II REVIEW OF LITERATURE -...
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II REVIEW OF LITERATURE
India is richly endowed with alternate energy resources – solar, wind
biomass and small hydros that are widely distributed across the country.
These sources can be utilized through commercially viable technologies to
generate energy to provide fuel security, without endangering the
environment. The Government has been making efforts to popularize
alternate energy technologies – improved chulahs, biogas plants, biomass
gasifiers, solar photovoltaic systems, energy recovery from urban, municipal
and industrial waste etc. The management of wastes treats all materials as a
single class, whether solid, liquid gaseous and tries to reduce the harmful
environmental impacts of each through different methods (Krishnan, 2012).
Waste management is a challenging problem in all countries more so in
developed countries.
Organic waste are produced wherever there is human habitation such
as household food waste, agricultural waste, human and animal waste and
they can be decomposed under aerobic or anaerobic condition. But some
unscientific methods are followed in disposing of organic wastes leads to loss
of organic matter and also cause environmental pollution.
The present chapter attempts to comprehend the issues related to
“Resource Recovery from Organic Waste through Insti tutional and
Community Biogas Plants” under the following five headings:
A. Alternate energy sources for sustainable development
B. Waste – concept, generation, problems and waste management
C. Waste to Energy – Biogas technology
D. Institutional and Community Biogas Plant – A boon for waste
management
E. Challenges ahead for future perspectives.
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A. Alternate Energy Sources for Sustainable Develop ment
Sustainable and equitable development is the most important
challenge before humankind in the coming century and is likely to be the
critical issue in the rural areas of developing countries (Chopra, 2004).
Preventing resource degradation resulting from increasing demands, and
preserving valuable natural forests, wetlands, and other fragile ecosystems
from relatively low value uses have been identified as the urgent requirement
for sustainable world (Kausik, 2002). After food, the most pressing concern in
the foreseeable future will be to provide energy for both, subsistence and
economically productive activities in the rural as well as urban areas of the
developing countries. The challenges that India will be called upon to face are
typical. The population is expected to cross one billion by 2000 AD from the
1991 figure of over 843 million. Substantially higher energy would be required
for both, subsistence as well as economic development.
Loulou et al. (2007) points out that the sustainable economic
development implies an improvement in the quality of life and guarantees
fulfillment of subsistence requirement in addition to enhance economically
productive activities. Singh (2008) documents that the sustainability is now
regarded as a major consideration for both urban and rural development world
wide. Although the definition of sustainability has been articulated in many
ways and in different contents, the main challenge lies in its realistic
application in practical situations. Many criteria can be and have been
proposed as a means of judging sustainability. The current debate over
sustainable development is especially poignant in relation to energy supply.
The provision of energy has a significant influence on the pattern of
development and on the particular shape of human settlements (Lal, 2008).
Bhowmik (2010) expresses that the supply of energy is no exception to
this situation. Traditionally, there is need to import fuels and electricity into
towns and cities from other, often distant locations has not been regarded as
a problem. The creation and growth of means of supply, such as roads,
railways, waterways, and associated facilities for transporting coal and
petroleum products, pipelines for carrying oil and natural gas, and networks
for transmitting electricity, have ensured that energy self-sufficiency in an
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irrelevant issue for towns and cities. However, concern over sustainable
development in urban areas is beginning to raise important questions about
the wisdom and desirability of continuing current arrangements for energy
supply to urban areas (Carazan and Siddayas, 2008).
Rao (2004) states that in the past, standard statistics describe
the pattern of global energy supply have tended, for obvious reasons, to
concentrate on sources of commercially – tradeable fuels and electricity.
Hence, the importance of firewood and dried dung has generally been under
estimated or totally overlooked. In addition to firewood and dried dung,
electricity from hydro power is a renewable source of energy which makes a
significant contribution to global energy supplies. The energy sector has
become a matter of more concern over the years due to the fast rising petrol
and diesel prices over the globe. Heavy reliance upon the conventional fossil
fuels has given birth indefinite headaches for the economies over the globe.
So the need of the hour is to rely more upon the alternate energy sources like
Sun, Wind, Biomass and Organic wastes which are available plenty in our
country. Unlike fossil fuels and uranium for nuclear power, these and other
alternate energy sources, such as solar, wind and tidal, and wave power,
other forms of biomass energy, and to a given extent, geothermal energy,
which cannot be depleted or exhausted (Khattar, 2011).
Provision of adequate energy is a key element in the development
process and one of the main infrastructure requirements for agriculture and
industrial development, employment generation and improvement in the
quality of life of people, especially in the rural and remote areas. It was
expressed by Agarwal (2003) that the present energy portfolio in India is
based on a complex energy mix. The primary energy requirement is more
than 380 millions tons of oil equivalents (mtoe) per year, coming mainly from
indigenous coal, and imported petroleum. Nearly, thirty percent the total
primary energy consumption constitutes biomass in the form of firewood,
agricultural residues, and dung cakes. These traditional energy sources are
used for cooking and village industries in the rural areas. Dayanandan (2003)
pointed out that the use of biomass in traditional store results in par levels
of efficiency and high emissions, causing enormous health damages.
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Alternate energy devices such as biogas plants, biomass gasifier system and
turbo stores can provide clean energy to the rural masses in an affordable
manner.
The potential of alternate energy sources, in general, and their
individual characteristics and features in particular, are adequately described.
Ahlavat (2008) identified that the alternate energy sources have other
characteristics which have resulted in being regarded as an essential
component for sustainable development. In particular, their frequently quoted,
main attraction is their apparently low environmental impact in comparison
with the use of fossil fuels and nuclear power. This is usually expressed in
terms of comparative carbon dioxide emissions which are specifically relevant
to current concerns about global warming and climate change. The potential
benefits of alternate energy sources can be summarized by comparing
estimates of direct and indirect CO2 emissions, resulting from combustion and
use of fossil fuels in the manufacture, construction and installation of the given
energy technologies under consideration (Goldembatee, 2000).
The production of biomass energy, especially in the form of energy
crops, is particularly appropriate for rural areas, chiefly because of extensive
land requirements and the need for established agricultural skills
(Qasim, 2003). Economics are, of course a primary consideration for biomass
energy production, but nor only in relation to the competitiveness of these
fuels with conventional fuels. Extra capital investment in specialized
agricultural machinery for cultivating and harvesting energy crops and in
facilities for processing, storing and transporting such biomass energy to final
consumers is a major consideration for farmers. Apart from difficulties in
obtaining necessary finance, farmers must also have confidence that, as
suppliers, a realistic and profitable market in biomass energy will emerge and
be sustained. This problem is compounded by lack of confidence of
consumers who are unwilling to invest in new biomass energy-consuming
equipment unless a vibrant and secure market exists to supply these new
fuels. Such concerns need to be addressed realistically and a number of
possible solutions have been proposed (Thakur, 2008).
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Pachauri (2005) articulates that the energy consumption is bound to
increase over the years with the development of the country. As developing
countries seek to revitalize their economic, their demand for energy will
increase whatever the move towards the dimensions of their development.
There we have to move towards higher generation of energy as a corollary of
development. Agarwal (2005) utters that the science and technology over the
long term must adapt to forms of energy whose use does not harm the
environment.
Sukhatme (2003) views that the word “energy crisis” continues to
dominate the world. With the fluctuating high cost of petroleum, minimizing
dependence on importing conventional energy resources stewardship to
protect the planet and providing affordable energy to all countries including
India have stepped up their energy path for harnessing indigenous alternate
energy sources (Lal, 2008).
Today India is one of the few leading countries in the development and
utilization of alternate sources of energy. The country is blessed with various
sources of alternate energy. In order to understand how alternative energy
sources can help in preserving the earth’s delicate ecological balance, also to
help in conserving its renewable sources of fuel, we need to know that what
kind of alternative energy resources are available, which can be incorporated
in our daily lives.
1. Alternate Energy Sources in India
In India, energy is a mixed combination of commercial and traditional
sources. In present times, some of the major and extensively used alternate
sources of energy include wind, tides, solar, geothermal heat, biogas
including animal waste and organic waste as well as human excreta
(Khan and Rahaman, 2012). This energy of future is capable in solving
the twine problems of energy supply in decentralized manner and helping in
sustaining cleaner environment.
a. Wind energy: India ranks fourth in the world in wind power installed
capacity. Areas with constant and high speed winds are suitable for the
purpose of wind generated energy. Wind power accounts for 6 per cent of
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India’s total installed power capacity (Sathyasundaram, 2011). One problem
with wind energy is its high initial cost. While development of a coal-based
power plant required around 4 crore per MW, the investment required for wind
and solar power based plant with capacity utilization of 25 per cent requires
an investment of 6 crore per MW. Hence for wider application the cost should
be affordable.
b. Solar energy: India receives abundant energy from the sun because of its
location in the equatorial Sun Belt of the earth. It is a universal, most copious
and inexhaustible source of energy. Harnessing of solar energy can be done
through both the thermal and photovoltaic routes for a variety of application
like cooking, water heating, drying of farm produce, water pumping and so on
(Sukhatme, 2007). At present solar projects contribute less than one per cent
to the total power generated in the country. For instance, wherever the arrays
are installed, nothing can grow on the ground below it because it cuts off
sunlight. If agricultural land were to be used, it would no longer be fit for
cultivation. Except for desert areas and roof tops of building, solar cells cannot
be installed on a large scale (Rao, 2006).
c. Biomass energy: India a tropical country blessed with abundant sunshine
and rains is offering an ideal environment for biomass production. Biomass is
resources which are agriculture related like wood, cow dung, human excreta
and other organic wastes. Among other biomass sources, Waste is all the
more attractive since its valorization enables to produce energy and
disposal of waste streams. Methanisation is a fast growing process that
transforms organic wastes into biogas through a biological fermentation
(http://ec.europa.eu/ environment/etap).
d. Small hydro power: India has been a pioneer in Small Hydro Power
(SHP) and some of the old and languishing plants are being renovated.
