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This study aimed to investigate the impacts of straw and biochar on greenhouse gas (GHG) emissions and grain yield in a double rice cropping system under optimal N fertilizer reduction. Conventional fertilization (CF) was used as the control group, and treatments included optimal fertilization and 15% less nitrogen (OF), together with straw (S) or biochar (B) applied under different fertilization conditions, namely CF + S, CF + B, OF + S, and OF + B. The effects of treatments on soil CH4 and N2O emissions were studied, and changes in soil physicochemical properties were analyzed. The results showed that relative to CF, CF + S and OF + S increased the cumulative CH4 emissions by 11.80% and 2.35%, respectively, while CF + B and OF + B resulted in significant reductions in cumulative CH4 emissions by 27.80% and 28.46%, respectively. Biochar was effective in reducing N2O emissions, and OF further increased the potential, with CF + B and OF + B achieving the best N2O reductions of 30.56% and 32.21%, respectively. Although OF reduced yields by 0.16%, this difference was within reasonable limits; the remaining treatments increased grain yields by 2.55% to 3.47%. CF + B and OF + B reduced the global warming potential (GWP) by 27.93% and 28.63%, respectively, and ultimately reduced the greenhouse gas emission intensity (GHGI) by 30.42% and 30.97%. Both straw and biochar increased the soil organic matter, NH4+-N, and NO3−-N contents, and biochar increased the soil pH, which may be the potential mechanism regulating soil GHG emissions. Overall, OF + B is beneficial for reducing GHG emissions and may be a better agronomic cropping pattern in double season rice growing areas. [ABSTRACT FROM AUTHOR]

Within Mediterranean cropping systems, legume forage crops that last up to 6 years or more (e.g., alfalfa) are replaced with cereal crops (e.g., wheat). The change from forage to cereal crops has negative climate and environmental impacts that must be addressed with mitigation actions. This study evaluated the synergies and tradeoffs between the ecosystem services provided by three management systems after forage legume. A field trial was set up from October 2017 to September 2019 on a 6-year-old alfalfa field subjected to the following management systems: (i) alfalfa termination followed by wheat for 2 years (WW, control); (ii) alfalfa termination followed by single amendment with 60 Mg ha−1 recalcitrant biochar and then by wheat for 2 years (WWB60); and (iii) extension of alfalfa for 2 years (AEXT). A range of regulating, supporting, and provisioning ecosystem services were assessed during the 2018 and 2019 cropping seasons. The results highlight that WWB60 can guarantee carbon sequestration without causing tradeoffs with other services, while AEXT can enhance soil conservation while not increasing soil greenhouse gas emissions. Future policies should support the WWB60 system if the goal is to increase the supporting services. Conversely, the AEXT system should be used if the goal is to increase the regulating and provisioning services. [ABSTRACT FROM AUTHOR]

Methane and N2O are two important greenhouse gases, which are the main emission in paddy ecology system. China is the highest rice planting country, so the greenhouse gas emission is huge in China. Application of biochar in paddy field can decrease the emissions of greenhouse gases. In this study, we investigated the greenhouse gas (GHG) emissions, carbon sequestration and economics of different rates of biochar application in a double rice cropping system. The experiment was carried out in rice variety area promotion experiment field in Huizhou of Guangdong from March 2012 to September 2015. Four treatments were designed as CK (famer traditional operation without biochar application), BC1 (biochar amendment at 5 t/hm²), BC2 (biochar amendment at 10 t/hm²), and BC3 (biochar amendment at 20 t/hm²), each treatment has 3 repeat. Biochar used in this study was obtained from wheat straw and produced by Henan Sanli New Energy Company. LCA (life cycle assessment) method was employed to calculate GHG emissions from the collection and transportation of raw materials, the production, transportation, and broadcasting of biochar, and from the avoidance of the straw burning and the soil carbon stocks. Static chamber-GC (gas chromatography) method was used to monitor the CH4 and N2O emissions under different rates of biochar application from 2012 to 2015. Then, the net GHG emissions and the percentage of emission reduction in the paddy field with different biochar amendment rates were calculated. The total GHG emissions from the double rice cropping system were 19.5, 15.6, 16.1, and 12.4 t/hm2 under CK, BC1, BC2, and BC3 treatments respectively in four years. Moreover, the total GHG emission reduction percentage of BC1, BC2 and BC3 were 19.70%, 17.46%, and 36.40%, respectively. Considering the GHG emissions of biochar in all stages of life cycle, the net GHG emissions of CK, BC1, BC2 and BC3 in the four years were 19.5, 20.3, 10.9, and 4.2 t/hm², respectively, the treatment of BC1 increased the net emissions of 4.3% in the four years. BC2 and BC3 reduced the net GHG emissions by 44% and 78.6%, respectively in four years. The economic analysis indicated that the BC1treatment had more economic benefits compared to other treatments. The different biochar amendment rates significantly reduced the GHG emissions from the double rice cropping system, the highest application rate of biochar had the best emission reduction effect. The LCA of biochar application indicated that from medium to high application levels, biochar reduces emissions, for higher application rates of biochar, the effects are stronger. Moreover, the economic analysis indicated that the more amounts of biochar application, the least profitable to gain economic benefits. [ABSTRACT FROM AUTHOR]

