CHANDANI GOYAL
LECTURER (EE)
8764271425
goyal.chandni7@gmail.com
BIOMASS-BASED POWER PLANTS
Biomass is plant or animal material used as fuel to produce electricity or heat. Examples are wood,
energy crops, and waste from forests, yards, or farms.
Types of biomass include:

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
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Agricultural residues. Crop residues include all sorts of agricultural waste such as straw, bagasse, stems,
leaves, stalks, husks, pulp, shells, peels, etc.
Animal waste. Various animal wastes are suitable as sources of energy.
Forest residues.
Industrial wastes.
Solid waste and sewage.
When burned, the chemical energy in biomass is released as heat, which can be converted into biofuels
and/or biogas and finally, into useable energy such as fuels, electricity or heat. For it to be produced, the
organic material must undergo a biomass conversion process, of which there several routes to take.
How is biomass energy generated?
Most electricity generated from biomass is produced by direct combustion. Biomass is burned in a boiler
to produce high-pressure steam. This steam flows over a series of turbine blades, causing them to rotate.
The rotation of the turbine drives a generator, producing electricity.
4.1 Properties of Solid fuel for biomass power plants:
4.1.1 Bagasse
Bagasse is the dry pulpy fibrous material that remains after crushing sugarcane or sorghum stalks
to extract their juice. It is used as a biofuel for the production of heat, energy, and electricity, and in the
manufacture of pulp and building materials. Sugar cane is a kind of tropical and subtropical crop and is
the main sugar crop worldwide. Global sugar crop acreage is approximately 31.3 million hectares, among
which sugar cane accounts for approximately 70%.
Sugar cane is typically used to produce sugar and ethanol. After the extraction of sugar juice from sugar
cane, sugar cane bagasse is produced, which is approximately 50% of the sugar cane quality. Bagasse is
commonly used as a fuel in cogeneration to produce steam and generate electricity. In this process,
sugar cane bagasse ash remains as the final waste in the sugar production chain. Each ton of burnt
bagasse may generate 25–40 kg of bagasse ash and, subsequently, a considerable amount of it could be
generated. With the increasing demand for more sugar and ethanol production in recent years, outputs
have substantially increased. In China alone, there may be 1.25–2 million tons of it produced each year.
After mixing with sugar cane filter cake or vinasse, it is commonly used as a fertilizer in sugar cane
plantations in Brazil and China. However, it is generally disposed of in landfills in India
Bagasse contains mainly cellulose, hemicellulose, pentosans, lignin, sugars, wax, and minerals. The
quantity obtained varies from 22 to 36% on sugarcane and is mainly due to the fibre portion in the
sugarcane and the cleanliness of sugarcane supplied, which, in turn, depends on harvesting practices.
The composition of bagasse depends on the variety and maturity of sugarcane as well as harvesting
methods applied and efficiency of the sugar processing. Bagasse is usually combusted in furnaces to
produce steam for power generation. Bagasse is also emerging as an attractive feedstock for bioethanol
production.
It is also utilized as the raw material for production of paper and as feedstock for cattle. The value of
Bagasse as a fuel depends largely on its calorific value, which in turn is affected by its composition,
especially with respect to its water content and to the calorific value of the sugarcane crop, which
depends mainly on its sucrose content.
Moisture contents is the main determinant of calorific value i.e. the lower the moisture content, the higher
the calorific value. A good milling process will result in low moisture of 45% whereas 52% moisture would
indicate poor milling efficiency. Most mills produce Bagasse of 48% moisture content, and most boilers
are designed to burn Bagasse at around 50% moisture.
Bagasse also contains approximately equal proportion of fibre (cellulose), the components of which are
carbon, hydrogen and oxygen, some sucrose (1-2 %), and ash originating from extraneous matter.
Extraneous matter content is higher with mechanical harvesting and subsequently results in lower
calorific value.
4.1.2 Wood ChipsWoodchips may be used as a biomass solid fuel and are raw material for producing wood pulp.
They may also be used as an organic mulch in gardening, landscaping, and ecosystem restoration; in
bioreactors for denitrification; and as a substrate for mushroom cultivation. Wood chips are
considered the cheapest form of fuel for heating your home or business because they are a residual
wood that come from sustainable wood waste products. Dry wood chips have more fuel value per ton
since they have more water removed and are more resistant to mold and other storage issues. Wood
can be burned in a boiler to heat water and produce steam. The steam can be used to power machines or
heat buildings. Using steam to rotate turbines generates electricity. Convert Wood to Gas – Gasification
uses high heat and pressure, in a low oxygen environment to produce syngas.
