Energy plays a crucial role in diverse processes and activities that take place in the society. Energy is a complex process as it is possible to convert it into different forms, transport it, store it in some forms and use it in various end use modes in numerous places. Most of the energy sources are substitutable to each other due to the fact that some form of energy can be converted to other form (Ramachandra, 2003). The burgeoning population coupled with developmental activities based on ad-hoc decisions has led to resource scarcity in many parts of India. Energy demand is increasing and its inability to step up production to meet demand, has increased India's reliance on costly imports, the gap between consumption and production projected to widen into the next century, as demand for energy is projected to grow at an annual rate of 4.6%- one of the highest in the world (Ramachandra et al., 2006). Present fossil fuel potential is unable to meet the growing demands of the society. In an attempt to stem the projected deficit between production and consumption, particularly for the increasing residential sector, which accounts for approximately 10% of total energy use and provide for an expanding rural sector, the government is pursuing alternative measures of energy provision. Post oil crises shifted the focus of energy planners towards renewable resources and energy conservation. Biomass is one such renewable, which accounts for nearly 33% of a developing country's energy needs. In India, it meets about 75% of the rural energy needs. In Karnataka, non-commercial energy sources like firewood, agricultural residues, charcoal and cow dung account for 53.2%. Renewable energy potential is high on the subcontinent and rational decision-making at disaggregated levels is necessary to eliminate wasteful use of resources (Ramachandra and Shruthi, 2007).
Detailed planning would be required from National, to State, to District, to Taluk and Village levels. The inappropriate selection and site matching of species or management strategies can have adverse effects and lead to the degradation and abandonment of land. However, the correct selection of plant species can allow the economic production of energy crops in areas previously capable of only low plant productivities. Simultaneously multiple benefits may accrue to the environment. Such selection strategies allow synergistic increases in food crop yield and decreased fertiliser applications while providing a local source of energy and employment.
Rural population of India still depends on the traditional devices for cooking and water heating, space heating, which is energy inefficient, leading to excess consumption of local resources. Lack of information about the resources and technologies may be cited as the reason for this situation. This necessitates the understanding of the present energy consumption pattern and exploring locally available alternative energy sources in order to ensure resource sustainability. Cattle dung is predominantly being used in rural area either for preparing farmyard manure by composting it or directly preparing dung cakes for burning as cooking fuels. Preparation of cakes and burning are highly uneconomical and unhygienic. In this context, anaerobic digestion of animal residues not only provides valuable cooking fuel, in the form of biogas and enhances the manure value of the waste but also provides a convenient, safe and aesthetic waste disposal method.
In this study, the biogas resource base in Kolar District in Karnataka State, India is analysed villagewise andtalukwise. This entails spatial analysis of resources, necessitating the usage of spatial technologies such as GIS. This would help the planners at disaggregated level (villages) to implement development programmes to meet the daily requirement of energy. This analysis is replicable to any region across the globe. Geographical Information System (GIS) is an information system that is designed to work with data referenced by spatial or geographic coordinates used to map spatially the resources and demand. It helps to efficiently store, manipulate, analyse and display spatial data according to the user specifications. Maps provided by GIS reveal the spatial patterns that cannot be captured by conventional methods such as tables and histograms. GIS integrates common database operations, such as query and statistical analysis, with the spatial data (maps). These abilities distinguish GIS from other information systems and make it valuable to a wide range of public and private enterprises for planning strategies and managing infrastructure in a region.
Energy and biogas potential of livestock residues of all major groups of stock-raising animals (cattle, buffalo, sheep, goat) can be evaluated using GIS. GIS based database management system is superior over conventional methods for estimation of biogas potential from livestock residues as temporal information (such as number and type of livestock, dung yield) can be incorporated into spatial databases. GIS provides the area of the region of interest, which can be used for calculating livestock density and dung yield and hence the biogas potential can be estimated. The GIS layer containing such information is useful to identify regions of extensive availability of dung for biogas generation. Biogas from plant and animal wastes is a viable energy alternative to meet the growing demand in rural areas for domestic and agricultural activities. Biogas technology has made inroads in rural economy in many districts (such as Uttara Kannada, Udupi, Shimoga) in Karnataka state during the last two decades due to economic viability, ecological soundness, technical feasibility and social acceptance.
Biogas is produced by biological decomposition of organic material in the absence of air. The conversion of animal waste and agricultural residues to biogas through anaerobic digestion processes can provide added value to farm livestock manure as an energy resource. Since the 90's, India has supported projects involving studies related to the generation of renewable energy. To that effect, a series of strategies and political initiatives have been built to support research and for the generation and utilization of this type of energy, which have favored programs of sustainable development in the country. In this context the biogas technology (anaerobic digestion) has gained importance (Chanakya et al.,2007) .
