Energy

Biomass - Upload Knowledge

Biomass is the energy from organic plant or animal material used to make electricity (“biopower”), biofuels, or biobased products that were traditionally made from petroleum. As you read this section, please keep an open mind and remember that although biomass offers some promising benefits as a renewable energy source, it also has considerably more potential negative environmental and social impacts than solar, wind, or geothermal. However, your school may be in a unique position where it could potentially benefit from a local sustainable source of biomass to generate heat on-site or acquire power from a nearby modular system.

Biomass material can come from land or water crops grown specifically for energy or from byproducts of agriculture or forestry. It can even come from municipal solid waste or industrial waste. To learn more about these biomass sources collectively referred to as “feedstock” and to learn where the industry is headed, read this page from the U.S. Department of Energy. To learn more about the actual compounds in feedstock that are used to produce energy or biofuels, click here.

Biomass generates electricity through the technologies of direct-firing, co-firing, gasification, pyrolysis, anaerobic digestion, collection of landfill gas, or through modular systems. Direct firing is where the biomass is burned to produce steam that turns turbines which turn generators to create electricity. It is the most common technology used in biomass power plants. Cofiring works the same way as direct firing except that the biomass is added to another source such as coal before it is burned to produce steam. Gasification is where the biomass is heated in a way where it breaks down to make a flammable gas. The flammable gas is then cleaned and filtered before it’s burned which results in less chemical emissions and when used in a combined-cycle turbine system, can reach efficiency levels of 60%. Pyrolysis is where the biomass is chemically decomposed in the absence of oxygen by some sort of heating process to produce a liquid which is then used for power generation. Anaerobic digestion is where the biomass is broken down naturally by bacteria in the absence of air. It creates biogas, which is a combination of carbon dioxide and methane that is used to produce heat or electricity. Landfill gas technology collects the gas that forms from decomposed solid waste and uses that to produce energy. Modular systems can produce electricity using a variety of the technologies mentioned above, but do so on a much smaller scale. The benefit of modular systems is that they can be used for small production like a village or a single location.

A significant portion of biomass power production currently taking place is on-site at paper mills or other industrial facilities using the byproducts of their own production processes to generate a combination of heat and power for their own facility.

Besides a source of electricity generation, biomass is also valuable for the production of biofuel or as an alternative raw material for solid petroleum-based products.

Biofuel includes ethanol and biodiesel, both of which can produce less air pollution than fossil fuels if the industry can run on sustainable farming practices, but in most parts of the industry, sustainable farming has not been a reality. Ethanol is formed by fermenting biomass, typically corn and soybeans, into an alcohol product that can be used as fuel for vehicles. The two common types of ethanol fuel are E10 and E85. E10 is a mixture of 10% ethanol with 90% gasoline, and most vehicles sold today can run on this mixture in their engine. E85, on the other hand, is a mixture of 85% ethanol with only 15% gasoline, and in order to use this in your engine, you need a flex-fuel vehicle. Biodiesel is formed by combining an alcohol with animal fat or vegetable oil, often used cooking oil. For a listing of alternative fuel stations in your area, please see the Department of Energy Alternative Fuels Data Center, the National Ethanol Vehicle Coalition, or the National Biodiesel Board. To learn more about biofuels, check out our Transportation section.

Biomass can also be used for producing biobased products to replace petroleum-based products. Some of these products are green chemicals, plastics, and structural fibers. Many of the technologies used to produce biobased products are still developing, but for more information, see the ABC's of bioproducts by the U.S. Department of Energy.

Pros—

Biomass technology has the unique potential to make use of left-over products from many industrial processes to produce combined heat and electricity for on-site use. For example, paper companies that have residuals in wood products, or agricultural businesses that have left-over animal waste may be able to use those for CHP systems for their facility. This not only makes use of waste, but provides an energy source that is more efficient than bringing in energy from another location and thereby losing energy from transport.

Biomass technologies are also developing that may make use of left-over materials that have little other value or economic benefit, such as the corn husks and corn stalks left over from corn harvesting. Other left-over plant matter may be used on a large scale if cellulosic ethanol technology progresses. This would be most important for the production of biofuel for transportation, and not so much for electricity production, but it still represents significant potential for the industry as a whole.

According to NESEA, biomass power systems contribute less to global warming because the carbon dioxide that’s released while burning them is the same amount the plants absorbed when they were alive. Therefore, creating power from biomass is not directly producing more carbon dioxide than would otherwise be in the atmosphere. However, as you’ll see when reading the cons, the step of producing power is not the only source of carbon dioxide emissions in the long production process. NESEA also explains that biomass is cleaner because it does not release sulfur dioxide in the direct-firing process like conventional energy sources. Sulfur dioxide contributes to acid rain.

Finally, biomass is the one renewable energy source that offers a host of other potential products besides just energy, including various biofuels and everyday biobased consumer items that could replace petroleum-based clothing, chemicals, and plastics.

Cons—

Biomass makes a lot of sense as a sustainable energy source when scraps and waste are used to produce energy. It can even make sense as sustainable and responsible harvest of natural forest resources. However, many forests are being harvested at too fast a rate.

Most biomass is actually grown as a crop, though, and this part of the industry creates a whole list of environmental and social issues. Biomass crops are already placing a high demand on land, which may not be a sustainable practice in the long-run. Food production needs and biomass crops together require a lot of farming area, and as a result, deforestation is occurring in many places where land demand is high. Also, massive production of biomass crop often depends on the heavy use of petro-chemical pesticides and fertilizers which degrade the environment. Some farmers have successfully used natural fertilizers instead. However, even extensive use of natural fertilizers can sometimes transform the local environment in undesired ways. Another issue is the large amount of carbon dioxide emissions produced whether it’s from the use of land-clearing equipment, the farming equipment for maintenance and harvesting, or the transportation of biomass crop to where it’s used. Sometimes these emissions can be comparable to what emissions would be if the biofuel burned as dirty as a fossil fuel. Furthermore, the costs to the producer to grow and harvest biomass for energy can sometimes be considerable when compared to fossil fuels and weighed against the relative benefit that supposedly results by using a “clean” energy source.

But, perhaps the most notorious problem of growing biomass crop is the competition it creates between food and fuel production. The same amount of land that used to be used mostly for mostly food production alone is now demanded for food and biomass production. The crops grown on that land, including corn products, are also under the pressure of two different demands. This competition often results in rising food prices. These rising food prices have already been felt around the world, especially in developing countries.

A final roadblock to widespread biomass use is that the current technology of biomass energy production in the direct-fired power plant industry is not as efficient on a large scale as other direct-fired technologies, such as coal. The major reason is because biopower is mostly produced in small capacity plants. The DOE explains that biomass power boilers are usually in the 20-50 MW range compared to the 100-1500 MW range of coal plants. However, technology to make it more efficient does exist.

Because of the current small production capability of biomass plants, many proponents of the biomass industry are advocating an increase of co-firing production, especially by mixing biomass with coal because it is the quickest, easiest, and cheapest way to add the environmental benefits of biomass to our current mix of energies. However, the obvious downside of this is the ongoing dependence and promotion of coal as an energy source because conventional coal based power is very polluting! Of course, there are carbon sequestration technologies that may help to make coal a cleaner energy source, but as outlined in the Clean Coal section, this is not necessarily a cut and dry solution.