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In view of the fact that biomass supports nearly 85 % of the rural population's need for food, fodder and fuel, feasible technological and management options need to be implemented to cater to their demands in a sustainable manner. Some of the options are to increase the supply of biomass energy resources by the optimization of land use at micro level and intensive cultivation of energy plantations and the other is the dissemination of efficient biomass based energy devices. The first option is discussed below:
The State has about 812420 ha of barren land and 1636646 ha of fallow land (current and others) and 436589 ha of cultivable wasteland. The taluk wise figures of wastelands are given in the annexure. These lands can be utilized for energy plantations especially in the bioresource deficit zones- Agro-climatic zones 1, 2, 3, 5, 6 and 8.
The need for stepping up biomass resources has paved way for a variety of programmes like social forestry, community forestry, agro forestry and joint management of forests. The forthcoming section provides insight into such schemes that can be successfully incorporated in reclaiming the neglected wastelands for bioenergy.
Wasteland can be defined as the areas where current biomass production seldom exceeds 20% of its overall management. On the basis of ecological constraints they are the lands that are ecologically unstable and whose topsoil has been completely lost. This includes all those lands, which are affected by erosion (wind and water), floods, water logging, salinity and alkalinity and sand deposition. The National Remote Sensing Agency defines wasteland as the degraded land which can be brought under vegetative cover with reasonable effort, and which is currently under-utilized and deteriorating for lack of appropriate water and soil management or on account of natural causes.
Wastelands would primarily consist of cultivable and uncultivable areas. Cultivable wasteland includes all lands available for cultivation, whether taken up for cultivation or not taken up for cultivation once, but not cultivated during the current year and the last five years or more in succession (ICAR, 1980). The land potentiality is generally good and only marginal efforts are needed for its development . Cultivable wasteland would comprise of gullied and/or ravenous land, undulating land, surface waterlogged land and marsh land, salt affected land, shifting cultivation area, degraded forest land, degraded non-forest plantation, sandy area, mining and industrial wasteland, strips land and pasture and grazing land. Barren and uncultivable wasteland covers all those categories of lands, including mountains, deserts, etc. which cannot be brought under cultivation, except at a high cost (ICAR, 1980).
The overall objective of development of such lands should be the improvement and stabilization of soil and water regime, especially in soil eroding areas, to an optimum level. This will support the plantation of suitable trees for fuel, fodder and small timber; agro-forestry practices, and prevents the further extension of the already existing wastelands.
For the optimum utilization of such degraded lands by energy plantation, choice of the appropriate species specific to the agro climatic zone is required. Of all the factors in an agro climatic zone, the soil characteristics are critical. Salt content particularly sodium concentration, pH, texture, porosity, nature and content of organic matter, soil depth and water table influence root penetration and thus the biomass production. The appropriate choice of tree and shrub species in relation to habitat is of decisive importance in afforestation programmes. Inherent characters of survival and adaptability to specific wasteland sites are important parameters for both species selection. Species of Acacia, Prosopis, and Zizyphus are widely distributed in wastelands. The chosen species should be such that they require low input of water, fertilizer and protection measures. They should serve multipurpose and have higher regeneration potential and coppicing ability even under competition. Species having higher nitrogen fixing ability is preferred as high density and short rotation will cause a high drain of nutrients from the soil, with hardly any litter available for recycling. It would be desirable to have germplasm collection of all the relevant species and their variants for the purpose of location-specific adaptability trials.
The soils in the coastal region are sandy, slightly alkaline and poor in nutrients. Casuarina can be used as the main species used for fixing the sands. A wide strip of Casuarina plantation along the coast also acts as a shelterbelt. The wastelands of the coastal zone can be afforested using species like Acacia auriculiformis, Anacardium occidentale, Borassus flabellifer, Casuarina equisetifolia, Cocos nucifera and Thespesia populnea .
