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The CH4 storage by adsorption on activated carbons for natural gas handling has gained interest due to the appearance of lightweight materials with large surface areas and pore volumes. Consequently, kinetic parameters estimation of the adsorptive process can play a crucial role in understanding and scaling up the system. Concerning its versatility, banana peel (BP) is a biomass with potential for obtaining different products, such as biochar, a solid residue from the biomass' thermal decomposition of difficult disposal, where through an activation process, the material porous features are taken advantage to application as adsorbent of gaseous substances. This research reported data for the CH4 adsorption kinetic modeling by biochar from BP pyrolysis. The activated biochar textural characterization showed particles with fine mesoporous structure (pore diameter ranging between 29.39 and 55.62 Å). Adsorption kinetic analysis indicated that a modified pseudo-first-order model was the most suitable to represent the experimental data, with equilibrium adsorption of 28 mg g−1 for the samples activated with 20.0% vol wt.−1 of H3PO4 and pyrolysis at 500 °C. The equilibrium constant was consistent with the Freundlich isotherm model, suggesting a physisorption mechanism, and led to a non-ideal, reversible, and not limited to monolayer CH4 adsorption. [ABSTRACT FROM AUTHOR]

Biochar as an agricultural soil amendment plays vital roles in mediating methane (CH4) and nitrous oxide (N2O) emissions in soils. The link between different types of biochar, bulk soil, and rhizosphere microbial communities in relation to CH4 and N2O emissions is being investigated in this study. The rice pot experiment was conducted using biochar at two temperatures (300°C and 500°C) in combination with three biochar levels (0, 2, 10% w/w). Soil properties and the abundance of genes associated with CH4 and N2O emissions from both rhizosphere and bulk soils were investigated. The study also aimed to examine the structure of microbial communities (pmoA, nosZ) in rhizosphere and bulk soils whereas CH4 and N2O emissions were monitored while growing rice. Results showed that biochar at 300°C and 10% incorporation significantly increased the CH4 emissions by up to 59% rise compared to the control group. Random Forest analysis revealed that the ratio of mcrA/pmoA along with the abundance of mcrA from both rhizosphere and bulk soils, the abundance of AOA, TN, DOC, and the community composition of pmoA-harboring microorganisms from both bulk and rhizosphere soils were important predictors of CH4 emissions. Therefore, the ratio of mcrA/pmoA in rhizosphere soil and the abundance of AOA in bulk soil were the main factors influencing CH4 emissions. Variation Partitioning Analysis (VPA) results indicated that the effects of these factors on bulk soil were 9% of CH4 emissions variations in different treatments, which contributed more than rhizosphere soils' factors. Moreover, random forest analysis results indicated that the abundance of AOB in bulk soil was the most important predictor influencing N2O emissions. The VPA result revealed that the factors in rhizosphere soil could explain more than 28% of the variations in N2O emissions. Our study highlights that rhizosphere soil has a more significant effect than bulk soil on N2O production. Our findings further the understanding of the link between bulk and rhizosphere attributes, and their impact on CH4 and N2O emissions in paddy soils. In summary, we recommend the application of biochar at 500°C and 2% incorporation rate for agricultural production in the area. [ABSTRACT FROM AUTHOR]

Biochar as an agricultural soil amendment plays vital roles in mediating methane (CH4) and nitrous oxide (N2O) emissions in soils. The link between different types of biochar, bulk soil, and rhizosphere microbial communities in relation to CH4 and N2O emissions is being investigated in this study. The rice pot experiment was conducted using biochar at two temperatures (300°C and 500°C) in combination with three biochar levels (0, 2, 10% w/w). Soil properties and the abundance of genes associated with CH4 and N2O emissions from both rhizosphere and bulk soils were investigated. The study also aimed to examine the structure of microbial communities (pmoA, nosZ) in rhizosphere and bulk soils whereas CH4 and N2O emissions were monitored while growing rice. Results showed that biochar at 300°C and 10% incorporation significantly increased the CH4 emissions by up to 59% rise compared to the control group. Random Forest analysis revealed that the ratio of mcrA/pmoA along with the abundance of mcrA from both rhizosphere and bulk soils, the abundance of AOA, TN, DOC, and the community composition of pmoA-harboring microorganisms from both bulk and rhizosphere soils were important predictors of CH4 emissions. Therefore, the ratio of mcrA/pmoA in rhizosphere soil and the abundance of AOA in bulk soil were the main factors influencing CH4 emissions. Variation Partitioning Analysis (VPA) results indicated that the effects of these factors on bulk soil were 9% of CH4 emissions variations in different treatments, which contributed more than rhizosphere soils’ factors. Moreover, random forest analysis results indicated that the abundance of AOB in bulk soil was the most important predictor influencing N2O emissions. The VPA result revealed that the factors in rhizosphere soil could explain more than 28% of the variations in N2O emissions. Our study highlights that rhizosphere soil has a more significant effect than bulk soil on N2O production. Our findings further the understanding of the link between bulk and rhizosphere attributes, and their impact on CH4 and N2O emissions in paddy soils. In summary, we recommend the application of biochar at 500°C and 2% incorporation rate for agricultural production in the area.