Wood chips will consist mainly of mixtures of stem wood, bark and foliage in different proportions
depending on tree species, origin and handling procedures. As pointed out in section 00-02 of this
handbook, there are fundamental differences between these three main categories of biomass with
respect to heating value, to ash content and to ash properties. The heating value for stem softwood in
northern Europe – mainly pine and spruce – is typically about 20 MJ/kgDAF (Dry, Ash-Free) substance
while the heating value for hardwood trees is about 5 % lower, around 19 MJ/kg. In stem wood, the ash
content is low, generally less than 1 % by weight and the ash also has a high melting point. The
properties of wood chips, as delivered to the energy plant, are very much determined by the design of the
supply chain. Therefore, only very general aspects can be outlined and the quality control at reception is
crucial.
4.1.3 Rice HuskRice husk contains about 30–50% of organic carbon and have high heat value of 13–16 MJ per kg.
It can be used to generate fuel, heat, or electricity through thermal, chemical, or bioprocesses.
Rice husk is collected after rice milling, with moisture content of about 14–15%. This fits the requirement
for further pretreatment or processing. Thermal processes, including combustion, gasification, and
pyrolysis, are applied for rice husk processing. Energy products from rice husk are heat, electricity, and
biofuel (solid or liquid). Heat generated from this could be used for house heating and cooking, industrial
boilers, drying, and generating electricity. Figure 2 shows a schematic diagram of a combined system for
processing biomass, including mechanical pretreatment, pyrolysis, gasification, and gas refinery. This
system has been observed in the UK recently and known as the newest technology for biofuel conversion
from biomass.
The following is a summary of the characteristics of rice husk compared with other solid fuels in terms of
energy use:

Its high silica content causes the wearing of the components in processing machines, such as the
chopper or grinder. Content of volatile matter in rice husk is higher than in wood and much higher than in

coal, whereas fixed carbon is much lower than in coal. Ash content in rice husk is much higher than in
wood and coal, which cause barriers for energy conversion (Jenkins 1998).
Its high content of ash, alkali, and potassium causes agglomeration, fouling, and melting in the
components of combustors or boilers (Baker 2000).
4.1.4 Municipal WasteMunicipal solid waste (MSW) is a source of biomass material that can be utilized for bioenergy production
with minimal additional inputs. MSW resources include mixed commercial and residential garbage such
as yard trimmings, paper and paperboard, plastics, rubber, leather, textiles, and food wastes.
The main advantages of WTE-T are: reduction of organic contaminants; reduction of mass and volume of
waste (80% and 90% respectively); high potential for the saving of land; use of recyclables; reduction of
emissions and environmental burdens; environmental compatible for co-generation (heat and electricity
production) ...
The characteristics of fresh municipal solid waste (MSW) are critical in planning, designing, operating or
upgrading solid waste management systems. Physical composition, moisture content, compacted unit
weight, permeability are the most important MSW characteristics to be considered in planning a system.
4.2 Properties of liquid and gaseous fuel for biomass power plants:
4.2.1 JatrophaJatropha is a genus of flowering plants in the spurge family, Euphorbiaceae. As with many members
of the family Euphorbiaceae, Jatropha contains compounds that are highly toxic. Jatropha species have
traditionally been used in basketmaking, tanning and dye production. Jatropha curcas L. (Euphorbiaceae)
is a multiple purpose plant with potential for biodiesel production and medicinal uses. It has been used for
treatment of a wide spectrum of ailments related to skin, cancer, digestive, respiratory and infectious
diseases.
Biogas (methane) is produced by anaerobic digestion. Biogas has wide utilities as it can be applied
directly for cooking, heating and stationary engine operation in dual fuel mode. The biogas is purified,
compressed and stored in cylinder as CNG (Compressed Natural Gas) for automotive transport purposes,
power generation as well as in agricultural unit operation.
Jatropha seed cake has good potential as biogas feedstock due to confer 60% higher biogas and also
better calorific value than the cattle dung.
4.2.2 Bio-dieselBiodiesel is a renewable, biodegradable fuel manufactured domestically from vegetable oils, animal
fats, or recycled restaurant grease. Renewable diesel, also called “green diesel,” is distinct from biodiesel.
Biodiesel is a liquid fuel often referred to as B100 or neat biodiesel in its pure, unblended form. Biodiesel
is a domestically produced, clean-burning, renewable substitute for petroleum diesel. Using biodiesel as a
vehicle fuel increases energy security, improves air quality and the environment, and provides safety
benefits.
Some of the properties included in standards can be traced to the structure of the fatty esters comprising
biodiesel. The properties of a biodiesel fuel that are determined by the structure of its component fatty
esters include ignition quality, cold flow, oxidative stability, viscosity, and lubricity.
Furthermore, biodiesel is sometimes superior to petroleum diesel with improved physical and chemical
properties, such as a higher flash point, higher cetane number, ultralow sulfur content, better lubricity,
improved biodegradability, and a smaller carbon footprint.
