02-27-2009, 09:28 AM
I found the following excerpt on the web:
"However, not all biochar performs the same. The importance of biochar’s variable chemical composition was illustrated in studies by Goro Uehara, a professor of soil science at the University of Hawaii, who grew plants both with and without biochar made from macadamia nutshells. He says, "As we added more [biochar], the plants got sicker and sicker." Uehara’s colleague, University of Hawaii extension specialist Jonathan Deenik, says that when they repeated the experiment with a more highly carbonized version of the nutshell biochar, which contained lower levels of volatile compounds, "preliminary results in a greenhouse study showed that low-volatility [biochar] supplemented with fertilizer outperformed fertilizer alone by 60%, in a statistically significant difference." This research was presented at the October 2008 annual meeting of the Soil Science Society of America."
It seems to imply that you can under-cook biochar. Previously I had read statements that suggested low temperature cooking was better. To say the answer is probably in the middle is to say you believe either or both of these sources. I tend to believe the source quoted above. JWFITZ, when you make your charcoal, are you attempting to limit the temperature of the process in any way? It sounds as though you are putting biomass in a drum, getting it burning, and slapping the lid on for a while. As charcoal manufacturing processes go this is probably on the cool end of the spectrum because you are using one small drum and not routing the burning gasses to a burner under the retort (drum).
As an aside I offer the town of Centralia, PA, where an underground fire has been smoldering for more than 40 years in the coal seams beneath the town. Coal is a very dense fuel source and terra-pretta would not have any where near that density of carbon in the soil, but I wonder what if any danger there is of the charcoal catching fire. I am tempted to say it could never catch in Puna's wet climate but I read years ago about thick peaty deposits from swamps in FL burning after the swamps were drained.
"However, not all biochar performs the same. The importance of biochar’s variable chemical composition was illustrated in studies by Goro Uehara, a professor of soil science at the University of Hawaii, who grew plants both with and without biochar made from macadamia nutshells. He says, "As we added more [biochar], the plants got sicker and sicker." Uehara’s colleague, University of Hawaii extension specialist Jonathan Deenik, says that when they repeated the experiment with a more highly carbonized version of the nutshell biochar, which contained lower levels of volatile compounds, "preliminary results in a greenhouse study showed that low-volatility [biochar] supplemented with fertilizer outperformed fertilizer alone by 60%, in a statistically significant difference." This research was presented at the October 2008 annual meeting of the Soil Science Society of America."
It seems to imply that you can under-cook biochar. Previously I had read statements that suggested low temperature cooking was better. To say the answer is probably in the middle is to say you believe either or both of these sources. I tend to believe the source quoted above. JWFITZ, when you make your charcoal, are you attempting to limit the temperature of the process in any way? It sounds as though you are putting biomass in a drum, getting it burning, and slapping the lid on for a while. As charcoal manufacturing processes go this is probably on the cool end of the spectrum because you are using one small drum and not routing the burning gasses to a burner under the retort (drum).
As an aside I offer the town of Centralia, PA, where an underground fire has been smoldering for more than 40 years in the coal seams beneath the town. Coal is a very dense fuel source and terra-pretta would not have any where near that density of carbon in the soil, but I wonder what if any danger there is of the charcoal catching fire. I am tempted to say it could never catch in Puna's wet climate but I read years ago about thick peaty deposits from swamps in FL burning after the swamps were drained.