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]

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.

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]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Straw returns to the soil is an effective way to improve soil organic carbon and reduce air pollution by straw burning, but this may increase CH4 and N2O emissions risks in paddy soils. Biochar has been used as a soil amendment to improve soil fertility and mitigate CH4 and N2O emissions. However, little is known about their interactive effect on CH4 and N2O emissions and the underlying microbial mechanisms. In this study, a 2-year pot experiment was conducted on two paddy soil types (an acidic Utisol, TY, and an alkaline Inceptisol, BH) to evaluate the influence of straw and biochar applications on CH4 and N2O emissions, and on related microbial functional genes. Results showed that straw addition markedly increased the cumulative CH4 emissions in both soils by 4.7- to 9.1-fold and 23.8- to 72.4-fold at low (S1) and high (S2) straw input rate, respectively, and significantly increased mcrA gene abundance. Biochar amendment under the high straw input (BS2) significantly decreased CH4 emissions by more than 50% in both soils, and increased both mcrA gene and pmoA gene abundances, with greatly enhanced pmoA gene and a decreased mcrA/pmoA gene ratio. Moreover, methanotrophs community changed distinctly in response to straw and biochar amendment in the alkaline BH soil, but showed slight change in the acidic TY soil. Straw had little effect on N2O emissions at low input rate (S1) but significantly increased N2O emissions at the high input rate (S2). Biochar amendment showed inconsistent effect on N2O emissions, with a decreasing trend in the BH soil but an increasing trend in the TY soil in which high ammonia existed. Correspondingly, increased nirS and nosZ gene abundances and obvious community changes in nosZ gene containing denitrifiers in response to biochar amendment were observed in the BH soil but not in the TY soil. Overall, our results suggested that biochar amendment could markedly mitigate the CH4 and N2O emissions risks under a straw return practice via regulating functional microbes and soil physicochemical properties, while the performance of this practice will vary depending on soil parent material characteristics.

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]

Straw returns to the soil is an effective way to improve soil organic carbon and reduce air pollution by straw burning, but this may increase CH4 and N2O emissions risks in paddy soils. Biochar has been used as a soil amendment to improve soil fertility and mitigate CH4 and N2O emissions. However, little is known about their interactive effect on CH4 and N2O emissions and the underlying microbial mechanisms. In this study, a 2-year pot experiment was conducted on two paddy soil types (an acidic Utisol, TY, and an alkaline Inceptisol, BH) to evaluate the influence of straw and biochar applications on CH4 and N2O emissions, and on related microbial functional genes. Results showed that straw addition markedly increased the cumulative CH4 emissions in both soils by 4.7- to 9.1-fold and 23.8- to 72.4-fold at low (S1) and high (S2) straw input rate, respectively, and significantly increased mcrA gene abundance. Biochar amendment under the high straw input (BS2) significantly decreased CH4 emissions by more than 50% in both soils, and increased both mcrA gene and pmoA gene abundances, with greatly enhanced pmoA gene and a decreased mcrA / pmoA gene ratio. Moreover, methanotrophs community changed distinctly in response to straw and biochar amendment in the alkaline BH soil, but showed slight change in the acidic TY soil. Straw had little effect on N2O emissions at low input rate (S1) but significantly increased N2O emissions at the high input rate (S2). Biochar amendment showed inconsistent effect on N2O emissions, with a decreasing trend in the BH soil but an increasing trend in the TY soil in which high ammonia existed. Correspondingly, increased nirS and nosZ gene abundances and obvious community changes in nosZ gene containing denitrifiers in response to biochar amendment were observed in the BH soil but not in the TY soil. Overall, our results suggested that biochar amendment could markedly mitigate the CH4 and N2O emissions risks under a straw return practice via regulating functional microbes and soil physicochemical properties, while the performance of this practice will vary depending on soil parent material characteristics. [ABSTRACT FROM AUTHOR]

