Bio-char Sequestration in Terrestrial Ecosystems A Review

Publication Type:

Journal Article

Source:

Mitigation and Adaptation Strategies for Global Change, Number 11, p.403-42 (2006)

Accession Number:

10.1007/s11027-005-9006-

URL:

http://www.css.cornell.edu/faculty/lehmann/publ/MitAdaptStratGlobChange%2011,%20403-427,%20Lehmann,%202006.pdf

Keywords:

black carbon, Carbon sequestration, Charcoal, emissions trading, globalwarming potential, greenhouse gas emissions, soils, terra preta de indio

Abstract:

The application of bio-char (charcoal or biomass-derived black carbon (C)) to soil is proposed as a novel approach to establish a significant, long-term, sink for atmospheric carbon dioxide in terrestrial ecosystems. Apart from positive effects in both reducing emissions and increasing the sequestration of greenhouse gases, the production of bio-char and its application to soil will deliver immediate benefits through improved soil fertility and increased crop production. Conversion of biomass C to bio-char C leads to sequestration of about 50% of the initial C compared to the low amounts retained after burning (3%) and biological decomposition (<10?20% after 5?10 years), therefore yielding more stable soil C than burning or direct land application of biomass. This efficiency of C conversion of biomass to bio-char is highly dependent on the type of feedstock, but is not significantly affected by the pyrolysis temperature (within 350?500 ?C common for pyrolysis). Existing slash-andburn systems cause significant degradation of soil and release of greenhouse gases and opportunies may exist to enhance this system by conversion to slash-and-char systems. Our global analysis revealed that up to 12% of the total anthropogenic C emissions by land use change (0.21 Pg C) can be off-set annually in soil, if slash-and-burn is replaced by slash-and-char. Agricultural and forestry wastes such as forest residues, mill residues, field crop residues, or urban wastes add a conservatively estimated 0.16 PgCyr?1. Biofuel production using modern biomass can produce a bio-char by-product through pyrolysis which results in 30.6 kgC sequestration for each GJ of energy produced. Using published projections of the use of renewable fuels in the year 2100, bio-char sequestration could amount to 5.5?9.5 PgCyr?1 if this demand for energy was met through pyrolysis, which would exceed current emissions from fossil fuels (5.4 PgC yr?1). Bio-char soil management systems can deliver tradable C emissions reduction, and C sequestered is easily accountable, and verifiable.