At present there is hardly 0.4 percent forest below 25cm rainfall zone and 1.3 percent above 30 cm rainfall zone. Laticiferous plants with their rich hydrocarbon contents offer such potential plant systems which on one hand, due to their water conversion ability they thrive on limited amount of water, produce sufficient biomass and are unpalatable to the cattle folk due to their sticky latex. Degraded and denunded soils are no hindrance to their growth. During the present invstigations a account of possible bio-fuel plants from semi-arid and arid regions shall be presented.
1.1 Biomass is renewable source of Energy and is produced annually in amounts greater than the annual global requirement of the biomass.
1.2 The main sources of biomass can be classified in two groups one is waste materials including those derived from agriculture, forestry and municipal wastes1, 2,3.
1.3 Assessing the total above ground biomass, defined as biomass, when expressed as dry weight per unit area, either total biomass or by components (eg. leaves, branches and bole), is a useful way of quantifying the amount of resource available for traditional uses. Most plant species are herbaceous in nature and appear during rainy season. They are the first colonizers&are generally herb, which have important uses4, 5.
1.3 Biomass can be converted in to solid, liquid and gaseous forms through biological thermochemical route for deriving thermal electrical and mechanical forms of energy. Thus biomass offers multiple options for transition from the use of conventional, exhaustible and polluting forms to non-conventional, renewable, non-exhaustible, non polluting and perennial forms so as to ensure sustained growth and economic development6,7,8.
1.4 Some herbaceous and shrub plants are also important for biomass production in the form of bioenergy9,10,11,12,13.
1.5 Beside the solid biomass some plant species are important for liquid biomass in form of hydrocarbon and non edible oil production, which provides an alternative source of petroleum14,15,16.
1.6 Present studies were conducted on characterization of bio-energy resources in the semi arid region of Rajasthan because the growing demand for fuel wood as a result of rapid population growth has made it increasingly difficult for many people in this region to meet their basic energy need.
2.1 Solid Biomass:
Collection of plant species in all the seasons was carried out and three replicates were taken. The fresh weight and dry weight was recorded.
2.2 Extraction of hydrocarbons:
The determination of hydrocarbon content was made following17 the same procedure was employed for extraction of hydrocarbons (biocrude) by using solvent methanol and hexane in the soxhlet apparatus. The methanolic extracts (60°C) were collected after 18 h. The hexane (55°C) extractables were also collected after 18 h, respectively.
2.3 Extraction of non-edible oil:
Non edible oils were estimated following18. Non-edible oil yielding plants were selected for the study. For the extraction of non edible oil, seeds were collected and dried. After drying a fine powder was made which was placed in a thimble Whatman filter paper no. 1. Ten gram of powder was placed in each thimble. Extraction was done by using solvent petroleum ether in a soxhlet apparatus at 40°C to 50°C for about 30 h. The petroleum ether extractable was collected after 30 h, and excess of solvent was removed by distillation at 45°C. The fractions were transferred to the previously weighed flask and were finally dried at 40°C for 24 h or till the weights become constant for determination of oil.
3.1 Solid Biomass:
The characterization of plant diversity was another aspect of study on plant community. 130 plant species were recorded. Out of the out of which 40 plant species were selected for biomass production in their natural habitat.
Plants were collected from studied areas in natural condition. Three replicates of each plant were collected and their fresh and dry weights were recorded in each season.
Out of the 40 plants following plant species were suitable for biomass production due to their high dry matter contents. These plants included (weights in g/plant) Verbesina encelioides (Cav.) Benth. & Hk.: 80.33; Calotropis procera (Ait) R.Br.: 648.33; Leptadenia pyrotechnica (Forsk.) Decne. : 486.66; Sericostoma pauciflorum Stocks. : 352.66; Amaranthus spinosus Linn. : 167.66; Withania somnifera (L.) Dunal. : 350; Lepidagathis trinervis Wall. ex Nees. : 204; Lantana indica Roxb. : 373.33; Aerva tomentosa (Burm.) Juss. : 283.33; Croton bonplandianum Baill. : 155.33; Abutilon indicum (L.) Sweet. : 1453.33; Acacia jacquemontii Benth. : 693.33; Crotalaria burhia Buch.-Ham. ex Benth. : 266; Saccharum bengalense Retz. : 1900 and Artemisia scoparia Waldst. et Kit. : 90. The plant biomass in terms of fresh weight and dry weight was recorded in all the three seasons.