4.2.3 Gobar GasBiogas is produced when bacteria digest organic matter (biomass) in the absence of oxygen. This
process is called anaerobic digestion. It occurs naturally anywhere from the within the digestive system to
the depth of effluent ponds and can be reproduced artificially in engineered containers called digesters.
Biogas is comprised primarily of methane and carbon dioxide. It also contains smaller amounts of
hydrogen sulphide, nitrogen, hydrogen, methylmercaptans and oxygen. Biogas originates from bacteria in
the process of bio-degradation of organic material under anaerobic (without air) conditions.
Biogas contains roughly 50-70 percent methane, 30-40 percent carbon dioxide, and trace amounts of
other gases. The liquid and solid digested material, called digestate, is frequently used as a soil
amendment.
4.3 Layout of a Bio-chemical based (e.g. biogas) power plantBiogas is a mixture of gases, primarily consisting of methane and carbon dioxide, produced from raw
materials such as agricultural waste, manure, municipal waste, plant material, sewage, green
waste or food waste. It is a renewable energy source.
Biogas is produced by anaerobic digestion with anaerobic organisms or methanogen inside an anaerobic
digester, biodigester or a bioreactor.
Biogas can be compressed after removal of Carbon dioxide, the same way as natural gas is compressed
to CNG, and used to power motor vehicles. In the United Kingdom, for example, biogas is estimated to
[4]
have the potential to replace around 17% of vehicle fuel. It qualifies for renewable energy subsidies in
some parts of the world. Biogas can be cleaned and upgraded to natural gas standards, when it becomes
bio-methane. Biogas is considered to be a renewable resource because its production-and-use cycle is
continuous, and it generates no net carbon dioxide. As the organic material grows, it is converted and
used. It then regrows in a continually repeating cycle. From a carbon perspective, as much carbon
dioxide is absorbed from the atmosphere in the growth of the primary bio-resource as is released, when
the material is ultimately converted to energy.
Typical composition of biogas
Compound
Methane
Carbon dioxide
Formula
CH
Percentage by
volume
50–80
4
CO
15–50
2
Nitrogen
N
0–10
2
Hydrogen
H
0–1
2
Hydrogen sulfide
H
S
0–0.5
2
Oxygen
O
0–2.5
2
A biogas plant is a decentralized energy system, which can lead to self-sufficiency in heat and power
needs, and at the same time reduces environmental pollution. The key components of a modern biogas
power (or anaerobic digestion) plant include: manure collection, anaerobic digester, effluent
treatment, biogas storage, and biogas use/electricity generating equipment.
Working of a Biogas Plant
The fresh organic waste is stored in a collection tank before its processing to the homogenization tank
which is equipped with a mixer to facilitate homogenization of the waste stream. The uniformly mixed
waste is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into
suitable-capacity anaerobic digester where stabilization of organic waste takes place.
In anaerobic digestion, organic material is converted to biogas by a series of bacteria groups into
methane and carbon dioxide. The majority of commercially operating digesters are plug flow and
complete-mix reactors operating at mesophilic temperatures. The type of digester used varies with the
consistency and solids content of the feedstock, with capital investment factors and with the primary
purpose of digestion.
Biogas Cleanup
Biogas contain significant amount of hydrogen sulfide (H2S) gas which needs to be stripped off due to its
highly corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a
limited quantity of air is added to biogas in the presence of specialized aerobic bacteria which oxidizes
H2S into elemental sulfur.
Utilization of Biogas
Biogas is dried and vented into a CHP unit to a generator to produce electricity and heat. The size of the
CHP system depends on the amount of biogas produced daily.
Treatment of Digestate
The digested substrate is passed through screw presses for dewatering and then subjected to solar
drying and conditioning to give high-quality organic fertilizer. The press water is treated in an effluent
treatment plant based on activated sludge process which consists of an aeration tank and a secondary
clarifier. The treated wastewater is recycled to meet in-house plant requirements.
Monitoring of Environmental Parameters
A chemical laboratory is necessary to continuously monitor important environmental parameters such as
BOD, COD, VFA, pH, ammonia, C:N ratio at different locations for efficient and proper functioning of the
process.
Control System
The continuous monitoring of the biogas plant is achieved by using a remote control system such as
Supervisory Control and Data Acquisition (SCADA) system. This remote system facilitates immediate
feedback and adjustment, which can result in energy savings.
Biogas technology, the generation of a combustible gas from anaerobic biomass digestion, is a wellknown technology. There are already millions of biogas plants in operation throughout the world.
Whereas using the gas for direct combustion in household stoves or gas lamps is common, producing
electricity from biogas is still relatively rare in most developing countries. In Germany and other
industrialised countries, power generation is the main purpose of biogas plants; conversion of biogas to
electricity has become a standard technology.
