A review on bioenergy and biofuels: sources and their production

Bioenergy refers to renewable energy produced from biomass. Biomass is any organic material which has stored sunlight in the form of chemical energy. Depleting fossil fuel reserves and growing demand for energy has necessitated the renewed search for alternative energy resources such as plants. Biofuels are an alternative to fossil fuels, which are liquid or gaseous fuels that are derived from biomass sources. Biofuels can be used alone or in combination with other fossil fuels such as petrol. Biofuels are classified into first, second and third generation biofuels. In this review paper, emphasis on the production of biodiesel and bioethanol and how to modify the methods that involve their formation has been carried out. Biodiesel and bioethanol come under first generation biofuels. The first generation biofuels are produced from starch and sugars (bioethanol) and from seed oils (biodiesel). The direct use of vegetable oils and non-edible oils can prove harmful for the diesel engines due to their high viscosity, high density and various other problems that are related to them. So there is a need of converting these sources into biodiesel so that it can be used as a replacement for petroleum based diesel. Another important biofuel, referred to as bioethanol has gained a lot of importance. This review article deals with the conversion of non-edible oils to biodiesel or by modifying the process of transesterification as well as the conversion of sugars to bioethanol by genetic modification of yeast cells and by changing the substrates required for ethanol production by yeast.