Part 5. If we can’t drink and drive, then burn baby burn.
Energy Crop Combustion

Wood is a crop, subject to the same issues as corn, and takes a lot longer to grow. Burning wood in your stove at home delivers far more energy than the logs would if converted to biofuels (Pimentel 2005). Wood was scarce in America when there were just 75 million people. Electricity from biomass combustion is not economic or sustainable.

Combustion pollution is expensive to control. Some biomass has absorbed heavy metals and other pollutants from sources like coal power plants, industry, and treated wood. Combustion can release chlorinated dioxins, benzofurans, polycyclic aromatic hydrocarbons, cadmium, mercury, arsenic, lead, nickel, and zinc.

Combustion contributes to global warming by adding nitrogen oxides and the carbon stored in plants back into the atmosphere, as well as removes agriculturally essential nitrogen and phosphate (Reijnders 2006)

EROEI in doubt. Combustion plants need to produce, transport, prepare, dry, burn, and control toxic emissions. Collection is energy intensive, requiring some combination of bunchers, skidders, whole-tree choppers, or tub grinders, and then hauling it to the biomass plant. There, the feedstock is chopped into similar sizes and placed on a conveyor belt to be fed to the plant. If biomass is co-fired with coal, it needs to be reduced to ¼ inch or less, and the resulting fly ash may not be marketable to the concrete industry (Bain 2003). Any alkali or chlorine released in combustion gets deposited on the equipment, reducing overall plant efficiencies, as well as accelerating corrosion and erosion of plant components, requiring high replacement and maintenance energy.

Processing materials with different physical properties is energy intensive, requiring sorting, handling, drying, and chopping. It’s hard to optimize the pyrolysis, gasification, and combustion processes if different combustible fuels are used. Urban waste requires a lot of sorting, since it often has material that must be removed, such as rocks, concrete and metal. The material that can be burned must also be sorted, since it varies from yard trimmings with high moisture content to chemically treated wood.

Biomass combustion competes with other industries that want this material for construction, mulch, compost, paper, and other profitable ventures, often driving the price of wood higher than a wood-burning biomass plant can afford. Much of the forest wood that could be burned is inaccessible due to a lack of roads.

Efficiency is lowered if material with a high water content is burned, like fresh wood. Different physical and chemical characteristics in fuel can lead to control problems (Badger 2002). When wet fuel is burned, so much energy goes into vaporizing the water that very little energy emerges as heat, and drying takes time and energy.

Material is limited and expensive. California couldn’t use crop residues due to low bulk density. In 2000, the viability of California biomass enterprise was in serious doubt because the energy to produce biomass was so high due to the small facilities and high cost of collecting and transporting material to the plants (Bain 2003).