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This article in JEQ

  1. Vol. 43 No. 3, p. 971-979
     
    Received: July 24, 2013
    Published: June 24, 2014


    * Corresponding author(s): n.borchard@fz-juelich.de
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doi:10.2134/jeq2013.07.0290

Greenhouse Gas Production in Mixtures of Soil with Composted and Noncomposted Biochars Is Governed by Char-Associated Organic Compounds

  1. Nils Borchard *ab,
  2. Kurt Spokasc,
  3. Katharina Prosta and
  4. Jan Siemensa
  1. a Institute of Crop Science and Resource Conservation, Soil Science and Soil Ecology, Univ. of Bonn, Nussallee 13, 53115 Bonn, Germany
    b Agrosphere (IBG-3), Jülich Research Centre, 52425 Jülich, Germany
    c U.S. Department of Agriculture–Agricultural Research Service, Soil and Water Management Research Unit, 1991 Upper Buford Circle, St. Paul, MN 55108. Assigned to Associate Editor Amy Townsend-Small.

Abstract

Biochar application to soil has the potential to increase soil productivity while reducing anthropogenic greenhouse gas (GHG) emissions to the atmosphere. However, techniques for conditioning this material for maximizing its effects as a soil amendment require elucidation. We examined changes of organic matter associated with two biochars after 175 d of composting and the resulting effects on GHG emissions during a 150-d incubation period. Composting decreased the amount of organic compounds that could be thermally released from the biochars and affected their molecular nature. These thermally desorbable organic compounds from initial biochars likely stimulated the oxidation of CH4 and inhibited the production of N2O in soil–biochar mixtures. However, these reductions of GHG emissions disappeared together with thermally desorbable organic compounds after the composting of chars. Instead, addition of composted gasification coke and charcoal stimulated the formation of CH4 and increased N2O emissions by 45 to 56%. Nitrous oxide emissions equaled 20% of the total amount of N added with composted biochars, suggesting that organic compounds and N sorbed by the chars during composting fueled GHG production. The transient nature of the suppression of CH4 and N2O production challenges the long-term GHG mitigation potential of biochar in soil.

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