Biochar Carbon Accounting and Climate Change
Replacing slash-and-burn agriculture with slash-and-char and use of agricultural and forestry wastes for biochar production could provide a CO2 drawdown of ~8 ppm or more in half a century....Carbon sequestration in soil also has significant potential. Biochar, produced in pyrolysis of residues from crops, forestry, and animal wastes, can be used to restore soil fertility while storing carbon for centuries to millennia. Biochar helps soil retain nutrients and fertilizers, reducing emissions of GHGs such as N2O....
Dr. James Hansen, Director, NASA Goddard Institute for Space Studies
Photo: US House of Representatives Select Committee on Energy Independence and Global Warming
There is one way we could save ourselves and that is through the massive burial of charcoal....It would mean farmers turning all their agricultural waste – which contains carbon that the plants have spent the summer sequestering – into non-biodegradable charcoal, and burying it in the soil. Then you can start shifting really hefty quantities of carbon out of the system and pull the CO2 down quite fast.
James Lovelock, scientist, inventor, author and originator of the Gaia Theory
Photo: Bruno Comby
The international research effort on biochar continues to indicate that biochar production and use has the potential to fight global warming by holding carbon in soil instead of releasing it into the atmosphere. There are several pathways by which biochar can accomplish emissions offsets.
The most immediate path to consider is the direct burial of highly recalcitrant char in soil. This pathway has the obvious advantage of providing a physical pool of carbon that is measurable and verifiable. However, while biochar is far more stable in soil than other forms of organic matter, monitoring will still be required to determine biochar residence times in a variety of soils and for different types of biochar.
Other, more indirect pathways include:
- Avoided emissions of N2O and methane from soil
- Displaced fertilizer and agricultural inputs
- More fertile soil to boost food security and preserve cropland diversity
- Fossil fuel displacement
Carbon accounting is a complex and dynamic field. As researchers delve further into concepts and methodologies for establishing robust biochar carbon accounting systems, they will have many parameters to consider.
For more on biochar and carbon accounting, see Chapter 18: Biochar, greenhouse gas accounting and emissions trading, by John Gaunt, GY Associates, UK and Annette Cowie, New South Wales Department of Primary Industries, in the book Biochar for Environmental Management, published by Earthscan.