Biochar amendment can reduce CH 4 emissions from paddy soils. However, little is known about how the soil microbial communities associated with paddy soil CH 4 emissions respond to biochar aging after biochar amendment. In this study, we examined the effects of biochar on CH 4 emissions, soil properties, and abundance/community composition of methanogens and methanotrophs in a double rice cropping system from 2012 to 2016. Straw-derived biochar was applied once in 2012 at 24 and 48 t ha−1. Biochar application decreased the annual CH 4 emissions by 20–51%. Biochar increased the abundances of both methanogens and methanotrophs, with a larger increase of methanotrophs than methanogens in the first year, mainly caused by the increases in soil dissolved organic carbon, NH 4 +-N, and porosity. Biochar suppressed the abundance of methanogens and had little effect on the methanotrophs in the following three years, probably due to the increased soil porosity. Eventually, the ratios of abundance of methanogens to methanotrophs decreased by 11–31% in each of the four years and were positively correlated to CH 4 emissions. Biochar addition increased the relative abundances of Methanocella and Methanospirillum and reduced those of Methanoregula and Methanosaeta for methanogens, while it increased the proportion of the basophilic methanotrophs Methylomicrobium and decreased that of Methylocaldum in the growing season 2014. Our results demonstrate that biochar aging greatly alters the responses of abundances and community compositions of soil methanogens and methanotrophs to biochar addition. The reduction of CH 4 emissions owing to biochar in the long run was probably mainly due to the lesser suppression of abundance and activity of methanotrophs compared with methanogens. • Biochar decreased paddy CH 4 emissions across four years. • Biochar significantly reduced methanogen:methanotroph ratios in four years. • Fresh biochar with nutrients stimulated methanotrophs and methanogens in year one. • Aged biochar suppressed methanogen growth in years 2–4 due to increased soil porosity. • Biochar reduced the acetoclastic methanogen abundances at tillering and ripening. [ABSTRACT FROM AUTHOR]

• Biochar reduced soil N 2 O emissions and enhanced CH 4 uptake in a chestnut plantation. • Biochar altered key soil environmental factors important for GHG emissions. • Biochar altered the relationships between soil GHG emissions and labile organic C. • Soil temperature and water-soluble organic C were major controls on GHG emissions. Biochar application has been proposed as an effective measure to mitigate greenhouse gas (GHG) emissions from soil. However, the effects of different biochar application rates on soil GHG emissions and their linkages with biochar-induced changes in soil environmental factors remain unclear in managed plantations. This study examined the responses of soil GHG emissions to different application rates of bamboo leaf biochar in a Chinese chestnut plantation. A two-year field trial was conducted to determine the changes in soil GHG emissions and key soil properties over time in B0 (control), B2, B5 and B10 treatments, representing biochar application rates of 0, 2, 5 and 10 t ha−1, respectively. Biochar application significantly (P < 0.05) decreased soil N 2 O emissions (from 2.60 to 2.11 t ha−1 yr−1) and increased soil CH 4 uptake (from 3.13 to 4.22 t ha−1 yr−1), but did not change soil CO 2 emissions. The biochar inhibition effect on soil GHG emissions increased with increasing biochar application rates, with greater inhibition in the first year than in the second year. Biochar application also decreased the concentrations of soil NH 4 +-N, NO 3 –-N and water-soluble organic N (WSON), but increased the concentrations of water-soluble organic C (WSOC) and microbial biomass C (MBC). Regardless of the treatments, the soil GHG emissions were significantly (P < 0.01) correlated with soil temperature, but not with soil moisture content. Soil CO 2 and N 2 O emissions, and soil CH 4 uptake were positively (P < 0.05) correlated with WSOC concentration under the B0, B2 and B5 treatments only. A significant relationship (P < 0.05) was observed between soil MBC and soil CO 2 emissions (only for the B0 and B2 treatments), and soil MBC and soil N 2 O emissions (only for the B0, B2 and B10 treatments). The results suggest that biochar application rates can alter the relationships between GHG emissions and soil WSOC and MBC concentrations. The soil N 2 O emissions were positively (P < 0.05) correlated with the NH 4 +-N, NO 3 −-N and WSON concentrations in all treatments. This study demonstrated that the management practice (i.e. biochar application to soil) decreased soil GHG emissions in a Chinese chestnut plantation via changes in key soil properties, with implications for the mitigation of soil GHG emissions in subtropical plantations. [ABSTRACT FROM AUTHOR]

