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Labile water soluble components govern the short-term microbial decay of hydrochar from sewage sludge |
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| Authors: | Marc Breulmann Katrin Kuka Manfred van Afferden François Buscot Christoph Fühner Roland Müller |
| Institution: | 1. Environmental and Biotechnology Centre (UBZ), Helmholtz-Centre for Environmental Research – UFZ, Leipzig, Germany;2. Department of Soil Ecology, Helmholtz-Centre for Environmental Research – UFZ, Halle, Germany;3. Department of Soil Physics, Helmholtz-Centre for Environmental Research – UFZ, Halle, Germany;4. Research Centre for Cultivated Plants, Institute for Crop and Soil Science, Federal Julius-Kühn Institut, Braunschweig, Germany;5. Department of Soil Ecology, Helmholtz-Centre for Environmental Research – UFZ, Halle, Germany;6. Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany |
| Abstract: | Due to higher proportions of labile carbon (C) compounds the suitability of biochar produced by hydrothermal carbonization (HTC) for C sequestration is questionable. We hypothesized that pre-treatment with water would reduce the biological decay of hydrochar from sewage sludge. Unwashed and washed feedstock and hydrochar were incubated in a short-term experiment. The kinetics of the biological decomposition of the materials was calculated on the basis of a double exponential model and the C sequestration potential using the CANDY Carbon Balance (CCB) model. Biological decomposition of the carbonized materials was governed by the percentage of labile C compounds. Mean residence time of a fast (MRTfast) and slow decay pool (MRTslow) of unwashed hydrochars varied clearly (MRTfast: 0.8 – 5.0 months and the MRTslow: 5.0–18.6 months). The pre-treatment with water removed labile hydrochar C and reduced the biological accessibility. MRTfast and MRTslow was increased by intensive washings (MRTfast: 5.0–7.4 months and the MRTslow: 14.9 months). High synthesis coefficients suggest that hydrochar C was humified and transferred into stabilized SOC. The results clearly show that once adsorbed components were eliminated, and as compared to pyrolysed biochar hydrochar from sewage sludge may also be useful for soil C sequestration. |
| Keywords: | Biochar carbon sequestration CCB model hydrochar respiration sewage sludge |