ECO-COMPATIBILITY:
GREEN CHEMISTRY
Buddhadeb Chattopadhyay
Government College of Engineering
and Leather Technology, Kolkata
HISTORICAL EVOLUTION OF GREEN CONCEPTS
• MODERN ENVIRONMENTAL
MOVEMENT (1962)
Rachel Carson’s Book
“Silent Spring”
• GREEN CHEMISTRY MOVEMENT
(1974)
Molina & Rowland’s Book
“CFCs – Ozone layer”
• SIGNING OF MONTREAL
PROTOCOL (1986)
CFC Phase out
• FIRST CONCEPT OF ATOM ECONOMY
in Science JL (1991)
BH Trost
“A search for synthetic Efficiency”
• TOTAL SYNTHESIS OF A NATURAL
PRODUCT (1996)
Nicolaou & Sorensen
Vitamin B 12
• eFACTOR IN SPECIALITIES (1998)
(1998)
Anastas & Warner
“Green Chem Practice”
What is Ecology ?
• Greek, “Oikos” + “Logos”
= Ecology.
• Household + Study.
• “Study of structure & function
of Nature” (Odum, 1971).
• “Distribution and abundance of
animals” (Andrewartha, 1961).
• “Interactions that determines
the distribution & abundance
of organisms” (Krebs, 1985).
Study of Ecosystem
• Ecosystem is an open
system.
• It exchange both
matter (mass) and
energy.
• This exchange process
takes place through
environment.
Environment:
The complete range of external
conditions, physical and biological,
in which an organism lives.
Environment includes social,
cultural, and (for humans) economic
and political considerations, as well
as the more usually understood
features such as soil, climate and
food supply.
Ecosystem
A discrete unit that consists of living and non-living parts,
interacting to form a stable system.
The term first used by A. G. Tansley in 1935
Fundamental concepts include the flow of energy via foodchains and food-webs, and cycling of nutrients
biogeochemically.
Ecosystem components
Abiotic &
Biotic
Producers,
Consumers
(different levels)
Decomposers
Food- chain
The transfer of energy from the primary producers (green plants) through
a series of organisms that eat and are eaten, assuming that each organism
feeds on only one type of organism.
E.g. earthworm
blackbird
sparrow hawk
At each stage much energy is lost as heat, a
fact that usually limits the number of steps,
the trophic levels.
Food-chain
Food chain…Two types:
Grazing: Primary producers are eaten by grazing herbivores, with subsequent
energy transfer at various levels of carnivores.
Detritus: The living primary producers are not consumed by grazing herbivores,
but eventually form litter (detritus) on which decomposers (microorganisms) and
detritivores feed, with subsequent energy transfer at various levels of carnivores.
e.g. leaf litter
earth worm
blackbird
sparrow hawk
Food-web
A diagram that
represents the
feeding relationships
of organisms
within an ecosystem.
It consists of a
series of
interconnecting
food-chain.
Essential elements
Vital for successful growth and development of
organisms
Macronutrients (needed in relatively large amount): C, H,
N, O, S, P, K, Mg, Ca etc.
Micronutrients: Cu, B, Fe, Zn, Mb, Cr (III) etc.
Non-essential elements: Pb, Hg, As etc.
Dose-effect curve showing the relationship between concentrations and biological effects of
essential (red) and of non-essential (green) elements.
Ecological pyramid
A graphical representation of the trophic structure and function of an
ecosystem.
3 types of pyramids: of Numbers, of Biomass and of Energy.
Energy flow
The exchange and dissipation of energy along the food-chains and foodwebs of an ecosystem.
Hydrosphere
Total body of water which exists on or close to the surface of the Earth
Hydrological cycle
Environmental Pollution
The defilement of the natural environment by
pollutant(s).
Pollutants may affect Air, Water, Soil.
Air pollution
Air pollutants and their consequences
1.
Gases like, COx, SOx, NOx
2.
Hydrocarbons and
photochemical smog
3.
Particulates
4.
Acid rain
5.
Radioactivity and its effects
Water Pollution
Water pollutants and their consequences:
1.
Toxic chemicals including heavy
metals
2.
Organic pollutants
3.
Inorganic pollutants
4.
Eutrophication
5.
Thermal pollution
Tannery & Ecology
Typical Mass Balance
• TYPICAL MASS BALANCE
• 1,000 Kg of hides + 30 m3 of water + 247 Kg.
Chemicals
• = 150 Kg. of Leather + 150 Kg. Splits + 700 Kg.
Solid wastes + 30 m3 of Effluent.
• (30 m3 of Effluent contains 400 Kg. of total
solids)
Global Water Resources (Est.)
• Earth’s atmosphere: 13,000 km3.
• Earth’s interior:
37,800,000 km3.
• Earth’s surface:
1,320,000,000 km3.
• Total water: 1,357,813,000 km3.
For every kg. of hide processing
• 30 L of fresh ground
water is converted
into effluent and
discharged in the
ecosystem.
• Who will replenish?
