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1 April 2008 Response from Day and Hawkins
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For brevity we did not include an important detail in one use of our biochar, to create a nitrogen-enriched char by capturing carbon dioxide (CO2). The Energy citation referenced by Gutschick (doi:10.1016/j.energy.2004.07.016) provides fuller details. The values for nitrogen content used were measured for pelletized peanut hulls, and were quantified using standardized analytical techniques. In our process, hydrogen from biomass pyrolysis, as demonstrated in our recent 1000-hour process demonstration, can be used to produce ammonia. We did not claim that the ammonia was manufactured on site, but stated that hydrogen generated from our process could be used to produce ammonia. To generate ECOSS [enriched carbon, organic slow-release sequestering], ammonia is hydrated and adsorbed on the porous biochar surfaces, aided by binding to the surface acid functional groups. This treated biochar powder is then injected into a cyclone slipstream of gases high in CO2, such as recovered exhaust from coal combustion or the exhaust of the biomass conversion system. (For more information on the ammonia carbonation process and its use in CO2 scrubbing, see research and patents by James W. Lee, our coauthor on the Energy article.) The fuel for the pyrolysis comes from the biomass, and therefore the carbon emissions of the process do not need to be debited. The efficiency of manufacturing of ammonia is low, but single-pass production using microscale technology can generate enough ammonia for our purposes.

The amendment of soil through the use of biochar has not been researched for all soil types, and further research is needed. Johannes Lehmann and others have shown positive effects of biochar on soil properties and crop yields. The examples we gave are known instances where the increase in soil carbon was beneficial; we did not speculate about other possible cases.

Danny Day and Bob Hawkins "Response from Day and Hawkins," BioScience 58(4), 285, (1 April 2008). https://doi.org/10.1641/B580421
Published: 1 April 2008
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