New and emerging technologies, like hydrogen, fuel cells, bio-fuel, battery-
operated vehicles, geothermal and tidal energy, hold promise for meeting the
growing energy needs (Abbasi and Abbasi, 2005).
e. Energy from Organic Waste: It has been estimated that there is about
30 million tonnes by solid waste and 4400 million cubic meters of liquid waste
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generated every year in urban areas through domestic as well as commercial
establishments. The manufacturing sector also contributes high quantity of
waste. It has been estimated that through recycling garbage there is a
potential to generate 1700 MW of electricity (Vanitha, 2009; Hartmann, 2009).
B. Waste – Concept, Generation, Problems and Waste Management
This heading can be reviewed under the following sub headings:
1. Concept of waste
2. Waste scenario in India
3. Problems of waste
4. Organic wastes as an alternate source of energy
5. Waste management
1. Concept of waste
Waste (also known as rubbish , trash , refuse , garbage , junk , and
litter ) is unwanted or useless materials. Waste is directly linked to human
development, both technological and social. The compositions of different
wastes have varied over time and location, with industrial development and
innovation being directly linked to waste materials. Waste is sometimes a
subjective concept, because items that some people discard may have value
to others. It is widely recognized that waste materials can be a valuable
resource, whilst there is debate as to how this value is best realized.
Such concepts are colloquially expressed in western culture by such idioms
as "One man's trash is another man's treasure ."
In 1997 Hodges defined waste in simpler terms as, “Resources out of
place”. “Solid waste consists of goods and products which society finds that it
cannot be used productively”. Solid waste is a very general term which
includes all kinds of unwanted solid and semisolid wastes other than excreta
produced in urban and rural environment.
According to the Basel Convention, Waste is defined as "Substances
or objects which are disposed off or are intended to be disposed off or are
required to be disposed off by the provisions of international law".
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United Nations Statistics Division defines "Wastes are materials that
are not prime products (that is products produced for the market) for which
the generator has no further use in terms of his/her own purposes of
production, transformation or consumption, and of which he/she wants to
dispose. Wastes may be generated during the extraction of raw materials, the
processing of raw materials into intermediate and final products,
the consumption of final products, and other human activities. Residuals
recycled or reused at the place of generation are excluded."
Under the Waste Framework Directive (European Directive 75/442/EC
as amended), the European Union defines Waste as an object the holder
discards, intends to discard or is required to discard. Once a substance or
object has become waste, it will remain waste until it has been fully recovered
and no longer poses a potential threat to the environment or to human health.
The UK's Environmental Protection Act 1990 indicated Waste includes
any substance which constitutes a scrap material, an effluent or other
unwanted surplus arising from the application of any process or any
substance or article which requires to be disposed of which has been broken,
worn out, contaminated or otherwise spoiled; this is supplemented with
anything which is discarded otherwise dealt with as if it were waste shall be
presumed to be waste unless the contrary is proved. This definition was
amended by the Waste Management Licensing Regulations 1994 defining
waste as: any substance or object which the producer or the person in
possession of it, discards or intends or is required to discard but with
exception of anything excluded from the scope of the Waste Directive.
Classification of waste
Venkateswaran (1994) classifies solid wastes as:
• Household / commercial refuse
• Street sweeping
• Construction and demolition debris
• Hospital waste and industrial waste
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Based on the sources Park (1995) classifies waste as
• Refuse that is collected from the street is called street refuse.
It consists of leaves, straw, paper, animal droppings and litter of all
kinds.
• Refuse that is collected from markets is called market refuse.
It contains a large proportion of putrescible vegetable and animal
matter.
• Refuse collected from stables is called stable litter. It contains mainly of
animals droppings and left over animal feeds.
• Industrial refuse comprises a wide variety of wastes ranging from
completely inert compounds such as calcium carbonate to highly toxic
and explosive compounds.
• The Domestic Refuse consists of ash, rubbish and garbage.
Tchobanglous et al. (1997) classified solid waste as
• Food wastes: They are animal, fruit or vegetable residues resulting
from the handling, preparation cooking and eating of foods. It is also
called garbage.
• Rubbish: Consists of combustible and non combustible solid waste of
house holds and institutions excluding food wastes and other putrifiable
material.
• Ashes and Residues: Material from burning of wood, coal, coke and
other combustible wastes in homes, institutions etc., for purposes of
heating, cooking and disposing combustible waste.
• Demolition and construction wastes: From razed buildings and other
structures, waste from constructions, remodeling and repairing of
buildings.
• Special wastes: Such as street sweepings, road side litter, dead
animals and abandoned automobile.
a. Garbage: These wastes have a moisture content of about 70 per
cent and heating value of around 6x10 j/kg
b. Rubbish: These waste contain a moisture content of 25 percent
and heating value of the waste is 15 x 106 j/kg
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In addition to this classification Umadevi (1994) also includes – Large
waste termed as Bulky wastes which includes auto parts, tree branches etc.,
and special wastes consisting of hazardous wastes eg., radioactive materials
and security wastes namely documents negotiable papers etc.
According to Anubhav (1996) garbage is divided into organic and
inorganic. Household solid waste can also be classified into Biodegradable –
Vegetable peels, left over food etc. Non Biodegradable – Plastic bags, metal
containers and glass bottles etc.
‘Waste wise’ a non governmental agency in Bangalore (1997)
categories waste generated from household as
Biodegradable / Compostable (Wet)
Non Biodegradable / Non Compostable (Dry)
Insanitary waste Non Compostable (Infectious)
Vegetable and fruit peeling, left over food, leaves, flowers, soft shells, animal dung, human excreta etc.,
Plastic, rubber, glass, metal, cans, hardshells wooden blocks, cloth, blades, staple pins etc.
Solid diapers, sanitary pads, used bandages, syringes, expired medicine, pesticide and other toxic matter.
There are many Waste types defined by Modern Systems of Waste
Management, notably including:
• Municipal Waste includes household waste, commercial waste,
demolition waste
• Hazardous Waste includes Industrial waste
• Bio-medical Waste includes clinical waste
• Special Hazardous Waste includes radioactive waste, explosives
waste, E-waste
Waste can be broadly classified into
• Urban Waste
• Industrial Waste
• Biomass Waste
• Biomedical Waste
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Urban waste includes Municipal Solid Waste, Sewage and Fecal
Sludge, whereas Industrial waste could be classified as Hazardous industrial
waste and Non-hazardous industrial waste.
2. Waste scenario in India
Solid waste generation in India was 229 million tons in 2001 and solid
waste generation per capita per day in India ranged from 100 to 500 grams
(Arrifa and Jayalakshmi, 2005). It is further projected that an additional 1400
acres of land is needed to dispose waste, most of it in urban areas. Modern
urban living brings the problem of waste, increase in quantity, and changes in
composition with each passing day (Singh and Shekhawat, 2002). It has been
estimated that overall municipal waste generated in urban centers anywhere
constituted organic matter. It is also important to note that waste consumption
varied significantly across areas of different economic levels of residents.
Manimozhi et al. (2006) points out that the per capita solid waste reaching
disposal sites in Bombay, Chennai, Calcutta and New Delhi ranges from
0.45 to 0.6 kilo gram per person per day, while in other Indian Cities it is from
0.15 to 0.53 kilogram per person per day. It is established that about
500 grams of biodegradable kitchen waste is generated per day in a family
consisting of four members (Gupta, 2002). Proper waste management helps
to protect human health and the environment and preserve natural resources.
Selvaraj (2012) views that many do not realize the solid waste impact
on climate changes. When organic waste decomposes in land fills and
uncontrolled dumps, it produces methane, one of the major green house
gases contributing to climate change methane emissions from land fills are
projected to reach 39 million tonnes in 2047 from seven million tonnes
in 2007. Proper solid waste management can reduce green house gas
emissions (warming). As most of our urban areas are already congested,
waste disposal sites have to be located far from source, with considerable
cost implications in terms of transport and infrastructure (Murphy and
Mckay, 2007).
