Use of biochar (charcoal) to replenish soil carbon pools, restore soil fertility and sequester CO2

Author: 
Tom Miles

Use of biochar (charcoal) to replenish soil carbon pools, restore soil fertility and sequester CO2

Submission by the United Nations Convention to Combat Desertification
4th Session of the Ad Hoc Working Group on Long-term Cooperative Action under the
Convention (AWG-LCA 4), Poznan, 1-10 December 2008
Submission containing ideas and proposals on Paragraph 1 of the Bali Action Plan:
Use of biochar (charcoal) to replenish soil carbon pools, restore soil fertility and sequester CO2

Abstract

The world's soils hold more organic carbon than that held by the atmosphere as CO2 and vegetation, yet the role of the soil in capturing and storing carbon dioxide is often one missing information layer in taking into consideration the importance of the land in mitigating climate change. Extraordinary demands are being placed on agricultural systems to produce food, fiber and energy and yet the inevitable changes in the flow of carbon into or out of soils have significant effect on a global scale. Biomass burning and the removal of crop residues reduce carbon in soil and vegetation, which has implications for soil fertility and the global carbon cycle.
The land has an unparalleled capacity to hold carbon and to act as a sink for green house gases making it imperative to focus on activities that enhances rehabilitation, protection and sustainable management of degraded lands. Conventional means to increase soil carbon stocks depend on climate, soil type and site specific management. Over the years, most efforts to manage greenhouse gases have involved planting trees, since the amount of carbon that can be sequestered in this way is substantial. However, the drawback of conventional carbon enrichment is that this carbon-sink option is of limited duration. The associated humus enrichment follows a saturation curve, approaching a new equilibrium level after some 50 to 100 years. The new carbon level drops rapidly again as soon as the required careful management is no longer sustained.

There exist opportunities to include sustainable land management processes and in particular the use of biochar into the CDM negotiation process through focused policy actions that include institutional synergy as well as better understanding of the sustainability cost-benefit of Biochar. This process could be undertaken starting in Poznan and towards the Copenhagen agreement.
Pyrolysis (of agricultural residues resulting in charcoal and energy production) with biochar carbon sequestration provides a tool to combine sustainable soil management (carbon sequestration) and renewable energy production. The process of pyrolysis or carbonization is known globally and can be implemented at both small scale (e.g. cooking stove) and large scale levels (e.g. biorefinery).

About 50% of the carbon can be captured if biomass is converted to biochar. Charcoal enriched soils like Chernozems and in particular Terra Preta soils are among the world