Knowledge about the impacts of fresh and field-aged biochar amendments on greenhouse gas (CH4, N2O) emissions is limited. A field experiment was initiated in 2012 to study the effects of fresh and field-aged biochar additions on CH4 and N2O emissions and the associated microbial activity during the entire rice-growing season in typical rice-wheat rotation system in Southeast China. CH4 and N2O fluxes were monitored, and the abundance of methanogen (mcrA), methanotrophy (pmoA), ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), nitrite reductase (nirS, nirK), N2O reductase (nosZ), and potential soil enzyme activities related to CH4 and N2O were simultaneously measured throughout different rice developmental stages. There were three treatments: control (urea without biochar), fresh BC (urea with fresh biochar added in 2015), and aged BC (urea with 3-year field-aged biochar added in 2012). Results showed that field-aged biochar significantly decreased seasonal CH4 emissions by 16.8% in relation to the fresh biochar, though no significant differences were detected between biochars and control treatment. The structural equation model indicated that soil pH, microbial biomass carbon (MBC), pmoA, and mcrA were the main factors directly influenced by fresh and aged biochar amendments; aged biochar showed a negative effect while fresh biochar showed positive effects on CH4 fluxes. Both fresh and field-aged biochar obviously increased AOA and AOB abundances and reduced the (nirS+nirK)/nosZ ratio during the entire rice-growing season, although no significant effects were observed on seasonal N2O emissions. Therefore, biochar amendment produced long-term effects on total CH4 and N2O emissions through observed influences of soil pH and functional gene abundance.The figure shows how fresh and field-aged biochar differentially affected CH4 production and oxidation and N2O production and reduction through related functional gene abundances. Blue arrows indicate suppressing while pink arrows indicate promoting effect. [ABSTRACT FROM AUTHOR]

Research Highlights: Biochar is the carbonaceous product of pyrolysis or the gasification of biomass that is used as soil amendment to improve soil fertility and increase soil carbon stock. Biochar has been shown to increase, decrease, or have no effect on the emissions of greenhouse gases (GHG) from soil, depending on the specific soil and biochar characteristics. However, the temperature sensitivity of these gas emissions in biochar-amended soils is still poorly investigated. Background and Objectives: A pot experiment was set up to investigate the impact of woodchips biochar on the temperature sensitivity of the main GHG (CO2, CH4, and N2O) emissions from soil. Materials and Methods: Nine pots (14 L volume) were filled with soil mixed with biochar at two application rates (0.021 kg of biochar/kg of soil and 0.042 kg of biochar/kg of soil) or with soil alone as the control (three pots per treatment). Pots were incubated in a growth chamber and the emissions of CO2, CH4, and N2O were monitored for two weeks with a cavity ring-down gas analyzer connected to three closed dynamic chambers. The temperature in the chamber increased from 10 °C to 30 °C during the first week and decreased back to 10 °C during the second week, with a daily change of 5 °C. Soil water content was kept at 20% (w/w). Results: Biochar application did not significantly affect the temperature sensitivity of CO2 and N2O emissions. However, the sensitivity of CH4 uptake from soil significantly decreased by the application of biochar, reducing the CH4 soil consumption compared to the un-amended soil, especially at high soil temperatures. Basal CO2 respiration at 10 °C was significantly higher in the highest biochar application rate compared to the control soil. Conclusions: These results confirmed that the magnitude and direction of the influence of biochar on temperature sensitivity of GHG emissions depend on the specific GHG considered. The biochar tested in this study did not affect soil N2O emission and only marginally affected CO2 emission in a wide range of soil temperatures. However, it showed a negative impact on soil CH4 uptake, particularly at a high temperature, having important implications in a future warmer climate scenario and at higher application rates.

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]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Research Highlights: Biochar is the carbonaceous product of pyrolysis or the gasification of biomass that is used as soil amendment to improve soil fertility and increase soil carbon stock. Biochar has been shown to increase, decrease, or have no effect on the emissions of greenhouse gases (GHG) from soil, depending on the specific soil and biochar characteristics. However, the temperature sensitivity of these gas emissions in biochar-amended soils is still poorly investigated. Background and Objectives: A pot experiment was set up to investigate the impact of woodchips biochar on the temperature sensitivity of the main GHG (CO2, CH4, and N2O) emissions from soil. Materials and Methods: Nine pots (14 L volume) were filled with soil mixed with biochar at two application rates (0.021 kg of biochar/kg of soil and 0.042 kg of biochar/kg of soil) or with soil alone as the control (three pots per treatment). Pots were incubated in a growth chamber and the emissions of CO2, CH4, and N2O were monitored for two weeks with a cavity ring-down gas analyzer connected to three closed dynamic chambers. The temperature in the chamber increased from 10 °C to 30 °C during the first week and decreased back to 10 °C during the second week, with a daily change of 5 °C. Soil water content was kept at 20% (w/w). Results: Biochar application did not significantly affect the temperature sensitivity of CO2 and N2O emissions. However, the sensitivity of CH4 uptake from soil significantly decreased by the application of biochar, reducing the CH4 soil consumption compared to the un-amended soil, especially at high soil temperatures. Basal CO2 respiration at 10 °C was significantly higher in the highest biochar application rate compared to the control soil. Conclusions: These results confirmed that the magnitude and direction of the influence of biochar on temperature sensitivity of GHG emissions depend on the specific GHG considered. The biochar tested in this study did not affect soil N2O emission and only marginally affected CO2 emission in a wide range of soil temperatures. However, it showed a negative impact on soil CH4 uptake, particularly at a high temperature, having important implications in a future warmer climate scenario and at higher application rates. [ABSTRACT FROM AUTHOR]