Conversion to ElectricityTheoretically, biogas can be converted directly into electricity by using a fuel cell. However, this process
requires very clean gas and expensive fuel cells. Therefore, this option is still a matter for research and is
not currently a practical option. The conversion of biogas to electric power by a generator set is much
more practical. In contrast to natural gas, biogas is characterized by a high knock resistance and hence
can be used in combustion motors with high compression rates.
Schematic of a biogas plant used for power generation:
In most cases, biogas is used as fuel for combustion engines, which convert it to mechanical energy,
powering an electric generator to produce electricity. The design of an electric generator is similar to the
design of an electric motor. Most generators produce alternating AC electricity; they are therefore also
called alternators or dynamos. Appropriate electric generators are available in virtually all countries and in
all sizes. The technology is well known and maintenance is simple. In most cases, even universally
available 3-phase electric motors can be converted into generators. Technologically far more challenging
is the first stage of the generator set: the combustion engine using the biogas as fuel. In theory, biogas
can be used as fuel in nearly all types of combustion engines, such as gas engines (Otto motor), diesel
engines, gas turbines and Stirling motors etc.
Block Diagram of Biogas Power Plant
Advantages of Biogas
1. Renewable Source of Energy
Organic materials are derived from plants, animals, and humans. Raw materials can be reproduced,
making biogas a green energy source. It also lessens the damaging impact and improper wastes
disposal.
2. Utilization of Waste
Instead of letting the wastes rot in landfills, it is more advantageous to ut
utilize
ilize and turn them into biogas.
An environmental hazard is reduced due to lesser methane, carbon dioxide, and other greenhouse gases
produced. Wastes are turned into energy to utilize for electricity, heating, cooking, and as fertilizers.
3. Produces a Circular
lar Economy
Animal manure, food wastes, wastewater, and crop residue are wastes produced by humans and
animals. These wastes can cause harm if not process correctly. By turning these organic wastes into
biogas, the wastes are converted into a more helpful way. The wastes are made into biogas for electricity
and heating use, natural gas for cars and cooking, and digestate as fertilizers.
4. A Good Alternative for Electricity and Cooking in Rural Areas and Developing Countries
Some areas have limited access to e
electricity,
lectricity, hampering their way of living. Biogas can provide them a
good alternative. It is economical to set up and possible both for small
small- and large-scale
scale production.
Disadvantages of Biogas
1. Few Technological Advancements
The biogas industry is not yet advanced. Additional research is needed to develop new technology and
make production efficient. Also, governments provide more support on established energy sources such
as solar, geothermal, wind, and hydropower.
2. Weather Dependence
Like other intermittent
ttent energy sources (solar, wind), biogas production is also affected by the weather.
Anaerobic digestion happens in an environment with a temperature of 37°C. Heat energy is required in
cold climates to produce biogas continually.
3. Foul Odor Emitted from Biogas Power Plant
Biogas plant emits foul odor from the wastes they process. Power plants should be built in a location
away from residences and other industrial areas.
Applications of Biogas
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Biogas as a Cooking Fuel and Some Common Indian Burner Designs.
Burner Designs Commonly used in China.
Use of Biogas as a Lighting Fuel.
Utilisation of Biogas for Pumping Water and Miscellaneous other Applications.
Biogas as a Fuel for Running IC Engines.
Biogas as a Vehicle Fuel.
4.4 Layout of a Thermo-chemical based (e.g. municipal waste) power plantThermochemical conversion is an efficient method to convert biomass into biofuels. It includes two
different categories: dry (nonaqueous) techniques and hydrothermal techniques. In a dry thermochemical
conversion process, with the temperature increasing, biomass mainly experiences structure destruction,
degrading to condensable vapors, and finally decomposing to gaseous molecules. The dry
thermochemical conversion processes have sequence connections; taking a burning fresh wood chip as
an example, torrefaction happens deep inside the wood chip at the region below 300°C, where volatiles
are released. Carbonization and pyrolysis happen in the region between 300°C and 700°C, close to the
surface of the wood chip, where the wood material is converted to pyrolyzed vapors, and the vapors are
further gasified to be combustible gases at the 700°C–900°C region, and are burnt over the surface of the
wood at above 900°C. It is the gas combustion which gives rise to the flame. That is why we can always
see flame over burning wood but seldom see it over burning charcoal. In a hydro-thermochemical
conversion process, mainly charcoal (solid product) is produced at mild conditions (below 280°C, selfgenerated pressure), and the process is known as hydrothermal carbonization (HTC). At the medium
temperature range (280°C–370°C) and high pressures (up to 22 MPa), mainly tar (liquid) would be
formed, and the process is termed hydrothermal liquefaction (HTL). When the temperature and pressure
increase to exceed the supercritical state for water (above 370°C and 22 MPa), the dominant products
are gaseous substances, and the process is normally called HTG. Different thermochemical conversion
techniques correspond to different physical parameters of temperature, heating rate, residence time, and
particle size, etc. Temperature is usually crucial for the thermochemical conversion of biomass to the
reactivity of both reactant and catalyst, and it determines product distribution directly. The residence time
of the feedstock in the reactor also plays an important role in biofuel production; a longer residence time
may result in higher yields of gases and char but less liquid products. Particle size has a large impact on
heat and mass transfer within the biomass particles. The duty of reactors is to convey a good heat and
mass transfer to feedstock during the thermochemical conversion process with the least energy
consumption. Most current thermochemical conversion techniques for biofuel production were adapted
from fossil fuel industries since 1970s, therefore they lack industrial standards dedicated for biomass
processing. In addition, because of the complex composition of both biomass and its degradation
products, the knowledge of biomass conversion techniques is still inadequate for biofuel production and
application. Better understanding, ranging from the decomposition mechanism of a single compound to
the technoeconomic assessment of the biofuel industry, needs to be gained, in order to realize the largescale industrial production of biofuels through thermochemical conversion of biomass.
