In photosynthesis, CO2 from the atmosphere and water from the earth combine to produce carbohydrates, which are the components of bio­mass and solar energy that drive this process. When biomass is effi­ciently utilized, the oxygen from the atmosphere combines with the carbon in plants to produce CO2 and water (see Fig. 2.1). Typically, pho­tosynthesis converts less than 1% of the available sunlight to be stored as chemical energy.

The advantages of using plants for renewable energies (fuels and chemicals) are listed follows:

■ Advances in agriculture and forestry technologies have resulted in increased utilization of land resources for cultivation of energy crops.

■ By increasing harvesting of solar energy, there is effective usage of biomass-based resources.

■ Multiple economic benefits can be derived—for example, sugar can be used as such for fermentation to alcohol—depending on the market.

■ Biomass combustion, unlike fossil fuels, does not contribute to increased CO2 levels in the atmosphere [2].

■ Increased employment opportunities resulting from the above.

While the advantages of using biomass-based energies are apparent, it is important to note that biomass cannot by itself provide complete replace­ment of fossil fuels. Hence, it is one of the solutions toward achieving energy efficiency. Further factors, such as competition for biomass between energy production and human nutritional needs, as well as the possible environ­mental effects, must be kept in mind. There are several factors that should be considered in using plants for the generation of energy; efficiency of solar energy absorption and conversion, quality of biomass produced, plant growth, growth under marginal conditions, soil characteristics, and cost — effectiveness of production of energy and conversion. We will focus on the utilization of terrestrial plants for production of renewable energies.