Abstract
Biochar production and application as soil amendment is a promising carbon (C) negative technology to increase soil C sequestration and mitigate climate change. However, there is a lack of knowledge about biochar degradation rate in soil and its effects on native soil organic carbon (SOC), mainly due to the absence of long term experiments performed in field conditions. The aim of this work was to investigate the long term degradation rate of biochar in a field experiment of 8 years in a poplar short rotation coppice plantation in Piedmont (Italy), and to modify the RothC model to assess and predict how biochar influences soil C dynamics. The RothC model was modified by including two biochar pools, labile (4 % of the total biochar mass) and recalcitrant (96 %), and the priming effect of biochar on SOC. The model was calibrated and validated using data from the field experiment. The results confirm that biochar degradation can be faster in field conditions in comparison to laboratory experiments; nevertheless, it can contribute to substantially increase the soil C stock in the long-term. Moreover, this study shows that the modified RothC model was able to simulate the dynamics of biochar and SOC degradation in soils in field conditions in the long term, at least in the specific conditions examined.
Highlights
20 Biochar, the solid product of pyrolysis or gasification of biomass, has a large potential for increasing soil carbon (C) stocks and improve soil quality worldwide (Woolf et al 2010; Smith 2016; European Academies’ Science Advisory Council 2018)
There is a lack of knowledge about biochar degradation rate in 10 soil and its effects on native soil organic carbon (SOC), mainly due to the absence of long term experiments performed in field conditions
The understanding and assessment of the C sequestration potential of biochar requires the development of models able to take into account the turnover of biochar-C and SOC and effects on the SOC of added biochar
Summary
20 Biochar, the solid product of pyrolysis or gasification of biomass, has a large potential for increasing soil carbon (C) stocks and improve soil quality worldwide (Woolf et al 2010; Smith 2016; European Academies’ Science Advisory Council 2018). Due to its stability and resistance to mineralization, adding biochar to soil is considered a viable strategy for climate change mitigation (Lehmann et al 2006; Zahida et al 2017), since it can increase soil C stocks for hundreds or thousands of years (Wang et al 2016). Among the negative emission strategies proposed by IPCC (2014), biochar has the lowest impact in 25 terms of water footprint, land use and costs (Smith 2016). The generalisation of results from experiments is not easy, since biochar degradation depends on several factors such as: biochar characteristics, e.g. the original feedstock and the production.
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