Greenhouse gas mitigation potential in crop production with biochar soil amendment—a carbon footprint assessment for cross‐site field experiments from China

Abstract

Biochar soil amendment (BSA) had been advocated as a promising approach to mitigate greenhouse gas (GHG) emissions in agriculture. However, the net GHG mitigation potential of BSA remained unquantified with regard to the manufacturing process and field application. Carbon footprint (CF) was employed to assess the mitigating potential of BSA by estimating all the direct and indirect GHG emissions in the full life cycles of crop production including production and field application of biochar. Data were obtained from 7 sites (4 sites for paddy rice production and 3 sites for maize production) under a single BSA at 20 t/ha−1 across mainland China. Considering soil organic carbon (SOC) sequestration and GHG emission reduction from syngas recycling, BSA reduced the CFs by 20.37–41.29 t carbon dioxide equivalent ha−1 (CO2‐eq ha−1) and 28.58–39.49 t CO2‐eq ha−1 for paddy rice and maize production, respectively, compared to no biochar application. Without considering SOC sequestration and syngas recycling, the net CF change by BSA was in a range of −25.06 to 9.82 t CO2‐eq ha−1 and −20.07 to 5.95 t CO2‐eq ha−1 for paddy rice and maize production, respectively, over no biochar application. As the largest contributors among the others, syngas recycling in the process of biochar manufacture contributed by 47% to total CF reductions under BSA for rice cultivation while SOC sequestration contributed by 57% for maize cultivation. There was a large variability of the CF reductions across the studied sites whether in paddy rice or maize production, due likely to the difference in GHG emission reductions and SOC increments under BSA across the sites. This study emphasized that SOC sequestration should be taken into account the CF calculation of BSA. Improved biochar manufacturing technique could achieve a remarkable carbon sink by recycling the biogas for traditional fossil‐fuel replacement.

Life cycle assessment of carbon dioxide removal technologies: a critical review

“…Some studies generated alternative functional units to demonstrate the impacts per land area (e.g. 57,79,82,97 ). Few studies presented extended functional units based on the by-products produced (e.g.…”

A Review on Current Status of Biochar Uses in Agriculture

“…The carbon footprint of biochar must include production, persistence in soil, rate of degradation in soil and degree of soil fertility. An example of this was a study carried out in mainland China in which four paddy rice fields and 3 maize fields were amended with biochar [ 76 ]. The addition of biochar reduced the amount of released carbon by 18,479.35–37,457.66 kg of carbon dioxide [ 76 ], i.e., a reduction of 47% and 57% for both rice and maize, respectively [ 75 ].…”

“…An example of this was a study carried out in mainland China in which four paddy rice fields and 3 maize fields were amended with biochar [ 76 ]. The addition of biochar reduced the amount of released carbon by 18,479.35–37,457.66 kg of carbon dioxide [ 76 ], i.e., a reduction of 47% and 57% for both rice and maize, respectively [ 75 ]. Spokas and Reicosky, 2009 looked at 16 different types of biochar and their effect on GHG emissions in soils [ 77 ].…”

Greater microbial carbon use efficiency and carbon sequestration in soils: Amendment of biochar versus crop straws

“…In contrast, incorporation of biochar into soils has been recognized as a promising strategy to increase C sequestration, mitigate greenhouse gas emissions, and promote soil health (Han et al., 2020; Lehmann, 2007; Smith, 2016; Xu et al., 2019). Biochar is pyrolyzed from organic materials under oxygen‐limited conditions, and often contains a relatively larger proportion of condensed aromatic C that can persist in soils for hundreds to thousands of years (Lehmann et al., 2011).…”