BPA: Study demonstrates emissions benefits of forest residue use

By Erin Voegele | May 10, 2017

The Biomass Power Association has released the results of a study demonstrating dramatic carbon benefits can be achieved by using forest residue-based biomass instead of natural gas in power generation facilities. The research determined that emissions from a biomass power facility using forest residue-based fuel are 115 percent lower than those of a natural gas facility in one year. Over 100 years, emissions savings remain at 98 percent after accounting for emissions from logging activities.

The study was conducted by Madhu Khanna, distinguished professor in Environmental Economics at the University of Illinois Department of Agricultural and Consumer Economics, and Puneet Dwivedi, assistant professor in Sustainability Sciences at the University of Georgia Warnell School of Forestry and Natural Resources.

“Assessment of the carbon intensity of biopower, in the near term, depends a lot on whether the carbon accounting is conducted at the stand level or at the landscape level,” said the study’s authors. “When biomass is being sourced continuously for a power plant, as in this case, accounting for carbon effects across the landscape from which it is being obtained is more appropriate than at a single stand level. When we do that, we find that the savings from avoiding emissions from decay of residues that would be left in the forest more than make up for the emissions generated in the process of collecting, transporting residues for power generation.”

To complete the study, the researchers examined the carbon intensity of a 50 MW biomass power facility in New Hampshire and compared it to a typical combined cycle natural gas facility.

Within the study, the researchers explain that fuels used at the biomass plant are residues left over from fiber harvesting operations, comprised of tops limbs and other byproducts. These low-value waste-like materials are generated whether or not they are used for power production. If not used as fuel in a biomass power plant, these materials are typically left to decay in the forest.

As part of the study, Khanna and Dwivedi accounted for the rate of decay of forest biomass, and the carbon emission emissions that would result from this decay if the materials were left in the forest rather than used in power generation. The study also accounts for carbon emissions generated during harvesting, chipping and transportation.

During a media call to announce the results of the study, Bob Cleaves, president and CEO of the Biomass Power Association, provided some historical context and background and discussed why the study is important to the biomass industry.

The issue of how biogenic carbon is accounted for in the atmosphere is a long-standing discussion that essentially dates back to a report issued by the Manomet Institute on behalf of the Commonwealth of Massachusetts, he said. At that time, Cleaves said the Manomet study showed there were distinct benefits associated with the use of forest residues, namely the material that is left over as a result of forestry operations. The biomass power sector largely uses these forest residues to power its operations. However, Cleaves said the BPA feels the carbon benefits of using these left over materials has never really been studied and the biomass power industry’s story has never really been told. This is a first-of-its-kind study that we hope can play a role in the overall debate over the biogenic benefits of biomass power, he continued.

A fully copy of the study and a one-page summary of its findings can be downloaded from the BPA website.