling uranium to keep a 1000 MW nuclear reactor running in a year, will emit 2000-5000 tonnes of CO2, depending on the grade of the uranium ore. • Nuclear power plants do not emit GHGs but they do create other environmental issues which include the pollution of water from its use and the generation of radioactive waste. 01-02-2022 33 Industrial Emissions Fig. Pollution from different power plants 01-02-2022 34 Industrial Emissions • Industrial pollution is the pollution which can be directly linked with industry. This form of pollution is one of the leading causes of pollution worldwide. • There are a number of forms of industrial pollution. Industrial pollution can also impact air quality, and it can enter the soil, causing widespread environmental problems. • Industrial activities are a major source of air, water and land pollution, leading to illness and loss of life all over the world. • A great deal of industrial pollution comes from manufacturing products from raw materials—(1) iron and steel from ore, (2) lumber from trees, (3) gasoline and other fuels from crude oil, and (4) stone from quarries. • Each of these manufacturing processes produces a product, along with several waste products, which include air pollutants. • Industrial pollution is also emitted by industries that convert products to other products—(1) automobile bodies from steel, (2) furniture from lumber, (3) paint from solids and solvents, and (4) asphaltic paving from rock and oil. • Industrial sources are stationary, and each facility emits relatively consistent qualities and quantities of pollutants. • A paper mill, for example, will be in the same place tomorrow that it is today, emitting the same quantity of the same kinds of pollutants unless a major process change is made. 01-02-2022 35 Industrial Emissions • Almost 45% of worldwide CO2 emissions are attributed to industrial activities, mostly related to the large primary material industries, such as chemicals and petrochemicals, iron and steel, cement, pulp and paper, and aluminium. • Although their energy intensity has lessened significantly in most sectors as a result of improvements in energy efficiency and material flow management, the demand for industrial products is expected to double or triple over the next 40 years. • Furthermore, some of these industries’ CO2 emissions are integral to the production process. Cement production results in CO2 emissions from calcination, which contributes more than half of total emissions. • In the iron and steel sector, the main sources of CO2 emissions are power production, iron ore reduction in either a blast furnace, coke and sinter plants. 01-02-2022 36 Transport Emissions • Transport emissions — which primarily involve road, rail, air and marine transportation — accounted for over 24% of global CO2 emissions in 2016. 1. How big a problem are emissions from transport? • Emissions from the transport sector are a major contributor to climate change — about 14% of annual emissions (including non-CO2 gases) and around a quarter of CO2 emissions from burning fossil fuels. • Even more concerning: At a time when global emissions need to be going down, transport emissions are on the rise, with improvements in vehicle efficiency more than offset by greater overall volume of travel. 2. Where do transport emissions come from? • Road travel accounts for three-quarters of transport emissions. Most of this comes from passenger vehicles – cars and buses – which contribute 45.1%. The other 29.4% comes from trucks carrying freight. • Since the entire transport sector accounts for 21% of total emissions, and road transport accounts for three-quarters of transport emissions, road transport accounts for 15% of total CO2 emissions. • Aviation – while it often gets the most attention in discussions on action against climate change – accounts for only 11.6% of transport emissions. It emits just under one billion tonnes of CO2 each year – around 2.5% of total global emissions 01-02-2022 37 Transport Emissions • Rail travel and freight emits very little – only 1% of transport emissions. Other transport – which is mainly the movement of materials such as water, oil, and gas via pipelines – is responsible for 2.2%. 