Short-term greenhouse emission lowering effect of biochars from solid organic municipal wastes

Qatar economy has been growing rapidly during the last two decades during which waste generation and greenhouse gas emissions increased exponentially making them among the main environmental challenges facing the country. Production of biochar from municipal solid organic wastes (SOWs) for soil application may offer a sustainable waste management strategy while improving crop productivity and sequestering carbon. This study was conducted to (1) investigate the physicochemical parameters of biochars for SOW, (2) select the best-performing biochars for soil fertility, and (3) evaluate the potential benefits of these biochars in lowering greenhouse gases (GHGs) during soil incubation. Biochars were produced from SOW at pyrolysis temperatures of 300�750��C and residence times of 2�6�h. Biochars were characterized before use in soil incubation to select the best-performing treatment and evaluation of potential GHG-lowering effect using CO2 emission as proxy. Here, soil�biochar mixtures (0�2%w/w) were incubated in greenhouse settings for 120�days at 10% soil moisture. Soil properties, such as pH, EC, TC, and WHC, were significantly improved after soil amendment with biochar. Two biochars produced from mixed materials at 300�500��C for 2�h and used at 0.5�1% application rate performed the best in enhancing soil fertility parameters. A significant decrease in CO2 emission was observed in vials with soil�biochar mixtures, especially for biochars produced at 500��C compared the corresponding raw materials which exhibited an exponential increase in the CO2 emission. Hence, application of biochar to agricultural soils could be beneficial for simultaneously improving soil fertility/crop productivity while sequestering carbon, thereby reducing anthropogenic emissions of GHGs. 2017, Islamic Azad University (IAU).Acknowledgements This research project was made possible by grant # NPRP -5 - 1020 - 4 � 011 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The authors would like to express sincere gratitude to the Central Labs Team, Qatar University, for providing assistance with the characterization of biochar and soil samples analysis

Physico-chemical characterization of biochars from solid municipal waste for use in soil amendment

The fast economic and demographic growth lead to generation of large amounts of solid wastes placing Qatar on top of most nations with a per capita solid waste generation of nearly 2.5 milliontons/year of which 60% is organic. A substantial amount of this solid waste ends up in landfills generating greenhouse gases that contribute to global warming. At the same time, the soil in most of the country is depleted and/or naturally poor. These issues can be addressed through conversion of this waste into biochar to improve soil quality and act as carbon sink. The objectives of this study were to (1) produce biochar from 4 different groups (paper, soft materials, hard wood, and mixed materials) at 3 different pyrolysis temperatures (300, 500, and 750°C) and residence times (2, 4, and 6h), and (2) evaluate biochars⿿ properties relevant to soil applications, namely physico-chemical properties [yield, pH, bulk density, ash, total surface area (TSA), surface charge (SC), and electrical conductivity (EC)] and elemental composition. Feedstocks were ground and pelleted then pyrolyzed under N2 using a Lindberg furnace equipped with a retort using the above conditions. Results showed that biochars⿿ pH, TSA, and ash content increased with temperature while the yield recovery and SC were higher at low temperature, with 94% biomass recovery observed for hard wood at 300°C versus 23% at 750°C. The pH of the four types of biochar increased from 5.7 at 300°C for hard wood to 12 at 750°C for mixed materials which make them suitable for a range of pH remediation in both acidic and alkaline soils. The TSA was limited in all biochars produced at 300°C but reached 241m2g⿿1 and 163m2g⿿1 for hard wood and mixed materials produced at 750°C, respectively. This suggests that biochars produced at high temperature can provide an internal surface area for soil microbiota while contributing to retention of water and nutrients. The C content increased as the temperature increased to reach 97% and 62% at 750°C for HW and mixed materials, respectively, suggesting that biochars obtained at high temperature could increase the soil CEC and sequester carbon in the soil for long term. SEM analysis clearly showed the development of well-defined pores as the temperature increases. This study suggests that solid waste-based biochars have the potential to enhance soil properties, if produced under careful selection of precursor and pyrolysis conditions.NPRP grant # NPRP - 5 -1020 - 4-011 from the Qatar National Research Fund (a member of Qatar Foundation)

Effect of biochars produced from solid organic municipal waste on soil quality parameters

Abstract New value-added uses for solid municipal waste are needed for environmental and economic sustainability. Fortunately, value-added biochars can be produced from mixed solid waste, thereby addressing solid waste management issues, and enabling long-term carbon sequestration. We hypothesize that soil deficiencies can be remedied by the application of municipal waste-based biochars. Select municipal organic wastes (newspaper, cardboard, woodchips and landscaping residues) individually or in a 25% blend of all four waste streams were used as feedstocks of biochars. Three sets of pyrolysis temperatures (350, 500, and 750 °C) and 3 sets of pyrolysis residence time (2, 4 and 6 h) were used for biochar preparation.The biochar yield was in the range of 21–62% across all feedstocks and pyrolysis conditions. We observed variations in key biochar properties such as pH, electrical conductivity, bulk density and surface area depending on the feedstocks and production conditions. Biochar increased soil pH and improved its electrical conductivity, aggregate stability, water retention and micronutrient contents. Similarly, leachate from the soil amended with biochar showed increased pH and electrical conductivity. Some elements such as Ca and Mg decreased while NO3-N increased in the leachates of soils incubated with biochars. Overall, solid waste-based biochar produced significant improvements to soil fertility parameters indicating that solid municipal wastes hold promising potential as feedstocks for manufacturing value-added biochars with varied physicochemical characteristics, allowing them to not only serve the needs for solid waste management and greenhouse gas mitigation, but also as a resource for improving the quality of depleted soils.Qatar National Research Fun