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Biofuel availability and consumption studies
Joshi et al (1992) study confirms the predominance of firewood use in rural areas with analysis indicating the 95% confidence interval for per capita consumption (national aggregates) for cooking in the range of 1.10-1.34 kg/capita/day. The consumption of dung cake was lower with 95% confidence interval of the per capita consumption showing 0.40-0.49 kg/capita/day. The agricultural residue consumption was marginally higher with 95% confidence interval range of 0.47-0.63 kg/capita/day. The rural energy database generated across the agro climatic zones showed variation in the firewood used for cooking to have a high degree of statistical significance and a significant use in the variation of dung cakes in cooking across the agro - climatic zones.
In India, different groups such as the Energy Survey of India Committee- ESI (1965), Fuel Policy Committee (1974), Working Group on Energy Policy - WGEP (1979), Advisory Board on Energy- ABE (1985), and Energy Demand Screening Group - EDSG (1986) have assessed the rural energy requirements. The study by ESI projects the variation in the consumption of commercial and biomass fuels at the urban and rural areas. The figures are aggregated at the national level and the regional variations were not examined. The per capita daily useful energy requirement was assumed at 510 kcal for rural areas and 535 kcal for urban areas. The WGEP also made similar estimations assuming the per capita energy requirements of the ESI. The projections were forecast at the national level and the regional variations owning to economic disparities at the household level were ignored. The EDSG was established to bring out common estimates of energy requirements as the values given by ABE were felt to be high at the rural level. The survey results of this group predicted the level of requirement for 2004/2005 as 520 kcal/capita/day. To arrive at this figure the committee used the energy requirements and the level of growth of the energy requirements over time as suggested by the ESI committee. The wide variations that were noticed in the estimates given by the above study groups were attributed mainly to the change in population figures.
Energy plantation and management of wastelands
Bhel and Goel (2001) have studied the genetic selection and improvement of hardwood tree species for fuel wood production on sodic wastelands (pH 8.6-10.5). Field trials were conducted using leguminous species like Acacia auriculiformis, A.nilotica, Albizia lebbeck, Acacia procera, Dalbergia sissoo, Leucaena leucocephala, Pongamia pinnata, Prosopis juliflora and Pithecellobium dulce. Other tree species like Azadirachta indica, Eucalyptus teriticornis and Terminalia arjuna were also chosen for this study. Prosopis juliflora was the most promising species in terms of biomass productivity (68.7 tonne/ha) and fuel index (148.8) after 8 years of growth. Acacia nilotica ranked second.
Rupam Kataki and Dolon Konwer (2001) have studied the fuel wood characteristics of four indigenous perennial species of northeast. Physio-chemical parameters like moisture and ash content, density, solubility in cold water, hot water and alkali, cellulose, holocellulose, lignin and extractive contents of different parts of these species were determined. Leaf component of all the species contained the highest calorific value presumably because of the higher extractive content, followed by heartwood. The study identified A . lucida, S. fruticosum and P.lanceaefolium to have better fuel wood properties to be raised as energy plantation.
Bungart and Huttl (2001) have studied the production of biomass for energy in post-mining landscape of Lusatian mining region. The yield potential of fast growing tree species under poor soil conditions of the mined area were studied. The study revealed that even under unfavorable soil conditions of N and P supply, above ground biomass supply after 4 years since planting ranged from 5.3 tonnes to 19.6 tonnes of dry matter per hectare. For the biomass accumulated within this four-year period, a calorific value of 42 MJ/ha/year was calculated.
Patrick and lowore (1998) have identified and discussed the management options of some indigenous firewood species of Malawi's central region. This study proposes the local people's involvement in the management domestic firewood on a coppice rotation of five years upwards.
Pal and Sharma (2001) have studied the reclamation of salt affected wastelands in arid and semi-arid regions of Aravalli Hills. Twelve tree species were planted and were analyzed for growth parameters, soil pH, organic carbon, electrical conductivity, available phosphorous and various socio-economic benefits after 5.5 and 13.5 years. Only five species survived and three grew more than 40 cm in GBH as well as 10 m high in 13.5 years. The soil pH, electrical conductivity, organic carbon and available Phosphorous recorded significant improvement in three depths (up to 45 cm) and ages over the initial status. The village community was also benefited through fodder supply, employment generation, income generation and other community facilities.
Fuel potential of biomassPesonen et al (2001) have determined the potential of logging residues and first thinning as wood fuel in Southern Finland based on the four cutting scenarios. The calculations were carried out using the MELA program which simulates a finite number of feasible forest management schedules for each forest stand according to the given simulation instructions. The annual potential harvest of energy wood was 3.6 million m 3 /year.
Yamamoto et al (2001) have evaluated the global bioenergy potential in the future using a multi-regional global-land-use-and–energy-model (GLUE-11). Through a set of simulations the following results were obtained. North America, Eastern and Western Europe, Latin America and former U.S.S.R will have the potential of energy produced from crops growing on surplus arable land. Variation in food supply and demand will be influencing this potential. The ultimate bioenergy supply potential of biomass residues in the world will be 265 EJ/year in the year 2100. The practical potential of biomass residues in the world will be 114 EJ/year, which is equivalent to one-third of the energy consumption in the world in 1990. Considering the current land use pattern, the global mature forest area will decrease by 24% between 1990 and 2100 because of growth of both population and wood biomass demand per capita in the developing regions.
Seiler et al (2002) estimate the potential hydrocarbon in selected species of Western Ghats, Tamil Nadu, which show that Sarcostemma brevistigma has the highest concentration of hydrocarbon of 3.6%. While species such as Tylophora asthmatica, Euphorbia tirucalli, Cryptostegia grandiflora, Ficus ealstica and Euphorbia antisyphylitica contained more than 2%. The gross heat value of hydrocarbon fraction in Ficus elastica (leaf) is 9834 Cal/g, which is comparable to fuel oil calorific value.