Municipal waste is defined as waste collected and treated by or for municipalities. The definition excludes
waste from municipal sewage networks and treatment, as well as waste from construction and demolition
activities.
The municipal solid waste industry has four components: recycling, composting, disposal, and waste-toenergy via incineration. Municipal solid waste can be used to generate energy. Several technologies have
been developed that make the processing of MSW for energy generation cleaner and more economical
than ever before, including landfill gas capture, combustion, pyrolysis, gasification, and plasma
arc gasification.
Production of thermal energy is the main driver for this conversion route that has five broad pathways:
1.
2.
3.
4.
5.
Combustion
Carbonization/torrefaction
Pyrolysis
Gasification
Liquefaction
Combustion involves high-temperature exothermic oxidation in oxygen-rich ambience to hot flue gas.
Carbonization covers a broad range of processes by which the carbon content of organic materials is
increased
through
thermochemical
decomposition.
In
a
more
restrictive
sense
for
biomass, carbonization is a process for production of charcoal from biomass by slowly heating it to the
carbonization temperature (500–900°C) in an oxygen-starved atmosphere. Torrefaction is a related
process where biomass is heated slowly, but to a lower temperature range of 200–300°C without or little
contact with oxygen.
Unlike combustion, gasification involves chemical reactions in an oxygen-deficient environment producing
product gases with heating values. Pyrolysis involves rapid heating in the total absence of oxygen. In
liquefaction, the large molecules of solid feedstock are decomposed into liquids having smaller
molecules. This occurs in the presence of a catalyst and at a still lower temperature.
1. CombustionGiven that civilization began with the discovery of fire, combustion represents the oldest means of
utilization of biomass. The burning of forest wood taught humans how to cook and how to keep
themselves warm. Chemically, combustion is an exothermic reaction between oxygen and hydrocarbon in
biomass. Here, the biomass is oxidized into two major stable compounds, H2O and CO2. The reaction
heat released is presently the largest source of energy consumption, accounting for more than 90% of the
energy from biomass.
Heat and electricity are two principal forms of energy derived from biomass. Biomass still provides heat
for cooking and warmth, especially in rural areas. District or industrial heating is also provided for by
steam generated in biomass-fired boilers. Pellet stoves and log-fired fireplaces are a direct source of
warmth in many cold-climate countries. Electricity, the foundation of all modern economic activities, may
be generated from biomass combustion. The most common practice involves the generation of steam by
burning biomass in a boiler and the generation of electricity through a steam turbine.
Biomass is used either as a standalone fuel or as a supplement to fossil fuels in a boiler. The latter option
is becoming increasingly common as the fastest and least-expensive means for decreasing the emission
of carbon dioxide from an existing fossil fuel plant.
2. CarbonizationCarbonization including torrefaction is being considered for effective utilization of biomass as a clean and
convenient solid fuel. In torrefaction, the biomass is slowly heated to 200–300°C without or little contact
with oxygen. This process alters the chemical structure of biomass hydrocarbon to increase its carbon
content while reducing its oxygen. Torrefaction also increases the energy density of the biomass and
makes the biomass hygroscopic. These attributes thus enhance the commercial value of wood for energy
production and transportation. Other forms of carbonization take place at different conditions with the
common goal of forming carbon rich solid products.
3. PyrolysisUnlike combustion, pyrolysis takes place in the total absence of oxygen, except in cases where partial
combustion is allowed to provide the thermal energy needed for this process. This process thermally
decomposes biomass into gas, liquid, and solid by rapidly heating biomass above 300–650°C.
