Dr. Ramachandra T.V.

METHODOLOGY

Bioresource inventory helps in describing the quality, quantity, change, productivity and condition of bioresources in a given area.  These inventories may be for regional or national level assessments.  Bioenergy status assessment is based on compilation and computation of bioresource supply for the energy generation. Bioresource availability is computed based on the compilation of data on the area and productivity of agriculture and horticulture crops, forests and plantations. Sector-wise energy demand is computed based on the National Sample Survey Organisation (NSSO study) data, primary survey data and from the literature. Bioresource supply from agricultural residue, forest, horticulture residue, plantation, and livestock dung are considered to assess the energy status taluk wise.

Forest Inventory: For an assessment of forest biomass, forest inventory is most commonly used to measure forest biomass rather than or in addition to traditional volume.  The forest inventory area is usually one or more management units, each ranging in size from a few hundred to many thousand hectares.  Each unit may be divided into forest-based strata or administrative sub-populations for which separate estimates are required.  The attribute of primary interest is merchantable wood volume, with stem frequency.  Basal area data is of secondary importance.  These attributes are usually given by tree size classes and by a number of forest and administrative classes that are described in a classification system such as the following:

• Total inventory area is divided into land and water
• Land is divided into forest and non-forest
• Forest is divided into productive forest and unproductive forest
• Productive forest is classified by ownership and status into forest and covers type, and by stands density, height, age, and site quality classes.

The information required for management inventories are obtained from the existent base maps, soil maps, and geological maps, narrative descriptions of the area and its history, remote sensing data, which are used to obtain information about individual stands, and field samples, from which detailed volume data are obtained through sampling procedures.

Above ground standing biomass of trees is the weight of trees above ground, in a given area, if harvested at a given time.  The change in standing biomass over a period of time is called productivity.  The standing biomass helps to estimate the productivity of an area and also gives information on the carrying capacity of land.  It also helps in estimating the biomass that can be continuously extracted.  The standing biomass is measured using the harvest method or by using biomass estimation equations.  In the harvest method, vegetation in the selected sample plots are harvested and the weight is estimated in fresh and dry form to measure biomass.  For trees, this method is inappropriate, as it requires their felling or destructive sampling. However, this could be computed by the knowledge of its height and girth (at 130 cm).

Standing biomass (in Kg) is given by  = b+ (aD²H), where D is the diameter at breast height, H is the height of the tree, a and b are constants.  Equations involving the basal area are used for all tree species and therefore are used to estimate the standing biomass of mixed forests.  Productivity, which is the increase in weight or volume of any biomass over a period of time, can be estimated when the standing biomass estimates are available for two consecutive years.  It can also be calculated by knowing the age of the forest stand in addition to the litter available annually. Productivity=standing biomass per hectare/age of a tree or the trees per forest stand.  Productivity estimates are important as they help calculate the extent of biomass that can be extracted for fuel purposes.

Data on the land use pattern was collected from the Directorate of Economics and Statistics, Govt. of Karnataka.   The major source of information on forest lands is the Karnataka forest department (KFD), which maintains a variety of records like the annual administration reports, working plans, forest inventory reports, which gave information on the growing stock, current status of these forests, the management practices adopted, plantations maintained and their prescribed felling cycle.    The inventory of forest resources published by the Forest Survey of India (FSI) was also referred for this study.    The forest area by types, given division wise in the forest records was used to compute the forest type at the taluk level.  The biomass potential of the forests is dependent on the type of forest and its distribution cover.  The biomass production varies with the type of the forest.  The biomass productivity of the different types of forests are [14]: Dense evergreen and semi evergreen (13.41-27.0 t/ha/yr), Low evergreen (3.60-6.50), Dense deciduous forest (3.90-13.50), Savanna woodland (0.50-3.50) and Scrub (0.9-3.60). Using the low, high and average productivity values given above, the annual biomass production from each forest type was computed at the taluk level.  Energy equivalent of 4000Kcal/Kg was taken for evergreen, semi-evergreen and moist-deciduous forest types, while for the dry deciduous and scrub type vegetation 4800Kcal/Kg and 3400Kcal/Kg were taken respectively. Total bioenergy from forests (Bio₁) is computed by

                                       Bio₁ = Bioenergy from forests (kcal)
                                               = Forest area * Productivity * (Energy equivalent)  ………. (1)

Computation requires inputs such as forest types (i.e. Deciduous, Evergreen, etc.); respective spatial extent, annual productivity (tonne/hectare) and energy equivalent (kcal/tonne) and outputs would be annual bioenergy--forest type wise, regionwise, etc.

