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Biochar has been recommended as a soil amendment to improve soil fertility and mitigate methane (CH4) emissions from rice cultivation. Its effects, however, vary depending on soil type, biochar characteristics, and application rate. This study was aimed to evaluate the potential of mangrove biochar on CH4 mitigation, soil properties, and the productivity of rice cultivated in a clay loam soil in Thailand. Biochar was used at a rate equivalent to 10 t ha−1 season−1, both with (biochar + fertilizer: BF) and without (biochar alone: BI) fertilizer, for two cultivation seasons. BI reduced CH4 flux at most stages of rice growth. Relative to control soil (no biochar, no fertilizer: CT), BI significantly decreased cumulative CH4 emissions by 21.1% in the first season and 24.9% in the second season. CH4 emissions from BF soil were also less than those from the use of fertilizer alone (FE). Rice grain yield in BI was 7.85% and 14.4% greater than in CT, and in BF by 1.47% and 3.72% greater than FE, in the first and second seasons, respectively. The decrease in CH4 emissions and increase in rice grain yield decreased CH4 emission intensity under biochar treatments. Soil pH, organic carbon, cation exchange capacity, and available nutrients in the soil increased with biochar addition. The soil organic carbon stock was significantly increased by 32.6% in BI and 27.5% in BF after the first season, and by 43.5% in BI and 39.6% in BF after the second season. [ABSTRACT FROM AUTHOR]

• Long term (3 years) CH 4 emissions from field-scale semi-aerobic test cell was studied. • CH 4 emission during wet and dry seasons were systematic measured and compared. • The presence of gas vents reduced average CH 4 emissions to half of that without them. • CH 4 hotspots developed in semi-aerobic cell after rainfall. • Gas vents maintain semi-aerobic conditions when rainwater infiltration is low. Two landfill test cells, with and without gas vents, were used to investigate the effectiveness of passive aeration, through basal leachate pipes, in mitigating methane emissions from municipal solid waste disposal in the tropical climate of Thailand. Surface methane emission rate, as well as methane content in the landfill gas, were determined for a period of three years. The results indicate that the average methane emission rate from the test cell with passive gas vents (42.13 g/t dry wt./d) was about half of that from the test cell without gas vents (90.33 g/t dry wt./d). Methane emission rates from both test cells fluctuated and were influenced by precipitation. The emission rate during the wet period in the test cell with gas vents (61.67 g/t dry wt./d) was 3 times as much as that observed during the dry period (20.95 g/t dry wt./d). The emission rate during the wet period in the test cell without gas vents (120.33 g/t dry wt./d), was twice the value of that observed during the dry period (60.32 g/t dry wt./d). The measurements also revealed the formation of methane hotspots in the test cell with passive vents after rainfall events, leading to higher localized surface emissions. Introduction of gas vents helped reduce methane emissions from solid waste landfills in a tropical region. However, rainfall should be limited to avoid turning semi-aerobic conditions into anaerobic conditions. [ABSTRACT FROM AUTHOR]

The mitigation of greenhouse gas (GHG) emissions and water usage optimization in rice cultivation is challenging for many agricultural countries, including Thailand, who have set goals of reaching net zero emissions and coping with droughts caused by climate change. Alternate wetting and drying (AWD) and biochar application are possible practices for achieving cleaner rice production through reduction of GHG emissions and water consumption. However, these methods' potential varies by site, especially in areas with limited control of water levels. This study assessed the effects of AWD at different drying levels (10, 15, and 20 cm below the soil surface) and rice straw biochar on GHG emissions, yield production, water use, soil characteristics, and economic aspects. This study was conducted over two rice cultivation seasons: a major season in 2022 and a second season in 2023 at a field in Kalasin Province, northeastern Thailand. Using AWD and biochar reduced annual GHG emissions by 48.2% and 8.01%, respectively. Deeper drying levels of AWD showed greater mitigation potential than shallow levels. The combination of AWD and biochar had additional potential for GHG mitigation, however, this impact did not show statistical change as compared to their separate potentials. The adoption of AWD and biochar could also maintain the amount of rice yield compared to traditional practice. All levels of AWD saved irrigation water consumption by an average of 16.8% per season; the highest potential was observed in AWD at 10 cm below the soil surface. Biochar improved soil health after two seasons by enhancing soil pH and organic carbon sequestration. The combination of AWD and biochar did not additionally augment the capacity in water saving of AWD or soil improvement of biochar. The AWD water regime also did not increase net profits, while biochar decreased net profits due to the required investment in biochar production. Using AWD is a feasible way to mitigate GHG emissions and save water without affecting rice productivity and net profits in northeastern Thailand. [Display omitted] • Alternate wetting and drying (AWD) mitigated greenhouse gas emissions by 48.2%. • AWD reduced irrigation water use by an average of 16.8%. • AWD at 15 cm of drying level without biochar is suggested as a mitigation tool. • Rice straw biochar showed the significant impact on soil organic carbon stock. [ABSTRACT FROM AUTHOR]