01-02-2022 38 Transport Emissions 01-02-2022 39 Noise Pollution • Noise comes in all shapes, sizes and sounds. It’s part of our everyday lives. However, in order to understand it properly, it’s important to know what the different types of noise are. • Whether it’s the generic beep that punctuates our lives, a plane flying overhead or heavy machinery in your workplace, we simply cannot escape noise. If you want to accurately measure and analyse it, you need to understand the difference between the types of noise. It then becomes much easier to choose the right equipment and parameters to use. What is noise? • It’s important to understand the distinction between noise and sound. • Noise is a type of sound and is defined as unwanted, annoying, unpleasant or loud. • Our ears are excellent at telling us what noise is. Most commonly, noise is an annoying tone that causes mild to major discomfort or irritation. These tones pierce through the background noise that accompanies our lives. Types of noise 1. Continuous noise 2. Intermittent noise 3. Impulsive noise 4. Low-frequency noise 01-02-2022 40 1. Continuous noise • Continuous noise is exactly what it says on the tin: it’s noise that is produced continuously, for example, by machinery that keeps running without interruption. This could come from factory equipment, engine noise, or heating and ventilation systems. • You can measure continuous noise for just a few minutes with a sound level meter to get a sufficient representation of the noise level. 2. Intermittent noise • Intermittent noise is a noise level that increases and decreases rapidly. This might be caused by a train passing by, factory equipment that operates in cycles, or aircraft flying above your house. • We measure intermittent noise in a similar way to continuous noise, with a sound level meter. However, you also need to know the duration of each occurrence and the time between each one. To gain a more reliable estimate of the noise level, you should measure over multiple occurrences to calculate an average. If you’re using an integrating-averaging sound level meter, this will make the calculation for you and present this in terms of an LAeq. 3. Impulsive noise • Impulsive noise is most commonly associated with the construction and demolition industry. These sudden bursts of noise can startle you by their fast and surprising nature. Impulsive noises are commonly created by explosions or construction equipment, such as pile drivers. • To measure impulsive noise, you will need a sound level meter or a personal noise dosimeter that can calculate Peak values. 01-02-2022 41 4. Low-frequency noise • Low-frequency noise makes up part of the fabric of our daily soundscape. Whether it’s the low background hum of a nearby power station or the roaring of large diesel engines, we’re exposed to low-frequency noise constantly. • It also happens to be the hardest type of noise to reduce at source, so it can easily spread for miles around. What is Noise Pollution? • Noise pollution is generally defined as regular exposure to elevated sound levels that may lead to adverse effects in humans or other living organisms. • It can affect people at home, in their community, or at their place of work. • According to the World Health Organization, sound levels less than 70 dB are not damaging to living organisms, regardless of how long or consistent the exposure is. • Noise is measured in terms of Decibel units. 01-02-2022 42 Transport Ambient Air Quality standards in respect of Noise Emissions • Note: 1. Day time shall mean from 6.00 a.m. to 10.00 p.m. 2. Night time shall mean from 10.00 p.m. to 6.00 a.m. 3. Silence zone is defined as an area comprising not less than 100 meters around hospitals, educational institutions and courts. The silence zones are zones, which are declared as such by the competent authority. 4. Mixed categories of areas may be declared as one of the four-above mentioned categories by the competent authority. 01-02-2022 43 Ambient Air Quality standards in respect of Noise contd, • *dB (A) Leq denotes the time weighted average of the level of sound in decibels on scale A which is relatable to human hearing. • “A” in dB (A) Leq, denotes the frequency weighting in the measurement of noise and corresponds to frequency response characteristics of the human ear. • Leq: It is an energy mean of the noise level over a specified period. • Leq is the preferred method to describe sound levels that vary over time, resulting in a single decibel value which takes into account the total sound energy over the period of time of interest. 