Biomass is one of the fastest-growing sources of renewable energy. But what exactly is biomass? How is it used? And how likely is it to replace the oil, natural gas, and coal we are so dependent on?

The name biomass tells us what it is: biological material—in this case plants, mostly—in large amounts (mass). Biomass fuel takes the energy in plants and converts it into a form that can be used to generate power or to fuel a car.

Here’s how it works. During photosynthesis, plants create carbohydrates—sugars and starches. Carbohydrates are organic compounds made from carbon and hydrogen. These compounds store energy in the bonds that hold them together. This stored energy is released when the plants are eaten, or, more importantly in this case, when plants are burned. Oxygen from the air combines with the carbon in the plants to release energy, water, and carbon dioxide (CO2). The energy is applied to boiling water, turning it to steam. The steam powers turbines to create electricity.

There is another way to release the energy in plants. The process of fermentation converts the sugars in plants to alcohol. In liquid or gas form, the alcohol can then be burned to release energy. Fuel created by biomass this way is called biofuel.

The best thing about biomass is that because it comes from plants, it is easily renewable—plants grow and regrow. The potential uses for biomass are great. Since plants use the same hydrogen and carbon building blocks as fossil fuels do, biomass may be able to replace oil as the starting substance for what are called commodity chemicals. These are chemicals used in manufacturing common products such as plastics, paints, and adhesives. Right now, however, biomass remains a largely untapped renewable resource.

What Is Biomass?

Biomass, a very broad term, covers almost any type of plant waste. This includes wood waste, agricultural waste, and landfill wastes, as well as certain crops grown specifically for use as biomass fuel.

Thousands of years ago, someone deliberately put wood on a fire to create heat. That was the first use of biomass fuel. Wood has been used as fuel for a long time. People in many countries still heat their homes with and cook their food over wood fires. But despite its availability, wood is a relatively inefficient fuel when burned in a traditional fire. However, when used as biomass, wood becomes a much more efficient fuel.

People are making use of the wood or plant wastes from different industries by burning them for power. The wastes come from such sources as lumbering, the building trade, or paper mills; agricultural wastes from farming; and even solid wastes from municipal landfills and the methane gas created in these landfills. Certain grasses can be grown for fermentation into biofuels.

How Are Biomass Fuels Used?

Around the world, biomass fuel—mostly wood products—is being added to coal-fired electricity plants. This process is called co-firing because it uses two fuels instead of one. Co-firing works with all the different types of coal boilers. The boilers need only minor adjustments to get the most from biomass fuel. The most efficient process adds biomass fuel after the coal has been pulverized.

In 2005, European Union countries used biomass for almost 4% of their energy supply. Finland and Sweden led the way, with biomass making up between 16% and 20% of their energy supply. Projects to use biomass waste are under development in Asia, to replace wood, which is still used in many places. Biomass fuel projects are also being developed in Africa.

As of 2002, the United States had 9,733 megawatts of biomass fuel capacity. Much of this biomass is co-fired with coal for the base power load—the steady power provided by a power plant. (Power needed to meet high demands, as in a heat wave, is peak load.) Biomass supplies more than 3% of total American power. Biomass fuel has surpassed hydroelectric power as the leading U.S. source of renewable fuel.

Often, the biomass fuel is used by the industry that created it. For example, the forest products industry burns its own wood wastes to create steam and electricity to operate its plants. These wastes include sawdust, unused tree limbs, and wood chips. In fact the forest products industry generates more than half of its own electricity using its own wastes. The pulp and paper industry does the same thing to provide power to paper mills.

The other major use of biomass is to create biofuels. A starch- or sugar-based crop is fermented into ethyl alcohol, better known as ethanol. Brazil powers most of its vehicles with ethanol rather than gasoline. The conversion to ethanol started in the mid-1970s when gasoline prices soared for the first time. Brazil’s leaders decided to eliminate the country’s dependency on oil. Slowly through the years, the ethanol industry developed. Brazil grows the sugarcane, ferments it, and processes it into ethanol. Brazilian cars are required to be “flexfuel” capable; that is, they must be able to use both ethanol and gasoline. Consumers choose which to use at the pump, where they are able to see the price of each fuel.

Other countries are slowly following Brazil’s lead. China and the European Union countries are increasing ethanol production. There were 12.9 billion l (3.4 billion gal) of ethanol produced in the United States in 2004, almost double that of 2002. The ethanol made is added to gasoline to boost octane and reduce emissions. In the United States, corn is the source of the ethanol. However, it is a much less efficient source of ethanol than sugarcane or sugar beets, producing the least amount of ethanol per acre compared with the other two.

A plant called switchgrass may be an alternative to corn as a source for ethanol in the United States. Native to the plains of North America, switchgrass is a much more efficient source of ethanol than corn. Use of this crop remains in the testing stages.

A blend of diesel and ethanol called E-diesel is being tested in city bus fleets in the United States. With gasoline prices climbing, interest in ethanol-powered vehicles will continue to increase.

Use of biodiesel biofuel is growing rapidly in Europe. Biodiesel forms when vegetable oil undergoes a process called transesterification. Animal fat and restaurant grease can also be made into biodiesel. This biofuel can fully replace diesel fuel or can be used in a blend that is 80% diesel and 20% biodiesel. European countries produced more than 3 millions metric tons of biodiesel  in 2005. Germany is by far the biggest user and producer. There are programs promoting the use of biodiesel starting up around the world.

Drawbacks

Biomass as a fuel has its drawbacks. Like fossil fuels, it burns, and burning produces CO2. But fossil fuels release CO2 from eons ago, creating an extra load of CO2 in the atmosphere. In contrast, the CO2 released when biomass fuels are burned is taken up by the plants grown to replace them. Thus biomass fuel is considered to be “carbon neutral.”

However, at this time fossil fuels still play a key role in the biomass equation. They are used in all stages of the production of biomass: plant growth, harvesting, shipping, and processing. Biomass will not truly be carbon neutral until all parts of the business use renewable fuel. When this will happen is anyone’s guess. In the meantime, biomass fuel remains a step forward in cutting CO2 emissions, because overall less CO2 is added to the atmosphere using biomass.

Down the Road

Potentially, biomass can replace oil, gas, and coal in many applications. Governments around the world sponsor research to further develop biomass as a sophisticated fuel feedstock. Things under development include biomass refineries. These refineries would take various types of biomass fuel and create consistent feedstocks to use in a variety of industries. One type of refinery uses the sugar in the cellulose and lignin of the plant as a basis for fermentation, to make products such as ethanol. This way, woody plants and grasses can be used for biofuels. The other type of refinery takes a thermochemical approach to standardize biomass, making it a more efficient liquid or gas fuel.

Ultimately, researchers see biomass fuel replacing petroleum as the source for many chemicals used in the modern world. Products such as plastics, paints, and adhesives may come from biomass fuel rather than from oil-based chemicals.

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