Abstract: Many commercial pig farms in Thailand have used pigs' dropping and sewage to produce biogas, which reduces odor around the farms. However, small farms have excess biogas since the biogas is only used for household purpose. Therefore, the excess gas is normally released to the atmosphere and consequently exacerbates the greenhouse effect. Thus this project is aimed to use the excess biogas in a diesel engine for a fertilizer pelletising machine. The performance of the fertilizer pelletising machine and greenhouse gas emission reduction were analyzed. The pelletiser machine run by diesel engine was partly powered by the excess biogas. A reduction in diesel use of 63% was achieved compared to the control case where only diesel was used. The reduction of greenhouse gas due to the utilization of methane was equivalent to 13tCO2/year/farm. Moreover, the feasibility study revealed that this project had a payback period of 0.46years and an IRR of 210.4%. [Copyright &y& Elsevier]

Measurements of landfill methane emission were performed at nine solid waste disposal sites in Thailand, including five managed sanitary landfills (four deep and one shallow landfills) and four unmanaged landfills (three deep and one shallow dumpsites). It was found that methane emissions during the rainy season were about five to six times higher than those during the winter and summer seasons in the case of managed landfills and two to five times higher in the case of unmanaged landfills. Methane emission estimate using the Intergovernmental Panel on Climate Change (IPCC) Waste Model was compared with the actual field measurement from the studied disposal sites with methane correction factors and methane oxidation factors that were obtained by error function analysis with default values of half-life parameters. The methane emissions from the first-order decay model from the IPCC Waste Model yielded fair results compared to field measurements. The best fitting values of methane correction factor were 0.65, 0.20, 0.15, and 0.1 for deep landfills, shallow landfills, deep dumpsites, and shallow dumpsites, respectively. Using these key parameters in the case of Thailand, it was estimated that 89.22 Gg of methane were released from solid waste disposal sites into the atmosphere in 2006. [ABSTRACT FROM AUTHOR]

Organic amendment is a traditional practice for rehabilitating saline patches in north-east Thailand, but organic matter is known to enhance methane emission. However, a high degree of salinity might mitigate methane emission. The objective of the present study was to quantify the effects of salinity and organic amendments on methane emission from rain-fed paddy fields exposed to increasing salinity. A paddy field on a salt-affected Typic Natraqualfs was selected. Eighteen experimental plots were located in two randomized complete block designs placed inside and outside a saline patch. Each design of nine plots presented three replicates of two different organic amendments and a control treatment without organic amendment. During the rainy season the soil electrical conductivity, measured with an electromagnetic conductivity meter (ECEM), was greater than 300 mS m−1 inside the saline patch, whereas outside the saline patch the values were lower than 200 mS m−1. Rice straw (6.25 t ha−1) and cow manure (8.99 t ha−1), representing similar amounts of carbon, were incorporated. Methane emission from the soil, EC1:5 and soil redox potential (Eh) were monitored during the rice-growing season. High methane emission was mostly associated with low Eh, 48% of the Eh measurements were between −100 mV and −200 mV. In the saline patch, the average methane emission ranged from 251 to 334 mg CH4 m−2 day−1; outside the saline patch the values had a wider range from 209 to 544 mg CH4 m−2 day−1. The addition of rice straw or cow manure significantly enhanced methane emission by an approximate factor of 2.5 outside the saline patch, but did not significantly increase methane emission inside the saline patch. The attenuating effect of salinity on methane emission was particularly strong at the beginning of flooding during the first 20 days after transplanting and at the end of flooding (from 54 days after transplanting). When applied to saline patches, organic amendment did not significantly enhance methane emission in the first year. [ABSTRACT FROM AUTHOR]

The increasing municipal solid waste (MSW) generation along with the high fraction of organic waste and a common disposal of open dumping is the current scenario in many areas in Thailand. As a response to this problem, the country’s Pollution Control Department (PCD) aims to reduce the MSW generation rate to less than 1 kg/capita/day, increase the collection efficiency, and improve the recovery of recyclables. For many years, more than 60% of the solid waste disposal system in Thailand has been carried out by open dumping. According to the survey conducted by this study, in 2004 there were 425 disposal sites (95 landfills; 330 open dumps) in Thailand and an estimated methane emission of 115.4 Gg/year was generated based on this practice. It has been estimated that the anticipated methane emission in Thailand will rise from 115.4 Gg/year to 118.5 Gg/year if the largest open dumpsites in provinces with no existing landfill are upgraded to sanitary landfill; and it will increase to 193.5 Gg/year if the existing sanitary landfill is upgraded to integrated waste management facilities. Moreover, Bangkok metropolitan have the highest methane emission (54.83 Gg/year) among all the regions in Thailand. The methane emission forecast of 339 Gg/year by 2020 (based on LandGEM methodology) provides a stimulus to create a comprehensive plan to capture and utilize methane as an energy source. [ABSTRACT FROM AUTHOR]

