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Biomass
The Environmental Issues
Biomass burning, like any combustion, does present some environmental problems—notably air emissions. Both sulfer oxide and nitrogen oxide emissions from a biomass plant will generally be less than that from a comparably sized coal-fired plant, but they are still not zero. In addition, biomass plants can have significant emissions of carbon monoxide and particulates. municipal solid waste burning can create additional air pollution problems, including emissions of heavy metals and dioxins from plastics.
Biomass does however have a clear advantage over fossil-fired plants in carbon dioxide emissions. If the biomass fuel is sustainably harvested—that is, if new vegetation comes up to replace what has been burned—then there are no net carbon dioxide emissions. This can be done through growing "energy crops" – planted specifically and exclusively to be burned for electricity – or through, for example, replanting of forests cut down for lumber.
There can be environmental effects—both positive and negative—associated with biomass fuel harvesting. For example, collecting in-forest residue can promote healthy growth and reduce fire risk. But it can also reduce biological diversity and habitat for wildlife. There are also a number of secondary environmental impacts, depending on the specifics of the project. If the biomass material would otherwise be landfilled, then burning it conserves landfill space. If land is converted from another use to biomass crops, there can be effects—both good and bad—on soil chemistry and local ecosystems.
Landfill methane has fewer environmental issues. It converts methane to carbon dioxide, which provides considerable climate change benefits. (Methane is a potent greenhouse gas, with 21 times the climate impact potential, by weight, of carbon dioxide.) There are some air emissions resulting from burning of landfill gas, notably nitrogen oxide, but they are relatively small.
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