The arid and semi-arid areas like the dry zones (zones 1-8) where the rainfall is uncertain, the moving winds dislodge the soil particles and transport them to considerable distances. The climate of the arid region is characterized by extremes of temperature variations. The soils in these areas are of purely mineral type with low organic matter and less fertility. High accumulation of salts and poor water holding capacity render these soils unproductive. Shrub species like Prosopis juliflora can grow on calcareous soils with pH between 9 and 10 and soluble salt content up to 0.54 percent. It is effective in reducing soil pH. Acacia grows well on soils with pH above 9. Azadirachta indica, Dalbergia sissoo, Pongamia pinnata, Terminalia arjuna grow well on soil with pH 8.3 and soluble salt up to 0.15 percent in the top 60 cm soil. Eucalyptus teriticornis grows well on soils with pH 9 and soluble salt content up to 0.3 percent. The performance of various species on saline lands have shown that Acacia nilotica, Prosopis juliflora, Azadirachta indica and Albizzia procera are more suitable than any other species. The above-mentioned species can be used to reclaim the wastelands of the dry zones (1-8).
Besides agro climatic factors, the management of wastelands for bioenergy purpose will also depend on the people, their socio-economic conditions and infrastructural development in the proposed region. Hence an integrated approach needs to be formulated inclusive of the above-mentioned factors for the successful implementation of projects related to wasteland reclamation. Some of the aspects that need to be studied prior to the initiation of wasteland development projects are given below:
• Identification and classification of wastelands in terms of various factors responsible for their formation and growth
• Existing inadequacies in wasteland information should be overcome by building a reliable database through field surveys
• Thorough knowledge regarding the physio-chemical properties of the soil of wasteland
• Careful selection of multipurpose trees suitable for the agro-climatic zone for afforestation and energy plantation
• Create public awareness and encourage people's participation in such programmes and;
• Constant monitoring and follow up actions once the project is initiated.
Wasteland reclamation can also be integrated with social forestry, community forestry and joint forest management schemes. Some of these afforestation programmes are discussed below.
Productivity, sustainability and adaptability are the three main attributes of an ideal agro forestry system. The prime objectives of agro forestry systems are biomass production, soil conservation, soil improvement, agro-based village industries and moderation of microclimate (Nair, 1991). The important criteria for the selection of trees in agro forestry involve many parameters like fast growth, response to management practices, compatibility with associated crops and nitrogen fixing ability. Identification of tree species for plantations was taken up seriously during 1976 when at the national level a list of different climatic regions was published by the Government. A list of potential multi purpose species for different edaphic situations is given below.
Soil Type |
Tree / shrub species |
Acidic soils |
Albizia falcataria, A.procera, Acacia auriculiformis, Gmelina arborea |
Sandy arid |
Prosopis cineraria, Prosopis juliflora, Acacia tortillas, Zizyphus mauritiana |
Coastal sandy |
Prosopis juliflora, Casuarina equisetifolia, Anacardium occidentale |
Poorly drained soil |
Eucalyptus camaldulensis, Albizia procera, Terminalia arjuna, Acacia nilotica, Syzygium cumini and Casuarina equisetifolia |
Alluvial soils |
Acacia nilotica, Azadirachta indica, Dalbergia sissoo, Eucalyptus teriticornis, Leucaena leucocephala, Mangifera indica |
Calcareous soils |
Acacia nilotica, Albizzia lebbeck, Azadirachta indica |
Saline soils |
Acacia nilotica, Acacia tortilis, Prosopis juliflora, Albizia procera and Terrminalia arjuna |
Shallow gravelly soils |
Albizia amara, Zizyphus mauritiana, Hardwickia binata, Anogeissus pendula |
The choice of multi purpose species for agro forestry should be based on the agro climatic conditions. Special attention needs to be given for nitrogen fixing species like Acacia, Casuarina, Dalbergia, Leucaena Prosopis, Sesbania and Robinia. Agro forestry system with its multi species, multifunction and multi product nature provides a wide range of social, economic and environmental benefits. The success of such ventures is dependent on the environmental, political, social and cultural factors of the region. Identifying the unique aspects of the local conditions, cultural values and environmental situations can better respond to people's need, increase their participation and lead to increased chances of tree planting.
Social forestry is yet another option for reclamation of degraded lands and also to meet the local energy requirements by rising selected multi purpose species. The National Commission on Agriculture realized that a stage had come when the country could not depend on traditional forests alone for forest produce and extending the forest activity outside the forest area was imperative. Since then social forestry was popularized on a large scale. The land available under different categories as identified by the Fuel wood Study committee of the Planning Commission (1982) were barren and wastelands, road, canal and rail sides, degraded forests and agricultural lands. The main objectives of social forestry are fuel wood supply to the rural areas; small-scale timber supply; fodder supply; protection of agricultural fields against wind; erosion control and recreational needs.
