ABSTRACT
The conversion of solar energy by the fundamental process of photosynthesis is the basis for almost all life. Although chemoautotrophic bacteria obtain their energy from chemical reactions, they are not important for the production and consumption of bioenergy. For example, the food chain in vents in the deep oceans is sustained by chemoautotrophic bacteria. Of course, humans are also dependent on biomass for food, fiber, and energy. In terms of the mass of the Earth, the thin layer of biomass is inconsequential, but it is significant in the regulation of the atmosphere and temperature of the Earth. There are three aspects for biomass: overall biomass (which is essentially steady state: growth, storage, and decay), food and fiber (Table 10.1), and bioenergy. In general, 13% of the total primary energy supply of the world is renewable energy, with solid biofuels (primarily fuel wood), accounting for around 75% of the renewables [IEA energy atlas]. In some developing countries, renewable energy can be 70%–90% of the energy supply, again with solid biofuel as the main source. Even in developed countries, the contribution from bioenergy can reach 25% due to a large forest industry, and in some of the developed countries, the contribution of bioenergy has been increasing. It is difficult to estimate the percentage of biomass for food, fiber, and bioenergy in the world, as in the developing world food, fiber, and sources of bioenergy are grown and traded locally.
