6 . Results and Discussion

Renewable energy resources are those having a cycling time less than 100 years. These are the resources that are renewed by nature again and again and their supply is not affected by the rate of consumption. Biomass is a renewable energy source arising from a range of organic matter derived from biological organisms like plants and animals and the energy obtained from it is known as bio energy. When energy demand exceeds the supply (availability), it is considered as non-renewable resource.

The bioresource potential and demand (from forests, plantations, agriculture, horticulture and animal residues) for Karnataka across the agro-climatic zones was calculated from the available secondary data. The ratio of the availability to demand indicates the bioresource status of various agroclimatic zones in the State. Ratio greater than one indicates the presence of surplus bioresource, while a value less than one characterises a bioresource deficient zone. Bioresource status computed for various zones listed in Table 36 shows that the value ranges from 0.23 (north-eastern dry zone), 0.93 (eastern dry zone), 1.4 (central dry zone) to 3.79 (hilly zone). These values reveal that among the ten agro-climatic zones, the central dry zone, the Southern transition zone, Hilly zone and the Coastal zone are bioresource surplus, while the North Eastern transition zone, North Eastern dry zone, Northern Dry zone, Eastern dry zone, Southern dry zone, Northern transition zone are biomass deficient zones. In these zones, biomass resource is non-renewable as the demand has exceeded the available stock, which would further erode the availability unless suitable intervention measures are undertaken to augment the resources.

Table 36: Bioresource status across agro-climatic zones (energy units in 10⁶ Mkcal)

6.1 Bioresource availability

The computation of bioresource availability from various sectors (agriculture, forest, etc.) indicates that the northeastern dry zone (zone 2) characterised by dry deciduous and scrub vegetation has the lowest energy potential (1120312.39 Mkcal). Hilly zone (zone 9) accounts for the maximum energy potential of 31820303.1 Mkcal. The taluk wise details of bioenergy from forest residues for each of the agro climatic zones are given in the annexure 5. Energy from forest across agro-climatic zones is shown in Table 37. Talukwise computation of bioenergy availability from forests as shown in Figure 2, indicates that, Kollegal (zone 6) taluk in Chamrajnagar district has highest energy (5678778 Mkcal) compared to six taluks in the State where there are no forests and have least potential.

Table 37: Energy from forest across agro-climatic zones (energy units in 10⁶ Mkcal)

Southern dry zone (zone 6) has the lowest energy potential from plantations amounting to 1141.29 Mkcal. Hilly zone (zone 9) has the maximum energy potential with 97344.0 Mkcal. The taluk wise details of the energy equivalents of plantation residues for each of the agro climatic zones are given in the annexure 7. Energy from plantation across agro-climatic zones is shown in Table 38. Talukwise computation of bioenergy availability is illustrated in Figure 3, which indicates that Sagar ( zone 9) taluk in Shimoga district (41607.5 Mkcal) yields maximum energy from plantation when compared to 75 taluks in the State with zero potential.

Table 38: Energy from plantation across agro-climatic zones (energy units in 10³ Mkcal)

Agriculture is predominant in zone 3 (northern dry zone). The highest amount of bioenergy available from agro residues in this zone amounts to 10595592.78 Mkcal. Of the 10 zones, Zone 10 (coastal zone) has the lowest potential for bioenergy from agriculture residues amounting to about 338755.28 Mkcal. Energy from agro-residues across agro-climatic zones is given in Table 39.

Table 39: Energy from agro-residues across agro-climatic zones (energy units in 10⁶ Mkcal)

The taluk wise details of the energy equivalents of agro residues for each of the agro climatic zones are given in the annexure4 The coastal zone (Zone 10) has the highest potential for bioenergy from horticulture residues. About 25282919 Mkcal of energy is available from coconut, areca and horticulture residues. Energy from horticulture residues across agro-climatic zones is shown in Table 40. The northeastern transition zone (Zone 1) has the lowest potential for bioenergy with 1883.8 Mkcal. The annexure 6 gives the taluk wise details of energy from horticulture residues. Talukwise computation of bioenergy availability as illustrated in Figure 4 indicates that Athani taluk (in zone 3) in Belgaum district has highest energy (1.51 x 10⁶ Mkcal) compared to Bantwal taluk ( zone 10) in Dakshina Kannada district that has the least potential (1147.72 Mkcal). Talukwise computation of bioenergy availability from horticulture as illustrated in Figure 5 which indicates that Channagiri (zone 7) taluk in Shimoga district yields maximum energy (7549933 Mkcal) and 5 taluks in Bidar (zone 1) district yield no energy.