The potential of biogas from agricultural residues and dung from India's 300 million cattle is approximately estimated at 17,000 MW. Biogas technology is a particularly useful system in the agro-ecosystems and can fulfill several end uses. The gas is useful as a fuel substitute for firewood, agricultural residues, electricity, etc. depending on the nature of the task and local supply conditions and constraints, thus supplying energy for cooking and lighting. Biogas systems also provide a residue organic waste, after anaerobic digestion that has superior nutrient qualities over the usual organic fertilizer, cattle dung, as it is in the form of ammonia. Small-scale industries are also made possible, from the sale of surplus gas to the provision of power for rural-based industries, which may also provide the user with income generating opportunities. The gas can also be used to power engines, in a dual fuel mix with diesel (http://mnes.nic.in/achl .htm) and can aid in pumped irrigation systems.
Apart from the direct benefits gleaned from biogas systems, there are other, perhaps less tangible benefits associated with this renewable technology. By providing an alternative source of fuel, biogas can replace the traditional biomass based fuels, notably wood. Introduced on a significant scale, biogas may reduce the dependence on wood from forests and create a vacuum in the market, at least for firewood. With 70% population still in rural areas, there is tremendous demand on resources such as fuelwood, agricultural residues, dung cake, etc. to meet the fuel requirements for cooking, water heating and space heating (during winter). Dependence on bioresource to meet the daily requirement of fuel, fodder in rural areas is more than 85% in many rural districts in India (Ramachandra et d., 2004).
India is a pioneer in the field of developing technology for biogas production from animal residues (dung) since mid 90's. About 70,440 plants have been completed during the period April to December 2002, which is almost 117 per cent over the target of 60,000 plants planned for the corresponding period (MNES Annual Report, 2003). Animal dung is a potentially large biomass resource and dried dung has the same energy content as wood. When burned for heat, the efficiency is only about 10%. About 150Mt (dry) of cow dung are used for fuel each year across the globe, 40% of which is in India. But dung is readily recoverable only from confined livestock or in settings where the labour costs associated with gathering dung are modest. The efficiency of conversion of animal residues could be raised to 60% by digesting anaerobically (to produce biogas). Biogas production will also resolve the conflict between energy recovery and nutrient utilisation as the effluent from the digester could be returned to the fields.
Biogas has a higher healing value than producer gas and coal gas, which implies increased services. As a cooking fuel, it is economical and extremely convenient. Based on the effective heat produced, a 2 m3 biogas plant could replace, in a month, fuel equivalent of 26 kg of LPG (nearly two standard cylinders), or 37 litres of kerosene, or 88 kg of charcoal, or 210 kg of fuelwood, or 740 kg of animal dung. Also biogas has no danger of health hazards, offensive odour and burns with clean bluish soot less flame thereby making it non-messy to cooking utensils and kitchens. In terms of cost, biogas is more economical, on a life cycle basis, than conventional biomass fuels (dung cakes, fuelwood, crop wastes) as well as LPG and is only fractionally more expensive than kerosene; the commercial fuels like kerosene and LPG, however, have severe supply constraints in the rural areas (Soma et a/., 1997). Biogas technology enhances energy supply decentralization, thus enabling rural areas meet their energy requirements especially when the commercial fuels are inaccessible for their use. A comparison of directly using the dung and its use as biogas shows a 25 kg fresh dung would give about 5 kg of dry dung, which is equivalent to one m3 of biogas. Comparative analysis of direct burning and biogas considering various parameters are listed in Table 1.
Biogas is basically methane (CH,) produced through the anaerobic fermentation of dung and other organic wastes. Besides methane, biogas also contains carbon dioxide and traces of nitrogen, sulphur and moisture. Biogas production is primarily a microbial process wherein the carbohydrates in the organic matter break down in the absence of oxygen. The methane content in the gas produced depends on the feedstock. The gas production is also influenced by temperature, acidity, solid content and C/N ratio. A temperature of 35°C-40°C, pH range 6.6-7.5, solid content of 7-9% and C/N ratio of 25:1-30:1 are considered optimum (Chanakya et al., 2007). Animal residue has a solid concentration of 20% and therefore to attain the desired value of 7-9%, it is mixed with water (1:1). It also has a C/N ratio of 25:1 (the ratio varies for different raw materials) and thus is an ideal choice as it meets most of the requisites for optimum gas production. A kilogram of dung produces 40 L of biogas and a family size biogas plant (2-4 m3) requires 50 kg of dung and equal amounts of water to produce 2000 L of gas/day, which would be sufficient for cooking purposes in a family of 4-5. The calorific value of biogas is obtained by multiplying that of methane with the volume fraction of methane in biogas. The calorific value of methane is 8548 Kcal m~3 (Ravindranath and Hall, 1995; http://www.teriin.org/).