3.2 Extraction of hydrocarbons:
Hydrocarbons were extracted by using two different solvent hexane and methanol. Among the different plant extractions Euphorbia antisyphilitica Zuce. showed the best extraction results in heptane 12.5 % and Calotropis procera (Ait.) R.Br. showed best results in methanolic extraction 33.8%.
Percent hydrocarbon contents in above ground part of different plants in Heptane extraction (HE) and Methanolic extraction (ME)
Name of the plant ME HE
Calotropis procera (Ait.) R.Br. 38.8 6.2
Euphorbia antisyphilitica Zuss. 27.5 8.5
Calotropis gigantea 26.5 5.2
Euphorbia neriifolia 7.13 6.31
Euphorbia lathyris 21.56 5.57
Euphorbia tirucalli 6.31 3.48
Padilanthus tithymaloides var 6.68 3.12
Euphorbia nivulia 12.0 6.40
3.3 Extraction of non-edible oil :
In order to study non-edible oil production, 6 plants were selected for studies. Non-edible oil was extract by using solvent petroleum ether. Among different seed oil contents determined maximum seed oil was recorded in Ricinus communis Linn. This was followed by others.
Non-edible oil content in seeds of different plant species
Name of the plants Percent seed oil
Argemone mexicana Linn. 34.0
Azardirachta indica A. Juss 29.3
Pongamia pinnata (L.) Pierre. 39.2
Jatropha curcas Linn. 37.2
Ricinus communis Linn. 48.2
Calotropis procera (Ait.) R.Br. 36.2
A large number of potential plants are found under semi arid and arid conditions of Rajasthan. Biomass contributes a significant share of global primary energy consumption and its importance is likely to increase in future world energy scenarios. Current biomass use, although not sustainable in some cases, replaces fossil fuel consumption and results in avoided CO2 emissions, representing about 2.7% to 8.8% of 1998 anthropogenic CO2 emissions. The global biomass energy potential is large, estimated at about 107 EJ/a. Hence, biomass has the potential to avoid significant fossil fuel consumption, potentially between 17% and 36% of the current level and CO2 emissions potentially between 12% and 44% of the 1998 level. Modern biomass energy use can contribute to controlling CO2 emissions to the atmosphere while fostering local and regional development. There is significant scope to integrate biomass energy with agriculture, forestry and climate change policies. Further the advantages from utilization of biomass include: liquid fuels produced from biomass contain no sulphur, thus avoiding SO2 emissions and also reducing emission of NOx. The production of compost as a soil conditioner avoids deterioration of soil.
Improved agronomic practices of well managed biomass plantations will also provide a basis for environmental improvement by helping to stabilize certain soils, avoiding desertification which is already occurring rapidly in tropical countries. The creation of new employment opportunities within the community and particularly in rural areas will be one of the major social benefits.
The present investigations carried out with an object of biomass production and utilization in less fertile areas, will provide satisfactory answers to the double challenge of energy crisis and forced deforestation in the country and semi-arid and arid regions of Rajasthan17 has suggested that biomass from plants can be converted into liquid fuels. This will make it possible to supply part of the increasing demand for primary energy and thus reduce crude petroleum imports, which entail heavy expenditure on foreign exchange. Several families widely growing in Rajasthan have great potential as renewable source of energy. Euphorbiaceae (Euphorbia antisyphilitica, E. tithymaloides, E. caducifolia, E. lathyris, E. neerifolia etc. Aselipiadaceae (Calotropis gigantea and C. procera) Asteraceae and Apocynaceae have large number of valuable plants17.
Characterization of biomass production in wastelands during the present investigation offers a database of potential plants to be used in arid and semiarid regions and a three tier system has been developed.
However further studies are needed to establish gene pool database on the basis of RFLP and AFLP so that it could be used for genetic transformation studies. Which can help for development of bioenergy source from these arid and semiarid wasteland of Rajasthan.
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