As in any other afforestation programmes, the species selection has to be based on the agro-climatic zones. The preference again is for multipurpose tree species. But it is quite obvious from various studies that in a given set of soil, climatic and rainfall conditions, only few species predominate. Social forestry is pursued in Karnataka initiated by the State forest department. The commonly planted species are Acacia auriculiformis, Eucalyptus, Casuarina equisetifolia etc. Acacia auriculiformis , dominates the Western Ghats of Karnataka, while Acacia auriculiformis and Eucalyptus dominate in Southern Karnataka. In this regard, adopting native species which caters to the basic requirements of the system in terms of fuel, food and fodder would prove the programme successful. Most of the exotic species fails in this regard leading to the failure of the programme. Plantations are raised on roadside, canal bank, foreshore, school, community lands and institution premises.
India is experimenting with a diverse management system for protection, regeneration and biomass production in forests, village commons and degraded lands. Realization of the importance of people's participation in the conservation of natural resources has initiated the Joint forest management (JFM) programme. This movement focuses on the sustainable use of forests to meet the local needs equitably while ensuring sustainability. JFM was evolved on June 1 st 1990 by a circular from the ministry of environment and forests providing guidelines for the involvement of village communities and voluntary agencies in regeneration of degraded forests. Under JFM the village committees are entrusted with the task of protecting and managing these forests. Thus Joint forest management is a participatory forest management system between the village community and the State forest department, which came into effect on April 12, 1993. In India about 23 States have adopted JFM resolutions, covering an area of 10.25 M ha (Bahuguna, 2000).
In Karnataka JFM, commonly referred to as Joint Forest planning and Management was initiated on April 12th , 1993. The relative coverage of area under JFPM in the State varies from less than 1% to 65% of the total area brought under JFPM in the State. Uttara Kannada alone accounted for 65% of the area brought under JFPM in the State followed by Kolar (10.34%) and Shimoga (9.30%). In all other districts the areas brought under the JFPM is less than 4%. Assessment of JFPM and non-JFPM plantations over the last 6 years have shown that the nearly 66% of the stems in the non-JFPM plantations belong to fuelwood species while in JFPM plantations it was 47%. JFPM can help meet the biomass requirement of the masses especially with regards to fuelwood and this has proved to be realistic in Uttara Kannada (Jagannatha Rao et al, 2001).
Type of Plantation/location |
Productivity (tonnes/ha/year) |
Source |
Location |
|
Karnataka |
Farm forestry |
7.2 |
DES (1995) |
Kolar and Bangalore districts-semi arid |
Farm forestry |
8.2 |
Ravindranath et al (1992) |
Tumkur district-semi arid |
|
Forest department |
1.5 |
Ravindranath et al (1992) |
Tumkur district-semi-arid |
|
Forest Department |
5.3-7.9 |
Bhat, D.M and Ravindranath (1994) |
Western Ghats heavy rainfall |
|
National |
Farm forestry |
4.2 |
Seebauer (1992) |
National |
Forest Department |
2.6 |
Seebauer (1992) |
National |
|
Eucalyptus plantations |
6.6 |
Seebauer (1992) |
National |
|
National mean |
All plantations |
3.2 |
Seebauer (1992) |
India |
Irrespective of the kind of programme pursued to meet the biomass requirements, success comes in only if there is high biomass productivity. Lower yields will turn away the local communities, as it would be difficult for them to raise, protect and manage these plantations for little benefits. The annual above ground woody biomass productivity of forestry plantations (air-dry tonnes/ha/yr) in different locations and different categories are given below (Ravindranath and Hall, 1995).
Higher productivities can be obtained with proper site selection, right choice of species, practicing polyculture coupled with following good soil and water management practices.
