Biomass Heating 101

Posted on January 2nd, 2011 by

Biomass heat is the use of natural, renewable, organic materials such as wood, agricultural residues, and municipal “biogenic” waste to produce space or process heat. Generating heat from biomass is a relatively clean and simple process, and is cost effective, especially in regions that have well-developed forest and wood products industries, since biomass heat is most easily generated from the waste wood.

Modern biomass heating systems employ “phased combustion” or “close-coupled gasification” whereby the wood fuel is first converted into an energy-rich gas in a primary combustion chamber, and then completely combusted through the introduction of oxygen rich air in a secondary combustion chamber. The resulting heat of this combustion is transferred to water in a heat exchanger, which is then transferred to the building to be heated through pipes. It is a highly efficient process: modern biomass boilers have an energy conversion rate of 85 percent, meaning that 85 percent of the energy in the biomass is converted to heat. As a comparison, biomass-fired electricity generation in stand-alone applications is approximately 25 percent efficient, and the early indications from the cellulosic ethanol industry is that they are achieving a 50 percent efficient conversion rate.

The temperate forest countries of northern Europe offer a glimpse of the biomass industry’s potential. Over 20 percent of the energy used (electricity and heat) in Sweden, Finland and parts of Austria is supplied through biomass. Stockholm, Sweden heats the entire city from four central heating plants, the largest of which is biomass fueled, a strategy known as district heating. State-of-the-art European boilers, like the ones imported to heat the hospital in Burns, Oregon and the new airport facility in John Day, Oregon, are 20 percent more efficient and burn 70 percent cleaner than those manufactured in the United States.

Biomass heat can also be economical, particularly where timber and wood products industries exist. The cost for biomass heating fuel in forested regions (which is usually manufactured into pellets, chips or bricks) is about half the current price of oil, propane and electricity, and is similar to the price of natural gas. Better yet, the price of wood-derived biomass fuel is stable compared to fossil fuels.

As long as trees are replanted after harvesting, or wood waste from some other process is used for fuel, biomass boilers add no additional greenhouse gases to the atmosphere (it is carbon-neutral). Where fuel sources are readily available and sustainably produced, biomass heat generation is the perfect complement to sustainable forestry and green building. In fact, biomass heat generation from wood waste meets the LEED requirements for green buildings, and because it is so cost effective, biomass heat can help capture all of the LEED credits available for on-site renewable energy generation.

Biomass heat is not the same as biomass electricity generation, which is only 25 percent to 30 percent efficient at best. Stand-alone biomass electricity generation facilities are also frequently so large that they require the sourcing of fuel from hundreds of miles away. Biomass boilers, on the other hand, can easily be installed into schools, airports, hospitals, and other buildings, and located close to the source of waste wood, reducing the need to transport fuel.

Widely used and promoted in Europe as a way to reduce reliance on coal and oil, biomass heating systems for commercial and institutional buildings are currently spawning a brand new and fast-growing industry in the U.S., giving rise to new jobs and clean, efficient heat for a new generation of buildings.

Written by Andrew Haden, A3 Energy Partners

Andrew Haden is vice president of A3 Energy Partners. He focuses on developing infrastructure in rural communities that increases economic self-reliance using local natural resources.

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