Huy Sokchea, Khieu Borin and Preston T R 2011 Effect on growth of rice of biochar from rice husks or bagasse gasified in downdraft gasifier or updraft gasifier stove.  Workshop on Reducing Greenhouse Gas Emissions from Livestock and Soils (Editors: Reg Preston and Sisomphone Southavong). National Institute of Animal Science, Hanoi, 14-15 November 2011. httm://www.mekarn.org/workshops/GHG-CC/sokchea2.htm