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Future of biochar to reduce greenhouse gas and support agricultural market

A potential "game-changing" soil amendment called biochar has the potential to change the agriculture sector and be a partial solution to greenhouse gas reduction.

A potential "game-changing" soil amendment called biochar has the potential to change the agriculture sector and be a partial solution to greenhouse gas reduction.

Biochar, a soil amendment that can be made from any biomass carbon material, continues to be looked at by researchers in South Dakota and Minnesota.

An assistant professor and collaborators at South Dakota State University (SDSU) were the first group in South Dakota to start research on biochar in 2008. Their most recent project is sponsored by the United States Department of Agriculture to specifically target understanding of biochar application, how it benefits crops and soil.

The goal of the research is to make biochar more efficient for sustainable agriculture as well as look into the capabilities of biochar as a material for energy storage. The research team mostly focuses their research on biochar made from corn stalks and walnut shells.

Kurt Spokas, a research soil scientist at the USDA and Agricultural Research Service lab at the University of Minnesota, has analyzed more than 250 different types of biochar created from feedstocks, wood stocks, grasses, chicken feathers, bamboo and different types of manure. But, his end goal is similar--to find the mechanisms behind biochar.

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Typically, biochar production targets various agricultural wastes from manures to different crop residues to tree prunings and urban waste, Spokas said.

One of the challenges of research in biochar is in terms of its application, Spokas said. In order to optimize its usage in current agricultural practices, researchers have to determine what mechanisms of biochar increase fertility.

"We have yet to find the mechanisms and it's a difficult area because biochar is so diverse chemically," Spokas said.

Songxin Tan, a research collaborator at SDSU, said since not all biomasses are the same, the resulting biochar also has different properties.

"The thing about biochar is it's nothing really new," Tan said. "Farmers have been unintentionally using char for thousands of years when they burn fields, but we don't understand how it is benefitting the crops."

Spokas said researchers are looking for the mechanisms behind biochar to give more guidance to farmers on how much biochar amendment to add to see specific results.

"The important thing to stress is it's not a fertilizer directly," Spokas said. "Yes, it contains some nutrient value depending on feedstock used and temperature created, but it's very difficult to get char up to the level of fertilizer ranking unless it's from manures."

Instead, Spokas said biochar is more useful when mixed with compost or fertilizer. Data suggests biochar increases retention of nitrogen in compost, and through that, the compost amendment would have a higher nutrient value.

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Biochar can hold and slowly release nutrients like nitrogen for plant use, Tan said. The microstructure of biochar material is extremely porous, which allows it to hold material well.

Both Spokas and Tan agree this would mean that biochar may allow farmers to use half the amount of fertilizer. Spokas said studies have been done on the greenhouse level to support this, but when used in studies for field application, biochar has had a less significant impact.

But, once the mechanisms are found, the use of biochar could reduce costs that farmers spend on fertilizers, pesticides and herbicides, Tan said.

"Once we do understand these mechanisms, we should be able to engineer a biochar that would target specific soil process deficiencies and whether that's to increase overall nutrient retention in soil, water holding capacity alterations or just a general soil structural improvement," Spokas said.

The time frame of when researchers will understand these mechanisms is unknown.

"What I usually tell people is that it took humans over 3000 years to fully understand how to activate charcoal for water filtration," Spokas said. "I'm not saying it's going to take longer than that. Tonight we might have the secret to all these mechanisms. But it's something that could take time, and it's important that we don't prematurely jump on an idea before we have the science to support it."

There is not enough data yet to indicate what the path will be going forward, Spokas said. But, biochar continues to be looked at as a potential solution to greenhouse gas reduction.

Untreated biomass eventually releases carbon back into the atmosphere through carbon dioxide or methane, but biochar can hold the carbon in the soil for thousands of years or longer, Tan said.

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"The material is only partially burned, so the majority of the carbon is still in the material," Tan said. "This is a very important part of reducing greenhouse gas emission."

About 50 percent of the original carbon is retained in the biochar when converting biomass to biochar, according to research from Cornell University. Biochar is able to cut the current fossil fuel emission by about 10 percent. And, it was estimated by 2050 one gigaton of carbon can be stored in biochar per year, significantly reducing carbon dioxide emission.

"There's a lot of future potential applications with biochar," Tan said. "It's not just an amendment to soil to improve soil quality and efficiency of fertilizers."

Though there is still research to be done, Spokas said there are a few ideas about biochar that are concrete. Initially everyone assumed biochar was a non-reactive material, but research has supported the idea that the material itself is microbially inert, meaning that microbes will not mineralize it.

Physically biochar breaks down into smaller and smaller particles and does react with oxygen, carbon dioxide or water vapor, but those reactions are still being analyzed. Though other data exists for individual chemicals and nutrients, it is not applicable on the larger-scale idea of biochar.

Although the SDSU research team does not do economic analysis, Tan said there is a potentially large market opportunity for biochar in South Dakota in terms of both production and usage. Tan speculates biochar could allow corn and corn stalks to be sold at higher prices.

"The overall conclusion is that biochar is a very intriguing material that has the potential to be a revolutionary or game-changing amendment for the agricultural sector," Spokas said. "But we're still early in the game."

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