Solid waste characteristics and landfill gas emission rate in tropical landfill was investigated in this study. The experiment was conducted at a pilot landfill cell in Thailand where fresh and two-year-old wastes in the cell were characterized at various depths of 1.5, 3, 4.5 and 6 m. Incoming solid wastes to the landfill were mainly composed of plastic and foam (24.05%). Other major components were food wastes (16.8%) and paper (13.3%). The determination of material components in disposed wastes has shown that the major identifiable components in the wastes were plastic and foam which are resistant to biodegradation. The density of solid waste increased along the depth of the landfill from 240 kg m−3 at the top to 1,260 kg m−3 at the bottom. Reduction of volatile solids content in waste samples along the depth of landfill suggests that biodegradation of solid waste has taken place to a greater extent at the bottom of the landfill. Gas production rates obtained from anaerobic batch experiment were in agreement with field measurements showing that the rates increased along the depth of the landfill cell. They were found in range between 0.05 and 0.89 l kg−1 volatile solids day−1. Average emission rate of methane through the final cover soil layer was estimated as 23.95 g−2day−1 and 1.17 g−2day−1 during the dry and rainy seasons, respectively. [ABSTRACT FROM AUTHOR]

Abstract: One of the important cultural practices that affect methane and nitrous oxide emissions from tropical rice plantations is the water drainage system. While drainage can reduce methane emissions, it can also increase nitrous oxide emissions, as well as reduce yields. In this experiment, four different water drainage systems were compared in a rice field in central Thailand including: (1) continuous flooding, (2) mid-season drainage, (3) multiple drainage and (4) a local method (drainage was done according to local cultural practice) in order to find a system of drainage that would optimize yields while simultaneously limiting methane and nitrous oxide emissions. Methane and nitrous oxide emission were observed and compared with rice yield and physical changes of rice plants. It was found that drainage during the flowering period could reduce methane emission. Interestingly, nitrous oxide emission was related to number of drain days rather than the frequency of draining. Fewer drain days can help reduce nitrous oxide emission. The mid-season drainage and the multiple drainage, with 6.9% and 11.4% reduction in rice yield, respectively, had an average methane emission per crop 27% and 35% lower when compared to the local method. Draining with fewer drain days during the flowering period was recommended as a compromise between emissions and yield. The field drainage can be used as an option to reduce methane and nitrous oxide emissions from rice fields with acceptable yield reduction. Mid-season drainage during the rice flowering period, with a shortened drainage period (3 days), is suggested as a compromise between the need to reduce global warming and current socio-economic realities. [Copyright &y& Elsevier]

Rice is an important economic crop in Thailand. However, paddy rice fields are one of the largest anthropogenic sources of methane (CH4) emissions. Therefore, suitable crop management practice is necessary to reduce CH4 emissions while rice grain yield is maintained. This study aimed to evaluate appropriate options of fertilizer and water management practices for Thai rice cultivation with regards to improving rice grain yield and reducing CH4 emissions. The Denitrification–Decomposition (DNDC) model was used to simulate grain yield and the emission of CH4 under the three fertilizer options (chemical fertilizer (F), manure (M) and chemical fertilizer + manure (F + M)) with three water management options (continuous flooding (CF), mid-season drainage (MD) and alternate wet and dry (AWD)) during the years 2011–2050. Rain-fed and irrigated rice cropping systems were used. A total of 24 sites distributed in 22 provinces were studied. The data sets of daily climate, soil properties, and rice management practices were required as inputs in the model. Model validation with observation data in a field experiment indicated that simulated grain yields (R2 = 0.83, slope = 0.98, NRMES = 0.30) and cumulative seasonal CH4 emissions (R2 = 0.83, slope = 0.74, NRMES = 0.43) were significantly and positively correlated with the observation. At the end of the simulation period (2046–2050), fertilizer management options of F and F + M gave more grain yield than the M management option by 1–44% in rain-fed rice cropping and 104–190% in irrigated rice cropping system, respectively. Among options, the lower CH4 emissions were found in AWD water management options. The appropriate options with regard to maintaining grain yield and reducing CH4 emissions in the long term were suggested to be F + M with AWD for the rain-fed rice, and F with AWD for the irrigated rice cropping systems. [ABSTRACT FROM AUTHOR]