Dr. Ramachandra T.V.

INTRODUCTION

The risk of climate change due to emissions of carbon dioxide from fossil fuels is considered to be the main environmental threat from the existing energy system. Other environmental problems are acidification, and dispersion of metals originating from fossil fuels. Fossil fuels supply a large part of the total primary energy use in the world, about 76% [1]. Sustainable development of a region depends on the health of renewable energy resources like water, vegetation, livestock, etc. The integrated development of all these components is essential for environmentally sound development of the region. To strive towards a sustainable society would imply a shift to renewable energy sources, such as biomass energy. Biomass offers tremendous opportunity to use renewable and sustainable resources available locally to provide its fuel, power, and chemical needs from plants and plant-derived materials. Biomass sources supply about 35 and 3% of the primary energy needs of developing and industrialised countries respectively [2]. Due to its flexibility as an energy resource, biomass share in regional energy balances in this part of the globe is very significant [3, 4, 5]. The term "biomass" means any plant derived organic matter available on a renewable basis, including dedicated energy crops and trees, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, animal wastes, municipal wastes, and other waste materials. Biomass cycle maintains the environmental balance of oxygen, carbondioxide, rain, etc. As estimated, globally photosynthesis produces 220 billion dry tonnes of biomass per year with 1% conversion efficiency. This natural process will fix about 2 x 10¹¹ tonnes of carbon per year with energy content of 3 x 10¹¹J. This is about 10 times world’s energy needs [6]. The conversion efficiency depends on the composition of the biomass.
Assessment of available bioresource is helpful in revealing its status and helps in taking conservation measures and ensures a sustained supply to meet the energy demand. Energy use patterns are closely linked to agro-climatic and socio-economic conditions. Hence, a detailed energy survey was conducted to understand the energy use patterns in various agro-climatic zones and seasons.  Assessment of bioenergy potential can be theoretical, technical or economic.  Natural conditions that favour the growth of biomass determine the theoretical potential.  Technical potential depends on the available technologies that can be exploited for the conversion of biomass to more flexible forms and so is subjected to change with time.  Of all the three potential estimates, the economic potential is subjected to high variability, as economic conditions fluctuate drastically over space and time.  Annually, 62–310 Mt of wood could be generated in India from the surplus land, after meeting all the conventional requirements of biomass, such as domestic fuelwood, industrial wood and sawn wood, with an investment of Rs. 168 – 780 billion. The annual energy potential of plantation biomass is estimated to vary from 930 to 4650 PJ. It is projected that the energy consumption in 2010 will be 19,200 PJ; thus an estimate show that plantation biomass could supply about 5 – 24% of projected total energy consumption in 2010 [7]. The estimation of the biomass and the carbon contained in biomass of Indian forests, using species-wise volume inventories for all forest strata in various states indicate that the aboveground biomass densities ranged from 14 to 210 Mgha^-1, with a mean of 67.4 Mgha^-1, which equals around 34 MgCha^-1 [8].

Karnataka Renewable Energy Development Limited (KREDL) estimate the total biomass from agricultural activity is 66,979 tons/year, and the estimated biomass available from the agrobased industries is 3375 tons / year in Pandavapura taluk, Karnataka. This study has revealed that surplus biomass, capable of  generating 19 million kWh of electricity per year through a 2.5 MW power plant, can meet 38% of energy requirement of the taluk, (including industrial power requirement) [9]. Decision support system (DSS) provides the tools to analyse spatially the biomass potential considering the theoretical, available, technological and economically exploitable potential. The main parameters that affect the location and number of bioenergy conversion facilities are plant capacity and spatial distribution of the available biomass potential [10].

Agro ecological zones were considered as sampling frame to create the link between supply and demand, and to provide a valid basis for extrapolating the result of the supply survey to the national level using GIS and remote sensing [11].  A GIS based modeling system estimates the costs and environmental implications of supplying specified amounts of energy crop feedstock across a state, while estimating potential biomass supplies from energy crops in eleven US states. The system considers where energy crops could be grown, the spatial variability in their yield, and transportation costs associated with acquiring feedstock for an energy facility [12]. The spatial patterns of biomass and net primary productivity in China's forests using empirical data sets, remote sensing methods, and climate–vegetation models indicate that the present spatial pattern of NPP is a result of both natural environmental factors and human land use patterns. Estimates of NPP for the tropical zone (seasonal rainforests and rainforests) were highest, ranging from 20 to 24 Mg ha^-1 year^-1. NPP was lowest in boreal zone forests comprised primarily of Scotch pine and Siberian pine, averaging only 6.7 Mg ha^-1 year^-1 [13].

Biomass 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 cowdung account for 53.2%. Bioenergy is one of the primary sources of fuel in the State. A recent study on energy utilization in Karnataka considering all types of energy sources and sector wise consumption   reveals that, traditional fuels such as firewood (7.440 million tonnes of oil equivalent  (MT) - 43.62%), agro   residues (1.510 MT - 8.85%), and biogas and cowdung (0.250   MT - 1.47%) account for 53.20% of total energy consumption [14].

Agriculture residues like rice husk, bagasse, groundnut shells, maize cobs etc. have immense potential to be used as fuel substitutes. In Karnataka, the agriculture residues are used as fodder, fuel, thatch and manure.  92% of the stalk from crops is used as fodder, 4% as thatch, 2% as manure and 2% have other use.  Major portion of the cotton stalk, groundnut shells, coconut shells and leaves are used as fuel [15]. The total cultivable area of the state including net sown area (55.06%), cultivable wasteland (2.28%), current fallows (6.66), and other fallows (2.10%) is 66.09%.  The gross and the net cultivated area under agricultural crops had increased from 100.65 lakh hectares to 106.09 lakh hectares (1998-1999). 

Firewood, is generally used as a traditional fuel, is got from the forests. The quantity of firewood released from the forest to the public for domestic and other uses in the year 2001, was around 109507 M3. Forest cover since 1997 in Bangalore, Gulbarga, Hassan, Mandya, Mysore and Tumkur districts has increased.  This has become possible because of the energy plantation efforts and protection of the degraded forest areas.  Plantations of Acacia auriculiformis and Eucalyptus species in Gulbarga district have mainly contributed to the increase of green cover. The total growing stock of Karnataka's forests is 272 million cubic metres.  The average volume per ha is 84 cum, which is 10cum more than the national average.  The estimated increment of the forest produce in Karnataka is 5.5m cum, and the productivity is 1.45 cum/ha annum for the whole area.  For wooded area the productivity is 1.72cum/ha/yr. The national average of productivity is 1.37 cum/ha [16].

The important horticulture crops of the state are Coconut, Arecanut and Cashewnut. The area under coconut plantation is 0.279 Mha with an average yield of 5204 nuts per hectare.  Arecanut is cultivated in about 0.78 lakh hectares with an average production of 5.48 lakh tonnes.  The area under cashew plantation in Karnataka is about 0.048 Mha with an average yield of 578 kg/ha.  About 47,390 ha of cashew plantation is raised in the Coastal zone.