Ponniah (2005) conveys that traditionally, disposal of solid wastes
were disposed to a ground. In the past, with low population densities
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biodegradable solid waste products disposal presented few ecological
problems. With high population densities and each household producing
significant quantity of both biodegradable and non-biodegradable solid waste
materials are accumulating on both the limited areas of land and the marine
water at ecologically damaging levels. The issue of urban poverty is
inextricably linked with waste. In India a million people find livelihood
opportunities in the areas of waste, engaged in waste collection and recycling
through well organized systems and also substantial population of urban poor
in other developing countries earn their livelihood through waste.
In domestic activities 30 to 40 per cent of the domestic waste is organic
in nature, which needs to be disposed on day to day basis. The bins overflow
and the entire street becomes dirty and attracts the street dogs and rag
pickers (Kumar and Singh, 1999). The average collection efficiency for MSW
(Municipal Solid Waste) in Indian cities is about 72.5 per cent as a result of
which, a substantial part of the waste generated remains unattended,
affecting the quality of life of millions of people. Solid waste should be
managed through a number of activities such as waste prevention, recycling,
composting, controlled burning or land filling. Using a combination of these
activities that protects the community and the local environment is referred to
as Integrated Solid Waste Management (ISWM). The ISWM programme can
help green house gas emissions and slow down the effects of climate change
(www.epa.gov/globalwarming).
Urban planners, municipal agencies, environmental regulators, labour
groups, citizens groups response which are rooted in local dynamics,
rather than borrow non-contextual solutions from else where. Expensive
technologies are being pushed to deal with our urban waste problem, ignoring
their environmental and social implication. The improved technologies are
now available for collection, treatment and processing standards with, which
enables to improve the quality of the garbage to meet the pollution advantage
of power generation world over (Kumar, 2002). Many innovative approaches
are being adopted for sustainable solid waste management Viz. reduces
waste technological interventions, and institutional reforms. India could learn
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from these experiences and devise strategies and approaches that best suit
its own MSW management requirements (Rampal, 2000)
Mapuskar, (2007) articulates that a significant large portion of the
municipal solid waste is organic in nature and a single large of such purely
organic waste is the vegetable market. All cities and towns have one or more
vegetable markets where everyday fresh vegetables and fruits arrive and, are
sold either on wholesale or on retail basis. The quantity of waste generated in
such markets varies from one to a few hundred depending upon the size of
market. As per an estimate, around 50,000 tonnes of vegetable market waste
is generated in India.
In the contemporary Indian situation, there is need for large amount of
energy from all possible sources. Human waste and household organic
wastes have large energy content and their potential can be tapped for
realization of energy in two ways. By drying and burning we can release
the energy and secondly by allowing it to decompose we get biogas by
anaerobic fermentation. Handling human excreta in open environment is
delicate and impractical, biogas is free from the above drawbacks and also
the nutrient value of biomass is retained in the form of manure which is
odourless and stable. This increases soil fertility and provides humus for solid
conditioning (Chauhan and Srivastava, 2006).
Every year, about 55 million tonnes of municipal solid waste (MSW)
and 38 billion litres of sewage are generated in the urban areas of India. In
addition, large quantities of solid and liquid wastes are generated by
industries. Waste generation in India is expected to increase rapidly in
the future. As more people migrate to urban areas and as incomes increase,
consumption levels are likely to rise, as are rates of waste generation
(Rao, 2004). It is estimated that the amount of waste generated in India will
increase at a per capita rate of approximately 1-1.33% annually. This has
significant impacts on the amount of land that is and will be needed for
disposal, economic costs of collecting and transporting waste, and the
environmental consequences of increased MSW generation levels
(Dhanuja, 2006).
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According to the Ministry of New and Renewable Energy (MNRE),
there exists a potential of about 1700 MW from urban waste (1500 from MSW
and 225 MW from sewage) and about 1300 MW from industrial waste.
The Ministry is also actively promoting the generation of energy from waste,
by providing subsidies and incentives for the projects. Indian Renewable
Energy Development Agency (IREDA) estimates indicate that India has so far
realized only about 2 per cent of its waste-to-energy potential. A market
analysis predicts that the Indian municipal solid waste to energy market could
be growing at a compound annual growth rate of 9.7 per cent by 2013.
3. Problems of waste
Waste management is a challenging problem in all countries, more so
in developed countries. Lakshmanan (2009) says that domestic waste from
urban areas, without proper planning, is turning to be a problem unconquered.
Waste which are produced in large quantities all over the world; create major
environmental and disposal problems. Nath (2003) views that the towns and
cities are characterized by over crowding, congestion, inadequate water
supply and inadequate facilities of disposal of human excreta, waste water
and solid waste. The waste accumulation has increased simultaneously with
the rapid increase in residential colonies, fast food outlets, vegetable vendors,
fruit shops and other customer outlets in the respective areas.
Viswanathan (2005) informs that the amount of large solid refuse has
been gradually increasing and its treatment and disposal has become a major
social and environmental problem as well as a challenge. The insanitary
methods adopted for disposal of solid wastes is a serious health concern
with significant environmental, social and health costs associated with it.
Open dumping of garbage facilities are the breeding of disease vectors such
as flies, mosquitoes, cockroaches, rats and other pests (Maheswari, 2005).
The recent estimates indicate that nearly two billion people (about one
third world’s population) are without any basic facilities and by 2021 the
number may increase to three billion. Waste generation increases with
population expansion and economic development. Solid waste generation is
one of the serious environmental issues in urban areas needing special
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attention (Rao, 2004). Today, solid wastes are considered as one of the major
sources for pollution in the human environment. The solid waste generated
causes enormous environmental damages to the soil and water sources
(Setua and Setua, 2008).
Mani (2006) views that in fact, waste is a misplaced resource and it is
not possible to destroy it. Materials may come to only two possible discharges
into the environment and the other is reuse or reclamation or recycling.
Conditioning of organic wastes can help in pollution abatement.
Problems of waste are reviewed under the following headings:
a. Environmental costs: Diaz et al. (2006) communicates that waste attracts
rodents and insects which harbour gastrointestinal parasites, yellow fever,
worms, the plague and other conditions for humans. Exposure to hazardous
wastes, particularly when they are burnt can cause various other diseases
including cancers. Waste can contaminate surface water, groundwater, soil,
and air which cause more problems for humans, other species, and
ecosystems. Waste treatment and disposal produces significant green house
gas (GHG) emissions, notably methane, which are contributing significantly to
global climate, change (Mani, 1996).
b.Social costs: Sivashankaraiah, et al. (2008) states that waste management
is a significant environmental justice issue. Many of the environmental
burdens cited above are more often borne by marginalized groups, such as
racial minorities, women and residents of developing nations. However, the
need for expansion and siting of waste treatment and disposal facilities is
increasing worldwide.
Ray (2008) express that there is now a growing market in the
transboundary movement of waste, and although most waste that flows
between countries goes between developed nations, a significant amount of
waste is moved from developed to developing nations.
c. Economic costs: Muck and Brash (2009) exhort that the economic costs
of managing waste are high, and are often paid for by municipal governments.
Money can often be saved with more efficiently designed collection routes,
modifying vehicles, and with public education. Environmental policies such as
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pay as you throw can reduce the cost of management and reduce waste
quantities. Wilson et al. (2006) opines that the informal waste sector consists
mostly of waste pickers who scavenge for metals, glass, plastic, textiles, and
other materials and then trade them for a profit. This sector can significantly
alter or reduce waste in a particular system, but other negative economic
effects come with the disease, poverty, exploitation, and abuse of its workers.
d. Education and awareness: Education and awareness in the area of waste
and waste management is increasingly important from a global perspective of
resource management. The Talloires Declaration is a declaration for
sustainability concerned about the unprecedented scale and speed of
environmental pollution and degradation, and the depletion of natural
resources. Local, regional, and global air pollution; accumulation and
distribution of toxic wastes; destruction and depletion of forests, soil, and
water; depletion of the ozone layer and emission of "green house" gases
threaten the survival of humans and thousands of other living species,
the integrity of the earth and its biodiversity, the security of nations, and
the heritage of future generations.
4. Organic wastes as an alternate source of energy
India being a large country, spread over in different agro climatic
zones, have variety of solid wastes in different regions which also vary in
season to season to regular production of biogas from this solid waste
materials. Biomethanation with concomitant production of biogas and a safer
end product for disposal of land (compost) has been the direction in which
many countries have put in a great deal of effort (Kausik, 2002).
Methane gas is the main ingredient of gas which is produced from
wastes. Smelly stiff, like rotting garbage, agricultural and human waste
releases methane gas-also called “Land fill gas” or biogas” (Amrit et al.,
2005). The energy produced from organic wastes has been one of the main
energy sources for the mankind ever since the dawn of civilization,
every year million tons of agriculture and forest residues are generated.
These are either wasted or burnt inefficiently in their loose causing air
pollution (Gunasegarana, 2002).
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Tester et al. (2006) point out that the energy crisis demands effective
planning and use of the limited energy sources. Since exhaustible energy
sources in the country are limited; there is an urgent need to focus attention
on development of alternate energy sources and use of energy efficient
technologies. Hence energy recovery from organic wastes could be one of the
best alternatives to overcome energy problem.
