[Terrapreta] Bio-Char Sequestration in Terrestrial Ecosystems - - A Review

[Tom Miles]

Here's an argument for making char through pyrolysis.
 
Bio-Char Sequestration in Terrestrial Ecosystems - - A Review, Johannes Lehmann, John Gaunt, Marco Rondon, Mitigation and Adaptation Strategies for Global Change, Issue 11, p.403–42, (2006)
 
See link:
http://terrapreta.bioenergylists.org/lehmanbiochar
 

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. 
 
Terra Preta website: http://www.terrapreta.bioenergylists.org
 
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