Methane and N2O are two important greenhouse gases, which are the main emission in paddy ecology system. China is the highest rice planting country, so the greenhouse gas emission is huge in China. Application of biochar in paddy field can decrease the emissions of greenhouse gases. In this study, we investigated the greenhouse gas (GHG) emissions, carbon sequestration and economics of different rates of biochar application in a double rice cropping system. The experiment was carried out in rice variety area promotion experiment field in Huizhou of Guangdong from March 2012 to September 2015. Four treatments were designed as CK (famer traditional operation without biochar application), BC1 (biochar amendment at 5 t/hm2), BC2 (biochar amendment at 10 t/hm2), and BC3 (biochar amendment at 20 t/hm2), each treatment has 3 repeat. Biochar used in this study was obtained from wheat straw and produced by Henan Sanli New Energy Company. LCA (life cycle assessment) method was employed to calculate GHG emissions from the collection and transportation of raw materials, the production, transportation, and broadcasting of biochar, and from the avoidance of the straw burning and the soil carbon stocks. Static chamber-GC (gas chromatography) method was used to monitor the CH4 and N2O emissions under different rates of biochar application from 2012 to 2015. Then, the net GHG emissions and the percentage of emission reduction in the paddy field with different biochar amendment rates were calculated. The total GHG emissions from the double rice cropping system were 19.5, 15.6, 16.1, and 12.4 t/hm2 under CK, BC1, BC2, and BC3 treatments respectively in four years. Moreover, the total GHG emission reduction percentage of BC1, BC2 and BC3 were 19.70%, 17.46%, and 36.40%, respectively. Considering the GHG emissions of biochar in all stages of life cycle, the net GHG emissions of CK, BC1, BC2 and BC3 in the four years were 19.5, 20.3, 10.9, and 4.2 t/hm2, respectively, the treatment of BC1 increased the net emissions of 4.3% in the four years. BC2 and BC3 reduced the net GHG emissions by 44% and 78.6%, respectively in four years. The economic analysis indicated that the BC1treatment had more economic benefits compared to other treatments. The different biochar amendment rates significantly reduced the GHG emissions from the double rice cropping system, the highest application rate of biochar had the best emission reduction effect. The LCA of biochar application indicated that from medium to high application levels, biochar reduces emissions, for higher application rates of biochar, the effects are stronger. Moreover, the economic analysis indicated that the more amounts of biochar application, the least profitable to gain economic benefits. [ABSTRACT FROM AUTHOR]

Methane and N2O are two important greenhouse gases, which are the main emission in paddy ecology system. China is the highest rice planting country, so the greenhouse gas emission is huge in China. Application of biochar in paddy field can decrease the emissions of greenhouse gases. In this study, we investigated the greenhouse gas (GHG) emissions, carbon sequestration and economics of different rates of biochar application in a double rice cropping system. The experiment was carried out in rice variety area promotion experiment field in Huizhou of Guangdong from March 2012 to September 2015. Four treatments were designed as CK (famer traditional operation without biochar application), BC1 (biochar amendment at 5 t/hm2), BC2 (biochar amendment at 10 t/hm2), and BC3 (biochar amendment at 20 t/hm2), each treatment has 3 repeat. Biochar used in this study was obtained from wheat straw and produced by Henan Sanli New Energy Company. LCA (life cycle assessment) method was employed to calculate GHG emissions from the collection and transportation of raw materials, the production, transportation, and broadcasting of biochar, and from the avoidance of the straw burning and the soil carbon stocks. Static chamber-GC (gas chromatography) method was used to monitor the CH4 and N2O emissions under different rates of biochar application from 2012 to 2015. Then, the net GHG emissions and the percentage of emission reduction in the paddy field with different biochar amendment rates were calculated. The total GHG emissions from the double rice cropping system were 19.5, 15.6, 16.1, and 12.4 t/hm2 under CK, BC1, BC2, and BC3 treatments respectively in four years. Moreover, the total GHG emission reduction percentage of BC1, BC2 and BC3 were 19.70%, 17.46%, and 36.40%, respectively. Considering the GHG emissions of biochar in all stages of life cycle, the net GHG emissions of CK, BC1, BC2 and BC3 in the four years were 19.5, 20.3, 10.9, and 4.2 t/hm2, respectively, the treatment of BC1 increased the net emissions of 4.3% in the four years. BC2 and BC3 reduced the net GHG emissions by 44% and 78.6%, respectively in four years. The economic analysis indicated that the BC1treatment had more economic benefits compared to other treatments. The different biochar amendment rates significantly reduced the GHG emissions from the double rice cropping system, the highest application rate of biochar had the best emission reduction effect. The LCA of biochar application indicated that from medium to high application levels, biochar reduces emissions, for higher application rates of biochar, the effects are stronger. Moreover, the economic analysis indicated that the more amounts of biochar application, the least profitable to gain economic benefits. [ABSTRACT FROM AUTHOR]

