Biogas Technology for Rural Development

Abstract

The utilization of microbial activity to treat agricultural, industrial, and domestic wastes has been common practice for a half century. In recent years, biogas systems have attracted considerable attention as a promising approach to decentralized rural development. Developed and developing countries and several international organizations have shown interest in biogas systems with respect to various objectives: a renewable source of energy, bio-fertilizer, waste recycling, rural development, public health and hygiene, pollution control, environmental management, appropriate technology, and technical cooperation. This paper provides an overview of biogas technology and opportunities to use this technology in livestock facilities across the ruler area. First, a brief description of biogas technology is provided. Then the benefits of biogas technology are discussed. Finally, the experience and status of biogas technology development in the India are described.

Keywords- Biogas, Fermentation, Methane, Rural Energy, Renewable Energy

 

1.      Introduction

Developing-country rural areas have a variety of available biomass materials, including fuel wood, agricultural wastes, and animal wastes. In particular, many countries have large cattle and buffalo herds, whose considerable wastes have much energy potential. Traditionally, these wastes are carefully collected in India and used as fertilizer, except in places where villagers are forced by the scarcity of fuel wood to burn dung-cakes as cooking fuel. Since biogas plants yield sludge fertilizer, the biogas fuel and/or electricity generated is a valuable additional bonus. It is this bonus output that has motivated the large biogas programmes in a number of developing countries, particularly India

Rural energy planning requires choices among energy technologies. Up to the day, the choices have been confined to centralized energy supply technologies - power plants based on hydroelectricity, coal, oil, or natural gas. The problem is local and global environmental degradation. It has, therefore, become essential to extend the list of technological alternatives for energy decision-making to include decentralized sources of supply.

          

2.      Biogas

Biogas is actually a mixture of gases, usually carbon dioxide and methane. It is produced by a few kinds of microorganisms, usually when air or oxygen is absent. (The absence of oxygen is called "anaerobic conditions.") Animals that eat a lot of plant material, particularly grazing animals such as cattle, produce large amounts of biogas. The biogas is produced not by the cows themselves, but by billions of microorganisms living in their digestive systems. Biogas also develops in bogs and at the bottom of lakes, where decaying organic matter builds up under wet and anaerobic conditions.

Besides being able to live without oxygen, methane-producing microorganisms have another special feature: They are among the very few creatures that can digest cellulose, the main ingredient of plant fibres. Another special feature of these organisms is that they are very sensitive to conditions in their environment, such as temperature, acidity, the amount of water, etc.

Methane, which is the main constituent a colourless, odourless, inflammable gas, it has been referred to as sewerage gas, klar gas, marsh gas, refuse-derived fuel (RDF), sludge gas, will-o'-the-wisp of marsh lands, fool's fire, gobar gas (cow dung gas), bioenergy, and "fuel of the future." The gas mixture produced is composed roughly of 65 percent CH₄, 30 percent CO₂, and 1 per cent H₂S. A thousand cubic feet of processed biogas is equivalent to 600 cubic feet of natural gas, 6.4 gallons of butane, 5.2 gallons of gasoline, or 4.6 gallons of diesel oil. For cooking and lighting, a family of four would consume 150 cubic feet of biogas per day, an amount that is easily generated from the family's night soil and the dung of three cows. In addition, rural housewives using the biofuel are spared the irritating smoke resulting from the combustion of firewood; cattle dung cakes, and the detritus of raw vegetables

3. History of Biogas

People have been using biogas for over 200 years. In the days before electricity, biogas was drawn from the underground sewer pipes in London and burned in street lamps, which were known as "gaslights." In many parts of the world, biogas is used to heat and light homes, to cook, and even to fuel buses. It is collected from large-scale sources such as landfills and pig barns, and through small domestic or community systems in many villages.

The decomposition breaks down the organic matter, releasing various gases. The main gases released are methane, carbon dioxide, hydrogen and hydrogen sulphide. Bacteria carry out the decomposition or fermentation. The conditions for creating biogas have to be anaerobic that is without any air and in the presence of water. The organic waste matter is generally animal or cattle dung, plant wastes, etc. These waste products contain carbohydrates, proteins and fat material that are broken down by bacteria.  The waste matter is soaked in water to give the bacteria a proper medium to grow. Absence of air or oxygen is 

important for decomposition because bacteria then take oxygen from the waste material itself and in the process break them down.