Agro-Residues Inventory: The crop residue inventory involves the measurement of both crop yields and crop residues to allow the development of residue-yield ratio estimators as well as area-based estimates of residue yields.   The ASF (Area Sampling frame) methodology provides a very efficient basis for estimating crop yields. This methodology involves the delineation of permanent or long-term sampling segments from satellite imagery (Multi spectral sensors).  These are then used as sampling frames for subsequent agricultural surveys.  The crop residues are surveyed during both the Kharif and Rabi season.  Field sampling is carried out within one week before harvest to ensure that crop yield and residue measurements are related to fully mature crops. The cultivated area and the biomass yield of each crop influence the biomass potential from agriculture residues. The taluk wise area of the dominant crops cultivated in a taluk was collected from the state agriculture department for the last 6 years. Area under cultivation was not variety specific for a crop at the taluk level.  The proportion of the area under high yielding variety and the traditional variety of a crop at the district level was used to segregate the area by variety at the taluk level. The grain yield and production figures for each crop were available only at the district level, which were used to compute the grain production at the taluk level.  The yield of a crop (season and variety wise) across an agro climatic zone was obtained by averaging the yields of the previous six years (1995-2000). The ratio of the main product to the by-product for each crop grown under local conditions along with their energy equivalents were used to compute the agro residues production.  The energy equivalent of these residues was taken based on what would be obtained if they were subjected to the most energy efficient transformation processes.  Portion of the residues available are used as fuel, while some is used as fodder and the rest is left behind in the field for nutrient recycling.  Apart from this, the actual availability of residues as energy supplements would also depend on other factors like efficiency of collection, mode of transportation and storage. Considering these, in the computation of bioresidue from agriculture only 50% is accounted for fuel. Bioenergy from agriculture residues (Bio₂) is computed by:

Bio₂=Bioenergy from agriculture (kcal)
                                                                               = (Productivity of waste * Crop area* Energy equivalent) …………………(2)

Computation of bioenergy from agricultural crops requires inputs such as crop type (i.e. Cotton, Green grams, etc.), spatial extent, crop yield or productivity, residue to crop ratio, energy equivalent (kcal/tonne), while outputs are annual energy--crop wise, regionwise, etc.

Plantation Inventory: The management of energy plantation would more closely resemble a farming operation than conventional forestry.  Plantation inventory involves the assessment of spatial extent of plantation, type of plantation, annual productivity, mean annual increment and cycling time. Cultivation of chosen fuel wood species, which can be harvested during a short period of time, could meet the energy demand of growing population. The species are so chosen that they provide plenty of biomass, are fast growing, have good survival rate (high tolerance or adaptability, pest resistant and drought resistant) and produce large volumes of wood.  Multipurpose species are mostly preferred.  Selecting a leguminous species will also help maintain the soil fertility in addition to meeting the fuel wood requirements. 

The area of plantations raised by the forest department under various schemes was obtained from the State forest department.  Some of the commonly planted species are Casuarina, Acacia, Pongamia, Hardwickia binnata, Azadirachta indica, Leuceana leucocephala etc. Species wise extent and age of these plantations was not available even at the division level. However, the details of plantations raised on different sites, like canal side, roadside, in institutional premises etc available at forest department was used for computation.  The biomass that could be obtained was calculated assuming that 30% were adult plantations.  The yield of eucalyptus plantations in Uttara Kannada, Bangalore, Tumkur and Kolar districts were estimated to be 5 t/ha.  The yield of Acacia auriculiformis plantations is known to be 10-34 m³/ha.  Based on these productivity figures, the biomass production of plantations was calculated using an average productivity of 5t/ha/year. Total bioenergy from forest plantation (Bio₃) is computed as:

Bio₃ = Bioenergy from plantations (kcal)
                                                       = Area * Productivity * (Energy equivalent) …………………(3)

Requires inputs such as forest plantation types, respective spatial extent, annual productivity (tonne/hectare) and energy equivalent (kcal/tonne). Outputs are annual bioenergy--forest type wise, regionwise, etc.

 Horticulture: The area under the horticulture plantations of coconut, areca and cashew at the taluk level were obtained from the State horticulture department for the previous four years.  The average yield figures of the district were used to compute the production at the taluk level.  The fuel biomass from coconut and areca nut plantations along with the energy equivalent of the husk, shells, leaves and inflorescence were considered [14].  For the computation of the number of trees in the given area, tree count of 150/hectare and 1000/hectare were assumed for coconut and Arecanut plantations. Energy from horticulture (Bio₄) is computed by:

Bio₄ = Bioenergy from horticulture (kcal)
                                                      = Area * Productivity * (Energy equivalent) …………………(4)

Computation requires input data such as crop type (i.e. Coconut, Arecanut etc.), spatial extent, number of trees per hectare, residues (leaf, shell, husk) actual count, anticipated use percent, conversion to weight (kg) and energy equivalent (kcal/kg), while output is annual energy--horticulture crop wise, regionwise, etc.