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7 . 1 Techno economic analysis of feasible bioenergy technology |
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In view of the fact that biomass is relied on to a great extent to meet the rural energy demand (nearly 75%) (Natarajan, 1985), it has become necessary to sustain the existing resources, alongside with trying out innovative technologies to increase the efficiency of its use. Biomass use for domestic wood burning, largely for cooking and water heating purposes is as high as 80%. In the rural areas of India, the traditional three pan mud stoves are used, which have a low efficiency of 5-10 % (Ravindranath & Hall, 1995). These stoves lack chimneys and release the smoke including carbon monoxide, carbon particulates and volatile hydrocarbons into kitchen, posing health hazards for women. The need to increase fuel use efficiency coupled with biomass scarcity led to the development of improved cooking stoves. In India, the current interest in the improved fuel wood stoves can be traced back to 1950's when the Hydrabad chulla was introduced. In Karnataka one such improvised design was developed by ASTRA (Applied science and Technology for Rural Advancement) of the Indian Institute of Science having a thermal efficiency of 45 percent in the laboratory (Lokras et.al, 1983) and 35% in the field (Ravindranath et al, 1989).
The ASTRA stove is a mud stove built in situ with stove holes custom-built to suit individual household vessels, consisting of an enclosed fire wood feeding port permitting long pieces of wood to be used, a grate on which the firewood burns, ports for primary and secondary air, snugly fitting pan scats and a chimney to remove smoke. In laboratory, percent heat utilization in the range of 40-45 percent and a specific fuel consumption of 150 gm per kg of cooked food was obtained (Lokras, 1983).
The stove is designed based on the principle of complete combustion of the fuel in little air to generate the highest temperature of the flue gases. Combustion of fuel wood is carried over a grate in an enclosed fuel box with ports of suitable size for the entry of air. The grate helps in the entry of air (primary air) below the fuel bed to burn the char as well as for separation of ash from fuel. Air required for the burning of volatile matter released as a consequence of heating the fuel (secondary air) enters through a port slightly above the grate. The heat produced by the complete combustion is transferred to the pan by conduction, convection and radiation. To increase the heat transferring efficiency, the pan is made of a poorly conducting material (Lokras, 1983).
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. Biogas is suitable for practically all the various 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. No direct correlation between deforestation and rural energy use has been established so far. In fact, the contribution of forests to total fuel wood use in the domestic sector mainly for cooking is only 8.7% (Ravindranath and Hall, 1995). Nevertheless, there is enough evidence at the micro level to suggest that fuel wood use contributes to degradation of biomass resources, especially in areas where external factors like timber extraction cause forest denudation. It has also considerably helped in improving the quality of life. The human effort involved in gathering is a cause of drudgery for women and children who travel long distances in search of fuel wood. It has been estimated that at the national level, the average number of hours spent in gathering biomass is about two hours/day/household which is likely to increase in future due to increasing scarcity of fuel wood resources (Ravindranath and Hall, 1995). 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 cow 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. Energy yields are 30-90 Nm3 of biogas per cu.m of biomass for different types of reactors (DEA, 1992). Biogas is basically methane (CH4) produced through the anaerobic fermentation of cowdung 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 and C/N ratio. A temperature of 35° C, pH range 6.6-7.5 and C/N ratio of 30:1 are considered optimum. At lower temperatures, bacterial activity decreases and ceases completely below 10° C. Solid concentration of the feedstock is crucial as it affects the gas production and the handling and mixing of characteristics. Cowdung has a solid concentration of 20%, and therefore to attain the desired value of 8-10%, it is mixed with water (1:1). It also has a C/N ratio of 25:1, and thus is an ideal choice as it meets most of the requisites for optimum gas production.
The hydraulic retention time (HRT), which is the number of days the feedstock is required to remain in the reactor to begin gas production, decides the cost of the plant. Lower the hydraulic retention time, higher is the cost of the plant. The HRT is dependent on the ambient temperature. The hydraulic retention time of a biogas reactor in Karnataka (ambient temperature > 20° C) would be about 30 days (http://www.teriin.org/renew/tech/biogas). 1 kg of dung produces 40L 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. (TERI, 1994). The biogas requirement for cooking two meals is estimated to be 150 l/capita/day (Dutt and Ravindranath, 1993).
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 8548.4 kcal/m3. The biogas plant in which the gas production is carried out has the following components:
• An inlet tank used to mix the feed and let it to the digester,
• A digester in which the slurry (dung and water) is fermented,
• A gas holder/dome in which the collected gas is stored,
• Distribution pipelines to carry the gas to end use point,
• An outlet tank to remove the spent slurry and
• A manure pit where the spent slurry is stored.
