Influence of production conditions on the yield and environmental stability of biochar

Abstract Biochar, a solid product of biomass pyrolysis, is a promising concept for climate change mitigation and adaptation, as it can sequester atmospheric CO 2 while improving quality of soil where it is stored. However, for this potential to be realised, it is necessary for biochar to have high environmental stability, i.e., resist various decomposition processes over long time. The main objective of this work has been to relate biochar production conditions to the yield, and properties of biochar, particularly its long-term stability. We used our lab-scale pyrolysis facilities to produce biochar at three temperatures between 350 °C and 550 °C, from selected feedstock (pine, mixed larch and spruce chips, softwood pellets). We measured the yield of biochar and then used an accelerated ageing assay to obtain information on the stability of biochar. Such information is very important for the assessment of the climate change mitigation potential of biochar, as it has not yet been clearly defined what proportion of biochar actually remains “permanently” sequestered and how much is released back to the atmosphere in the short to medium term. The results of this work showed that despite increase in the stability of biochar with increasing pyrolysis temperature, the yield of stable biochar fraction is nearly independent of the temperature. These findings are essential for the optimisation of pyrolysis conditions for production of biochar with selected properties, as well as for modelling biochar systems and their climate change mitigation potential as compared to other uses of biomass, such as bioenergy, biofuels and/or chemicals.

[1]  C. Schadt,et al.  Labile soil carbon inputs mediate the soil microbial community composition and plant residue decomposition rates. , 2010, The New phytologist.

[2]  C. Masiello,et al.  Black carbon in deep-Sea sediments , 1998, Science.

[3]  J. Amonette,et al.  Sustainable biochar to mitigate global climate change , 2010, Nature communications.

[4]  M. Engelhard,et al.  Long-term black carbon dynamics in cultivated soil , 2008 .

[5]  M. Engelhard,et al.  Stability of biomass-derived black carbon in soils , 2008 .

[6]  Johannes Lehmann,et al.  Black carbon decomposition under varying water regimes. , 2009 .

[7]  S. Sohi.  BIOCHAR, CLIMATE CHANGE AND SOIL: A REVIEW TO GUIDE FUTURE RESEARCH , 2009 .

[8]  S. Sohi,et al.  The priming potential of biochar products in relation to labile carbon contents and soil organic matter status , 2011 .

[9]  Jeff Baldock,et al.  Chemical composition and bioavailability of thermally altered Pinus resinosa (Red pine) wood , 2002 .

[10]  P. Brownsort.  BIOMASS PYROLYSIS PROCESSES: PERFORMANCE PARAMETERS AND THEIR INFLUENCE ON BIOCHAR SYSTEM BENEFITS , 2009 .

[11]  F. Gao,et al.  Engineering hybrid nanotube wires for high-power biofuel cells. , 2010, Nature communications.

[12]  J. Skjemstad,et al.  Australian climate–carbon cycle feedback reduced by soil black carbon , 2008 .

[13]  P. Thornley,et al.  An assessment of the benefits and issues associated with the application of biochar to soil , 2010 .

[14]  S. Sohi,et al.  An Assessment of the Benefits and Issues Associated with the Application of Biochar to Soil: A report commissioned by the UK Department for Environment, Food and Rural Affairs and Department of Energy and Climate Change , 2010 .

[15]  S. Sohi,et al.  A review of biochar and its use and function in soil , 2010 .