On bio-CDR in soil. "Despite the fact that the United Nations General Assembly declared 2015 to be “the international year of soils,” a global soil carbon sequestration campaign — one that recognizes direct links between climate mitigation, regenerative agriculture and food security — rarely ranks at the top of any high level accords, or even conversations."

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Saarnio, Sanna (2015): Impacts of Biochar Amendment on Greenhouse Gas Emissions from Agricultural Soils. In Zhongqi He, Fengchang Wu (Eds.): Agricultural and Environmental Applications of Biochar: Advances and Barriers. Madison, WI: Soil Science Society of America, Inc (SSSA special publication, 63). Available online at http://dx.doi.org/10.2136/sssaspecpub63.2014.0045  

"Biochar amendment influences soil greenhouse gas (GHG) emissions by altering the microbial transformation conditions in soils in numerous ways. Increased pH, improved nutrient availability, and additional C may increase microbial activity and the release of GHGs. On the other hand, biochar may disturb microbial processes by increasing the C-to-N ratio in the soil or by adsorbing substrates, processed products and enzymes, or by releasing compounds inhibiting microbial activity."

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An, Chunjiang; Huang, Gordon (2015): Environmental concern on biochar. Capture, then what? In Environ Earth Sci. DOI: 10.1007/s12665-015-4741-8 

"Biochar tends to become the sink of soil pollutants. The changing soil environment can result in the release of toxic compounds from biochar in the long term. Biochar can be deactivated by clogged pores or decreasing sorption capacity."

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"The discovery of elevated fertility of the Amazonian Terra Preta soils was widely reported in the news media starting in 2006, coinciding with the initial public awareness of the existential threat of climate change. Small groups of people worldwide seized on the idea of Terra Preta and biochar as a climate solution, and began to publicize and act on the promise of biochar."

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