Biomass – 03
First generation biofuel technology
The first generation biofuels are produced from cereal crops (e.g. wheat, maize), oil crops (e.g. rapeseed, palm oil) and sugar crops (e.g. sugar beet, sugar cane) using established technology. So the conversion of sugars (sugar cane) and starch (potato, cassava, maize) or oil (oil palm, rapeseed) accumulated in food crops into ethanol and biodiesel respectively accounts the first generation.
- Bioethanol – The alcohols such as bioethanol, propanol and butanol are produced by microbial fermentation of sugars or starches, derived from feedstocks of wheat, corn, sugar beet, sugarcane, molasses, potato, etc. In the first step complex sugars are hydrolysed and glucose released undergo second fermentation step carried out by yeasts such as Saccharomyces cerevisiae producing ethanol and carbon dioxide. Further diluted ethanol undergo distillation to obtain highly concentrated ethanol in the final step.
- Biodiesel – The biodiesel is produced mainly by transesterification of fatty acids of lipids (vegetable oils or aimal fat) with alchol to form a mix of fatty acid alkyl esters (FAAE). When methanol is used for transesterification biodiesel is fatty acid methyl esters (FAME), while the ethanol is used it is fatty acid ethyl esters (FAEE).
- Biogas- Biogas consists of methane produced by process of anaerobic digestion of organic material by anaerobic microorganisms which is used as an energy source and solid by-product, digested, is used as 6 Environmental Sciences Energy and Environment Types of Biofuels, Energy conversion routes from biomass an organic manure. The biogas can be produced from any waste with organic fraction in comparison to ethanol ad biodiesel production from crops.
- Syngas – Syngas is a mixture of carbon monoxide, hydrogen and other hydrocarbons produced by partial combustion of biomass, that is, the burning with a volume of oxygen that is not sufficient to transform the biomass waste completely to carbon dioxide and water. The syngas is more efficient than direct combustion of the original biofuel; more of the energy contained in the fuel is extracted. Syngas may be burned directly in internal combustion engines, turbines or high-temperature fuel cells. Syngas can be utilized to produce methanol, DME, and hydrogen.
- Biochar – Biochar is one of the prodcut of pyrolysis and is often used to pre-dry biomass feedstock or sold as charcoal briquettes. Its high stability against decay and ability to retain more plant nutrients as compared to other forms of organic matter made the biochar as a good soil amendment.
Second generation biofuel technology
Second-generation biofuels are produced from sustainable feedstock. The second-generation biofuels are produced from cellulosic materials and also based on the use of dedicated energy crops like switchgrass grown with reasonable inputs and using conversion techniques that provide high net energy efficiency (output/input). Many second generation biofuels are under development i.e. cellulosic ethanol, biohydrogen, methanol, DMF, Fischer-Tropsch diesel, etc.
Third generation biofuel technology
Microalgae has been considered as third generation potential feedstock for producing sustainable transport fuels (biodiesel). Microalgae are sunlight-driven cell factories that convert carbon dioxide to potential biofuels. Depending on species, microalgae produce kinds of lipids, hydrocarbons, and other complex oils. Certain algae and cyanobacteria have high lipid contents. This lipid contents derived from microalgae can be used for biodiesel production. Under proper conditions, these microorganisms can produce lipids for biodiesel with yields per unit area that are 50-l00% higher than those with any plant system. Microalgae can also provide various types of renewable biofuels which include methane by anaerobic digestion of the algal biomass and photo-biologically produced biohydrogen
Fourth generation biofuel technology
The 4th generation biofuels are based on photo-biological solar fuels, and electro fuel is expected to bring significant breakthroughs in the domain of biofuels. The solar biofuel relies on the direct conversion of solar energy into fuel using raw materials that are inexhaustible, inexpensive and widely available. This is expected to happen via advanced progress of synthetic biology as an enabling technology for such a change. These biofuels are obtained from the conversion of living organisms (microorganisms and plants) using biotechnological tools (bioengineering). The mean conversion efficiency for the total solar spectrum amounts to ca. 20%, which is on average about ten times higher than for seasonal crops. This excellent efficiency should be considered a potential level. Currently, this technology is still expensive and not yet ready for commercial exploitation