Fossil fuels, such as coal and oil, took millions of years to develop from organic matter. Biomass fuels short-circuit that process by adapting the same organic sources, such as plants, which are constantly replenished, and releasing their stored energy immediately.

Types of Biofuel

Crops can be grown specifically for biofuel, but any organic waste may be a usable source of bioenergy.

Perennial Crops

Some trees grow as much as 40 feet in three to eight years after cutting; they can be harvested for 20 or 30 years before they must be replanted. Native grasses, such as switchgrass, sugar cane and elephant grass, can be harvested for as many as 10 years before replanting.

Annual Crops

Some food crops, such as corn, sunflowers and soybeans, produce oil that can be used to make fuel. Most ethanol produced in the United States is currently derived from corn.

Aquatic Crops

Tiny aquatic plants called microalgae also produce oil and can be converted into a variety of fuels. They grow quickly in warm, shallow salt water.

Rural Waste

Tree tops and branches left by lumbering, sawdust and bark from sawmills, shavings from furniture manufacturing and organic sludge from pulp and paper mills are all adaptable biomass. Some crop residue left by harvesting is needed to prevent erosion, but some can be used for fuel. Livestock produce more manure than is needed for fertilizer; the excess can be processed for fuel.

Urban Waste

People generate tons of useful waste: scrap lumber; biodegradable garbage, such as food, paper and lawn clippings, as well as gas given off by garbage dumps. Some treatment plants even burn methane, produced by sewage, for heat and power.

Source:

Renewable Energy Policy Project: Biomass: FAQs

National Renewable Energy Laboratory: Biomass Energy Basics

Union of Concerned Scientists: How Biomass Energy Works