|How Biomass Works
The primary ways biomass is used to produce energy are:
Direct Combustion -- Producing heat, which can then be used for thermal applications or electricity) and Gasification -- Converting the biomass into a gas, which can then be combusted producing heat and then used for thermal applications or converted further to electricity or transportation fuels.
The low fuel cost is the main attraction of heating with woody biomass such as woodchips or pellets. Unlike fuel oil, propane, and natural gas, woody biomass has a history of stable prices that are unaffected by global economics and political events.
Biomass is a locally available fuel source that increases the region's energy independence and security while stimulating the local economy by keeping energy dollars circulating in the region rather than exporting them. Using wood also helps to support the forest products industry, creating markets, and forestry and agriculture jobs in the surrounding region.
Modern community-scale biomass systems burn cleanly, with virtually no visible emissions or odors, and, compared with modern residential-scale wood and pellet stoves, with far less emissions of particulate matter, an exhaust product of wood combustion known for its adverse effects on human respiratory health. For example, over the course of a winter season, the heating plant of a 200,000 square foot wood-heated school in a cold northern climate produces about the same amount of particle matter as five residential-scale wood stoves.
Burning wood for energy has a positive impact in moderating global climate change. Carbon dioxide (CO2) buildup in the atmosphere is a significant cause of global climate change. Fossil fuel combustion takes carbon that was locked away underground (as crude oil and gas) and transfers it to the atmosphere as CO2. When wood is burned, however, it recycles carbon that was already in the natural carbon cycle. Consequently, the net effect of burning wood fuel is that no new CO2 is added to the atmosphere.
source: Biomass Energy Resource Center (BERC)
Woody Biomass Technology [tabbed like Geothermal section] Woodchips, Pellets, Cordwood
Pellet Systems work very well at the residential scale and popularity is growing in the commercial building segment. In Europe , pellets are delivered in bulk to heat entire towns and they are even used as a zero carbon substitute for coal in large electric power plants. These systems are ideal for small to medium applications. Wood pellets are known as densified biomass - where most of the water and air have been squeezed out, leaving just wood energy - allowing twice the energy per pound as typical cordwood while occupying one third the volume.
Chip Systems are well-suited for large buildings and campuses. Successful projects get their chips locally, usually within 30 miles or so. Chip handling systems can be complex and somewhat expensive to operate. This is offset by the low cost of the fuel itself.
Cordwood Systems heat large mountain homes, winter lodges and camps and even swimming pools. In the right location, the fuel (basically firewood) is free or nearly so. These boiler systems must be manually loaded once or twice a day with up to 100 pounds of wood depending on size and heat output.
Combined Heat and Power (CHP) or cogeneration - The production of heat and electricity from wood is very promising. Today it works well in large lumber mills, paper mills and furniture factories. In the future it may work for smaller applications.
Wood Gasification is being developed as government and industry look for more low-carbon, low cost energy sources. The gas can be used to fire a boiler, drive an engine or turbine or even run a fuel cell. Wood can be liquefied into liquid biofuels for transportation. These technologies are being prototyped and may be commercially viable within the next decade.
A few things to think about when considering woody Biomass:
Supply Quantity: If you use wood pellets, the quality is usually very high and very uniform. However, wood chip quality varies a great deal depending on how the material is handled.
Supply Availability: For would-fuel systems to work, you will need a reliable, long-term supply. The weight and bulk of wood fuel will keep your supply geographically nearby. Significant transportation costs may make wood a higher-priced fuel.
Carbon-Neutrality: Wood fuel is considered carbon neutral. While carbon dioxide is emitted when wood is burned, the very same amount of carbon dioxide is absorbed when the tree grows. When wood-fuel is used to offset fossil fuels such as propane and natural gas, the net effect is lower carbon emissions, allowing carbon credits to be sold.
[source: Flexible Energy Communities Initiative]