In pyrolysis, large hydrocarbon molecules of biomass are broken down into smaller molecules. Fast
pyrolysis produces mainly liquid fuel, known as biooil, whereas slow pyrolysis produces some gas and
solid charcoal (one of the most ancient fuels, used for heating and metal extraction before the discovery
of coal). Pyrolysis is promising for conversion of waste biomass into useful liquid fuels. Unlike
combustion, it is not exothermic.
4. GasificationGasification converts fossil or nonfossil fuels (solid, liquid, or gaseous) into useful gases. For gasification
reactions one needs a medium, which can be gases, steam, or subcritical or supercritical water. Gaseous
medium includes air, oxygen, or a mixture of these.
For production of synthetic gases, gasification of fossil fuels is more common than that of biomass.
Gasification generally converts a fuel from one form to another. There are several major motivations for
such a transformation and are as follows:
•To increase the heating value of the fuel by rejecting noncombustible components like nitrogen and
water.
•To strip the fuel gas of sulfur such that it is not released into the atmosphere when the gas is burnt.
•To increase the hydrogen to carbon (H/C) mass ratio in the fuel.
•To reduce the oxygen content of the fuel.
In general, the higher the hydrogen content of a fuel, the lower the vaporization temperature and the
higher the probability of the fuel being in a gaseous state. Gasification or pyrolysis increases the relative
hydrogen content (H/C ratio) in the product through one the following means:
1.Direct: Direct exposure to hydrogen at high pressure.
2.Indirect: Exposure to steam at high temperature and pressure, where hydrogen, an intermediate
product, is added to the product. This process also includes steam reforming.
A typical biomass has about 40% oxygen by weight, but a fuel gas contains negligible amount of oxygen.
Gasification could remove part of the oxygen in biomass and produce a more energy dense product.
Production of hydrogen through gasification of natural gas is an important process especially for bulk
production of ammonia. Steam reforming of natural gas produces syngas (a mixture of H 2 and CO). The
CO in syngas is indirectly hydrogenated by steam to produce methanol (CH3OH), an important
feedstock for a large number of chemicals. These processes, however, use natural gas that is
nonrenewable and is responsible for net addition of carbon dioxide (a major GHG) to the atmosphere.
Biomass could, on the other hand, substitute fossil hydrocarbons either as a fuel or as a chemical
feedstock.
Gasification of biomass into CO and H2 provides a good base for production of liquid transportation fuels,
such as gasoline, and synthetic chemicals, such as methanol. It also produces methane, which can be
burned directly for energy production.
5. LiquefactionLiquefaction of solid biomass into liquid fuels can be done through pyrolysis, gasification, and
through hydrothermal process. In the latter process, biomass is converted into an oily liquid by contacting
the biomass with water at elevated temperatures (300–350°C) and high pressure (12–20 MPa) for a
period of time. There are several other means including the supercritical water process for direct
liquefaction of biomass.
Thermo-chemical conversion
4.5 Layout of a Agro-chemical based (e.g. bio-diesel) power plantBiodiesel is a renewable, biodegradable fuel manufactured domestically from vegetable oils, animal fats,
or recycled restaurant grease. Renewable diesel, also called “green diesel,” is distinct from biodiesel.
Biodiesel is a liquid fuel often referred to as B100 or neat biodiesel in its pure, unblended form.
Biodiesel is a vegetable oil-based (soy or canola oil) fuel that runs in the present diesel engines, without
any modifications to the hardware. Biodiesel and biodiesel blends can be used in all compressionignition (CI) engines that were designed to be operated on diesel fuel. It is cheaper than oil, sustainable,
and nontoxic; it does not produce acid rain (absence of sulfur); and it does not contribute as much as
fossil fuels do to global warming. Studies have shown it reduces engine wear by as much as 30%,
primarily because it provides excellent lubrication. Even 2% biodiesel in normal diesel will help achieve
this improvement. Biodiesel fuel yields 220% more energy than that required to produce, transport, and
distribute it, which is due to the fact that the feedstock crop collects solar energy and transforms it into
the biodiesel feedstock oil.
Various biodiesel blends, which include different ratios of biodiesel and diesel from crude oil, can be used
in vehicles depending upon the vehicle's requirement and weather conditions. A 20% biodiesel will
provide a higher octane rating, superior lubricity, significant emission reductions, and less toxic
emissions; will virtually eliminate visible soot emissions; and will have similar fuel
consumption, horsepower, and torque. Premium biodiesel is a fuel manufactured from vegetable oils by
a transesterification process. Soybean oil is currently the leading source of vegetable oil
for biodiesel manufacture in the United States.
Problems with biodiesel are that it is not readily available in large quantities and the amount of
x
NO increases by 15%, which contributes to the generation of smog. Another disadvantage is that the
viscosity increases at lower ambient temperatures, hence requiring additives for lowering the fuel's gel
point.
