Solar Thermal Pyrolysis is the Sustainable Route for Biofuel Production

The worldwide population has continuously increased which causes more energy consumption. With a rapid social and economic growth, demand of energy consumption is continued to increase while slowly exhaustion of fossil fuels. According to report, in 2014 the primary energy demand of oil was assessed to be around 13,000 megatons annually throughout the worldwide, indicating a raise of 22% and 54%, compared to 2004 and 1994, respectively. To fulfill the energy demand by using fossil fuels is one of the big challenges in front of scientific community. Therefore there is need to develop a pathway for biofuel production using some renewable, abundant available material such as biomass. Conversion of biomass into energy rich fuels through pyrolysis process has paid significant attention throughout the worldwide.

Biomass potential for energy generation in India
The total available land in India is about 328 Mha (million hectares) among this nearly 39 Mha area is covered by marginal land, which is 12% of the whole area. The marginal land is simply defined as the agricultural land which was initially used for sowing and cultivation purpose but presently is not in application due to reduction in productivity. Mostly, marginal land is not recognized for agricultural practices by the reason of high-risk lower production that simultaneously affect on agricultural economy. Therefore, reforming the marginal land for good agricultural production will require more amounts of chemical fertilizer dosages which can raise the economics and also affect on environment. However, many researchers found that marginal land is more capable to produce 230-720 MT of energy crops annually. These energy crops have a potential in between 1-13 EJ annually, which almost cover 11 to 160% energy demand of transport sector. The energy crops have a total bio-fuel potential is in between 3-103 GGE/y, which almost cover 5 to 160% of gasoline demand in transport sector. The total availability agriculture and forest residues in India are nearly about 439 and 19 MT, indicating potential to generate energy in 1.8-7.2 EJ annually that fulfills the 21- 84% energy demand in transport sector. In terms of biofuels, the energy crops have a potential to produce 6-37 GGE annually, which may cover 10-56% of gasoline demand.

What is biomass pyrolysis?
Pyrolysis is a thermochemical conversion process, where biomass is heated in absence of air or with a limited supply of air at a requisite temperature in the range of 400-600oC which yield three different end products like biochar, bio-oil, and syngases. Unlike combustion process, pyrolysis reaction is not exothermic and takes place in absence of air except in some cases where limited supply of air is needed. In pyrolysis, hydrocarbon molecules of biomass are subsequently broken down into smaller ones.
 

Need of solar based pyrolysis
Biomass pyrolyzers are mainly relies on fossil fuels to obtain desired heat for conversion of biomass into value added products. Most particularly, where energy resources are not available, biomass combustion is practiced for providing energy to pyrolyzer may results in emission of greenhouse gases. Thermochemical conversion system needs a large infrastructure and huge capacity reactor to manage the organic waste. Unfortunately, a large-scale infrastructure or reactors may not prefer in economically developing nations, require large source of fossil fuel which is not economically practical. Therefore, there is need to develop a solar thermal based pyrolysis system for biofuel production. In case of solar biomass pyrolysis, energy in the form of heat is concentrated on a reactor to achieve requisite carbonization temperature. For example, a tubular or box type reactor made of stainless-steel material act as an absorber, which is placed at a focus point of sunlight, such as concentrate parabola, solar chimney, Fresnel, etc. which delivers several salient benefits such as;
• Self-sustainable biofuel production technique
• No need of external commercial energy
• No operational cost
• Uniform biofuel production
• No need of skilled trainer for operation
• Easy for construction
• One time capital investment
• No environmental pollution
• Yield biochar, bio-oil, and syngases
 

Applications of Bio-fuels
Solar thermal pyrolysis mainly gives three end products such as biochar, bio-oil, and syngases which having many environmental applications such as;

Conclusion:
Over all, solar thermal pyrolysis open a new window to the researchers, scientific community, and in front of entrepreneurs for sustainable biofuel production. All the three products of pyrolysis i.e., bio-oil (liquid), biochar (solid) and pyrolytic (syngases) gas could be used efficiently in different sectors including transportation and industrial heating and power applications.

- Dr. Ashish Pawar, Research Associate, Sardar Swaran Singh National Institute of Bioenergy, Kapurthala (Punjab)