Can biochar reduce soil greenhouse gas emissions from a Miscanthus bioenergy crop?

GCB Bioenergy (Impact Factor: 4.88). 01/2014; 6(1):76-89. DOI: 10.1111/gcbb.12052


Energy production from bioenergy crops may significantly reduce greenhouse gas (GHG) emissions through substitution of fossil fuels. Biochar amendment to soil may further decrease the net climate forcing of bioenergy crop production, however, this has not yet been assessed under field conditions. Significant suppression of soil nitrous oxide (N2O) and carbon dioxide (CO2) emissions following biochar amendment has been demonstrated in short-term laboratory incubations by a number of authors, yet evidence from long-term field trials has been contradictory. This study investigated whether biochar amendment could suppress soil GHG emissions under field and controlled conditions in a Miscanthus × Giganteus crop and whether suppression would be sustained during the first 2 years following amendment. In the field, biochar amendment suppressed soil CO2 emissions by 33% and annual net soil CO2 equivalent (eq.) emissions (CO2, N2O and methane, CH4) by 37% over 2 years. In the laboratory, under controlled temperature and equalised gravimetric water content, biochar amendment suppressed soil CO2 emissions by 53% and net soil CO2 eq. emissions by 55%. Soil N2O emissions were not significantly suppressed with biochar amendment, although they were generally low. Soil CH4 fluxes were below minimum detectable limits in both experiments. These findings demonstrate that biochar amendment has the potential to suppress net soil CO2 eq. emissions in bioenergy crop systems for up to 2 years after addition, primarily through reduced CO2 emissions. Suppression of soil CO2 emissions may be due to a combined effect of reduced enzymatic activity, the increased carbon-use efficiency from the co-location of soil microbes, soil organic matter and nutrients and the precipitation of CO2 onto the biochar surface. We conclude that hardwood biochar has the potential to improve the GHG balance of bioenergy crops through reductions in net soil CO2 eq. emissions.

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    • "The microbial degradation of biochar C in soil is often associated with labile organic compounds, such as alkanoic and benzoic acids, and phenols, whose concentration falls with increasing pyrolysis temperature (Liang et al., 2010; Novak et al., 2009; Graber et al., 2010; Troy et al., 2013). Biochars produced from plant residues contain stable aromatic structures and are more resistant to microbial attack (Foereid et al., 2011; Ippolito et al., 2012; Case et al., 2014; Jeong et al., 2015). "
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    ABSTRACT: Manure-derived biochars can offer a potential option for the stabilization of manure, while mitigating climate change through carbon sequestration and the attenuation of nitrous oxide emission. A laboratory incubation study was conducted to assess the effects of four different manure-derived biochars produced from different feedstocks (poultry litter and swine manure) at different temperatures (400 or 600 °C). A commonly available standard wood chip biochar, produced at a greater temperature (1000 °C), and non-amended treatments were used as references. Two different soils (sandy and silt-loam) were amended with 2% (w/w) biochar on a dry soil weight basis (corresponding to 20 Mg ha(-1)), with the soil moisture being adjusted to 75% saturation level. After a pre-incubation period (21 days), 170 kg N ha(-1) of NH4NO3 fertilizer was added. Measurements of CO2, N2O, CH4 emissions and soil N mineralisation were carried out on different days during the 85 days of incubation. The net C mineralization and N2O emissions from both soils amended with poultry litter biochar at 400 °C were significantly greater than the other biochar treatments. Nitrate availability was greater in both soils in which the manure-derived biochar was used instead of the standard biochar. All of the biochars increased the pH of the silt-loam, sub-acid soil, but failed to improve the cation exchange capacities (CEC) in either soil. Total C and N, P, K and Mg (except Ca) were significantly increased in the manure-derived biochar amended soils, compared to the Control, and were positively correlated to the biochar nutrient contents. This study indicates that the soil application of biochar engenders effects that can vary considerably according to the biochar properties, as determined on the basis of the feedstock types and process conditions. Low-temperature biochar production from manure represents a possible way of producing a soil amendment that can stabilize C while supplying a significant quantity of nutrients.
    Journal of Environmental Management 10/2015; 166:73-83. DOI:10.1016/j.jenvman.2015.10.007 · 2.72 Impact Factor
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    • "The meta-analysis by Jeffery et al. (2011) indicated biochar to be able to improve acidic soils by a liming effect and soils with a coarse or medium texture by increasing soil water holding capacity. However, several other studies from field trial have showed little effects of biochar on soil hydraulic properties (Karhu et al. 2011; Case et al. 2013; Tammeorg et al. 2014). The inconsistency in the results among the studies is mainly attributed to the great differences in soil types and regional climate conditions. "
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    ABSTRACT: A hydrologically contained field study, to assess biochar (produced from mixed crop straws) influence upon soil hydraulic properties and dissolved organic carbon (DOC) leaching, was conducted on a loamy soil (entisol). The soil, noted for its low plant-available water and low soil organic matter, is the most important arable soil type in the upper reaches of the Yangtze River catchment, China. Pore size distribution characterization (by N2 adsorption, mercury intrusion, and water retention) showed that the biochar had a tri-modal pore size distribution. This included pores with diameters in the range of 0.1-10 μm that can retain plant-available water. Comparison of soil water retention curves between the control (0) and the biochar plots (16 t ha(-1) on dry weight basis) demonstrated biochar amendment to increase soil water holding capacity. However, significant increases in DOC concentration of soil pore water in both the plough layer and the undisturbed subsoil layer were observed in the biochar-amended plots. An increased loss of DOC relative to the control was observed upon rainfall events. Measurements of excitation-emission matrix (EEM) fluorescence indicated the DOC increment originated primarily from the organic carbon pool in the soil that became more soluble following biochar incorporation.
    Environmental Science and Pollution Research 06/2015; DOI:10.1007/s11356-015-4885-9 · 2.83 Impact Factor
    • ") Greenhouse experiments (Fungo et al., 2014; Sun et al., 2014; Zhao et al., 2014) Field experiments (Bian et al., 2013; Van Zwieten et al., 2013; Zhang et al., 2013; Anderson et al., 2014; Angst et al., 2014; Case et al., 2014; Felber et al., 2014; Hu et al., 2014; Pandey et al., 2014; Schimmelpfennig et al., 2014; Shen et al., 2014; Watanabe et al., 2014) "
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    ABSTRACT: A previously published meta-analysis of biochar impacts on soil N2O emissions by Cayuela et al. (2014) found a “grand mean” reduction in N2O emissions of 54 ± 6% following biochar application to soil. Here we update this analysis to include 26 additional manuscripts bringing the total to 56 articles. The updated meta-analysis confirms that biochar reduces soil N2O emissions by 49 ± 5% (mean ± 95% confidence interval). Importantly, this meta-analysis has sufficient data to investigate the impact of biochar under field conditions, showing a statistically significant lower average reduction in the field (28 ± 16%) compared to controlled laboratory studies (54 ± 3%). A key finding is the importance of the molar H:Corg ratio of biochar in determining mitigation of N2O. Biochars with a molar H:Corg ratio <0.3, indicative of a high degree of aromatic condensation, lowered N2O emissions by 73 ± 7% while biochars with a molar H:Corg ratio >0.5 were less effective at 40 ± 16%. Together with previously published information, our new results suggest that a key mitigation mechanism is linked to the degree of polymerization and aromaticity of biochar.
    Agriculture Ecosystems & Environment 04/2015; 202(135-138). DOI:10.1016/j.agee.2014.12.015 · 3.40 Impact Factor
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