Biomass estimation studiesThe standing woody biomass of trees is the weight of the trees above ground in a given area, if harvested at a given time. The change in the standing biomass over a period of time is referred to as productivity and is expressed as tonnes/ha/year. In ecological terms (Whittaker, 1970) primary productivity is the rate at which energy is bound or organic matter created by photosynthesis per unit of earth's surface per unit of time.
Rai (1982) found the above ground biomass in tropical rain forests of Karnataka to be 465.61 tonnes/ha and root biomass to be 13.21 tonnes/ha based on field investigations at four locations namely Agumbe, Bannadpare, Kagneri and Bhadra and subsequent regression analyses and the average net primary productivity ranges between 7.77 to 11.76 tonnes/ha/year.
Narendra Prasad (1987) showed the average standing biomass at sample locations - Nagur, Santgal, Sonda and Bidralli in Uttara Kannada district reserve forests to be 243.25 tonnes/ha.
Ravindranath et al (1999) assessed the biomass potential across the agro ecological zones and show an estimate of 321Mt, based on biomass productivity in the range of 2-17 tonnes/ha/year, considering a conservative estimate of 43 Mha land.
Bhat et.al (2002) investigations in differentially managed forests of Uttara Kannada indicate that tree biomass productivity decreases and herb productivity increases with increasing light gap (canopy gaps).
Haripriya (2000) measured biomass resources in Indian forests for the year 1993, using species-wise volume inventories for all forest strata in various States and show the above ground biomass densities ranging from 14-210 Mg/ha, with a mean of 67.4 Mg/ha, which equals around 34 Mg C/ha.
Shanmughavel et al (2000) have estimated the biomass production in Bambusa bambos plantations of different age class, and compared with its interspecies natural stands and between genera of natural and plantation stands. The study shows the mean annual biomass production of 49.6 tonnes/ha (over a period of six years) and with an increase in age, there was a linear increase in the total biomass of all compartments. In the aboveground biomass, the percentage contribution of culms (81%), branches (14%), and leaves (1%) was 96%, whereas in the below ground, the rhizome contribution was 4%.
Shanmughavel et al (2001) have studied the biomass and their distribution using standard regression analysis and the clear-cut method for shrubs and herbs. Results show the total biomass of 360.9 tonnes/ha and its allocation among different layers - tree layer 352.5, shrub layer 4.7, liana 3.1 and herb layer 0.5 tonnes/ha.
Fuwape et al (2001) have developed biomass equations and estimation for Gmelina arborea and Nauclea diderrichii stands in Akure forest reserve. The study revealed that more than 75% of total biomass yield of both species are from the stem and over 90% of the total above ground biomass is available as biofuel.
Dadhwal et al (2001) have estimated the forest biomass growing stock as 8683.7 MT based on the field inventory information of growing stock volume and corresponding area under different crown density classes for India for the year 1992-1993. The average growing stock volume density in Indian forests is about 74.42 m 3 /ha, but varied amongst the States with a range of 7.1 m 3 /ha in Punjab to 224.5 m 3 /ha in Jammu and Kashmir. The mean biomass density in Indian forests was estimated as 135.6 tonnes/ha and amongst the States it varied from 27.4 tonnes/ha in Punjab to 251.8 tonnes/ha in Jammu and Kashmir, respectively.
Studies on biomass technology and bioenergy projectsSeimons (2001) has identified the potential of biomass gasification for electrification of rural areas in developing countries taking the feasibility prospects into account. The analysis was carried out on the basis of an annuity-costing model taking into account the
time value of money, technological and site parameters. The capacity range considered was 10-200 kW, which was investigated in 10, 40 and 160 kW cases. For 10 kW the fuel considered was charcoal, wood and charcoal for 40 kW and wood for 160 kW. For smaller capacity plants, conditions for economically feasible projects were found to be satisfied easily under prevailing fuel price and investment levels. Charcoal even though more expensive cannot compete wood as a fuel for gasification systems up to a capacity of 40 kW. Mass production of gasifiers will result in considerable cost reduction that would promote the technology.
Junginger et al (2001) have evaluated the availability of agricultural and forest residues for electricity generation in northeastern Thailand considering the variations in the residue produced, limited accessibility, utilization by other competitors and logistical risks. In the current Thailand situation, only a combustion plant seemed to operate economically.
Zanzi et al (2002) have studied the effect of the process conditions such as heating rate, temperature and particle size on the product distribution, gas composition and char reactivity on the rapid pyrolysis of agricultural residues at high temperature. The study reveals that higher temperature leads to lower yields of tar and higher yields of gaseous products. At higher temperature, the heating rate is higher, which will favor a decrease in char yield. The yield of hydrogen is increased at higher temperature when the cracking of hydrocarbons is favored. Use of smaller particles increases the heating rate. Agricultural residues having higher ash content favour the formation of a more reactive char.
Gamborg (2000) has studied the different ways of increasing the production of whole tree chips for energy production. The influences of silvicultural factors like tree species, thinning programme, plant density and the quality of nursery trees on the production of wood chips were examined.
Akinbami et al (2001) have studied the biogas energy use in Nigeria. The study projects the quantity of family-sized biogas digesters in the future to vary between 144,350 and 2165,250 units. The projected energy from biogas would range between 5.0 -171.0 x 10 12 J in the period 2000-2030 and the associated aggregate financial commitment (first cost) was worked out to be US$72.16-1083.00 million. Other factors such as technology, political will, economics and personal motivation were also found to influence its popularization.