Table 40: Energy from horticulture residues across agro-climatic zones (energy units in 10³ Mkcal)

6.2 Bioresource Demand

The bioenergy demand for cooking and water heating calculated on the basis of the rural population shows that the northern dry zone has the highest demand (31228112.5 Mkcal), while the northeastern transition zone has the lowest demand with 6388346.4 Mkcal.

The bioresource status across the surplus and deficient agro-climatic zones is discussed below:

6.3 Bioresource surplus zones

The hilly zone (9) has the availability to demand ratio of 3.79 indicating surplus resources. In this zone forests contribute the maximum energy potential of 31820303.1 Mkcal and a majority of the area is under forest. The zone extends over an area of 2.56 Mha constituting 13.44% of the total area of Karnataka. As per the agricultural records about 0.64 Mha of the land come under the net cropped area. The ratio of the net irrigated area to the net-cropped area is about 19.71%. About 1.87 million tonnes of agro residues are available. The energy from the recoverable residues works out to be 1441657.50 Mkcal. Considering the four bioresources, forest contributes 56%, horticulture and agro-residues contribute 41% and 2% respectively towards the available bioenergy. This zone has a rural population of 2628250 persons requiring 14846830.3 Mkcal for domestic purposes.

In the coastal zone (10) the bioresource status being 3.40 indicates a biomass surplus. This zone extends over an area of 1.16 Mha, which is 6.13% of the total geographic area of the State. About 2.59 Mha of the land comes under the net-cropped area (2.45%). The ratio of the net-cropped area to the net irrigated area is about 40.83%. This zone has the lowest potential for bioenergy from agriculture residues and highest potential for bioenergy from horticulture residues. The amount of agro residues available for this zone is about 0.68 million tonnes having a recoverable energy equivalent of 338755.2 Mkcal. About 25282919 Mkcal of energy is available from coconut, areca and horticulture residues. From the Figure 7, it can be seen that horticulture contributes to 64%, forests 35% and agriculture 1% towards the available bioenergy. This zone has a comparatively higher rural population density of 2.21 persons/ha. For a rural population of 2580238 persons, the average domestic energy demand was calculated to be 11561091.53 Mkcal.

The southern transition zone (7) has a bioresource status of 3.12 indicating a biomass surplus zone. This zone has a geographic area of 1.21Mha, which is 6.39% of Karnataka's geographic area. As per agriculture records, about 0.61 Mha of land come under the net cropped area. The ratio of the net irrigated area to net-cropped area is 29.44%. The total amount of residues available from agriculture is about 2.73 million tonnes and the recoverable energy equivalent of the residues is 1761192.73 Mkcal. The zone has a rural population of 2416282 persons (1.98 persons/ha). The annual average energy demand for cooking and water heating worked out to be 9731318.8 Mkcal. Horticulture residues are the main contributors to the available energy contributing (66%), followed by forests (28%), and agriculture (6%) as shown in the Figure 7. Among the horticulture crops the major share of energy comes from areca (99%) and about 1% from coconut.

The Central dry zone (4) has a bioresource status of 1.4. This zone has a geographic area of 1.94 Mha, which is 10.20% of the total area of Karnataka. Data collected from the agricultural department reveals that the net cropped area of this zone is about 1.127 Mha. The ratio of the net irrigated area to the net-cropped area is 15.9%. The average total agro-residues produced in zone 4 are about 2.67 million tonnes. But not all residues are available for meeting the energy requirements. The stalk of crops like jowar, ragi (finger millet), wheat and paddy are largely used as fodder leaving the remaining for use as fuel. The average energy from the recoverable residues is about 1689907.1 Mkcal. As per the 2001 provisional census, the rural population of this zone is 1622769 persons (1.79 persons/ha). The rural average energy demand for cooking and water heating was worked out to be 6388346.4 Mkcal. Considering the average resource availability and average demand, from the Figure 7, it follows that the major contributor towards the available bioenergy potential is horticulture residues (78%), followed by forests (13%) and agriculture residues (9%). Areca biomass contributes to 90 % of the energy from horticulture residues. The bioresource status being 1.4 shows that the central dry zone is bioresource surplus.