While, the energy needs of our country is increasing at a rapid rate,
and the energy resources that are indigenously available are limited and may
not be sufficient in the long run to sustain the process of economic
development (Dayanadan, 2003). The need for of alternate energy increases
tremendously as they are available in zero or negligible cost. Vandana (2002)
brings forth that conventional sources of energy available to use are in the
form of coal, oil, electricity and nuclear energy, which are fast depleting.
Hence energy crisis can be reduced to large extent by combating energy
crisis through alternate sources of energy.
To meet the energy requirement, the effective use of organic wastes
has now emerged as potential alternative energy source (Ramasamy, 2011).
The energy produced from organic waste, as a source of energy is
environment friendly, renewable relatively cheap and locally available.
There is an urgent need to make available technologies for increasing the
producing of energy from organic waste and ensure its efficient utilization.
This would so a long way in promoting the sustainable use of wastes for
meeting energy requirements and would also result in additional benefits to
the society.
5. Waste management
Jha (2005) explains that the waste management is the collection,
transport, processing or disposal, managing and monitoring of waste
materials. The term usually relates to materials produced by human activity,
and the process is generally undertaken to reduce their effect on health,
the environment or aesthetics. Waste management is a distinct practice from
resource recovery which focuses on delaying the rate of consumption of
natural resources. Waste management practices differ for developed and
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developing nations, for urban and rural areas, and for residential and
industrial producers. Management for non-hazardous waste residential and
institutional waste in metropolitan areas is usually the responsibility of local
government authorities, while management for non-hazardous commercial
and industrial waste is usually the responsibility of the generator.
Waste is actually a misplaced resources and this concept is slowly
gaining recognition. There are various forms of resources recovery from
waste that are currently practiced to varying degrees.
According to Beukering (1994), the term “recycling” has evolved into a
concept encompassing any productive use of what would otherwise be a
residual requiring disposal. This generalizations, however, includes many
more activities than recycling alone.
Recycling can be defined as a method to reprocess waste in order to
recover an original raw material. Two categories of recycling can be
distinguished. Closed loop recycling is the processing of residuals in order to
recover and reuse the material in the same production activity. Open loop
recycling in this process, reclaiming residuals is preceded by marketing of the
waste. Since many producers or consumers are unable to recycle waste
themselves, it is either disposed off or marketed. This type of recycling occurs
most widely (Zafar, 2009).
Reuse is a process by which materials in its end-use form is reclaimed
and again used in the same form. No significant transformation of the residual
occurs. An example is the returnable bottle or the use of newspapers for
packaging purposes.
37
Diagram of the waste hierarchy
There are a number of concepts about waste management which vary
in their usage between countries or regions. Some of the most general, widely
used concepts include:
• Waste hierarchy - The waste hierarchy refers to the "3 Rs" reduce,
reuse and recycle, which classify waste management strategies
according to their desirability in terms of waste minimization. The waste
hierarchy remains the cornerstone of most waste minimization
strategies. The aim of the waste hierarchy is to extract the maximum
practical benefits from products and to generate the minimum amount
of waste i.e. resource recovery.
• Polluter pays principle - the Polluter Pays Principle is a principle where
the polluting party pays for the impact caused to the environment. With
respect to waste management, this generally refers to the requirement
for a waste generator to pay for appropriate disposal of the waste
(www.recoveredenergy.com).
Disposing of waste in a landfill involves burying the waste, and this
remains a common practice in most countries. Landfills were often
established in abandoned or unused quarries, mining voids or borrow pits.
A properly designed and well-managed landfill can be a hygienic and
relatively inexpensive method of disposing of waste materials. Older, poorly
designed or poorly managed landfills can create a number of adverse
environmental impacts such as wind-blown litter, attraction of vermin, and
38
generation of liquid leachate. Another common byproduct of landfills is gas
(mostly composed of methane and carbon dioxide), which is produced as
organic waste breaks down anaerobically. This gas can create odour
problems, kill surface vegetation, and is a greenhouse gas (Rasure, 2011).
Design characteristics of a modern landfill include methods to contain
leachate such as clay or plastic lining material. Deposited waste is normally
compacted to increase its density and stability, and covered to prevent
attracting vermin (such as mice or rats). Many landfills also have landfill gas
extraction systems installed to extract the landfill gas. Gas is pumped out of
the landfill using perforated pipes and flared off or burnt in a gas engine to
generate electricity (Baker et al., 2004).
Incineration is a disposal method in which solid organic wastes are
subjected to combustion so as to convert them into residue and gaseous
products. This method is useful for disposal of residue of both solid waste
management and solid residue from waste water management. This process
reduces the volumes of solid waste to 20 to 30 percent of the original volume.
Incineration and other high temperature waste treatment systems are
sometimes described as "thermal treatment". Incinerators convert waste
materials into heat, gas, steam and ash (Ahlavat, 2008).
Incineration is carried out both on a small scale by individuals and on a
large scale by industry. It is used to dispose of solid, liquid and gaseous
waste. It is recognized as a practical method of disposing of certain
hazardous waste materials (such as biological medical waste). Incineration is
a controversial method of waste disposal, due to issues such as emission of
gaseous pollutants.
Incineration is common in countries such as Japan where land is
scarcer, as these facilities generally do not require as much area as landfills.
Waste-to-Energy (WtE) or Energy-from-Waste (EfW) is a broad term for
facilities that burn waste in a furnace or boiler to generate heat, steam or
electricity. Combustion in an incinerator is not always perfect and there have
been concerns about pollutants in gaseous emissions from incinerator stacks.
Particular concern has focused on some very persistent organics such as
39
dioxins, furans, PAHs which may be created which may have serious
environmental consequences (Vinneras et al., 2006).
Hangaragi (2009) exhort that the energy content of waste products can
be harnessed directly by using them as a direct combustion fuel, or indirectly
by processing them into another type of fuel. Thermal treatment ranges from
using waste as a fuel source for cooking or heating and the use of the gas fuel
to fuel for boilers to generate steam and electricity in a turbine. Pyrolysis and
gasification are two related forms of thermal treatment where waste materials
are heated to high temperatures with limited oxygen availability. The process
usually occurs in a sealed vessel under high pressure. Pyrolysis of solid
waste converts the material into solid, liquid and gas products. The liquid and
gas can be burnt to produce energy or refined into other chemical products
(chemical refinery). The solid residue (char) can be further refined into
products such as activated carbon. Gasification and advanced Plasma arc
gasification are used to convert organic materials directly into a synthetic gas
(syngas) composed of carbon monoxide and hydrogen. The gas is then burnt
to produce electricity and steam. An alternative to pyrolisis is high
temperature and pressure supercritical water decomposition (hydrothermal
monophasic oxidation).
Resource recovery (as opposed to waste management) uses LCA
(life cycle analysis) to offer alternatives to waste management. For mixed
MSW (Municipal Solid Waste) a number of broad studies have indicated that
administration, source separation and collection followed by reuse and
recycling of the non-organic fraction and energy and compost/fertilizer
production of the organic waste fraction via anaerobic digestion to be the
favoured path (Dhussa and Varshney, 2000).
An important method of waste management is the prevention of waste
material being created, also known as waste reduction. Methods of avoidance
include reuse of second-hand products, repairing broken items instead of
buying new, designing products to be refillable or reusable (such as cotton
instead of plastic shopping bags), encouraging consumers to avoid using
disposable products (such as disposable cutlery), removing any food/liquid
remains from cans, packaging and designing products that use less material
40
to achieve the same purpose (for example, light weighting of beverage cans)
(Naveen et al., 2011).
C. Waste to Energy – Biogas Technology
Waste generation rates are affected by socio-economic development,
degree of industrialization, and climate. Generally, the greater the economic
prosperity and the higher percentage of urban population, the greater the
amount of solid waste produced. Reduction in the volume and mass of solid
waste is a crucial issue especially in the light of limited availability of final
disposal sites in many parts of the world. Although numerous waste and
byproduct recovery processes have been introduced, anaerobic digestion has
unique and integrative potential, simultaneously acting as a waste treatment
and recovery process (Zafar, 2009).
Studies have shown that communities that employ waste-to-energy
technology have higher recycling rates than communities that do not utilize
Waste-to-Energy (Narasith, 2008). The recovery of ferrous and non-ferrous
metals from these plants for recycling is strong and growing each year.
In addition, numerous studies have determined that WtE plants actually
reduce the amount of greenhouse gases that enter the atmosphere
(Selvaraj, 2012).
Nowadays, these plants based on combustion technologies are highly
efficient power plants that utilize municipal solid waste as their fuel rather than
coal, oil or natural gas. Far better than expending energy to explore, recover,
process and transport the fuel from some distant source, Waste-to-Energy
plants find value in what others consider garbage. These plants recover the
thermal energy contained in the trash in highly efficient boilers that generate
steam that can then be sold directly to industrial customers, or used on-site to
drive turbines for electricity production (Murphy and McKay, 2001). WtE plants
are highly efficient in harnessing the untapped energy potential of organic
waste by converting the biodegradable fraction of the waste into high calorific
value gases like methane. The digested portion of the waste is highly rich in
nutrients and is widely used as biofertilizer in many parts of the world.
