Even though use of fossil fuel leads to emission of harmful gases, which cause such negative environmental effects as receding of glaciers, loss of biodiversity, climate change, rise in sea level, etc., fossil fuel still remains a primary energy source with a contribution of around 80%, in which transport sector takes share of 58%. Many alternative fuel sources, however, exist including biofuel. Biofuels are liquid or gaseous fuels produced from biomasses. Gaseous biofuels are normally used for heat and power production, whereas liquid biofuels are generally employed in the transportation sector.
The advantages of biofuels over petroleum fuels include ease of extraction from the biomass, its combustion based on carbon-dioxide cycle, they are sustainable due to biodegradable property, more environmentally friendly. Sustainability of biofuel, however, as a whole may seem questionable, because in spite of its benefits the production and end use of biofuels have a serious impact on the environment such as destruction of forests, increase in soil degradation, reduction in food production, use of large amounts of water. Therefore, in addition to terrestrial and energy crops, many other types of biomass have been studied and used recently to overcome above mentioned negative effects.
Lignocellulosic biomass can be divided into several groups such as energy crops (perennial grasses and other dedicated energy crops), aquatic plants (water hyacinth), forest materials (soft wood, hard wood, sawdust, pruning and bark thinning residues), agricultural residues (cereal straws, stovers and bagasse), and even organic portion of municipal solid wastes. Each group of biomass has some potential to be used for ethanol production to complement traditionally used sugarcane and corn to meet growing bioethanol demand (https://www.permaculturenews.org/2010/06/02/biofuels-and-confirmation-bias/).
Marine biomass, including seaweeds, is a new source of biofuel feedstock, producing the highest percentage of biomass productivity in lesser time. The recent research focuses on the effective utilization of algal biomass for liquid biofuel production such as ethanol and butanol via sugar production by enzyme hydrolysis and fermentation by respective microbes. The reported advantages of seaweeds for biofuel research include: 1) the growth rate of seaweeds and biomass production was significantly higher than the flowering plants; 2) the land required for the cultivation is comparably low as compared to the terrestrial plants; 3) no requirement of fresh water, pesticides, and fertilizers for growth.
Recent research efforts are also aimed at increasing efficiency of the fermentation process. For instance, bacteria have drawn special attention because requires less fermentation time as compared to yeast. However, all microorganisms have limitations: either in the inability to process certain classes of simple sugars (pentoses and hexoses) or the low yields of the end product. Nonetheless, it has been reported that mid- to long-term technology development will improve the fermentation efficiency of the bacteria and yeast (yielding more ethanol in less time) as well as its resistance.
Numerous advancements in biomass gasification technology have made it possible to process diverse biomass feedstock in an efficient and cost-effective manner to generate H2-rich syngas, which can be used as a feedstock to produce multiple bio-fuels. Moreover, the latest developments in syngas clean-up and processing techniques have enabled its usage as a raw material for catalytic biofuel generation.
Biomass utilization has a number of advantages over other renewable sources such as solar energy, wind energy, and hydroelectric power because of its low dependence on site and climate as diverse biomasses can grow in varied conditions and can be easily stored and transported. The future of biofuel as alternative fossil fuel requires global acceptance and development of efficient biofuel-driven engines. Governments should provide necessary infrastructure and policies to support the development of biofuel industry.
References
1. Gaurav N., S. Sivasankari, GS Kiran, A. Ninawe, J. Selvin (2017) Utilization of bioresources for sustainable biofuels: a review. Renewable and Sustainable Energy Reviews 73, p. 205 – 214.
2. Sikarwar V. S., M. Zhao, P. S. Fennell, N. Shah, E. J. Anthony (2017) Progress in biofuel production from gasification. Progress in Energy and Combustion Science 61, p. 189 – 248.
3. Zabed H., J. N. Sahu, A. Suely, A. N. Boyce, G. Faruq (2017) Bioethanol production from renewable sources: current perspectives and technological progress. Renewable and Sustainable Energy Reviews 71, p. 475 – 501.