6.4 Bioresource deficient zones

The North Eastern Transition (1) zone has bioresource status of 0.48, indicating bioresource scarcity in this zone. This zone extends over an area of 0.87 Mha, about 4.57% of the geographical area of the State. The net cropped area is about 0.62 Mha (5.91%). The ratio between the net irrigated area to the net-cropped area is about 7.71%. About 1.10 million tonnes of agricultural residues is available in this zone with a recoverable energy equivalent of 1571391.5 Mkcal. From the Figure 7, it follows that agriculture residues are the major contributors of the available bioenergy-52%, followed by forests-48%. This zone has a rural population of 1622769, with an average domestic energy demand of 6388346.4 Mkcal.

The North Eastern dry zone (2) has bioresource status as 0.23, indicating bioresource scarcity in this zone. It covers about 1.76 Mha in geographical area i.e.9.25% of the total area of Karnataka. About 1.25 Mha of land come under the net-cropped area, with the ratio of the net irrigated area to the net-cropped area being 15.51%. This zone is characterised by dry deciduous and scrub vegetation and has the lowest energy potential (1120312.39 Mkcal). The amount of agro-residues available for this zone is about 1.37 million tonnes having a recoverable energy equivalent of 1000192.66 Mkcal. Forests contribute 53% to the available bioenergy (1120312.4 Mkcal), while agriculture contributes about 47%.

In the northern dry zone (3) the bioresource status being 0.58 indicates bioresource scarcity in this zone. This zone extends over an area of 4.78 Mha, covering 25.11% of the total area of Karnataka. The net-cropped area is about 3.48 Mha and the ratio between the net irrigated area to the net-cropped area is about 26.23%. The highest amount of bioenergy available is from agro residues in this zone amounting to 10595592.78 Mkcal. About 10.53 million tonnes of agriculture residues are available in this zone. Agriculture residues contribute to 59% of the total available energy, while forests contribute 40% and horticulture residues about 1%. This zone supports a rural population of 7935875 persons, with an average domestic energy requirement of 31228112.5 Mkcal.

The Eastern dry zone (5) is also bioresource deficient as bioresource status is 0.39. It covers a geographic area of 1.80 Mha, which is 9.49% of the geographic area of the State. The net-cropped area is about 0.88 Mha and the ratio of the net irrigated area to the net-cropped area is about 18.92%. The agro-residues available for this zone are about 1.81 million tonnes from which 557287.23 Mkcal can be obtained. From Figure 7, it follows that horticulture residues contribute 54% (4025853.012 Mkcal) to the total available energy followed by forests-39% and agro residues-7%. The rural population of this zone is 4704991 persons, with a population density of 1.79 persons/ha. The average rural energy demand for domestic purposes works out to be 19009680.2 Mkcal.

The Southern dry zone (6) has a bioresource status of 0.93, and hence is a bioresource deficient zone. It extends over an area of 1.73 Mha, covering 9.13% of the total geographic area of the State. The net cropped area is about 0.27 Mha, the ratio of the net irrigated area to the net-cropped area being 32.99%. The total agro residues available for this zone are 4.18 million tonnes, having an energy equivalent of 4385019.5 Mkcal. Forests contribute to 53% of the available energy (8362610.25 Mkcal) followed by agriculture residues-28% and horticulture-19%. This zone has the lowest energy potential from plantations amounting to 1141.29 Mkcal. The rural population of this zone is 4132307 persons. Of all the agro-climatic zones this is the most populated with a population density of 2.38 persons/ha. The calculated average rural energy demand is about 16772136.8 Mkcal.

The Northern transition zone (8) has bioresource status of 0.45, indicating it to be a bioresource scarce zone. It covers an area of 1.19 Mha, covering 6.27% of the total area of Karnataka. The net cropped area is about 0.89 Mha. The ratio of the net irrigated area to the net-cropped area is about 15.30%. The total agro-residues available from this zone are 2.76 million tonnes having an energy equivalent of 1761192.73 Mkcal. Agriculture contributes 61% towards the bioenergy available, followed by forests contributing 36% and horticulture residues contributing 2%.

Figure 6 illustrates bioresource surplus and deficit zones in the state. The computation of bioenergy availability, demand and status talukwise shows that Siddapura (zone 9) taluk in Uttara Kannada district has the highest bioenergy status of 2.004. Anekal (zone 5) taluk in Bangalore Urban district has the least status of 0.004.