Methane and N2O are two important greenhouse gases, which are the main emission in paddy ecology system. China is the highest rice planting country, so the greenhouse gas emission is huge in China. Application of biochar in paddy field can decrease the emissions of greenhouse gases. In this study, we investigated the greenhouse gas (GHG) emissions, carbon sequestration and economics of different rates of biochar application in a double rice cropping system. The experiment was carried out in rice variety area promotion experiment field in Huizhou of Guangdong from March 2012 to September 2015. Four treatments were designed as CK (famer traditional operation without biochar application), BC1 (biochar amendment at 5 t/hm2), BC2 (biochar amendment at 10 t/hm2), and BC3 (biochar amendment at 20 t/hm2), each treatment has 3 repeat. Biochar used in this study was obtained from wheat straw and produced by Henan Sanli New Energy Company. LCA (life cycle assessment) method was employed to calculate GHG emissions from the collection and transportation of raw materials, the production, transportation, and broadcasting of biochar, and from the avoidance of the straw burning and the soil carbon stocks. Static chamber-GC (gas chromatography) method was used to monitor the CH4 and N2O emissions under different rates of biochar application from 2012 to 2015. Then, the net GHG emissions and the percentage of emission reduction in the paddy field with different biochar amendment rates were calculated. The total GHG emissions from the double rice cropping system were 19.5, 15.6, 16.1, and 12.4 t/hm2 under CK, BC1, BC2, and BC3 treatments respectively in four years. Moreover, the total GHG emission reduction percentage of BC1, BC2 and BC3 were 19.70%, 17.46%, and 36.40%, respectively. Considering the GHG emissions of biochar in all stages of life cycle, the net GHG emissions of CK, BC1, BC2 and BC3 in the four years were 19.5, 20.3, 10.9, and 4.2 t/hm2, respectively, the treatment of BC1 increased the net emissions of 4.3% in the four years. BC2 and BC3 reduced the net GHG emissions by 44% and 78.6%, respectively in four years. The economic analysis indicated that the BC1treatment had more economic benefits compared to other treatments. The different biochar amendment rates significantly reduced the GHG emissions from the double rice cropping system, the highest application rate of biochar had the best emission reduction effect. The LCA of biochar application indicated that from medium to high application levels, biochar reduces emissions, for higher application rates of biochar, the effects are stronger. Moreover, the economic analysis indicated that the more amounts of biochar application, the least profitable to gain economic benefits. [ABSTRACT FROM AUTHOR]

Methane and N2O are two important greenhouse gases, which are the main emission in paddy ecology system. China is the highest rice planting country, so the greenhouse gas emission is huge in China. Application of biochar in paddy field can decrease the emissions of greenhouse gases. In this study, we investigated the greenhouse gas (GHG) emissions, carbon sequestration and economics of different rates of biochar application in a double rice cropping system. The experiment was carried out in rice variety area promotion experiment field in Huizhou of Guangdong from March 2012 to September 2015. Four treatments were designed as CK, BC1, BC2, and BC3, each treatment has 3 repeat. Biochar used in this study was obtained from wheat straw and produced by Henan Sanli New Energy Company. LCA (life cycle assessment) method was employed to calculate GHG emissions from the collection and transportation of raw materials, the production, transportation, and broadcasting of biochar, and from the avoidance of the straw burning and the soil carbon stocks. Static chamber-GC (gas chromatography) method was used to monitor the CH4 and N2O emissions under different rates of biochar application from 2012 to 2015. Then, the net GHG emissions and the percentage of emission reduction in the paddy field with different biochar amendment rates were calculated. The total GHG emissions from the double rice cropping system were 19.5, 15.6, 16.1, and 12.4 t/hm2 under CK (famer traditional operation without biochar application), BC1 (biochar amendment at 5 t/hm2), BC2 (biochar amendment at 10 t/hm2), and BC3 (biochar amendment at 20 t/hm2) treatments respectively in four years. Moreover, the total GHG emission reduction percentage of BC1, BC2 and BC3 were 19.70%, 17.46%, and 36.40%, respectively. Considering the GHG emissions of biochar in all stages of life cycle, the net GHG emissions of CK, BC1, BC2 and BC3 in the four years were 19.5, 20.3, 10.9, and 4.2 t/hm2, respectively, the treatment of BC1 increased the net emissions of 4.3% in the four years. BC2 and BC3 reduced the net GHG emissions by 44% and 78.6%, respectively in four years. The economic analysis indicated that the BC1treatment had more economic benefits compared to other treatments. The different biochar amendment rates significantly reduced the GHG emissions from the double rice cropping system, the highest application rate of biochar had the best emission reduction effect. The LCA of biochar application indicated that from medium to high application levels, biochar reduces emissions, for higher application rates of biochar, the effects are stronger. Moreover, the economic analysis indicated that the more amounts of biochar application, the least profitable to gain economic benefits. [ABSTRACT FROM AUTHOR]

