The Benefits of Biochar

SDSU researchers evaluate use of biochar as a soil amendment
By Erin Voegele | August 22, 2011

Logistics have proven to be a challenge for the biorefining industry. In many cases, bulky feedstocks can be difficult and prohibitively expensive to transport and store. One solution that’s been discussed for years is distributed collection and preprocessing locations modeled after the network of grain elevators that dot the landscape of rural America. Rather than storing grain, however, locations that serve as drop-off points for biomass feedstocks would feature pyrolysis systems to process those feedstocks into bio-oil that could more easily be transported to biorefineries for conversion into biobased fuels and chemicals. Biochar produced as a byproduct of the pyrolysis process could then be used to help rehabilitate degraded soils.

A research project as South Dakota State University is focused on determining the specific impact that various types of biochar can have on degraded soils. The project, which was recently awarded a five-year $1 million grant through the USDA’s National Institute of Food and Agriculture’s Agriculture and Food Research Initiative, is being led by SDSU professor Tom Schumacher. Together with a team of colleagues, Schumacher will produce biochar and bio-oil via a microwave fast pyrolysis process. The resulting biochar will be introduced to degraded soils in the university greenhouse for evaluation. The team will test biochar resulting from three different feedstocks: corn stover, switchgrass and woody biomass.

“The hypothesis for this project is the biochar will have different physical properties that will vary due to the feedstock source,” says Jim Julson, a professor in SDSU’s agriculture and biosystems engineering department. The processing parameters of the pyrolysis method are also expected to have an impact on the ability of the resulting biochar to function as a soil amendment.

In addition to studying the effect biochar could have on degraded soils, the research will also address emergent herbicide absorption, soil water-holding capacity, and nutrient cycling. “These are all things that have an effect on the overall soil productivity, and we’ll look at what effect the biochar has on [those elements.]”  The potential to sequester carbon dioxide and impact greenhouse gas emission levels will also be studied by researchers.

According to Julson, concerns have been raised regarding the quality of biomass or crop residues that can safely be removed from cropland for use as biorefining feedstock without impacting soil quality and production potential. Biochar soil amendments may play a role in mitigating these concerns. “In this case we are going to take biochar [and add it to lower producing soils] to try to maintain, if not enhance, the production potential of the whole landscape.” Although the project will initially involve soil trials in an SDSU greenhouse, Julson says that the goal is to gather data that would allow the research to scale-up to plot trials. That scale-up is likely to happen once the initial five-year research project is completed. 

—Erin Voegele