Fuels that have been extracted from plants and crops are known as biofuels. Of these, the most
commonly extracted and used one is Bioethanol or simply Ethanol and Biodiesel. It is blended with
gasoline and can be used as an alternative fuel for your car. Plant-based fuels come from renewable
sources, can be grown anywhere and have lower carbon emissions as compared to fossil fuels.
Biofuels not only help a struggling economy by providing jobs but also helps in reducing greenhouse
gases up to much extent by emitting less pollution.
As prices of crude oil are soaring day by day, most people are switching to biofuels to save money and
reduce their dependence on oil. Biofuels are produced from wheat, corn, soybeans and sugarcane, which
can be produced again and again on demand, so they are sustainable.
Though biofuels have many advantages over their counterparts, there are some other complicating
aspects that we need to look at.
Various Advantages of Biofuels1. Efficient Fuel
Biofuel is made from renewable resources and relatively less-flammable compared to fossil diesel. It has
significantly better lubricating properties.
It causes less harmful carbon emission compared to standard diesel. Biofuels can be manufactured from
a wide range of materials. The overall cost-benefit of using them is much higher.
2. Cost-Benefit
As of now, biofuels cost the same in the market as gasoline does. However, the overall cost-benefit of
using them is much higher. They are cleaner fuels, which means they produce fewer emissions on
burning. With the increased demand for biofuels, they have the potential of becoming cheaper in the
future as well.
According to the RFA (Renewable Fuels Association) February 2019 Ethanol Industry Outlook report,
“Ethanol remains the highest-octane, lowest-cost motor fuel on the planet.” Additionally, in 2019, U.S.
Department of Energy (DOE) allocated $73 million for 35 bioenergy research and development (R&D)
projects.
With goals such as reducing drop-in biofuel costs, it aims to “enable high-value products from biomass or
waste resources” and reduction in the cost of producing biopower. So, the use of biofuels will be less of a
drain on the wallet.
3. Durability of Vehicles’ Engine
Biofuels are adaptable to current engine designs and perform very well in most conditions. It has higher
cetane and better lubricating properties. When biodiesel is used as a combustible fuel, the durability of
the engine increases.
There is also no need for engine conversion. This keeps the engine running for longer, requires less
maintenance and brings down overall pollution check costs. Engines designed to work on biofuels
produce less emission than other diesel engines.
4. Easy to Source
Gasoline is refined from crude oil, which happens to be a non-renewable resource. Although current
reservoirs of gas will sustain for many years, they will end sometime in the near future.
Biofuels are made from many different sources such as manure, waste from crops, other byproducts,
algae and plants grown specifically for the fuel.
5. Renewable
Most of the fossil fuels will expire and end up in smoke one day. Since most of the sources like manure,
corn, switchgrass, soybeans, waste from crops and plants are renewable and are not likely to run out any
time soon, it makes the use of biofuels efficient in nature. Also, these crops can be replanted again and
again.
6. Reduce Greenhouse Gases
Studies suggest that biofuels reduce greenhouse gases up to 65 percent. Fossil fuels, when burnt,
produce large amounts of greenhouse gases i.e., carbon dioxide in the atmosphere. These greenhouse
gases trap sunlight and cause the planet to warm.
Besides, the burning of coal and oil increases the temperature and causes global warming. To reduce the
impact of greenhouse gases, people around the world are using biofuels.
7. Economic Security
Not every country has large reserves of crude oil. For them, having to import the oil puts a huge dent in
the economy. If more people start shifting towards biofuels, a country can reduce its dependence on fossil
fuels.
Biofuel production increases the demand for suitable biofuel crops, providing a boost to the agriculture
industry. Fueling homes, businesses and vehicles with biofuels are less expensive than fossil fuels. More
jobs will be created with a growing biofuel industry, which will keep our economy secure.
8. Reduce Dependence on Foreign Oil
While locally grown crops have reduced the nation’s dependence on fossil fuels, many experts believe
that it will take a long time to solve our energy needs. As prices of crude oil are touching sky high, we
need some more alternative energy solutions to reduce our dependence on fossil fuels.
9. Lower Levels of Pollution
Since biofuels can be made from renewable resources, they cause less pollution to the planet. However,
that is not the only reason why the use of biofuels is being encouraged.
They release lower levels of carbon dioxide and other emissions when burnt compared to standard
diesel. Its use also results in a significant reduction of PM emissions.
Although the production of biofuels creates carbon dioxide as a byproduct, it is frequently used to grow
the plants that will be converted into fuel. This allows it to become something close to a self-sustaining
system.
Besides, biofuels are biodegradable that reduces the possibility of soil contamination and contamination
of underground water during transportation, storage or use.
Disadvantages of Biofuels1. High Cost of Production
Even with all the benefits associated with biofuels, they are quite expensive to produce in the current
market. As of now, the interest and capital investment being put into biofuel production is fairly low, but it
can match demand.