Livestock: The livestock population of cattle, buffalo, sheep and goat were collected from the state veterinary department.  The quantity of dung yield varies from region to region.  It was taken as 12-15Kg/animal/day for buffalo, 3-7.5 Kg/animal/day for cattle, 0.1 kg/animal/day for sheep and goat. The total dung produced annually was calculated by multiplication of the animal dung production per year and the number of head of different animals (FAO) taking the lower and higher dung yield.  Assuming 0.036m³ –0.042m³ of biogas yield per Kg of cattle/buffalo dung, the total quantity of gas available was estimated.  The per capita biogas demand varies across the agro-climatic zones. A per capita requirement of 0.34m³/person/day (zones 1-8), 0.43m3/person/day (zone 9) and 0.23m³/person/day (zone10) was taken for the computation of the biogas demand across the agro-climatic zones. Total bioenergy from livestock (Bio₅) is computed by:

Bio₅ = Bioenergy from livestock (kcal)
                                        = (Biogas * Energy Equivalent)  …………………(5)

Where, Biogas (m³)= Biogas yield * Dung * 1000   and
Dung (tonnes)= Dung yield * Population * 365   (for annual energy computation).
Data input to compute energy from livestock are livestock type (i.e. Buffalo, Cattle, Goat, etc.); population, dung yield (kg/animal/day), biogas yield (m³/kg) and energy equivalent (kcal/m³), and output would be biogas (m³) and annual energy.

Total bioresource available from various sectors is computed by aggregating the energy computed from individual sectors (forestry, plantation, horticulture, agriculture, livestock) and is given by,

…………………(6)

Where i=1, 2…5 and Bio₁: Bioenergy from forest, Bio₂: agriculture, Bio₃: plantation, Bio₄: horticulture and Bio₅: livestock.

Bioresource demand: Most of the bio-fuels consumed in rural areas (nearly 75%) are for domestic purposes mainly for cooking and water heating.  The remaining is consumed by indigenous rural industries.  Estimation of rural energy demand for domestic purposes was based on the state rural population, which was obtained from the provisional population total, Census of India 2001-Karnataka.  Energy demand Survey results reveal that 80-85 % of the rural population is dependent on bioenergy and hence the demand was projected taking into account the entire rural population. Domestic fuel consumption depends on the size of the family.  Energy consumption patterns are seen to vary across geographical, agro climatic zones, seasons and the different economic strata of the society. The per capita fuel consumption is given by

PCFC = FC / P                                                                               ……..                (7)

Where FC is the fuel consumed in Kg/day and P is the number of adult equivalents, for whom the food was cooked.  Standard adult equivalents of 1, 0.85 and 0.35 for male, females and children (below 6 years) respectively were used.   The per capita values used for cooking and water heating across the agro-climatic zones are: hilly region (1.72 kg/person/day for water heating and  2.32 kg/person/day for cooking),  coastal region (1.17 kg/person/day for water heating and  2.07 kg/person/day for cooking) and the remaining zones (1.02 kg/person/day for water heating and  1.85 kg/person/day for cooking (Please note the variation in consumption due to seasons has been accounted in this computation). In urban areas too fuel wood is used for domestic purposes by a smaller fragment of the population. The urban fuel demand was computed by taking a per capita value of 1.65kg/person/day for cooking and 1.07kg/person/day for water heating.

Conversion Technologies: Besides satisfying the rural domestic energy requirements (cooking and water heating), biomass also finds use in the manufacture of construction materials like bricks, lime and tiles, and in agro-processing such as curing of tobacco, preparation of crude sugar etc.  Cooking energy requirements are also met from cattle dung, leaf biomass from energy plantations and crop residues.

In comparison to the fossil fuels, fresh biomass has certain drawbacks like, high moisture content that reduces its combustion efficiency, low bulk density and lack of a homogeneous physical form.  Biomass conversion helps to improve the characteristics of the material as a fuel.  The conversion processes largely involve the reduction of the water content and improving the handling characteristics of the material. The energy so obtained can be used for domestic purposes, in agriculture, small scale industries like jaggery making, sericulture activities, coffee/tea processing, paper making, paddy drying etc. To exploit the energy content, the biomass feedstock is subjected to either physical, chemical, biological or thermochemical conversion processes.