Carbon Sequestration with Biochar

Thomas W. Marrero, PhD 

The term “biochar” has only been around in scientific papers since the 1990s (Chemosphere, Vol. 39, No. 1, pp 23-32, 1999).  Drs. Stanley Manahan and Harsh Bapat utilized milo seed to create a carbon for remediation of hazardous waste.  Dr. Manahan was using a “ChemChar” gasification process and felt that the carbon derived from the milo seed should be called “biochar”.  It was my honor to join Dr. Manahan for my PhD research in 1998 and continue research on the chemchar process and the use of biochar.  In agriculture, the use of a carbon material (biochar) made from the conversion of biomass using heat with little to no oxygen has been around for thousands of years .  Since as long ago as 450 BC, terra preta, meaning black soil in Portuguese, was discovered along the Amazonian basin.  The terra preta was a blend of high-carbon material, food and agricultural residues, animal and fish bones, and broken pottery.  These areas of terra preta were known to generate higher yields of crops to feed the native people. It is the high carbon material that was made during the anthropogenic burning of biomass in pits that created biochar.  The biochar was found to be resistant to decomposition, made from biomass, and positively impacted the soil health. 

What is Carbon Sequestration?

The ability to take a biomass, like agricultural residues, and convert them to a stable carbon material is key to carbon sequestration.  

Just as the native people along the Amazon did with terra preta, creating the high-carbon material out of the material around them, the current production of biochar from waste biomass prevents the carbon from becoming greenhouse gases.  For example, waste wood will eventually decompose if you leave it out in nature. When it decomposes, the waste wood is converted into greenhouse gases like carbon dioxide and methane.  If you take the waste wood and convert it to a stable carbon (biochar) then you prevent the release of carbon dioxide and methane to the atmosphere.  This is carbon sequestration. 

How Can Carbon Sequestration Benefit Soil Health?

Sequestering carbon into the soil can benefit the soil health.  It is important to note that all biochar is not the same.  The type of biomass used and the heating conditions used to make it can impact its usefulness.  But, in general, adding biochar to the soil will benefit the soil health.  Amending soil with 5% to 10% (by volume) of biochar is like a coral reef is to the ocean.  It will provide structure, a place for beneficial microbes to live, and sinks for water and nutrients.  Biochar made from wood waste has high-carbon content that is very porous.  It can be described as a low-grade activated carbon.  The surface areas can vary, but are frequently seen around 350 m2/g.  The high surface area gives the biochar the ability to retain nutrients and hold water.  The use of fertilizers is more efficient in biochar amended soils because the biochar holds more of the fertilizer in the soil which, in turn, prevents the fertilizer from running off the farmland and into nearby streams.  The beneficial mycorrhizal fungi, microbes, and plant roots will all seek biochar amended areas of the soil to work together for better soil health.  A healthier soil will support plants that are less stressed and capable of adsorbing more nutrients.  More nutrients will allow for better plant growth with a higher nutrient density. 

The benefits of biochar in the soil are still being researched, but the body of evidence is growing that adding biochar to the soil will improve soil health.  Improving soil health will have a positive impact on food security.  It made a significant difference for the native Amazonian people to find ways to improve their soil for growing populations. 

Due to the growth of the global population, it is just as important for farmers in the present day to find ways to increase crop yields using techniques that will reduce carbon dioxide emissions and reduce fertilizer loss to ground water.  In addition, the production of biochar from waste biomass will prevent greenhouse gas emissions.  

When produced correctly, biochar is more than a carbon neutral material.  Biochar is carbon negative.  Wakefield BioChar has conducted a lifecycle assessment on our biochar.  For every dry ton of biochar we are sequestering approximately two tons of carbon dioxide equivalence from the atmosphere.  We are making a difference to the soil and our future.