01-02-2022 44 Sound Pressure • Sound Pressure (p) is the difference between the pressure caused by a sound wave and the ambient pressure of the media the sound wave is passing through. • The threshold of hearing is the quietest sound that can typically be heard by a young person with undamaged hearing. The reference sound pressure is the standardized threshold of hearing and is defined as 20 micropascals (0.0002 microbars) at 1,000 Hz. • Noise is measured in units of sound pressure called decibels (dB), named after Alexander Graham Bell. The decibel notation is implied any time a "sound level" or "sound pressure level" is mentioned. • Decibels are measured on a logarithmic scale: a small change in the number of decibels indicates a huge change in the amount of noise and the potential damage to a person's hearing. • By definition, 0 dB is set at the reference sound pressure (20 micropascals at 1,000 Hz, as stated earlier). At the upper end of human hearing, noise causes pain, which occurs at sound pressures of about 10 million times that of the threshold of hearing. On the decibel scale, the threshold of pain occurs at 140 dB. This range of 0 dB to 140 dB is not the entire range of sound, but is the range relevant to human hearing 01-02-2022 45 01-02-2022 46 Sound Power and Sound Intensity • Sound power, usually measured in watts, is the amount of energy per unit of time that radiates from a source in the form of an acoustic wave. • Understanding the relationship between sound pressure and sound power is essential to predicting what noise problems will be created when particular sound sources are placed in working environments. An important consideration might be how close workers will be working to the source of sound. As a general rule, doubling the sound power increases the noise level by 3 dB. • As sound power radiates from a point source in free space, it is distributed over a spherical surface so that at any given point, there exists a certain sound power per unit area. This is designated as intensity, I, and is expressed in units of watts per square meter. • Sound intensity is heard as loudness, which can be perceived differently depending on the individual and his or her distance from the source and the characteristics of the surrounding space. As the distance from the sound source increases, the sound intensity decreases. The sound power coming from the source remains constant, but the spherical surface over which the power is spread increases--so the power is less intense. In other words, the sound power level of a source is independent of the environment 01-02-2022 47 Sound Power and Sound Intensity • Sound power, usually measured in watts, is the amount of energy per unit of time that radiates from a source in the form of an acoustic wave. • Sound Power Level in decibels is ten times the logarithm of the ratio of the sound power (W) to the reference sound power (Wo) of 1 picowatt • Sound Power Level (Lw) 𝑊 = 10 log( ) 𝑑𝐵 𝑊𝑜 01-02-2022 48 Sound Power and Sound Intensity • Sound Intensity Level is the logarithmic ratio of the measured sound intensity to the reference sound intensity in decibels. 𝐼 • Sound Intensity Level Formula, 𝐿𝑖 = 10 log( ) dB, where I is the sound intensity in W/m² and Io is the 𝐼𝑜 -12 reference sound intensity of 10 W/m². Thus converting the W/m² levels into the more manageable range of 0 to 140 dB as the following list demonstrates. 140 dB = 100 W/m² 130 dB = 10 W/m² 123 dB = 2 W/m² 120 dB = 1 W/m² ≡ threshold of pain 100 dB = 0.10 W/m² 80 dB = 0.0001 W/m² 60 dB = 0.000001 W/m² 40 dB = 0.00000001 W/m² 20 dB = 0.0000000001 W/m² 0 dB = 0.000000000001 W/m² = 10-12 W/m² the threshold of hearing 01-02-2022 49 Problem • Calculate the intensity Q: The loudness of sound is measured to be 82 dB. What is the value of the intensity of sound? dB = 10log (I/Io) 82 = 10 log (I/10-12) Divide by 10 8.2 = log(I/10-12) Apply inverse 𝐼 log 108.2 = 10 10−12 108.2 = 𝐼 10−12 I =10-3.8 I = 1.585 10-4 W/m2 01-02-2022 50 OSHA regulations for noise exposure • Occupational Safety and Health Administration (OSHA) requires employers to implement a hearing conservation program when noise exposure is at or above 90 decibels averaged over 8 working hours, or an 8-hour time-weighted average (TWA). • Hearing conservation programs strive to prevent initial occupational hearing loss, preserve and protect remaining hearing, and equip workers with the knowledge and hearing protection devices necessary to safeguard themselves. 