Perhaps the best recent peer-reviewed overview of the science of forest bioenergy comes from the Journal of Forestry.
"Forest Carbon Accounting Considerations in US Bioenergy Policy” surveys a wide body of existing science and draws key conclusions about the environmental and economic benefits of biomass. Here’s the abstract:
"Four research-based insights are essential to understanding forest bioenergy and “carbon debts.” (1) As long as wood-producing land remains in forest, long-lived wood products and forest bioenergy reduce fossil fuel use and long-term carbon emission impacts. (2) Increased demand for wood can trigger investments that increase forest area and forest productivity and reduce carbon impacts associated with increased harvesting. (3) The carbon debt concept emphasizes short-term concerns about biogenic CO2 emissions, although it is long-term cumulative CO2 emissions that are correlated with projected peak global temperature, and these cumulative emissions are reduced by substituting forest bioenergy for fossil fuels. (4) Considering forest growth, investment responses, and the radiative forcing of biogenic CO2 over a 100-year time horizon (as used for other greenhouse gases), the increased use of forest-derived materials most likely to be used for bioenergy in the United States results in low net greenhouse gas emissions, especially compared with those for fossil fuels."
One crucial point raised by the authors is that many forest biomass studies show a net carbon benefit immediately, or in as little as a few years. The doom-saying reports frequently cited by activists, “represent only a small fraction of the work that has been, and is still being, performed to understand the GHG impacts of using biomass for energy."
Here are some other highlights of the article:
On the importance of an appropriate timescale for comparing biomass to fossil fuels:
“Using a time horizon of less than 100 years to judge the significance of emissions of biogenic CO2 implies that wood energy emissions are more damaging than fossil fuel-derived CO2 and other GHGs, which has no scientific basis.”
On how demand for biomass incentivizes responsible forestry practices:
“The demand for wood keeps land in forest, provides incentives for expanding forests and improving forest productivity, and supports investments in sustainable forest management that can help offset the forest carbon impacts of increased demand.”
“Policies that provide incentives for landowners to expand forest area, make forests more productive, and store more carbon could have important carbon benefits. On the other hand, policies that increase transaction costs to landowners or devalue forest biomass could have negative carbon consequences."
Read the entire article and you’ll be well armed to sort fact from fiction on biomass.