6.5 Viable Alternatives - Wasteland availability in each zone

In the bioresource deficient zones, wastelands provide a viable alternative for energy plantations. In the surplus zones too, they are very promising as they help in reducing the pressure on the existing bioresource. The percentage of wasteland in each of the agro climatic zones is listed in Table 41.

Table 41: Percentage of wasteland each in the Agroclimatic Zones

The central dry zone has 17.23% of wastelands followed by coastal zone (16.29%), southern transition zone (10.49%) and hilly zone (8.88%). These zones come under bioresource surplus regions and these wastelands can be utilised for growing energy plantations like Acacaia auriculiformis, Casuarina and Eucalyptus species. Assuming an average biomass productivity of 5 tonnes/ha/year from these plantations, the total amount of exploitable biomass becomes 4400945 tonnes/year.

In the bioresource deficient zones, the northeastern dry zone has the highest percentage of wastelands (18.46%), followed by the southern dry zone (18.09%), northern dry zone (17.79%), eastern dry zone (15.94%), northeastern transition zone (13.87%) and the northern transition zone (8.32%).

In the northern dry zone, agriculture contributes to 59%, forests 40% and horticulture 1% towards the total energy requirements. About 850998 ha of wastelands are available in this zone. In the eastern dry zone, horticulture contributes 53%, forests-39% and agro residues-8% towards the total energy requirements. About 228196 ha of wasteland is available in this region. In the southern dry zone, forests contribute 53%, while agriculture and horticulture residues contribute 28% and 19% respectively in meeting the bioenergy demand. 314755 ha of wastelands are available in this zone, capable of being used as energy plantations. In the northern transition zone, agriculture contributes 61%, forests 36% and horticulture residues 2% towards bioenergy demand. The extent of wastelands available in this zone is 99462 ha. The total extent of wastelands available for the energy deficient zones is 1999046 ha. Raising a mixed species energy plantation and assuming a productivity of 5 tonnes/ha/year, the total available biomass would be 9995230 tonnes/year.

The energy deficient zones can conserve biofuel by using improved cook stoves, utilisation of the wastelands for energy plantation and opting for alternative energy sources like biogas technology.

6.6 Biogas potential

The taluk wise livestock population and annual biogas produced are given in the annexure 8. Considering lower dung yield figures, the total dung available from cattle and buffalo is 11.83 million tonnes/year and 29.58 million tonnes/year respectively. If the higher dung yields figures are taken 19.11 million tonnes/year and 23.88 million tonnes/year of dung from cattle and buffalo are obtained. Assuming the biogas (m³) produced per kg of the cattle/buffalo dung to be 0.036 m³/day and taking the lower dung yield for each of the two about 1114012196 m³ of biogas can be produced annually. Using higher dung yields and higher biogas yields, the total amount of gas produced worked out to be 2245847836 m³. The annual biogas demand was computed for each of the zones using rural population figures of Census 2001. The fraction of bioenergy demand that can be met by biogas is given in tables 42 and 43. The Southern transition zone has the highest biogas potential. In this zone biogas provides a viable energy alternative capable of meeting 35.78% of the rural energy.

Livestock is predominant in northern dry zone. The highest amount of bioenergy available from livestock in this zone amounts to 1361001 Mkcal. Talukwise computation of bioenergy availability illustrated in Figure 8 indicates that Raibag (zone 3) taluk in Belgaum district (99588.87 Mkcal) has highest energy compared to Gudibanda (zone 5) taluk in Kolar district (6438.28 Mkcal), which has the least potential.

Table 42: Biogas availability based considering lower values for dung and biogas yield (energy units in 10³ Mkcal)

Table 43: Biogas availability based considering higher values for dung yield and lower value for biogas yield (energy units in 10⁶ Mkcal)

6.7 Urban Domestic Energy Demand

A part of the urban population also relies on bioresource to meet their domestic energy requirements. Taking this fraction to be 60%, and the average per capita consumption as 1.65 kg/person/day for cooking and 1.07 kg/person/day for water heating; the total fuelwood required would be 10.25 million tonnes whose energy equivalent would be 46139789.6 Mkcal. The average fuelwood and energy requirements computed for each of the agro-climatic zones are given in the Table 44.

Table 44: Urban Bioenergy Demand across Agroclimatic Zones (energy units in 10⁶ Mkcal)