Emission of CO₂ from biochar‐amended soils and implications for soil organic carbon

Abstract

Soil amendment with pyrogenic organic matter (PyOM), also named biochar, is claimed to sequester carbon (C). However, possible interactions between PyOM and native soil organic carbon (SOC) may accelerate the loss of SOC, thus reducing PyOM's C sequestration potential. We combined the results of 46 studies in a meta-analysis to investigate changes in CO 2 emission of PyOM-amended soils and to identify the causes of these changes and the possible factors involved. Our results showed a statistically significant increase of 28% in CO 2 emission from PyOM-amended soils. When grouped by PyOM C (PyC):SOC ratios, the group of studies with a ratio >2 showed a significant increase in CO 2 emissions, but those with a ratio <2 showed no significant effect of PyOM application on CO 2 emission. Our data are consistent with the hypothesis that increased CO 2 emission after PyOM addition is additive and mainly derived from PyOM's labile C fractions. The PyC:SOC ratio provided the best predictor of increases in CO 2 production after PyOM addition to soil. This meta-analysis highlights the importance of taking into account the amount of applied PyC in relation to SOC for designing future decomposition experiments.

Emissions intensity and carbon stocks of a tropical Ultisol after amendment with Tithonia green manure, urea and biochar

“…1A and 2A) concurs with what has been observed in previous studies and has been attributed to the supply of easily mineralizable C and improvement in soil physical properties for microbial activity (Lehmann et al, 2011; Sagrilo et al, 2014) and increased root respiration (Major et al, 2010). However, reduction in CO 2 emission after biochar addition has also been reported in incubations without plants, and is usually associated with limited N supply due to N immobilization by amended biochar (Laird et al, 2010, Wang et al, 2015).…”

Biochar additions can enhance soil structure and the physical stabilization of C in aggregates

“…The production of biochar and its use as a soil amendment is regarded as a promising strategy for soil carbon (C) sequestration (Lehmann, 2007) and has been shown to offer a range of agricultural benefits, such as reduced nutrient leaching (Laird et al, 2010), increased soil cation exchange (Liang et al, 2006) and water holding capacity (particularly in sandy soils) (Kammann et al, 2012). Biochar can also influence soil greenhouse gas (e.g., nitrous oxide and methane) emissions (Sagrilo et al, 2015; Verhoeven et al, 2017) and crop yields (Major et al, 2010; Schnell et al, 2012). Due to its impact on soil chemical properties, such as soil pH (Aciego Pietri and Brookes, 2008) and soil organic matter (SOM) composition (Mitchell et al, 2015), biochar can also induce shifts in soil microbial communities with important implications for a range of soil processes.…”

Effects of biochar application on fluxes of three biogenic greenhouse gases: a meta‐analysis

“…() and Sagrilo et al. () reviewed the effect of biochar application on N 2 O and CO 2 emissions, respectively. Clearly, the three major GHGs should be simultaneously considered when evaluating if a policy is effective to mitigate climate change (Tian et al.…”