41
Most wastes that are generated, find their way into land and water
bodies without proper treatment, causing severe water pollution. They also
emit greenhouse gases like methane and carbon dioxide, and add to air
pollution. Any organic waste from urban and rural areas and industries is a
resource due to its ability to get degraded, resulting in energy generation
(Murad, 2007).
The problems caused by solid and liquid wastes can be significantly
mitigated through the adoption of environment-friendly waste-to-energy
technologies that will allow treatment and processing of wastes before their
disposal (Saha et.al 2010). These measures would reduce the quantity of
wastes, generate a substantial quantity of energy from them, and greatly
reduce environmental pollution (Joseph, 2002). India’s growing energy deficit
is making the Central and State governments become keen on alternative and
renewable energy sources. Waste to energy is one of these, and it is
garnering increasing attention from both the Central and State governments
(WHO, 2006).
While the Indian Government’s own figures would suggest that the cost
of waste to energy is somewhat higher than other renewable sources, it is still
an attractive option, as it serves a dual role of waste disposal and energy
production.
The recovery of energy from wastes offers additional benefits as
follows.
• The total quantity of waste gets reduced by nearly 60 percent to over
90 percent, depending upon waste composition and adopted
technology.
• Demand for the land, which is already scarce in cities, for land filling its
reduced.
• The cost of transportation to far-away land fill sites also gets reduced
proportionately., and
• Net reduction in environmental pollution
(http://urban india.nic.in/public infor/swm/chap15.pdf)
42
Technologies for the Generation of Energy from Wast e
Mukherjee and Chakrabarti (2005) puts across that energy can be
recovered from the organic fraction of waste (biodegradable as well as
non-biodegradable) through thermal, thermo-chemical, biochemical and
electrochemical methods.
i. Thermal Conversion : This process involves thermal degradation of waste
under high temperature. In this process complete oxidation of the waste
occurs under high temperature. The major technological option under this
category is incineration. However incineration has been losing attention
these days because of its emission characteristics.
ii. Thermo-chemical conversion : This process entails high temperature
driven decomposition of organic matter to produce either heat energy or fuel
oil or gas. They are useful for wastes containing high percentage of organic
non-biodegradable matter and low moisture content. The main technological
options under this category include Pyrolysis and G asification.
The products of these processes (producer gas, exhaust gases etc) can be
used purely as heat energy or further processed chemically, to produce a
range of end products.
iii. Bio-chemical conversion : This process is based on enzymatic
decomposition of organic matter by microbial action to produce methane gas,
and alcohol etc. This process, on the other hand, is preferred for wastes
having high percentage of organic, bio-degradable (putrescible) matter and
high level of moisture/water content, which aids microbial activity. The major
technological options under this category are anaer obic digestion
(bio-methanation) and fermentation. Of the two, anaerobic digestion is the
most frequently used method for waste to energy, and fermentation is
emerging.
The USEPA defines Anaerobic Digestion as a process where
microorganisms break down organic materials, such as food scraps, manure
and sewage sludge, in the absence of oxygen. In the context of solid waste
management, anaerobic digestion (also called biomethanation) is a method to
treat source separated organic waste to recover energy in the form of biogas,
43
and compost in the form of a liquid residual. Biogas consists of methane and
CO2 and can be used as fuel. The liquid slurry can be used as organic
fertilizer.
iv. Electrochemical Conversion : Electrochemical conversion in the
context of waste to energy refers typically to microbial fuel cells (MFC).
These systems are developed to trap the energy from wastes, where the
reduction-oxidation machinery of immobilized microbial cells is catalytically
exploited, for the accelerated transfer of electrons from organic wastes, to
generate electricity and bio-hydrogen gas. However, this methodology needs
extensive evaluation studies on bulk scale liquid waste treatments and stands
at a nascent level in India as well as worldwide.
A potential for generating about 1000 mw of power from urban and
municipal wastes and about 700mw from industrial wastes has been
estimated for the country. This potential is likely to increase the further
economic development (Singh, 2007).
The main objectives of the National Programme or Energy Recovery
from Urban, Municipal and Industrial wastes are as follows:
• To create conducive conditions and environment with financial and
fiscal to help, promote, develop and demonstrate the utilization of
waste for recovery of energy.
• To improve the waste management practices through adoption of
renewable energy technologies for processing and treatment of
wastes prior to disposal.
• To promote setting up of projects for recovery of energy from
wastes from urban, municipal and industrial sectors.
In today's energy crisis, it is recognized that renewable energy sources
can be the alterable sources of energy to provide the basis for sustainable
energy development on account of their inexhaustible nature and
environment-friendly features (Viswanathan, 2005). The challenge now is to
implement the latest technology at the grass root level effectively. Additionally
the economy of biogas plants can be improved by using high biogas potential
44
substrates in combination with cattle dung. One such substrate being night
soil, rich in nitrogen content was added to the cattle dung digesters to combat
the nitrogen deficiency and also improve the gas production (Schertenleib and
Meyer, 2002).
Another thing is human waste disposal in an innocuous form in highly
populated and developing countries, such as India is an ever growing
problem. Improper disposal of human excreta results in the contamination of
water bodies, soil and food crops. This practice poses a serious health hazard
because human excreta is the principal source of pathogenic organisms,
which may be transmitted by direct contact, contaminated water and food,
insects and other vectors. Human excreta must therefore be treated before its
ultimate disposal into the environment or its use in agriculture in order to
reduce the spread of communicable diseases and prevent the pollution of the
environment, water sources and soil (Jha, 2005). The problem of treatment
and disposal is more aggravated at low temperature and high altitude regions,
such as Himalayan regions of India, where no proper human waste disposal
method is in practice. Although, aerobic degradation of organic waste is
considered to be efficient, anaerobic digestion appears to be more suitable in
view of the generation of biogas which can be used for maintenance of
digester temperature (in addition to better hygiene) with least human
intervention (Lakshminarayanan, 2011).
D. Institutional and Community Biogas Plant - A Boo n for Waste
Management
Biogas refers to a gas made from anaerobic digestion of agricultural
and animal waste, food waste and sometimes municipal solid waste and
biofuel crops. The design is based on the type of organic waste to be used as
raw material, the temperature to be used in digestion, and the material
available for construction. Methane is the combustible component of biogas
and the digestate slurry is a valued fertilizer. Most people are not aware that
as the world turns to using renewable energy, the one huge source that has
barely been used up to now is biogas methane.
45
There are differing definitions for biogas. Itodo and Philips (2011) says
that a methane rich gas that is produced from the anaerobic digestion of
organic materials in a biological-engineering structure called the design.
Bates (2007) describes that “a gas mixture comprises around 60 per cent
methane and 40 per cent carbon dioxide that is formed when organic material,
such as dung or vegetable matter are broken down by microbiological activity
in the absence of air, at a slightly elevated temperature and clean, cooking,
lighting fuel” also know as “swamp gas, marsh gas and gobar gas.
Manure, either from human beings or from animals, is a major pollutant
source in rural areas. Anyone who has visited India, for example will
remember the acrid smell of burning manure. The acrid smoke leads to
endemic eye disease, and the drying manure is a perfect breeding ground for
flies of all types. The manure would also go a long way to improve the quality
of the soil and hence increasing the harvest if these valuable mineral were
returned to it instead of going up in smoke.
Table 2: Gas Production per Kg of Dung
Types of Dung Gas production / Kg dung
cu.m
Cattle
Pig
Poultry
Human
0.023 – 0.04
0.04 – 0.059
0.065 – 0.116
0.02 – 0.028
Source: Energy Resources Development 2002.
Itodo and Philips (2011) opine that to produce the Biogas a feed stock
material must be used such as vegetable matter and dung. However, it is the
general belief that liquid – manure systems work best for anaerobic digestion
in the production of biogas. The yield from human waste is low in comparison
to other manures, but the gas gained should be seen as a bonus; the main
purpose is to find an alternative disposal method, also “reading the amount
that would otherwise be released naturally into the atmosphere and so
reduces the excessive green house effect”. Other benefits of digesting human
wastes are:
46
• Methane being a fuel reduces the amount of wood fuel required and
thus reduces desertification (Xuereb, 1997)
• The waste is reduced to slurry that has a high nutrient content
making an ideal fertilizer
• During the digestion process, dangerous bacteria in the dung are
killed, which reduced the pathogens dangerous to human health
(Bates et al., 2007).
Institutional Biogas Plant and Community Biogas Pla nt
The International Reference Centre for Waste Disposal (IRCWD)
examines a number of areas where it has been used and identifies that
institutional and community biogas plants provide benefits including:
• Economies of scale
• Surplus gas for income generating activities
• More efficient operation as the plant usually has a full-time operator
• Equity consideration, people can work in return for gas
Strieber et al., (2006) identifies that how biogas technology was used
for sanitation in Kigali, Rwanda on a community level and providing gas that
cost the household $0.23 per person per day “significantly less than the
current cost of improved oil”. These are the examples where biogas
technology has also been a success in institution such as prisons in Kaski,
Nepal and Kigali, Rwanda, where the prison holds “5000 people who together
produce 50cu.m toilet waste per day (producing) a whopping 250cu.m of
biogas per day” (Aryal, 2009). Biogas has also been used widely in schools, in
Maphephethini, Kwazulu – Natal (Sibisi and Green, 2005) and Lem, Ethiopia
where of schools with and average population of 5,500 were fitted with
digesters and the technology is still working today (Worku, 2009).
