80 Bioenergy-High

Bioenergy FOCUS Question What is biomass and how is it used to produce energy?

It's All Organic What do wood chips, corn, and cow manure have in common? (They're certainly not the ingredients in a good meal!) For one thing, they all consist of organic matter, which means they come from organisms. For another thing, people can use them to obtain energy. Matter from living or recently living organisms used as a source of energy is called biomass. People use some biomass directly as fuel— material burned to release energy. Some solid biomass is converted to a liquid or gas before it is burned. Either way, energy produced from biomass is referred to as bioenergy. Biomass is a renewable resource because it can be grown or replaced.

Energy from Wood For thousands of years, people primarily used just one type of biomass to produce light and heat energy— wood. Wood fires enabled people to see at night, keep warm, and cook food. Millions of people still burn firewood or wood waste such as bark, wood chips, sawdust, and branches from tree trimming. Some power plants burn wood or a combination of coal and wood chips to generate electricity. One problem with using wood as an energy resource is deforestation— cutting down trees faster than they can grow back. Trees provide homes for other organisms and remove carbon dioxide, a greenhouse gas, from the air. Clearing trees destroys habitats and contributes to global warming.

Sugar Power Using biomass to generate electricity can be a sweet deal, as it is in South Bay, Florida. That's where you'll find the New Hope Power Partnership. Its large mill and refinery produce sugar from sugarcane plants. Then the power plant next door turns the leftovers into bioenergy! The power plant also uses recycled wood, which helps the waste from sugarcane burn better. It's the largest biomass power plant in North America. The biomass is burned to heat water in a boiler and produce steam. The steam rotates turbines to produce electricity. This process generates enough power for the sugar mill and refinery as well as about sixty thousand homes.

Garbage, Manure, and Methane Think about all the banana peels, apple cores, and leftover food you've thrown away. A lot of biomass ends up as garbage, or solid waste. Every day, people discard plant and animal products. They throw away yard waste such as grass clippings and leaves. This organic matter can be used to produce bioenergy. Waste-to-energy power plants burn biomass and other solid waste (mainly plastics) and use the heat to make steam. The steam provides heat to buildings and generates electricity. Landfills can also harness the power of organic trash. Bacteria naturally digest, or break down, biomass. They release biogas, a mixture of mostly methane and carbon dioxide. Some landfills collect this gas, remove the carbon dioxide, and use the methane to generate electricity.

Some dairy farms and livestock operations use cow and pig manure in a similar way. Like organic garbage, animal manure gives off biogas as bacteria decompose it. Farmers use sealed tanks called digesters to break down manure and other kinds of farm waste. Some sewage treatment plants even use digesters to get biogas from human sewage! Then they use the biogas to make steam, which heats buildings and generates electricity.