Biochar research yields significant results

By Anna Austin
Posted August 12, 2010, at 12:18 p.m. CST

Although it will not solve climate change entirely, biochar has the potential to mitigate up to a tenth of current greenhouse gas emissions, according to a new study.

The extensive research paper, which has been in the works for several years, centered on the carbon sequestration capabilities of biochar was published this week in Nature Communication, and co-author James Amonette hopes it will have great influence on those in the scientific community who doubt biochar's climate mitigation potential.

Biochar is produced via a process called pyrolysis, where biomass is burned without or under low oxygen conditions so it doesn't combust. The result is a charcoal-like substance that can also be used to enhance soil conditions.

Amonette, a soil scientist at the U.S. DOE's Pacific Northwest National Laboratory, said he has wanted to conduct a solid biochar study for the past several years and finally got started in 2009 after discussions with study co-author Dominic Woolf of Swansea University in Wales. "We are extremely concerned about climate change and ways to mitigate it, and independently arrived at the conclusion that biochar is something that nobody has done a real thorough study on," he said. "We'd done some quick calculations, but nobody knew whether the numbers would be at 90 gigatons or 1 gigaton of carbon per year."

Amonette and fellow researchers calculated that when taking into consideration all biomass resources presently available, biochar has the potential to sequester one to two gigatons of carbon per year. "We really need in the area of 15 gigatons per year carbon equivalent, so It's not the panacea, but at the same time it's a significant player and that was the goal of this paper, to make a solid case for biochar that the scientific community could understand and accept because a lot of people are really turned off by the hype."

The most difficult component of the study, according to Amonette, was determining the amount of biomass sustainably available. "We relied heavily on some work done earlier, but basically we had to sort out how much is already being used for various purposes, how much is being left, and how much we can take off the soil/land without soil erosion," he said.

A surprising determination of the resource analysis was that a significant amount of biomass is already spoken for in one way or another, Amonette said. "There's not a lot of it just lying around. We were very careful , getting back to the sustainability issues, not to consider breaking natural ground and converting it to biomass plantations because that was absolutely not the right way to go; the carbon debt from doing that is very large."

Following the sustainable biomass assessment, the researchers began a comparison of the available material being used as a soil additive opposed to generating bioenergy out of it, in order to determine tradeoffs between the two. "Initially, we just came up with a single number-that on average, biochar is 20 percent more effective in mitigating climate change that bioenergy," Amonette said. "We then did a second analysis that proved-depending on the fertility of the soil to which the biochar was applied and on the power source or type of fossil energy being offset-in some instances, bioenergy was a better option for climate mitigation.

What is the better use for the biomass, however, varies greatly from one scenario to the next. "Instead of competing though, they can work together to solve this problem. Bioenergy is still a very good way to go, but it's not going to solve the problem by itself. It has the same limitations that biochar does."

For more information about the "Sustainable Biochar to Mitigate Global Climate Change" study and other recent biochar developments, see the September 2010 issue of Biomass Magazine.