01-02-2022 51 Sources of Noise Pollution • Street traffic sounds from cars, buses, pedestrians, ambulances etc. • Construction sounds like drilling or other heavy machinery in operation • Airports, with constant elevated sounds from air traffic, i.e. planes taking off or landing • Workplace sounds, often common in open-space offices • Constant loud music in or near commercial venues • Industrial sounds like fans, generators, compressor, mills • Train stations traffic • Household sounds, from the television set to music playing on the stereo or computer, vacuum cleaners, fans and coolers, washing machines, dishwashers, lawnmowers etc. • Events involving fireworks, firecrackers, loudspeakers etc. • Conflicts generate noise pollution through explosions, gunfire etc. 01-02-2022 52 Human Diseases Caused by Noise Pollution • Exposure to loud noise kills the nerve endings in our inner ear. More exposure will result in more dead nerve endings. The result is permanent hearing loss that cannot be corrected through surgery or with medicine. • Hypertension is, in this case, a direct result of noise pollution caused elevated blood levels for a longer period of time. • Hearing loss can be directly caused by noise pollution, whether listening to loud music in your headphones or being exposed to loud drilling noises at work, heavy air or land traffic, or separate incidents in which noise levels reach dangerous intervals, such as around 140 dB for adult or 120 dB for children. • Sleep disturbances are usually caused by constant air or land traffic at night, and they are a serious condition in that they can affect everyday performance and lead to serious diseases like cardiovascular dysfunctions. • Elevated blood pressure caused by noise pollution, especially during the night, can lead to various cardiovascular diseases. • Psychological dysfunctions and noise annoyance. Noise annoyance is, in fact, a recognized name for an emotional reaction that can have an immediate impact. 01-02-2022 53 Effects of Noise Pollution on Wildlife and Marine Life • Our oceans are no longer quiet. Thousands of oil drills, sonars, seismic survey devices, coastal recreational watercraft and shipping vessels are now populating our waters, and that is a serious cause of noise pollution for marine life. • Whales are among the most affected, as their hearing helps them orient themselves, feed and communicate. Noise pollution thus interferes with cetaceans’ (whales and dolphins) feeding habits, reproductive patterns and migration routes, and can even cause haemorrhage and death. • Other than marine life, land animals are also affected by noise pollution in the form of traffic, firecrackers etc., and birds are especially affected by the increased air traffic. 01-02-2022 54 Social and Economic Costs of Noise Pollution • The World Health Organization estimates that one out of three people in Europe is harmed by traffic noise. More than the purely medical effects of noise pollution on the individual, there is a significant social and economic impact. • Since noise pollution leads to sleep disturbance, it affects the individual’s work performance during the day, it leads to hypertension and cardiovascular disease and costs the health system additional time and money, and it negatively affects school performance in children. 01-02-2022 55 Tips for Avoiding Noise Pollution • Wear earplugs whenever exposed to elevated noise levels • Maintain a level of around 35 dB in your bedroom at night, and around 40 dB in your house during the day • If possible, choose your residential area as far removed from heavy traffic as you can • Avoid prolonged use of earphones, especially at elevated sound levels • If possible, avoid jobs with regular exposure to elevated sound levels 01-02-2022 56 Noise Footprint • We talk about our carbon footprint and what those concerned about climate change can do to try to reduce theirs, but we should think about how much noise we make, too. • The amount of carbon dioxide and related substances each person produces from fossil fuel use affects the world, including humans and animals. So does the amount of noise we each produce. • Some noise production is inevitable, but if we have a choice to use a quieter alternative, we should make that choice. Here are several ideas on how to minimize your noise footprint: • Expand your awareness of noise pollution • Ditch loud outdoor activities for quieter choices • Lower the volume of yard work • Be mindful of domestic noise Noise Footprint of Aircraft The noise footprint is the area on the ground within which the noise from an overflying aircraft exceeds a defined level. 01-02-2022 57 How to minimize your 'noise footprint’ • Here are several ideas on how to minimize your noise footprint: • Expand your awareness of noise pollution • Ditch loud outdoor activities for quieter choices • Lower the volume of yard work • Be mindful of domestic noise • Noise Footprint of Aircraft • The noise footprint is the area on the ground within which the noise from an overflying aircraft exceeds a defined level. 