UNIVERSITY PARK, Pa. -- Accounting for wildfire is essential in achieving an accurate and realistic calculation of the carbon payback period associated with converting forest biomass into energy, according to a new study. Researchers said their analysis of carbon-accounting methods is expected to inform the scientific debate about the sustainability of such conversion projects.
Some contend that biomass is inherently carbon neutral because the trees sequestered the carbon from the atmosphere, while others argue that when a forest is harvested to produce energy, it represents a substantial carbon debt because it will take many years for new trees growing in that location to sequester the carbon emitted when the energy was produced.
The time it takes to capture that carbon in new trees is called the carbon-payback period.
Defining a baseline for carbon stocks in a forest ecosystem has been the focus of research and policymaking of late because it is the carbon benchmark against which the effect of biomass energy development is evaluated. There is disagreement about the type of baseline to use; some have argued for the use of a static baseline and others for a dynamic baseline.
A static baseline uses the amount of carbon stored in the forest before the project and assumes it remains unchanged over time, whereas a dynamic baseline assumes that the carbon stock will vary as the forest changes.
But a recent analysis done by a team of researchers from around the country has found that the type of baseline isn't really all that influential in determining the carbon-payback period for projects. The research, published online this month in Global Change Biology – Bioenergy, reveals that there are other factors that have far more influence on the payback period.
First and foremost among these factors is forest disturbance, according to Matthew Hurteau, assistant professor of forest resources in Penn State's College of Agricultural Sciences, a leading member of the research team.
Quantifying the carbon balance of using forests for biomass feedstock is not a simple task because there are many factors that have to be considered, he explained. For example, if the forest is likely to be harvested for wood products, the demand for wood products such as paper doesn't go away if the trees instead are harvested for biomass energy.