Designs of Biogas Plant for Converting Waste to Ene rgy
The digester provides a sealed vessel that allows the input of feeds
tock and removal of gas, ideally being built of locally available materials.
47
The “Floating Drum”/“Indian” Digester
Developed in 1956, the chamber is made
of masonry and a steel drum placed on top to
catch the biogas. The drum moves up as it fills.
It requires high investment and maintenance.
In KVIC design, the digester chamber is made of
brick masonry in cement mortar. A mild steel
drum is placed on top of the digester to collect the biogas produced from the
digester. Thus, there are two separate structures for gas production and
collection. With the introduction of fixed dome Chinese model plant, the
floating drum plants became obsolete because of comparatively high
investment and maintenance cost along with other design weaknesses.
The “Fixed Dome”/”Chinese Digester”
Dating back to 1936, it consists of an
underground masonry compartment also know as
the fermentation chamber and a fixed dome for
gas storage. The single piece structure decreases
the complexity of maintenance whilst still having
two drains to feed waste. The life span is longer at
around 20 to 50 years increasing its economic feasibility. The Gas and
Agricultural Equipment Development Company of Nepal have developed a
cheaper concrete design built form this that has been around since the early
go’s showing the initial shape is tested and proven.
The Deenbandhu Model
It was originally developed by Action for
Food Production to bring down costs. It proved 30
per cent cheaper than a fixed dome design based
on the Chinese Digester and 45 per cent cheaper
than the Nepalese KVIC plant. It is made entirely
out of masonry with hemisphere gas storage at the
top and concave base working under the same principles as a normal fixed
dome digester.
48
ARTI Biogas plants
ARTI Biogas plants are manufactured using molded
plastic. These are floating dome type biogas plants
designed for household application. The primary use
of these biogas plants is waste management,
whereas the secondary use include biogas for partial
substitution of LPG in the kitchen and watery slurry available for irrigation.
Features:
• Available in two sizes, one for up to 500gm feedstock, and one for up
to 1-2kg feedstock.
• Feedstock required is any type of organic biodegradable waste (ideally,
kitchen and food waste).
• Daily addition of dung or faecal matter is not required more.
Water kiosk biogas plant: The water kiosk biogas plant has a
volume of 54cu.m with two expansion chambers.
The underground structure is located about 0.5 m
below surface. The required area for the toilet building
and biogas plant is approximately 10x15 metres. It is
not recommended to build any structures on top of the
biogas plant. The dimensions of the plant were based
on a sufficient settlement of solids which is achieved
with a hydraulic retention time (HRT) of 5 days. The solids settle and remain
in the system for digestion and biogas production. The system works like a
gas tight septic tank. The solids-free effluent is flowing over to the sewer
connection.
BCSIR biogas plant: In BCSIR Design, the present fixed biogas plants have
an underground cylindrical shaped biogas digester constructed with brick
walls and concrete. The digester is also connected to the outlet tank, which
includes a hydraulic chamber, and bio-fertiliser pit. The size of the plant
depends on the availability of raw materials and demand for gas. It works
according to the principles of constant volume and changing pressure.
49
When the rate of gas production is higher than that of gas consumption,
pressure inside the digester rises and expels some digester contents into the
outlet compartment. When the consumption is higher than production,
pressure inside the digester falls and the expelled materials in the outlet
compartment run back to the main digester.
Malaprabha biogas plant: The Malaprabha biogas plant comprises of
3 compartments. The first compartment is designed to provide for a HRT of
30 days and doubles-up as gasholder. In order to collect the biogas that is
generated in the process of anaerobic digestion of black water, the first
compartment is provided a gas tight cover made from reinforced cement
concrete (R.C.C.). The second and third compartments provide for a total
HRT of 15 days. The chambers act as compensation chambers and facilitate
build up of gas pressure. There is an opening at the bottom of the wall
separating the 1st and the 2nd chamber and an aperture in the wall separating
the 2nd and 3rd chamber to facilitate flow of water through the biogas plant.
The opening (1st to 2nd chamber) provides access to the sealed
1st compartment during construction and doubles-up as maintenance opening
afterwards. The biogas plant is provided with pressure release pipe that vents
biogas before excess gas pressure may damage the plant. Depending on site
conditions, the effluent from Malaprabha Biogas Plants may be drained to an
existing drainage system, infiltrated locally or collected for reuse. The digester
volume equals number of users into litres of water used for flushing (and anal
cleansing, if applicable) per person per day into 45 days HRT. For digestion of
night soil (i.e. excreta), optimum requirement of water is 2.17 litre per person
(Martin, 2009).
Fixed dome biogas plant: Fixed dome biogas plant consists of an
underground brick masonry compartment
(fermentation chamber) with a dome on
the top for gas storage. In this design,
the fermentation chamber and gas holder
are combined as one unit. This design
eliminates the use of costlier mild steel
gas holder which is susceptible to corrosion. The life of fixed dome type plant
50
is longer (from 20 to 50 years) compared to KVIC plant. Because of the
advantages the fixed dome biogas plant was adjudged as the best for
institutions and communities.
Institutional Biogas Plants- These types of plants is designed to cater to the
needs of hostels, schools, convents, hospitals,
industrial organizations where people coming in
large numbers and stay regularly. The generated
wastes will be treated by hygienic waste disposal
methods in an eco-friendly manner. The night soil
(human excreta) generated will directly be fed into
the treatment plant automatically in a hygienic way for production of biogas.
All the institutions have hostels for their students. The major problem
which they are facing today is the way to dispose the human excreta, food
and vegetable waste, hand washing water, vessel washing water. Biogas
plant can only solve the whole problem. There are regular waste disposal
problem in almost all institutions like hostels, hospitals, convents, old-age
homes where more peoples are staying together. The overflow and or
leakage of septic tank or drainage systems create severe environmental
problems and public nuisance, opposition and complaints from the neighbors,
(http://nwedc.in/night-soil-Biogas -plant.html).
In the same time, the cooking fuel consumption of these institutions is
also very high. The monthly budgets for firewood or other cooking fuels are
also increasing regularly for these institutions. The treatment of human
excreta through biomethanation is the remedy to overcome these two
problems at a time. Like any other bio waste, human excreta can be treated
with the help of anaerobic microbes (bacteria). These microbes are not
harmful to human beings. When human excreta are treated with the help of
biomethanation process, the biogas is generated from this waste, through
microbial action. This gas can be used for cooking. When a night soil plant is
installed, there is no need of a separate conventional septic tank. Treated
slurry coming out from the plant can be utilized as liquid fertilizer. All other
easily biodegradable waste can be treated together with human excreta in the
same plant.
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Through this installation of institution based biogas process
the beneficiary can treat all other degradable waste like cooked food. Fish,
meat and vegetable waste can also be treated in the same plant. The size of
the plant may be different depending upon the availability of human excreta
and other degradable waste. The treatment plant can be installed either as a
single unit or more units in different locations. The installation of a night soil
plant is more convenient during the building construction time. The conversion
of existing septic tanks to night soil treatment digester is a little expensive.
In accordance with the fast growing population, the demand for energy
and the discharge of waste are increasing day by day. To overcome
the energy crisis, alternative energy sources are the only remedy. Generation
of energy from waste is beneficial in many ways. It is most suitable for
eco-friendly waste disposal and also for energy generation.
All easily degradable materials including cooked and raw food wastes,
fruits and vegetable wastes, fish and meat wastes, excreta of all domestic and
wild animals and birds and waste water containing bio waste materials can be
treated with this technology. Slow degradable materials like vegetables, green
or wet plant parts can also be treated with this technology, using specially
designed anaerobic pre-digesters.
Socio-Economic Benefits
� Generation of Energy in the form of Biogas � Generation of organic fertlizer � Saving of garbage dumping land � Minimum waste collection expenses � Better utilization of wastes � Employment opportunities
Community biogas plant: In Institutional biogas system, Household biogas
generators have been accepted because the
connection between the latrine and the digester
requires no contact with the waste, bypassing
any taboos. Implementing the technology in a
more community-based situation may have its
limits but there is evidence that Community
Biogas Plants have been implemented.
52
Design Parameters for Sizing of Biogas Plants
Table 3: Design Parameters for Sizing of Biogas Pla nts
Source: Werner, Stohr ami Hccs (1989)
The optimum biogas production is achieved when the pH value of input
mixture in the digester is between 6 and 7. The pH in a biogas digester is also
a function of the retention time. Methanogenic bacteria are very sensitive to
pH and do not thrive below a value of 6.5. Loading rate is the amount of raw
materials fed per unit volume of digester capacity per day. If the plant is
overfed, acids will accumulate and methane production will be inhibited.
Similarly, if the plant is underfed, the gas production will also be low.
