Authors:Aman Jaiswal*, Ajay Kumar, Deepak Kumar, Swati Sagar
Division of Microbiology, ICAR-Indian Agricultural Research Institute, New Delhi (India) 110 012
*Corresponding author e-mail: amanjaiswal1989@gmail.com
Biofuels are energy carriers that store the energy derived from biomass. A wide range of biomass sources can be used to produce bioenergy in a variety of forms. For example, food, fibre and wood process residues from the industrial sector; energy crops, short rotation crops and agricultural wastes from the agriculture sector; and residues from the forestry sector can all be used to generate electricity, heat, combined heat and power, and other forms of bioenergy. The agricultural resources include grains used for biofuels production, animal manures and residues, and crop residues derived primarily from corn and small grains (e.g., wheat straw). A variety of regionally significant crops, such as cotton, sugarcane, rice, and fruit and nut orchards can also be a source of crop residues.
In addition, algae production has great promise because algae generate higher energy yields and require much less space to grow than conventional feedstocks. Algae also would not compete with food uses and could be grown with minimal inputs using a variety of methods. The biofuels produced from the renewable resources could help to minimize the fossil fuel burning and CO2 production. Biofuels produced from biomass such as plants or organic waste could help to reduce both the world’s dependence on oil and CO2 production. These biofuels have the potential to cut CO2 emission because the plants they are made from use CO 2 as they grow. Biofuels and bioproducts produced from plant biomass would mitigate global warming. This may due to the CO2 released in burning equals the CO2 tied up by the plant during photosynthesis and thus does not increase the net CO2 in the atmosphere. Additionally, biofuel production along with bioproducts can provide new income and employment opportunities in rural areas.
Types of biofuels
Biofuels can be classified according to source and type. They may be derived from forest, agricultural or fishery products or municipal wastes, as well as from agroindustry, food industry and food service by-products and wastes. They may be solid, such as fuelwood, charcoal and wood pellets; liquid, such as ethanol, biodiesel and pyrolysis oils; or gaseous , such as biogas- hydrogen and methane.
First-generation biofuels
- Such fuels are directly combusted, usually to supply cooking fuel, heating or electricity production needs in small- and largescale industrial applications.
- The first-generation liquid biofuels are made from sugar, starch, vegetable oil, or animal fats using conventional technology.
- The basic feedstocks for the production of first-generation biofuels come from agriculture and food processing.
- The three main types of first generation biofuels used commercially are biodiesel (bio-esters), ethanol, and biogas of which worldwide large quantities have been produced so far and for which the production process is considered ‘established technology’.
- The second generation technologies use a wider range of biomass resources – agriculture, forestry and waste materials.
- The examples of 2nd generation biofuels are cellulosic ethanol and Fischer–Tropsch fuels. In the context of biofuel production, the term ‘plant biomass’ refers largely to lignocellulosic material as this makes up the majority of the cheap and abundant nonfood materials available from plants.
- Plant biomass is comprised mostly of plant cell walls, of which typically 75% is composed of polysaccharides. These polysaccharides represent a valuable pool of potential sugars, and even in traditional food crops such as wheat (Triticum aestivum) there is as much sugar tied up in the stems as there is in the starch of the grains.
- The most accepted definition for third-generation biofuels is fuels that would be produced from algal biomass, which has a very distinctive growth yield as compared with classical lignocellulosic biomass.
- Production of biofuels from algae usually relies on the lipid content of the microorganisms. Usually, species such as Chlorella are targeted because of their high lipid content (around 60 to 70%) and their high productivity (7.4 g/L/d for Chlorella protothecoides). There are many challenges associated with algal biomass, some geographical and some technical. Typically, algae will produce 1 to 7 g/L/d of biomass in ideal growth conditions.
References:
1. Sukumaran RK, Singhania RR, Mathew GM, Pandey A (2009) Cellulase production using biomass feed stock and its application in lignocellulose saccharification for bio-ethanol production. Renewable Energy 34 (2):421-424.
2. Lee RA, Lavoie J-M (2013) From first-to third-generation biofuels: Challenges of producing a commodity from a biomass of increasing complexity. Animal Frontiers 3 (2):6-11.
3. Naik SN, Goud VV, Rout PK, Dalai AK (2010) Production of first and second generation biofuels: A comprehensive review. Renewable and Sustainable Energy Reviews 14 (2):578-597.
About Author / Additional Info:
I am pursuing PhD in department of microbiology from Indian Agricultural Research Institute, New Delhi-110012