A new study has shown that adding charcoal (biochar) to agricultural soils growing the perennial grass and biomass fuel Miscanthus can significantly reduce greenhouse gas emissions from those soils. Biochar is the word used to describe charcoal from current biological resources (trees and plants) when it is used for amending soils. Historically grassland and forest fires have added large quantities of biochar to soils but modern agricultural practices have since reduced the amount of charcoal that finds its way into soils.

The study, reported by UK scientists in the journal Global Change Biology – Bioenergy,  claims to be the first field study to demonstrate significant carbon dioxide emission reductions from addition of biochar to soils where bioenergy crops are being grown. The numbers, from this admittedly limited study, are quite dramatic: biochar amendment suppressed soil CO₂ emissions by 33% and annual net soil CO₂ equivalent (eq.) emissions (CO₂, N₂O and methane, CH₄) by 37% over 2 years.

There is still much work to be done on Lifecycle Analysis (LCA) of biochar production and use. For example, traditional methods of producing charcoal discharge large quantities of greenhouse gases and air pollutants but modern technologies using gasification, energy recovery and pollution controls with fuels such as purpose grown biomass and carbon-based wastes should improve the carbon footprint of biochar use very significantly.  A number of companies are exploring the potential for production and sale of biochar for agricultural use.

If further field research continues to show positive LCAs for biochar production and soil amendment, opportunities for use of biomass as a renewable fuel are likely to increase. Energy from the sun grows the plants, we use the plants for energy and retain, rather than burn, much of the charcoal, and the charcoal goes back into the soil to sequester more carbon dioxide and to help grow more crops. Biochar also helps to retain moisture in soil. Its use in agriculture has the potential to provide a big environmental benefit compared to the methods that have led to massive depletion of the carbon content of soils since European-style agriculture began in Canada.

It is early days yet but capital investments in thermal energy systems are made for the long term. Companies that burn fuels for energy may well benefit from monitoring developments in the biomass fuel area. Agricultural operators may gain in future years from application of biochar to their fields.

The new research can be found at http://onlinelibrary.wiley.com/doi/10.1111/gcbb.12052/abstract  Abstract is free; full article requires a subscription or payment.

There is lots of interesting information about biochar at the International Biochar Initiative at http://www.biochar-international.org/ Enter gardening in the search box to find ideas for use of biochar in gardening.