Retention time (also known as detention time) is the average period that a
given quantity of input remains in the digester to be acted upon by the
methanogens. For a night soil biogas digester, a longer retention time
(70-80 days) is needed so that the pathogens present in human faeces are
destroyed. The retention time is also dependent on the temperature.
The methanogens are inactive in extreme high and low temperatures.
The optimum temperature is 35 degrees C. Satisfactory gas production takes
place in the mesophilic range, between 25 degrees to 30 degrees C
(http://www.bioenergy.org.n2/biogas.asp).
Quality and Composition of Human Faeces and Urine
Human excreta consist of faeces and urine. The two are waste
products of the bodily metabolism. The appearance, physical and chemical
characteristics of urine or faeces depend largely on the health of the person
excreting the material, as well as on the amount and type of food and liquid
Design Parameters Parameter Value
pH
Digestion temperature
Retention time (HRT)
Biogas energy content
Gas production per kg of human excreta
Gas requirement for cooking
Gas requirement for lighting one lamp
6-7
20-35
40 - 100 days
6 kwh/m3
0.020-0.028 m3
0.2 - 0.3 m3 person
0.1 -0.15 m3/hr
53
consumed. Therefore, the excreta generated by healthy people eating a
similar diet are quite similar in both physical and chemical composition. In a
study on the composition of human excreta, it was reported that age, sex,
occupation or religion did not affect the chemical composition of the different
fractions. However, a significant variation was that older people excreted
larger amounts of total wet matter than younger, which was linked to a larger
water intake intended to reduce the risk of constipation (Daisy, 2011).
Available human excreta as per age group
It is not surprising that the per capital quantities vary widely. Figures for
collected septate, i.e., fecal sludge stored in septic tanks, can be as low as
0.3 liter/persons/day and as high as 1.31/litres/person/day. Most of the
reported values vary between 0.5 and 1liters/person/day. Based on literature
review, the excreta production per day for an adult is 0.4kg, 10 to 15 years is
0.3kg, 6 to10 years is 0.2kg (Schonning and Stenstrom, 2004).
Night soil based Biogas: Potential of biogas from human waste is 0.07cu.m
per kg in Bangladesh. Guidebooks reported that Biogas generated from
Human excreta is 0.020-0.028 cu.m per kg. The composition of night soil
based biogas is Methane 65-66%, Carbondioxide 32-34%, Hydrogen sulphide
1%, Nitrogen oxide and Ammonia in traces.
Retention Time of Biogas Plants
Water Kiosk comes under the low retention time based biogas plant.
The retention time of this plant is 5 days. But the reduction of BOD
performance is very poor as 30- 40%. Sulabh model, Community latrine cum
biodigester, and BCSIR, are coming under medium retention time based
biogas plant. The retention time of BCSIR is 10 to 15 days. The retention time
of Sulabh is 30 days. The BOD reduction of these two plants is 85%.
The retention time of Community latrine cum biodigester is 21 days.
The retention time of Malaprabha biogas plant is 45 days. It is high retention
time based biogas plant. The Hydraulic Retention Time (HRT) of Latrine cum
bio digester constructed in institutions / communities is 70 days. It ensures
that most of the pathogens are destroyed and have very high retention time.
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Programmes for Promoting Biogas Technology: The Government of
India’s Ministry of Non-Conventional Energy Sources started its biogas
development project in 1981 as one of its programs designed to meet rural
energy needs, especially for cooking.
The objectives of these biogas development programs are to provide
fuel to rural households for cooking, organic manure for application on
agricultural fields, mitigating the drudgery of rural women, and reducing the
pressure on forests. As a result, family-size biogas plants and more than three
thousand community and institution-based biogas plants have been set up in
the country so far. Most of the biogas plants constructed to date, however, are
based on cattle dung as the fuel source. Biogas plants based on night soil
have not yet been established in large numbers. This is due to
the unavailability of night soil at a single location in sufficient quantities
and the fact that the focus for development of biogas technologies has largely
been on technologies using cattle dung as the feedstock
(http://www.mnes.nic.in).
National Project on Biogas Development (NPBD): This project was initiated
during 1981-82 to provide clean cooking fuel and organic manure to the
farmers and other users. The concept of biogas plants has achieved a wide
and excellent appreciation both in rural and urban contexts, but the
performance of the project, methodology adopted for implementation,
technical and administrative support, financial assistance in the form of
subsidy and assistance from public financial institutions have collectively
advanced this program and is rated as “Good”;
This NPBD program is presently being implemented by all the State
nodal agencies, Khadi and Village Industries Commission, (KVIC), National
Dairy Development Board (NDDB), All India Women’s Conference (AIWC);
and Non-Governmental agencies. Incidentally, in some states in the country,
implementation of this program is directly by local rural development
departments/Panchayat/Zilla Parizad and the like, by associating local elected
bodies with these programs. Involvement of local bodies and panchayats is to
be encouraged more to improve the people’s participation and to integrate the
concept and gadgets as an integral part of the daily activity of a common man.
55
Under this National Program, a total of +/-30 lakhs family-size biogas plants
are installed covering 25% of the known potential and +/-3100 large size
biogas plants under institutional, community category. It is also estimated that
over 1.8 million tons of organic manure is recovered from these biogas plants
for agricultural purposes.
Indian Government Support for Waste to Energy: The Indian Government
has recognized Waste to Energy (WtE) as a renewable technology and
supports it through various subsidies and incentives. The Ministry of New and
Renewable Energy is actively promoting all the technology options available
for energy recovery from urban and industrial wastes. MNRE is also
promoting the research on waste to energy by providing financial support for
R&D projects on cost sharing basis in accordance with the R&D Policy of the
MNRE. In addition to that, MNRE also provides financial support for projects
involving applied R&D and studies on resource assessment, technology
up-gradation and performance evaluation.
A number of key statistics, such as the value of recyclables, the
amount of environmental pollution from waste sources, and the quantity of
industrial waste generated, need to be computed to gain a better
understanding of this sector. In terms of research related to waste to energy,
detailed analysis of costs and available funding is needed.
E. Challenges ahead for Future Perspectives
The appropriate technology should reach the people for whom it was
developed. But our country is facing several challenges to reach this goal set.
Social and cultural issues: Myles, (2001) identifies that socio-cultural
issues must be addressed before the implementation as there is a “good
chance of failure, as these technologies are new and alien to rural people”.
It is extremely difficulty to achieve change in excreta disposal practices as
they are part of the basic behavioral pattern of a community and are not
readily modified (Feachem and Cairncross,1978). Chaggu et al. (2002) views
that there is a lack of understanding why the disposal system has to be
changed because of the “lack of perceived benefits” (IRCWD, 1982). The low
education level result in “inadequate financial resources” so the priority is a
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not good excreta disposal when there is competition for financial resources.
According to Strauss et al. (2002) this lack of education level leads a low level
of involvement and without involvement, skills cannot be passed on. This lack
of knowledge and awareness can lead to an unwillingness to use the by-
products (Strauss et al., 2002) decreasing the values. Bates et al. (2007) also
identifies the importance of community involvement to develop a sense of
ownership because without it people will not feel obliged to maintain the plant.
A concern is religious issues over human excreta. Night workers carry
a stigma, Eales (2005) explains that in Kibera residents view this job as illegal
and it is therefore “legitimate to assault those who haul stinking buckets and
drums through narrow alleys.” This leads to working at night because there is
less chance they will be robbed or beaten. Moreover, it is not safe to work in
total darkness in such a dangerous environment. Bates et al. (2007) also
identifies that some communities may see the use of the gas as
unacceptable. A less direct use such as heating water may be a better
application in some societies. Education is also need to explain the hazards of
dumping as Vinneras (2006) explains that at present there is no “real demand
for implementing effective systems for wastewater and faecal sludge
management”. Community wide education would have to combat this issue.
There are also the health issues where “government public health authorities
often oppose excreta re-use because of the health risks involved” (Edwards
and Bater, 1992).
Economic issues: The major issue is the high set-up costs of a biogas
system (Bates et al., 2007). There are labour and material costs associated
with the digesters but also the construction of the gas delivery method.
Hasan et.al (2003) identifies that although decentralized systems do reduce
the cost of investment in comparison to large complex centralized treatment
infrastructure. The social activists projects that majority of government
agencies lack the funds to invest, so it is usual to look to the private sector
Bates et al., 2007., higher levels of government Parkinson and Tayler, 2003.,
or overseas agencies Myles, 2001., to help fund the project. Some labour
costs can be decreased by involving the community who will benefit from
the system providing a sense of ownership and improved maintenance.
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Bates (2007) describes how the system should be sold as a ‘win-win’ situation
to government organizations due to the free clean energy provided and
reduction in waste disposal problems.
The frequency of emptying pits will increase to make this technology
feasible. Strauss et al. (2003) brings forth “unaffordable emptying fees” as a
hindrance to good faecal sludge management. A number of case studies
outline that current emptying causes a burden due to high tariffs. Boot (2006)
explains that in Accra, Ghana the emptying systems are privately run and
have no governmental control over tariffs or disposal points. Where there is
little competition, the operating company charge unaffordable tariffs, whilst
also cutting their own costs by not transporting to a treatment facility and just
dumping it with many practicing the principle of “out of site, out of mind”
(Chaggu, et al., 2002). Increasing the frequency of emptying may be met with
hostility by most users, especially those who do not have a secure tenancy
agreement for their homes who will not want to invest in new wastewater
practices (Parkinson and Tayler, 2003).
