When state utility regulators held a workshop last month about increasing the use of forest biomass for power, one topic did not make it into the discussion: the emissions produced from burning small trees, branches and treetops hauled from Arizona's forests.
Compared to coal, burning biomass emits lower amounts of key pollutants like sulfur dioxide and nitrogen oxides, but it generally equals or surpasses coal in the amount of carbon dioxide it emits per unit of heat.
Bioenergy supporters, and many government agencies, have deemed the energy source carbon neutral, because trees grow back to replace ones that were cut, reabsorbing the carbon emitted by burning the woody matter...