As a controversial strategy to mitigate global warming, biochar application into soil highlights the need for life cycle assessment before large-scale practice. This study focused on the effect of biochar on carbon footprint of rice production. A field experiment was performed with three treatments: no residue amendment (Control), 6 t ha−1 yr−1 corn straw ( CS) amendment, and 2.4 t ha−1 yr−1 corn straw-derived biochar amendment ( CBC). Carbon footprint was calculated by considering carbon source processes (pyrolysis energy cost, fertilizer and pesticide input, farmwork, and soil greenhouse gas emissions) and carbon sink processes (soil carbon increment and energy offset from pyrolytic gas). On average over three consecutive rice-growing cycles from year 2011 to 2013, the CS treatment had a much higher carbon intensity of rice (0.68 kg CO2-C equivalent ( CO2-Ce) kg−1 grain) than that of Control (0.24 kg CO2-Ce kg−1 grain), resulting from large soil CH4 emissions. Biochar amendment significantly increased soil carbon pool and showed no significant effect on soil total N2O and CH4 emissions relative to Control; however, due to a variation in net electric energy input of biochar production based on different pyrolysis settings, carbon intensity of rice under CBC treatment ranged from 0.04 to 0.44 kg CO2-Ce kg−1 grain. The results indicated that biochar strategy had the potential to significantly reduce the carbon footprint of crop production, but the energy-efficient pyrolysis technique does matter. [ABSTRACT FROM AUTHOR]

Char is a product of thermochemical conversion of biomass via pyrolysis, together with gas (syngas), liquid (bio-oil), and heat. Fast pyrolysis is a promising process for bio-oil generation, which leaves 10-30% of the original biomass as char. Char produced for soil application, is defined biochar ( BC), and it may increase soil C storage, and reduce soil emissions of greenhouse gases ( GHG), such as N2O and CH4 -potentially making fast pyrolysis bioenergy generation a C-negative system. However, differences in production conditions (e.g., feedstock, pyrolysis temperature and speed, post handling, and storage conditions) influence the chemical properties of BC and its net effect when added to soils. Understanding if fast pyrolysis BC can increase C sequestration and reduce GHG emissions will enable full assessment of the economic value and environmental benefits of this form of bioenergy. We characterized a BC produced by fast pyrolysis for bio-oil generation and examined GHG ( CO2, N2O and CH4) efflux, C partitioning using δ13C, and soil C sequestration across four temperate soils and five BC rates; 0%, 1%, 5%, 10%, and 20% w/w. The fast pyrolysis process created a highly aromatic, low N, ash-rich BC with a O : C ratio of 0.01, which we expected to be highly recalcitrant. Across soils, CO2 emissions increased linearly and N2O emissions decreased exponentially with increasing BC addition rates. Despite still being actively respired after 2 years, total BC-derived C- CO2 comprised less than the BC volatile C content (4%). Expressed as CO2 equivalents, CO2 was the primary GHG emitted (97.5%), followed by N2O. All GHG emissions were small compared to the total SOC sequestered in the BC. Fast pyrolysis produced a highly recalcitrant BC that sequestered C and reduced GHG emissions. The recovery and soil application of BC would contribute to a negative carbon balance for this form of bioenergy generation. [ABSTRACT FROM AUTHOR]

Abstract: Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6kgm−2) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3months and 14months after char addition. N2O, CH4 and CO2 fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3months, but after 14months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N2O fluxes were from 26% to 79% lower than N2O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N2O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH4 fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14months after biochar incorporation. [Copyright &y& Elsevier]