4. Biogas is a Form of Renewable Energy

Flammable biogas can be collected using a simple tank, as shown here. Animal manure is stored in a closed tank where the gas accumulates. It makes an excellent fuel for cook stoves and furnaces, and can be used in place of regular natural gas, which is a fossil fuel. Biogas is considered to be a source of renewable energy. This is because the production of biogas depends on the supply of grass, which usually grows back each year. By comparison, the natural gas used in most of our homes is not considered a form of renewable energy. Natural gas formed from the fossilized remains of plants and animals-a process that took millions of years. These resources do not "grow back" in a time scale that is meaningful for humans

Biogas generation cycle

There are two types of bio gas plants that are used in India. These plants mainly use cattle dung called “gobar” and are hence called gobar gas plant. Generally a slurry is made from cattle dung and water, which forms the starting material for these plants.

The two types of bio gas plants are
1. Floating gas-holder type

2. Fixed dome type

                Floating gasholder type of plant: The diagram below shows the details of a floating gasholder type of bio gas plant. A well is made out of concrete. This is called the digester tank T. It is divided into two parts. One side has the inlet, from where slurry is fed to the tank. The tank has a cylindrical dome H made of stainless steel that floats on the slurry and collects the gas generated. Hence the name given to this type of plant is floating gas holder type of bio gas plant. The slurry is made to ferment for about 50 days. As more gas is made by the bacterial fermentation, the pressure inside H increases. The gas can be taken out through outlet pipe V.  The decomposed matter expands and overflows into the next chamber in tank T.  This is then removed by the outlet pipe to the overflow tank and is used as manure for cultivation purposes.

5. Energy in Biogas

               

                The main problem in the economic evaluation is to allocate a suitable monetary value to the non-commercial fuels, which have so far no market prices. For the majority of rural households biogas is primarily a means of supplying energy for daily cooking and for lighting. They use mainly firewood, dried cow dung and harvest residues as fuel. But even if the particular household does not purchase the required traditional fuel, it's value can be calculated with the help of fuel prices on the local market. Theoretically, the firewood collector of the family could sell the amount that is no longer needed in the household

                As an example, the rural households in India use the following quantities of non-commercial fuel per capita daily:

                                - firewood: 0.62 kg

                                - dried cow dung: 0.34 kg

                                - harvest residues: 0.20 kg

For rural households in the People's Republic of China the daily consumption of

                firewood is similar: between 0.55 - 0.83 kg per person.

                Which sources of energy have been used so far and to what extent they can be replaced must be determined for the economic evaluation of biogas by means of calorific value relations. The monetary benefits of biogas depend mainly on how far commercial fuels can be replaced and their respective price on the market.

                1 m3 Biogas (approx. 6 kWh/m3) is equivalent to:

                                Diesel, Kerosene (approx. 12 kWh/kg) 0.5 kg

                                Wood (approx. 4.5 kWh/kg) 1.3 kg

                                Cow dung (approx. 5 kWh/kg dry matter) 1.2 kg

                                Plant residues (approx. 4.5 kWh/kg d.m.) 1.3 kg

                                Hard coal (approx. 8.5 kWh/kg) 0.7 kg

                                City gas (approx. 5.3 kWh/m3) 1.1 m3

                                Propane (approx. 25 kWh/m3) 0.24 m3

 

6. The Benefits for Biogas

               

                Individual households judge the profitability of biogas plants primarily from the monetary surplus gained from utilizing biogas and bio-fertilizer in relation to the cost of the plants. The following effects, to be documented and provided with a monetary value, should be listed as benefits: expenditure saved by the substitution of other energy sources with biogas.

