Charcoal In The Soil: Experimenting With Biochar at The UBC Farm

Posted by: | September 3, 2013

The Potentials of Biochar: Soil Carbon Sequestration and Improved Soil Productivity

By Dennis Jessica, UBC Farm Field Research Assistant

Charcoal may seem like an unlikely candidate to improve farmers’ soils and mitigate climate change, but researchers at the UBC Farm are exploring the potential of biochar (charcoal produced from biomass) to do just that.

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UBC Farm Field Manager Tim Carter applies biochar to the trial plots using a small topdresser.

 

Last month the UBC Farm applied about 125 kg of biochar to our soils and 85% of this biochar is fixed carbon. Fixed carbon refers to a very stable form of carbon that is resistant to decomposition and is reported to remain in the soil, and out of the atmosphere, for centuries to thousands of years.

Many of us know that levels of atmospheric greenhouse gases continue to rise with detrimental impacts around the globe. What some people may be less aware of is the capacity of soils to store carbon. Increasing the amount of carbon in agricultural soils has been identified as an important way to decrease climate change. Adding biochar to soils is one proposed strategy for doing so.

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The image above (left) illustrates the carbon cycle in which the amount of CO2 taken up by plants is equal to the amount of CO2 released back into the atomosphere through plant respiration and normal soil processes. The right side illustrates how biochar reduces the amount of CO2 released from soil processes, thereby resulting in a net withdrawal of atmospheric carbon. Source: Lehmann, 2007.

 

Biochar is charcoal produced from biomass, specifically for use as a soil amendment. The biomass can be any variety of organic waste material including wood waste, crop residues, nut shells, poultry manure, pulp mill waste, and more.  It is produced by pyrolysis, which is the heating of biomass at a high temperature in the absence of oxygen. Pyrolysis technology can vary from a simple farm-scale kiln, a specialized type of oven, to a very complex industrial design.  The photo below shows Dave McCandless, our research partner at Fraser Common Farm Coop (FCFC) explaining his homemade biochar kiln to Kelvin Kou, a UBC Farm intern.  The biochar used in the UBC Farm trials was produced from wood scraps and donated by Diacarbon Energy Inc., a BC company who specializes in renewable fuels from biomass, sustainable waste solutions, and portable biomass refinery technology.

While soil carbon sequestration through biochar application represents a key climate change mitigation approach, any farmer will tell you that organic matter, or soil carbon, is also foundational to healthy agricultural soils. The addition of biochar to the soil can improve soil nutrient retention and availability, soil water retention, and beneficial soil microbial processes. Previous research on the addition of biochar to soil has shown an increase in crop yield from under 10% to nearly doubling productivity.  The variation in yield improvements stem from the fact that all biochars (like composts) are different depending on how they are made (ex. pyrolysis temperature) and what it is made out of. Plus, the impacts of biochar depend on the initial properties of the soil to which it is being added, the rate of application, other amendments added in conjunction, the climate of the region, and the crop being grown. Significant research on biochar has been done over the past 10-15 years (though charcoal in soils is an ancient practice), however little field research has been done in temperate climates or in organic systems.

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Dave McCandless teaching UBC Farm biochar intern, Kelvin Kou, about the kiln he constructed at Fraser Common Farm Coop to make biochar and apply it to their soils.

This summer, Fraser Common Farm Coop and the UBC Farm, with the support of the Certified Organic Associations of BC and guidance of Mark Johnson’s Ecohydrology Lab, combined their effort to conduct larger, controlled field trials of biochar application at the UBC Farm. The biochar project is just one of a range of exciting collaborative research projects happening on the UBC Farm site this season.

Twelve 20m2 trial plots were established, consisting of three replicates of four treatments: 1) control (nothing applied), 2) biochar alone, 3) compost alone, 4) biochar and compost. The biochar was applied at a rate of 10t/ha, the compost and biochar were turned into the topsoil, and then beets were direct seeded in the plots. It is important to note that biochar is not intended to be a replacement for compost, and is in fact very different, in that biochar contains minimal available plant nutrients and is biologically inert on its on. It is thought that adding biochar with a source of nutrients and microbial populations such as compost or compost tea, or inoculating the biochar with beneficial microbes before adding it to the soil will achieve greater benefits. This is the reason for including a biochar and compost treatment in the UBC Farm trials.

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Beets growing in the biochar trial plots. The blue flag indicates the beginning of a plot with biochar only added and the yellow flag indicates the beginning of a plot with biochar and compost added together.

As we move into the fall harvest season at the farm, the Biochar Project will soon be entering its harvesting and measuring yield stage. Stay tuned for part two of the story!

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