Bioenergy Technologies

Bioenergy comes from organic matter (biomass) like timber, crops, woodchips, landfill gas, and other gases created through natural decomposition. This biomass can be converted into heat and power in many different ways. Here we look at the types of biomass fuels, how they are used, and how they are connected to the electric grid.

What are Biomass Fuels?

Bioenergy can be produced using a variety of materials that include wood, crops like corn and soy beans, and waste from consumer, municipal, industrial, and agricultural processes. Each of these materials are sources of fuels that can be burned to produce energy.

Useable fuel can be extracted from these materials in a number of ways:

Solid fuels: In the case of woody biomass (wood chips, construction waste, and other solid wood sources), the wood itself is burned to produce energy. This energy can not only be used for heat but can be used to generate electricity.

Liquid fuels: In the case of some crop-based fuels like ethanol (corn) and bio-oil (soy), a liquid fuel is extracted from the crop or its wastes. Like solid fuels, this can be used to produce electricity as well as heat.

Gas fuel: When organic material decomposes, its chemical structure breaks down and releases gases in the process. This not only happens in nature but in human-produced wastes such as those found in municipal landfills. Landfills in particular produce large quantities of methane gas as the organic materials in them decompose. This methane can be used as a fuel.

Bioenergy technology converts the chemical energy stored in organic matter into heat and power. It encompasses a broad range of solid, gaseous, and liquid fuels that result from living organisms or from the wastes and by-products of human activities. The sun is the root source of all biofuels, making the Earth inhabitable for life itself and fueling the photosynthetic processes that transform seeds into trees and plants.

Organic matter can be used directly or indirectly as a fuel:

Bioenergy Technologies

Many different approaches exist for converting biomass into heat and power. Currently, direct firing technology is used to generate nearly all of the energy in the United States produced from solid biomass fuels (trees, plants, wastes). In both electricity generation and combined heat-and-power (cogeneration) applications, the fuel is collected and processed via mechanical or other means, then burned in a conventional boiler or other combustion chamber to produce steam, spin a turbine, and supply energy. Like conventional power plants, large-scale bioenergy facilities are equipped with back-end environmental control systems to reduce pollutant emissions. 

How Bioenergy is Connected to the Electric Grid

Because most bioenergy options for generating electricity involve the use of conventional combustion systems, they employ the same grid interconnection technologies as large-scale power plants and smaller-scale distributed generators running on fossil fuels. In addition, today's bioenergy technologies face many of the same environmental permitting issues as fossil-fired systems.

Although the overwhelming majority of bio-power plants serve on-site needs for electricity, the number of grid-connected facilities in the United States is growing rapidly. Larger power plants typically burn solid fuels such as wood wastes, municipal solid wastes, and construction materials. Smaller installations may burn these fuels or emerging bioenergy sources such as landfill gas, digester gas, and biodiesel fuel. Bioenergy may also be used as a supplemental fuel at existing coal-fired plants.