If the demand increases, then increasing the supply will be a long term operation, which will be quite
expensive. Such a disadvantage is still preventing the use of biofuels from becoming more popular.
2. Monoculture
Monoculture refers to the practice of producing the same crops year after year, rather than producing
various crops through a farmer’s fields over time. While this might be economically attractive for farmers
but growing the same crop every year may deprive the soil of nutrients that are put back into the soil
through crop rotation.
The problems with growing a single crop over large tracts of land are many. First, growing only one crop
changes the environment in terms of the food available to pests, and they are free to destroy an entire
crop.
Secondly, we could treat the pests mentioned above with pesticides, but a few of those pests will
inevitably be resistant to the chemicals we use to kill them, and that can inhabit a single field of crops.
The next problem comes with genetic engineering when we decide to modify the crop that is resistant to
the pest without the need for pesticides. It is still likely that at least a few pests aren’t affected by the
modification, and the problem remains.
Thus, the key to healthy crops worldwide is biodiversity that is simply having lots of different types of
plants and animals around.
3. Use of Fertilizers
Biofuels are produced from crops, and these crops need fertilizers to grow better. The downside of using
fertilizers is that they can have harmful effects on the surrounding environment and may cause water
pollution. Fertilizers contain nitrogen and phosphorus. They can be washed away from soil to nearby
lakes, rivers or ponds.
4. Shortage of Food
Biofuels are extracted from plants and crops that have high levels of sugar in them. However, most of
these crops are also used as food crops. Even though waste material from plants can be used as raw
material, the requirement for such food crops will still exist. It will take up agricultural space from other
crops, which can create a number of problems.
Using existing land for biofuels may not cause an acute shortage of food; however, it will definitely put
pressure on the current growth of crops. One major worry being faced by people is that the growing use
of biofuels may just mean a rise in food prices as well.
Some people prefer using algae, which grows in very inhospitable regions and has a limited impact on
land use. However, the problem with algae is water use.
5. Industrial Pollution
The carbon footprint of biofuels is less than the traditional forms of fuel when burnt. However, the process
with which they are produced makes up for that. Production is largely dependent on lots of water and oil.
Large scale industries meant for churning out biofuel are known to emit large amounts of emissions and
cause small scale water pollution as well.
Unless more efficient means of production are put into place, the overall carbon emission does not get a
very big dent in it. It also causes an increase in NOx.
6. Water Use
Large quantities of water are required to irrigate the biofuel crops, and it may impose strain on local and
regional water resources, if not managed wisely. In order to produce corn-based ethanol to meet local
demand for biofuels, massive quantities of water are used that could put unsustainable pressure on local
water resources.
7. Future Rise in Price
Current technology being employed for the production of biofuels is not as efficient as it should be.
Scientists are engaged in developing better means by which we can extract this fuel. However, the cost of
research and future installation means that the price of biofuels will see a significant spike.
As of now, the prices are comparable with gasoline and are still feasible. Constantly rising prices may
make the use of biofuels as harsh on the economy as the rising gas prices are doing right now.
8. Changes in Land Use
If the land is used to grow a biofuel feedstock, it has to be cleared of native vegetation, which then leads
to ecological damage done in three ways.
First, the damage is caused by destroying local habitat, animal dwellings, micro-ecosystems, and reduces
the overall health of natural resources of the region.
The native forest is almost always better at removing CO2 from the atmosphere than a biofuel feedstock
partly because the CO2 remains trapped and is never released by burning as with fuel stock.
Secondly, the damage is done in the carbon debt created. When it is needed to deforest an area and
prepare it for farming as well as to plant the crop, this leads to the production of greenhouse gases and
puts the region at a net positive GHG production even before a single biofuel is produced.
Estimates have shown that deforesting native land can actually produce a carbon debt that can take up to
500 years to repay.
Finally, changing land to an agricultural status almost always means fertilizers are going to be used to get
the most yields per area. The problem is runoff and other agricultural pollution.
Thus, creating more farmland is likely to damage waterways and energy used in treatment plants, and
other mitigation strategies lead to an even larger carbon debt.
9. Global Warming
The biofuels, which are mostly hydrogen and carbon, burning them produce carbon dioxide,
which contributes to global warming. It is true that biofuels produce less GHG emissions than fossil fuels,
but that can only serve to slow global warming and not stopping or reversing it.
Therefore, biofuels may be able to help ease our energy needs, but they won’t solve all of our problems.
It can only serve as substitutes for the short term as we invest in other technologies.
10. Weather Problem
Biofuel is less suitable for use in low temperatures. It is more likely to attract moisture than fossil diesel,
which creates problems in cold weather. It also increases microbial growth in the engine that clogs the
engine filters.