01-02-2022 58 Industrial Noise Control • Control of Noise at the Source • To control noise at the source, it is first necessary to determine the cause of the noise and secondly to decide on what can be done to reduce it. • Modification of the energy source to reduce the noise generated often provides the best means of noise control. • Among the physical phenomena which can give origin to noise, the following can be mentioned: 1. mechanical shock between solids, 2. unbalanced rotating equipment 3. friction between metal parts, 4. vibration of large plates, 5. irregular fluid flow, etc General source noise control can involve 1. Maintenance: - replacement of worn or loose parts; - balancing of unbalanced equipment; - lubrication of moving parts; - use of properly shaped and sharpened cutting tools 01-02-2022 59 Industrial Noise Control contd. 2. Substitution of materials (e.g., plastic for metal), a good example being the replacement of steel sprockets in chain drives with sprockets made from flexible polyamide plastics. 3. Substitution of equipment: - electric for pneumatic (e.g. hand tools); - stepped dies rather than single-operation dies; - rotating shears rather than square shears; - hydraulic rather than mechanical presses; - presses rather than hammers; - belt conveyors rather than roller conveyors. 01-02-2022 60 Industrial Noise Control contd. 4. Substitution of parts of equipment: - modification of gear teeth, by replacing spur gears with helical gears generally resulting in 10 dB of noise reduction); - replace straight edged cutters with spiral cutters (e.g. wood working machines 10 dB(A) reduction); - replace gear drives with belt drives; - replace metal gears with plastic gears (beware of additional maintenance problems); - replace steel or solid wheels with pneumatic tyres. 01-02-2022 61 Industrial Noise Control contd. 5. Change of work methods - in building demolition, replace use of ball machine with selective demolition; - replace pneumatic tools by changing manufacturing methods, such as moulding holes in concrete rather than cutting after production of concrete component; - use remote control of noisy equipment such as pneumatic tools; - separate noisy workers in time, but keep noisy operations in the same area, separated from non-noisy processes; - - minimise width of tools in contact with workpiece (2 dB(A) reduction for each halving of tool width); - woodchip transport air for woodworking equipment should move in the same direction as the tool; 01-02-2022 62 Industrial Noise Control contd. 6. Substitution of processes - mechanical ejectors for pneumatic ejectors; - hot for cold working; - pressing for rolling or forging; - welding or squeeze rivetting for impact riveting 7. Substitution of mechanical power generation and transmission equipment - electric motors for internal combustion engines or gas turbines; - belts or hydraulic power transmissions for gear boxes; 8. Replacement of worn moving parts (e.g., replace new rolling element bearings for worn ones); 9. minimising the number of noisy machines running at any one time 01-02-2022 63 Make Listening Safe • The World Health Organization (WHO) estimates that billion young people worldwide could be at risk of hearing loss due to unsafe listening practices. • Over 43 million people between the ages of 12–35 years live with disabling hearing loss due to different causes. • Among teenagers and young adults aged 12–35 years in middle- and high-income countries: ➢ Nearly 50% are exposed to unsafe levels of sound from the use of personal audio devices. *Hearing loss = A person has hearing loss if he or she is not able to hear or has a hearing threshold of 25 dB or more. 01-02-2022 64 Noise-induced hearing loss is irreversible. • Exposure to loud sounds for any length of time causes fatigue of the ear’s sensory cells. The result is temporary hearing loss or tinnitus (a ringing sensation in the ear). • The hearing improves as the sensory cells recover. When the exposure is particularly loud, regular or prolonged, it can cause permanent damage of the sensory cells and other structures, resulting in irreversible hearing loss. 01-02-2022 65 What is safe listening? • Safe listening levels depend on the intensity (loudness), duration (length of time) and frequency (how often) of the exposure. • 85 dB is considered the highest safe exposure level up to a maximum of eight hours. • The output of personal audio devices may range from 75 dB to as high as 136 dB . • Typically, users of personal audio devices choose to set the volume between 75 to 105 dB. • A person may expose themselves to the same level of loudness in 15 minutes of music at 100 dB that an industrial worker gets in an 8-hour day at 85 dB. How to make listening safe • Keep the volume down • Use earplugs • Limit time spent engaged in noisy activities • Monitor safe listening levels • Heed the warning signs of hearing loss 01-02-2022 66 01-02-2022 67 Thank you 01-02-2022 68
