First-generation technologies are well established, these include transesterification of plant oils, fermentation of plant sugars and starch for liquid biofuel production, anaerobic fermentation of organic residues to generate biogas, combustion of organic materials for heat recovery or combined heat and power (CHP) systems for the production of both heat and electrical power. Second-generation or advanced technologies often refer to the conversion of lignocellulose materials into fuels. These technologies comprise a range of alternatives such as enzymatic production of lignocellulose ethanol, syngas-based fuels, pyrolysis-oil based biofuels, gasifi­cation and others, but are not yet economically viable and technical aspects are still under development.

Much attention is currently focused on the production of liquid biofuels that are manufactured with first-generation technologies because they rely on feedstocks derived from food-crops, the so-called first-generation biofuel. Thus, this has heightened the needs to identify and work on agronomic potential of alternative bioenergy crops including non-edible oil crops such as jatropha, castor bean, jojoba, karanja that can be grown on land unsuitable for food crops and multi­purpose crops like sweet sorghum that can yield food in the form of grain, fuel in the form of ethanol from its stem juice, and fodder from its leaves and bagasse.

Deployment of second-generation technologies offers an opportunity to expand the type of feedstock and to take advantage of currently unused lignocellulose sources. It also facilitates the use of energy crops that can be grown on land unsuitable for food crops. These technologies offer a more efficient production making use of the entire plant beyond the carbohydrate component. Further research and development on bioenergy conversion technologies is required to overcome the technical barriers for them to become a viable option.

2.7 Conclusion

Various technology options are available from biomass which can serve many different energy needs from large-scale industrial applications to small-scale, rural end uses. Different types of solid, liquid or gaseous fuels exist in bioenergy. Such fuels can be utilized in transportation and also in engine and turbine electrical power generation. Chemical products can also be obtained from all organic matter produced. There are various conversion technologies that can convert biomass resources into power, heat and fuels for potential use. Biorefinery integrates bio­mass conversion processes and equipment to produce fuels, power and value — added chemicals from biomass.

First-generation biofuels can be derived from sources such as starch, sugar, animal fats and vegetable oil and can be produced through well-known processes such as cold pressing/extraction, transesterification, hydrolysis and fermentation, and chemical synthesis. The most popular types of first-generation biofuels are biodiesel, vegetable oil, bioethanol and biogas. Second-generation biofuels are not yet commercial on a large scale as their conversion technologies are still in the research and/or development stage. Second-generation biofuels are produced through more advanced processes, including hydro treatment, advanced hydrolysis and fermentation, and gasification and synthesis. A wide range of feedstocks can be used in the production of these biofuels, including lignocellulosic sources such as short-rotation woody crops. These produce biodiesel, bioethanol, synthetic fuels and bio-hydrogen.