ADOPTION OF CLEAN / GREEN TECHNOLOGIES
IN DEVELOPING SOCIETIES
• SCARCITY OF TECHNICAL AND FISCAL RESOURCES
• WEAK REGULATORY INSTITUTIONAL FRAMEWORK
LEGISLATIVE
POLLUTION
CONTROL
JUDICIAL
INDEPENDENT DATA
COLLECTORS
WATCH DOG
BODIES
• LESS PREVALENT STIMULUS PACKAGES
• WEAK R&D CAPABILITIES
• MORE FAVOURABLE PUBLIC SENTIMENT TO ECONOMIC DEVELOPMENT
AS COMPARED TO ENVIRONMENT
INDIA IS LUCKY TO HAVE OVERCOME MOST OF
ABOVE CONSTRAINTS; STILL LOT TO BE DONE
INDIAN PRIORITIES TO REALISE GLOBAL
POTENTIAL
CAPACITY
EXPANSION
TECHNOLOGY
HIGHER GLOBAL
MARKET ACCESS
PRIORITIES
 Environment driven in tanning sector
 Capability driven in product sector
• State of art products / processes
 Ecofriendly
Product and component sectors
 Creating new investments opportunities
 Aggressive global campaigns (FDIs)
ESSENTIALS FOR LEATHER /PRODUCT PROCESSING
INHERENT*
SAFETY
MINIMIZE*
WASTE
REAL TIME*
MONITORING &
CONTROL
LEAST
HAZARDOUS
SYNTHESIS
THE DOZEN
GREEN
MANTRAS
CRADLE TO
GRAVE
APPROACH
SAFER*
CHEMICAL(s)
EFFICIENT
REACTION
MEDIA
CATALYSTS
FOR HIGHER
EFFICIENCY
REDUCE
DERIVATIVES
ATOM
ECONOMY
RENEWABLE*
RESOURCES
MINIMUM*
ENERGY
GREENER LEATHER PROCESSING OPTIONS
Chemicals
Hides/Skins
CONTROLS
LESS SALT OR
SALTLESS
PRESERVATION
BY PRODUCT
UTILIZATION
LEATHER
PROCESSING
INTERNAL
RECYCLES
NEW
TECHNOLOGIES
ENERGY
PRIMARY
LW
& SW
SECONDARY
SW
TERTIARY
• Galatine
• Chrome
• High Exhaustion
• Salt (Reuse)
• Petfoods
• Pickle Liquors • Enzymatic Processes • SW Products
• Leather Products • Dehairing bath
• Water (Reuse)
Salt
ECONOMIC IMPLICATIONS OF ENVIRONMENTAL ACTIONS
• IMPLEMENTED MEASURES
•
•
•
•
Chrome Recycle
Dye Solution Recycle
Higher Cr exhaustion
Segregation of liming and washing waster waters
• ECONOMIC BENEFITS
• Waste Water Quantity reduction
• Chromium & dye bath reduction
• Investment
• Annual Savings
• TECHNICAL BENEFITS
Improved Productivity
Quality Enhancement
29 smell
Absence of H2S(g) and foul
: 8.5%
: 55% (Cr)
25% (Dye)
: USD 25,000
: USD 98,000
CHROME DISTRIBUTION (%)
GRAIN
LEATHER
CONVENTIONAL
TANNING
USABLE
SPLIT
SOLID
WASTE
LIQUID
EFFLUENT
34
11
30
25
HIGH EXHAUSTION
TANNING
45
15
38
2
CHROME RETANNING
--
--
60
40
GLOBAL CHROME RECOVERY BENCHMARKS
• LOWEST ATTAINABLE
IN LIQUID EFFLUENT
:
10-19 mg/lit
• ENVIRO LIMIT
:
1 – 4 mg/lit
• Water consumption by 60%
• Chromium Discharge by 90%
• Solvent emissions by 90%
• Unhairing residue by 50%
• BIOGAS from fat and fleshings
• Galatine /glue/ protein products /Bio-diesel from fleshings
• Recycled water for tanning
• Solid waste as dye adsorbents and ashpalt additives
• Water in place of solvent based coatings
• Enzymes in place of chemical agents
Ecology is the concern of everybody.
• Acid test for any
technology to be
sustainable lies in the
ability and efficiency
to reconcile it to be
compatible with
ecology.
• This is the major
challenge to combat.
Symbiotic Industrial Ecosystem
Golden Rules: Green Chemistry
• Reduce in-plant pollution load rather than
efficient end-of-pipe treatment of wastes.
• Optimise “Atom Economy.” All chemicals
needed to make leather should be incorporated
in it, means, look for higher exhaustion either by
exhaustion aids or by altering application
conditions.
• Avoid generation of hazardous substances: in
situ or outside.
Risk = f (Hazard x Exposure).
Golden Rules: Green Chemistry
• Design & use chemicals of lower toxicity. Look
for ecotoxicological profile of all auxiliaries.
• Minimise use of auxiliary substances that do not
form a part of the leather. Avoid unnecessary
loading, replace solvent based system by
aqueous based system etc.
• Minimise energy consumption.
• Minimise water consumption. Water do costs
and depletes underground resource.