As the first step in disseminating biogas technology, the Ministry of Agriculture launched the NPBD (National Project on Biogas development) in late 1981. These biogas plant models are based on one of the two basic designs available, floating metal drum type, fixed masonry dome type. The floating drum is an old Indian design with a mild steel or fiberglass drum that floats along a central guide frame and acts as a storage reservoir for the biogas produced. The fixed dome is of Chinese origin and has a dome structure made of cement and bricks. It is a low cost alternative to the floating drum, but requires high masonry skills and is prone to cracks and gas leakages (Ravindranath, 1995). Some of the commonly used models approved by NPBD are KVIC (Khadi Village Industries Commission), which is based on the fixed dome design; Deenbhandu, developed by Action for Food Production (AFPRO), a voluntary organization based in New Delhi; and Pragati, developed by the Socio-economic Development and Research programme.
Biogas has a higher heating value than producer gas and coal gas, which implies increased services. As a cooking fuel, it is cheap and extremely convenient. Based on the effective heat produced, a 2 cu. m biogas plant could replace, in a month, fuel equivalent of 26 kg if 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 cheaper, on a life cycle basis, than conventional biomass fuels (dung, fuelwood, crop wastes, etc.) 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 (TERI, 1994). 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 is given below: A 25 kg fresh dung would give about 5 kg of dry dung, which is equivalent to one cu.m of biogas. Differences in some of the parameters are given below.
Parameters |
Direct Burning |
Biogas |
Gross Energy |
10460 kcal |
4713 kcal |
Device efficiency |
10% |
55% |
Useful energy |
1046 kcal |
2592 kcal |
Manure |
None |
10 kg of air dried moisture |
(Source: http://www.terin.orgh/renew/tech/biogas)
At localized level, biomass can also be used for electricity generation by gasification. A biomass gasifier consists of a reactor where, under controlled temperature and air supply, solid biomass is combusted to obtain a combustible gas (consisting of hydrogen and methane). This gas passes through a cooling and cleaning system before it is fed into a compression ignition engine to run in dual fuel mode for generation of electricity (Ravindranath and Hall, 1995). An assessment of its potential reveals that India presents a unique opportunity for large-scale commercial exploitation of biogas gasification technology to meet a variety of energy needs, particularly in the agricultural and rural sectors (Jain, 1989). In the process of gasification, biomass undergoes partial combustion to generate gas and charcoal and the latter reduces the gas (carbon monoxide and water vapour) to a combustible gas consisting of carbon monoxide and hydrogen. The process also generates small amounts of methane and higher hydrocarbons, depending on the design and operating conditions (Mukunda et al, 1993). Crop residues and woody biomass from trees can be used as feedstock for producer gas systems. Wood gasifiers can thus help in decentralized electricity generation helping the rural community meet its energy needs of home electrification, pumping, flour milling etc. The Centre for Application of Science and Technology for Rural Development (ASTRA), Indian Institute of Science has successfully tried this option at Hoshalli village in Tumkur district. Here a decentralized energy generation system was established using a 5 kW wood gasifier for electrification in a non-electrified village. The wood was procured from a mixed species (poly culture) energy plantation whose annual productivity was 6.4 tonnes per hectare. The use of electricity for lighting has saved 0.803 tonne of kerosene per year in the village. The study demonstrates the technical feasibility of a decentralized electricity generation system (Dattaprasad et al, 1990).In the energy deficient zones, the extent of wasteland available is 1999046 ha. If a productivity of 5 tonnes/ha/year is assumed the fuelwood available would be 9995230 tonnes. Through the wood gasification mode of power generation, 1kWh can be generated per 1.2 kg of fuelwood (Ramachandra et al, 2000). Similarly in the bioresource surplus zones, which have about 880189 ha of wasteland, raising a mixed species plantation having a productivity of 5 tonnes/ha/year will produce 4400945 tonnes of fuelwood annually.
Biomass based electricity generation is quite feasible and offers immense scope for rural development. The procurement of woody biomass should be designed in such as way that they do not disturb the ecological roles of the existing forests, some of which are in various stages of degradation. Also, establishment of such systems should not compete with land used for food production. A judicial option would then be using wastelands for energy plantations, which is detailed in the next section. The three main kinds of lands that can be well used to serve this purpose are wastelands, degraded forestlands and village common lands.