Regulation and management: The implementation of decentralized
wastewater treatment system will only be successful if the necessary
knowledge and skills to operate and maintain them are “available at the local
level” (Parkinson and Tayler, 2003). It is necessary to consider the
development of an effective and needs responsive policy towards the issue of
wastewater management. The Household Centered Environment Sanitation
approach provides a framework where the emphasis not on waste as a
burden but as a resource, decisions about implementation start at household
level rising up through community making sure that all users fully understand
what is happening by making the system “Locally organized and people-
driven”. As per the statement Heymans et al. (2004) the community will gain
the necessary skills to operate the technology because they have been
made aware of all benefits that be told to embrace it by government.
Many wastewater systems stop working due to neglect and this kind
implementation will only lead to this situation.
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Critical Issues for Success
Future Perspectives : The literature and the present study demonstrate that it
is possible to use the anaerobic digester to anaerobically treat Night soil when
diluted appropriately. This holds an enormous potential for faecal wastes
treatment in developing countries where majority of sanitation facilities are
on-site systems. However before the system can be adopted on a scale
similar to its acceptance for the treatment of domestic sewage in tropical and
sub-tropical climatic conditions, it will be essential to carry out more
experimental studies. In this regard the following suggestions are made for
further research work:
1. Most of experiments similar undertaken in this research are for lesser
period only. It should be undertaken over a much longer period to establish
steady state conditions that will enable correct assessments of long term
treatment efficiencies, optimal loading rates, optimal hydraulic retention times,
suitable dilution ratio, and gas production potentials among others.
2. During such experiment, efforts should be made to minimise, if not
completely eliminate, the loss of biogas due to leakages and also an analysis
of the biogas produced must be carried out to determine the percentages of
methane and carbon dioxide in the biogas.
3. Production of biogas is significantly affected due to drop in temperature.
Thus, until now, this technology has been of little use in the higher altitude or
cold climate. Therefore, research work needs to be initiated in view of
increasing the efficiency of gas at the cold climate or in higher altitudes.
4. Research efforts should have undertaken to improve the designs of night
soil based biogas plant.
5. Such long term experiments should provide the required information for
optimum design and operation/maintenance guidelines when using the
anaerobic digester for the treatment of night soil. Biogas production is
diminished significantly in cold climate or at higher altitude, while the
methodology for warming the digester to raise the temperature seems
sophisticated, costly and unaffordable to the ordinary people. For example the
59
design propagated in Nepal is costly and no substantial research has been
initiated to lower its cost for wider application of the technology.
6. Several studies carried out in the past have confirmed that there is an
increase in mosquito breeding after the installation of biogas. Therefore,
serious thinking needs to be given to solve this problem because of the fact
that fatal disease like malaria can occur in the community due to unwanted
proliferation of mosquitoes.
7. Still there is less awareness amongst the farming community pertaining to
the utilization of bio-slurry as fertilizer. This aspect appears to be neglected in
the future. Agriculturists and Biogas promoters will be carried out sufficient
demonstrations and experiments to convince the farmers about the added
benefits of slurry as an organic fertilizer compared to Farm Yard Manure.
Public perception and participation: All socially oriented programme
end-up with success once the pulse and perception of public is accounted.
To achieve this, the role of local bodies is so important and to mobilize the
public opinion on the benefits individuals accrue and also collectively
reflecting on the society in larger interest. Educating the public automatically
makes them to participate at every level of technology integration in to the
society. This process can be accelerated by acting on complementary basis
by supporting each other by the local implementing mechanism and program
supporting organization, by identifying the needs and aspiration of local and
accommodating the same by way of extending help in all fronts.
Technology information dissemination: Once, public show and
understands the importance of a scientific program for development, providing
scientific information will be the next priority to stabilize the public perception.
Popular science articles etc play a major role. This can be achieved both by
head quarter of scientific organization and below the hierarchy.
Training local resource personnel: Training local personnel as a human
resource for development is the next step. This helps in calling innovations
from the bottom of the society, to suit local needs and utilization of local
material availability. This aspect of training may be handled by known
60
technical people, institutions, universities or NGO’s and the like. In fact, users
can train prospective users also.
Technical expertise development: For successful implementation, the
technical expertise of the implementing machinery needs to be refurnished at
the level of Panchayat units/Blocks/or the hills. To do so, specially tailored
technical information to suit this level of audience is a must and this can only
be handled by expert institutions or recognized technical back-up units set-up
for this purpose or laboratories associated with respective technologies.
However, lack of proper co-ordination at all levels of the sponsoring scientific
organization and unmindful continuation of useless centers, leads to chaos
and detrimental to the program itself.
Research and Development support: Providing financial support to
institutes associated in popularizing the technologies helps in developing user
oriented, location and raw material specific designs to upgrade the efficiencies
of a given design and penetration of the design in to the society. This
assistance helps in integrating these designs as a part of local social
economic activity by the rural entrepreneurs due to their interaction with R&D
center and this scenario only sustains the best in long run (MNRE, 2004).
Technical and administrative support: The institutional level support
(State level and District level) on the above said subjects and tuning the local
administration to understand the policies of the scientific organization and
providing day to day support in guidance and helping in promoting the
enthusiasm of the upper level staff must be the basic function of the first level
regional centers/offices. These centers must upgrade the technical knowledge
and arrange demonstration, work experience, studies, for the implementing
staff. This can be achieved by conducting workshops, seminars, conferences,
training programs, local meetings and arranging meetings with experts in
respective fields.
Financial assistance: Harnessing of natural energy sources by mankind is
not unknown. However, only in the past hundred years the present civilization
explored all possible methods to convert the energies of various fossil fuels to
suit day-to-day conveniences. The growing insecurity on continuous
61
availability of these fossil fuels made policy makers to harness energy from
natural sources in a systematic way to suit the present life styles. This was the
beginning of developing the designs to tap energy content from Solar and its
other forms. This naturally necessities to grant subsidies or other forms of
financial incentives to popularize these technologies (Linares and
Rosenweig, 1999).
Intervening Factors: For successful implementation of renewable energy
technologies, depending on the scale of operations, various intervening
factors also play their respective roles. These factor needs to be carefully
examined.
Technological Interventions: Technology driven approach to developmental
activities is a serious technological intervention. In fact, location specific, user
friendly and cost effective technologies penetrate the society faster than
complex systems involving complex activities (Lal, 2008). Frequent
introduction of new designs, changing certain parameters in the middle of the
program implementation, to accommodate gadgets not tested earlier and the
like, will have adverse effect on the success of the program.
Policy Changes: Frequent changes in the program implementation
brought-in due to modification in fiscal incentives, and operational parameters
of a program will have adverse effect on the success. Always, it is advisable
to notify and approve scientific program for at least three years to last without
any major changes. This helps and assures various segments of program
implementation to act and plan on a strong footing. Frequent changes also
indicate lack of clarity on the strengths of the program and on its positive
impact on the society (Mahalingam, 2011).
Political Interventions: Interference of politicians, information of program,
awarding subsidies etc., to suit their interest always felt detrimental to the
organisation itself. This kind of political interference forces scientific
organisation to adopt wait and see policy and fear of being victimized.
Also frequent changes of governing bodies also affect the working
atmosphere of the organisation, though the core programs go on without must
changes and become a routine and casual (Majumdar, 2006). At the same
62
time, if the political will is weak and heavily depends on coterie the out come
will be more disastrous. Similarly, though political will is strong, helpful, but not
able to withstand the tactical plan and vicious nature of the techno-
administration also yields no results.
Impediments in transforming and technology to the p ublic
• to get maximum support from the community, involvement of people in
technology development, transfer and monitoring should be made an
integral part of the process.
• a network of appropriate technology agencies should be established for
sharing regional and geographical responses to specific technologies.
• success stories and ‘failures’ need to be documented for further
research on the subject. Inter-regional exchanges on the subject will
help trigger the process.
• the list of proven and available appropriate technologies need to be
enlarged by getting some of the time-tested traditional technologies
(wisdom) into the list.
• there is a need to integrate traditional wisdom into the process of
technology development and dissemination. Traditional artisans and
craftsman should always be taken into account while planning
interventions.
• research and development be given priority for engineering products
that can withstand the changing market scenario and compete with the
products of modern technology.
• information on appropriate technology must be made available to
potential users. If needed, multi-media approach may be followed for
making the products of appropriate technology as popular as other
consumer products.
• use of folk art, folk media should be a good medium for effective
dissemination of technologies.
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• direct marketing of products should be encouraged through ‘village
fairs. Even ‘rural technology shops’ can be opened in selected places
in the country.
• efforts must be directed to get the planners and the government
interested in the products of appropriate technologies. Interventions for
getting policy directives must be attempted.
• periodic meetings on specific themes will help understand the process
better and will strengthen the appropriate technology movement which
is currently in the process of phasing out.