Golden Rules: Green Chemistry
• Look for by product utilisation. Only 15% of hide
mass is used as leather and 15% as splits. (70%
precious biomass is wasted.) Today’s drainage
can be tomorrow’s hidden treasure trove!
• Choose chemicals to provide maximum
selectivity of function.
• Products to be discarded ultimately should break
down rapidly into benign compounds.
• Design flawless mechanism for in-process
control in real time.
Golden Rules: Green Chemistry
• Maintain records at each stage of in-plant process
control.
• Care for temperature or pressure fluctuation or
fire hazards (in spray booth, air duct etc.).
• Involve & educate shop floor people.
• Discourage tendency for unduly saving time or
efforts.
• Stop drying Cr-tanned leather under Sun.
• Use computers or microprocessors.
Need of Energy Audit in Leather Industry
• Pollution has become a major challenge to leather
industry, energy is now going to become the next
big issue.
• Steep increase of fossil fuel and electricity prices
coupled with erratic bulk power supplies are
causing concern to the Indian tanners.
• A large amount of recoverable waste energy is
now going up the stack, down the sewer or out
through the dryer exhausts.
Energy Consumption Pattern in Tanneries
13%
Beaming &
Tanning
Finishing
40%
Comfort Heat
Drying
10%
37%
Energy Consumption in Tanneries
• Approximately 1400 – 1800 kcal of energy is required to
process 1 kg. of hide.
• About 30 – 50% of waste energy can be conserved or
recycled through mechanical engineering improvements of
machinery, readjustment of process parameters and
process innovations.
• Deployment of solar energy also deserve attention.
• So, there is a strong need for conducting an energy audit in
Indian tanneries.
• Unlike pollution abatement costs, energy efficiency pays us
back.
Biomass – A Potential Resource
• India predominantly agricultural country.
• Annual production of agro-forest
and processing residues: 350 million tons
• Power generation potential > 17,000 MW
• Advantages:
Feedstock
Examples
– Decentralized generation: close to
rural load centers.
– Technology reasonably
well developed
– Environmentally friendly: No net
CO2 emissions but does emit CH4.
Potential
Installed
Agro-forest
residues
Wood chips,
mulberry,
coconut
shells
17,000 MW
50 MW
Processing
residues
Rice husk,
sugarcane
bagasse
5,000 MW
1000 MW
BIOGAS FROM TANNERY BIO -WASTE
(5 ton hides)
• FLESHINGS + SLUDGE :- 8.5 M3 AT 70 gms/L concn.
• 193.5 M3 BIOGAS (75% METHANE)
• ENERGY EQUIVALENT (1,245,000 Kcal)
• 122 M3 DIGESTER VOLUME
• ACIDOGENISIS (MESOPHILIC) AND METHANOGENESIS
Energy from Tannery Waste
• Biomethanization of tannery waste offers distinct advantages in
waste disposal and generation of supplementary energy.
• The biodegradability of a pollutant is assessed by parameters like 5days Biochemical Oxygen Demand (BOD5) & its chemical oxygen
Demand and their ratio.
• The ratio, BOD5/COD < 0.3, the waste is difficult to biodegrade.
• If 0.3 < BOD5/COD <0.6, the compound (or waste) is potentially
biodegradable.
• The basis of biomethanation is based on nominal pretreatment of
solid wastes to get organics in liquid form as gelatine and take it for
biomethanation with additives and nutritives.
• Tannery of Tata International Ltd. in Dewas is regularly producing biogas from tannery wastes (250 m3/d) and the unit is fine since its
initialization.
Energy Saving Benefits of Automation in Tannery
• The present century carries on with the irresistible march of
progress electronics and its invasion of various sectors including
leather industry also.
• Microprocessor control systems have become popular in the
automation of leather finishing operations.
• Microprocessor controlled systems for tannery wet operations
make sure of the followings:
a) In-process quality control of leather.
b) Controlled chemical and water dosages.
c) Drum operation control.
d) Online colour matching techniques for dyed leathers.
e) Optimisation of spent energy in processing leather with
minimum wastage.
Simple Action
• Induction motors equal or less than 25 HP are
energy expensive.
• Motor armature has 1200-1400 r.p.m but drums
seldom require more than 16.
• There is a huge loss of energy.
• Remedy: Replacement by variable frequency &
voltage motors.
• Pay back periods: 2 years
Schumacher’s Mantra
• “Decrease Consumption”.
• “ Wise use of Knowledge is that which leads to
the well beings of the individual and the
society. Misuse of science and technology is
most poignant example of the danger when
increase in knowledge is out accompanied by
an increase of wisdom”
– E. F. Schumacher.
(“Small is Beautiful”)
Silent Spring: Rachel Carson
“ There was a strange
stillness… on the
morning that had
once throbbed with
dawn chorus of robins,
catbirds, doves, jays,
wrens and source of
other bird voices there
was now no sound;
only silence lay over
fields and woods and
marshes…”
Acknowledgement: Some slides were taken from the Lecture of Dr. K. V.
Raghavan, former Director, CLRI, Chennai.
THANKS FOR PATIENT HEARING