Influence of Digester Temperature on Methane Yield of Organic Fraction of Municipal Solid Waste (OFMSW)

Abstract

This study evaluates the anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) and digested sewage sludge (DSS) at lowered temperatures. AD batch tests for CH4 yield determination were carried out with DSS as inoculum between 23 and 40 °C. All results were related to organic dry matter and calculated for standard conditions (1013 hPa, 0 °C). The AD experiments at 40 °C and at 35 °C delivered specific CH4 yields of 325 ± 6 mL/g and 268 ± 27 mL/g for OFMSW alone. At lower temperatures, specific CH4 yields of 364 ± 25 mL/g (25 °C) and 172 ± 21 mL/g (23 °C) were reached. AD at 25 °C could be beneficial regarding energy input (heating costs) and energy output (CH4 yield). Plant operators could increase AD efficiencies by avoiding heating costs. The co-digestion of OFMSW together with DSS could lead to further synergies such as better exploitation of the energy potentials of DSS, but the digestate utilization could become problematic due to hygienic requirements. Efficiency potentials through lowered operating temperatures are limited. In further research, lowered process temperatures could be applied in the AD of energy crops due to large numbers of existing plants.

Efecto y evaluación agrícola de digestato anaeróbico de la FORSU como fertilizante en tritical invernal

“…Most of the analyzed parameters of the OFMSW such as TS, VS, pH and TKN had no significant difference (P < 0.05) with the broad range of values reported in the literature (Tampio et al 2016, Ahmed et al 2021. This was reflected in the CH 4 production by achieving quantities within the average reported by Ahmed et al (2021) and Sailer et al (2021). This allows to have some degree of certainty of the outcomes when using the OFMSW as feedstock in AD.…”

The Investigation of Chemical Composition and the Specific Heat Capacity of Cow Dung and Water Mixture

“…Specific heat capacity is defined as the measure of the amount of heat energy required to raise the temperature of a slurry inside the digester by 1°C [16]. The heat demand of AD systems depends on substrate characteristics, operating temperature, geographic region, and AD parameters such as digester type or size [17]. Thus, knowing the specific heat capacity of cow dung and the water mixture added to the digester is beneficial when determining the amount of heat required to raise the slurry temperature to the desired operating temperature.…”

Upgrading the Organic Fraction of Municipal Solid Waste by Low Temperature Hydrothermal Processes

“…Combining energy recovery by generating biogas together with the usage of the digestate is considered a more environmentally friendly approach [6,7]. Based on the material properties of OFMSW [8,9], hydrothermal treatment (HTT) processes could be an alternative to composting and AD.…”