For several decades, biogas has been promoted as an appropriate rural technology, enabling an effective utilization of a local resource. It is a clean and convenient fuel at low cost, besides being environmentally friendly. Women no longer have to spend hours away from their homes, traveling (often long) distances to collect wood for cooking and heating, they can free up valuable time for activities, which they would otherwise be unable to do. A smoke-free and ash-free kitchen means women are no longer prone to lung and throat infections and can look forward to a longer life expectancy. It is suitable for practically all the fuel requirements in the household, agriculture and industrial sectors. For instance, domestically, it can be used for cooking, lighting, water heating, running refrigerator, water pumps and generators. Agriculturally, it can be used on farms for drying crops, pumping water for irrigation and other purposes. An important benefit of the technology is saving on fuel wood. Construction of biogas plants also creates good employment opportunities in rural areas. The use of biogas plant produces fuel as well as fertilizer, while only one of these is possible if dung is used as it is. The greatest advantage of biogas plants is that they can digest almost any constant (wet) mixture of city waste, manure and plant residues due to complex bacterial process involved. It dose not reduce the ammonia nitrogen content from livestock manure during anaerobic process and kills all the pathogens and weed seeds.
While the overall impacts of the biogas programme have been appreciable, there are several aspects, which need to be strengthened and streamlined further to enhance effectiveness. There are several technical, economical and institutional barriers, which hinder the dissemination of biogas development in India (Soma et al., 1997). Most of these barriers are interlinked and often have a cause-and-effect relationship with each other. The barriers in biogas dissemination programme could be categorized as:
Total energy generation potential from the anaerobic digestion of industrial wastewater in India is estimated to be 2963 GWh/a equivalent electric energy by Kusum et al. (2002). The study indicates a potential of 565 MW plant installations with anaerobic digestion technology. The pulp and paper industry has the maximum potential among others of the order of 1131 GWh/a followed by distillery with a contribution of 830 GWh/a to a total potential of 2963 GWh/a equivalent electric energy.Purohit et al. (2002) explored the renewable energy option for domestic cooking in India. The estimate shows 38 million family size biogas plants in the optimistic scenario and 29 million in the realistic scenario based on 1991 statistics on the bovine population and ownership pattern. In the optimistic scenario a total of about 65 million m3 of biogas can be produced daily using bovine dung at the household level with about 38 million (about 18.5 million of 1 m3, 12.1 million of 2 m3 and 7.4 million of 3 m3 capacity biogas plants). The realistic scenario estimates are 19.3 million 1 m3 biogas plants, 6 million 2 m3 biogas plants and 4 million 3 m3 biogas plants totaling to about 29.3 million biogas plants capable of producing about 43.4 million m3 biogas everyday. In both the scenarios the potential number of 1 m3 biogas plants is far larger than the combined potential 2 and 3 m3 biogas plants. With a properly maintained 1 m3 biogas plant it may be possible to meet a major fraction of the domestic cooking requirement of a family of three to four adult members during most of the year. Village level domestic energy consumption pattern across coastal, interior, hilly and plain zones considering regional and seasonal variation for Uttara Kannada District, Karnataka, India show that biogas for cooking ranges from 0.276 to 0.775 nf/person/day. 1304 households were surveyed among which only 18 households used biogas for cooking where, 2 households were from low income category, 9 from middle and 7 from high income category. Biogas consumption ranges from 0.200 (low income) to 0.596 (high income) mVperson/day. Households using biogas for cooking also uses kerosene to supplement their cooking fuel requirements (Ramachandra et al., 2000a). Energy and biogas potential of livestock residues of all major groups of stock-raising animals were evaluated using ABEPE (Animal (data)Base for Energy Potential Estimation), a GIS based biomass resource assessment application using a relational database management system. The estimated biogas production and energy potential as forecasted through ABEPE for the year 2010 is 423.6 million m3 and 9148 TJ respectively (Batzias et al., 2005). Ecologically sound development of the region is possible when energy needs are integrated with environmental concerns at local and global levels, for which an integrated planning framework would be necessary. A GIS based decision support system would provide the planner a receptive and efficient tool to analyse and visualize spatial and temporal data. This would help in formulation of an integrated planning framework necessary for the ecologically sound development. Currently, energy planning in India is not an integrated activity. Since there are many energy sources and end uses, many organisations and agencies deal with different aspects of energy. The current approach to planning in the energy sector does not offer any significant role to the district or local level institutions. Moreover, the coordination needed between the energy sector and the overall planning and development at district (Federal State is divided into districts for administrative purposes), taluk (a district is divided into taluks) and village (a taluk is divided into villages) levels is missing. Although the forest department carries out forestry planning, its most significant aspect pertaining to energy is extremely weak and receives very little attention in the planning exercises of the sector. The biomass situation in hilly taluks has, therefore, gradually worsened and has reached a point of crisis (Ramachandra, 2003). This deteriorating situation obviously demands immediate attention in two directions.