                If applicable, income from the sale of biogas; expenditure saved by the substitution of mineral fertilizers with bio-fertilizer. Increased yield by using bio-fertilizer. If applicable, income from the sale of bio-fertilizer; savings in the cost of disposal and treatment of substrates (mainly for waste-water treatment); time saved for collecting and preparing previously used fuel materials (if applicable), time saved for work in the stable and for spreading manure (if this time can be used to generate income). Monetarizing individual benefits The economic evaluation of the individual benefits of biogas plants is relatively simple if the users cover their energy and fertilizer demands commercially. In general, the monetary benefits from biogas plants for enterprises and institutions as well as from plants for well-to-do households should be quite reliably calculable. These groups normally purchase commercial fuels e.g. oil, gas and coal as well as mineral fertilizers. In industrialized countries, it is common practice to feed surplus electric energy, produced by biogas-driven generators, in the grid. Biogas slurry is a marketable product and the infrastructure allows it's transport at reasonable cost. Furthermore, treatment of waste and waste water is strictly regulated by law, causing communes, companies and farmers expenses which, if reduced with the help of biogas technology, are directly calculable benefits. In contrast, small farmers in developing countries collect and use mostly traditional fuels and fertilizers like wood, harvest residues and cow dung. No direct monetary savings can be attributed to the use of biogas and bio-fertilizer. The monetary value of biogas has to be calculated through the time saved for collecting fuel, the monetary value for bio-fertilizer through the expected increase in crop yields. Both in theory and in practice, this is problematic. In practice, a farmer would not value time for fuel collection very highly as it is often done by children or by somebody with low or no opportunity costs for his/her labor. In theory, it is difficult to define the value of unskilled labor. Similarly, the improved fertilizing value of biogas slurry will not be accepted by most farmers as a basis for cost-benefit analysis. They tend to judge the quality of slurry when counting the bags after harvest. Because a monetary calculation is not the only factor featuring in the decision to construct and operate a biogas plant, other factors come in which are less tangible: convenience, comfort, status, security of supply and others that could be subsumed under 'life quality'. Acceptance by the target group Besides the willingness and ability to invest considerable funds in biogas technology, there is a complex process of decision making involved when moving from traditional practices to a 'modern' way of producing fertilizer and  acquiring energy. Hopes and fears, expected reactions from the society, previous experiences with modern technology, all these feature in a decision. For a biogas program, it is important to realize that economic considerations are only part of the deciding factors in favor or against biogas technology. All these factors can be subsumed under acceptance. Acceptance is not a collection of irrational, economically unjustifiable pros and cons that a biogas extension project is called upon to dissolve. Rural households, as a rule, take rational decisions. But rural households and biogas programs often have information deficits that lead to non-acceptance of biogas technology by the target groups. Bridging this information gap from the farmer to the project and vice versa is a precondition for demonstrating the economic viability in a way that is understandable, relevant and acceptable to the farmer.

 

7. Biogas programs

               

                Biogas programs, however, should not neglect the argument of improved yields.

Increases in agricultural production as a result of the use of bio-fertilizer of 6 - 10 % and in some cases of up to 20 % have been reported. Although improved yields through biogas slurry are difficult to capture in a stringent economic calculation, for demonstration and farmer-to-farmer extension they are very effective. Farmers should be encouraged to record harvests on their plots, before and after the introduction of biogas. Statements of farmers like: "Since I use biogas slurry, I can harvest two bags of maize more on this plot" may not convince economists, but they are well understood by farmers.

                As mentioned earlier, to tap the potential of various renewable resources of energy, a variety of technology dissemination programmes are being implemented by the government in active collaboration with NGOs (non-governmental organizations), like TERI. In the last two decades, complexities in rural energy planning have been seriously considered and linked with overall development planning by way of decentralized planning. Programmes are being implemented at block level, such as the IREP (Integrated Rural Energy Programme), which was coordinated by the Energy Cell of the Planning Commission. The MNES earlier started with village-level planning and implementation of projects. Later, it attempted to develop a methodology for district-level energy planning in select districts of the country. In order to be more effective in implementation as well as administration of energy activities, the MNES has now chosen to devise energy plans at the block level. The studies are being undertaken in select 100 blocks in different states.

8. Conclusions-

    Biomass is available all round the year. It is cheap, widely available, easy to transport,
store, and has no environmental hazards.
 It can be obtained from plantation of land having no competitive use.
 Biomass-based power generation systems, linked to plantations on wasteland, simultaneously address the vital issues of wastelands development, environmental restoration, rural employment generation, and generation of power with no distribution losses.
 It can be combined with production of other useful products, making it an attractive
byproduct.

Biogas, although typically used for heating and cooking, can also be used to fuel a genset to produce electricity. 3.4 million biogas digesters are in daily use in India, and smaller