Biomass - the old and new renewable fuel

Biomass sounds like one of those new renewable fuels produced by some exotic modern technology. In reality, it's one of the most ancient forms of clean fuel.

Long, long before people were extracting energy from water wheels and whale oil, they were igniting wood -- or biomass -- for warmth.

Today, wood continues to be the largest biomass source of energy. Whether straight from the tree or from the residue of lumber mills, wood is used all over the world. Other sources of biomass include crops, grasses, and the organic components of animal, industrial and municipal waste.

Biomass can be burned to generate heat or to make steam for driving turbines that produce electricity. Some kinds of biomass, like corn, sugar cane and certain grasses, can be fermented and transformed into liquid fuel. Methane released by decomposing organic waste can be used either directly as fuel, or converted to methanol, added to animal and vegetable fat, and turned into biodiesel.

The range of applications for this clean, renewable source seems limitless.

If you're wondering why biomass is called a clean source when burning it deposits ash on the ground and releases carbon dioxide into the air, here's the answer.

The carbon in biomass is "new" carbon, absorbed from the air during photosynthesis. This carbon is returned to the air when the biomass is burned, for no net gain of CO2 in the atmosphere. (Some carbon is consumed and emitted while harvesting, processing and transporting the biomass, but ignore that for now.)

The carbon in fossil fuels, on the other hand, is "old" carbon, captured millions of years ago. When a fossil fuel is burned, it increases the amount of carbon dioxide in the air today.

And the ash from biomass combustion isn't left to smother the soil, but used in agriculture, industry, mining and wastewater treatment.

Biomass currently supplies about 3% of the US's energy. Raising that percentage is not easy, mainly because of the limitations of biomass.

Growing biomass for energy takes up a lot of land and requires a well-developed transportation infrastructure. If food crops are diverted to energy production, foodstocks get depleted and prices rise. The spurt in food prices during 2008 was blamed partly on the dispatch of huge amounts of corn to ethanol-processing plants and not to our dinner tables.

Further, unsustainably grown biomass causes deforestation and barren cropland. And third, biomass combustion technology is different from that of fossil fuels. Improper or inefficient combustion methods can lead to polluted air, ground or water.

Biomass will probably remain a niche, distributed source of clean energy. It's hard to see biomass ever approaching the mass availability and acceptance of solar, wind or geothermal.