Raphael Thys
Biochar in a wheelbarrow. (Photo by La Huertina De Toni on Shutterstock)
COLUMBUS, Ohio — The nature-based technology, biochar, could help save the planet. The work it takes to grow crops produces greenhouse gases that trap carbon in the atmosphere and would speed up the planet’s heating. New research finds biochar’s potential to eliminate large amounts of greenhouse gases could make farming more climate-friendly.
Biochar is a charcoal-like porous substance made by heating organic material — things like wood chips, crop residues, or even manure — in a low-oxygen environment. This process, called pyrolysis, transforms the material into a stable, carbon-rich substance that looks a bit like barbecue charcoal. But unlike the stuff you use for grilling, biochar has some remarkable properties when added to soil. The material is mainly used for crop production as a soil additive or to capture atmospheric carbon.
“When farmers grow their crops, they apply fertilizer and/or manure and use different kinds of machinery to till the soil,” says Raj Shrestha, a research associate in horticulture and crop science at The Ohio State University, in a statement. “In the process, greenhouse gases are produced and released into the atmosphere.”
In recent years, researchers have grown an interest in the technology because of the several agricultural and environmental benefits. Now the challenge is convincing farmers to adopt biochar in their farming practice. One way is to steer the conversation on how it can help extend soil life.
“If we can convince farmers that converting biomass to biochar is good for the long-term sustainability of soils, the economy, and good for the environment, then we’ll be able to see wide adoption of this technology,” Shrestha says.
In the study, the researchers reviewed over 200 field studies worldwide that examined the impact of biochar application in agriculture and the release of gases such as nitrous oxide, methane, and carbon dioxide. All three are heat-trapping gases that majorly contribute to Earth’s warming atmosphere.
Findings showed the amount of biochar in the soil mattered in whether it decreased or had no change in gas emissions. Generally, using biochar in the field reduced the amount of nitrous oxide in the air by 18 percent and methane by 3 percent. On the other hand, biochar did little by itself to change carbon dioxide emissions. Mixing biochar with commercial nitrogen fertilizer or other organic materials like manure or compost did help with reducing carbon.
“We can achieve negative emission in our agroecosystems by reducing the carbon source and enhancing carbon sink,” adds Shrestha. He says the results show it is still possible to eliminate most of Earth’s carbon by reducing greenhouse emissions from human activities and developing technology to absorb more carbon than it releases into the atmosphere. In this case, farmers increased the long-term soil carbon pool by converting organic waste into biochar.
When crop residues are left on the field, only 10 to 20 percent of the leftover carbon is recycled into the soil during decomposition. “By converting the same amount of residue to biochar and then applying it to the field, we can store about 50% of that carbon into stable carbon forms,” explains Shrestha.
In other words, farms using biochar could actually help cool the planet rather than warm it.
Biochar-carbon in the soil can last from a few hundred to thousands of years, making it a great strategy for controlling greenhouse gas levels. Between 2011 and 2020, carbon dioxide rose by 5.6%, methane by 4.2%, and nitrous oxide by 2.7%. Agriculture makes up 16% of total greenhouse emissions. If we could flip that script and turn farms into carbon sinks, it could be a major step towards mitigating climate change.
The study is published in the Journal of Environmental Quality.
Paper Summary
Methodology
The researchers conducted a comprehensive review of peer-reviewed journal articles published in English before 2022. They focused on field studies related to biochar application in croplands and its effects on greenhouse gas emissions. They identified 33 field studies for nitrous oxide, 31 for methane, and 20 for carbon dioxide. The data from these studies were standardized and converted to uniform units for comparison.
Results
The study found that across all reviewed studies, biochar application reduced nitrous oxide emissions by an average of 18% and methane emissions by 3%, but slightly increased carbon dioxide emissions by 1.9% compared to control conditions. When biochar was combined with nitrogen fertilizer, it reduced emissions of carbon dioxide, methane, and nitrous oxide in 61%, 64%, and 84% of observations, respectively. When combined with other amendments like manure or straw, biochar reduced emissions in 78%, 92%, and 85% of observations for the same gases.
Limitations
The study primarily relied on short-term field studies (1-3 years), with only 11% of reviewed studies being medium-term (5-7 years). Long-term studies are needed to fully assess the durability of biochar’s effects. Additionally, most studies were conducted in Asia, with limited representation from other regions. The review also noted variability in biochar’s effects depending on factors like soil type, climate, and biochar properties, highlighting the need for more diverse studies.
Discussion and Takeaways
The researchers emphasize that biochar shows significant potential for reducing greenhouse gas emissions from agriculture, but more research is needed to optimize its use. They suggest that biochar may be most effective when combined with other soil amendments or fertilizers. The study also highlights the need for more long-term field studies in diverse environments to better understand biochar’s effects over time and in different conditions. The authors note that while biochar shows promise as a climate change mitigation tool, its widespread adoption is currently limited by high costs and lack of awareness among farmers.
Funding and Disclosures
The study was supported by a grant from the Alfred P. Sloan Foundation. The authors declared no conflicts of interest related to the research.