Sewage Sludge Biogas Research Articles

Towards Circular Economy: Evaluation of Sewage Sludge Biogas Solutions

Today it is obvious that the existing linear model of the economy does not correlate with the principles of sustainable development. The circular economy model can replace the current linear economy whilst addressing the issues of environmental deterioration, social equity and long-term economic growth. In the context of effectively implementing circular economy objectives, particular importance should be attributed to wastewater treatment sludge management, due to the possibility of recovering valuable raw materials and using its energy potential. Anaerobic digestion is one of the methods of recovering energy from sewage sludge. The main goal of this study is to make a preliminary evaluation of possible sewage sludge biogas and biomethane solutions using a computation model called MCBioCH4 and compare its results with laboratory tests of sewage sludge fermentation from the northern wastewater treatment plant (WWTP) of Ekaterinburg (Russian Federation). Laboratory experiments were conducted to determine the volume and qualitative composition of biogas produced throughout anaerobic fermentation of raw materials coming from the WWTP. The specific productivity of samples ranged between 308.46 Nm3/tvs and 583.08 Nm3/tvs depending if mesophilic or thermophilic conditions were analyzed, or if the experiment was conducted with or without sludge pre-treatment. Output values from the laboratory were used as input for MCBioCH4 to calculate the flow of biogas or biomethane produced. For the case study of Ekaterinburg two possible energy conversion options were selected: B-H (biogas combustion with cogeneration of electrical and thermal energy) and M-T (biomethane to be used in transports). The results of the energy module showed a net energy content of the biogas between 6575 MWh/year and 7200 MWh/year. Both options yielded a favorable greenhouse gas (GHG) balance, meaning that avoided emissions are higher than produced emissions. The results discussion also showed that, in this case, the B-H option is preferable to the M-T option. The implementation of the biogas/biomethane energy conversion system in Ekaterinburg WWTP necessitates further investigations to clarify the remaining technical and economic aspects

Olive Mill Industrial Waste as Co-substrate in Anaerobic Digestion with Aim at its Energetic Exploitation

The aim of this paper is to assess the feasibility of the co-digestion of olive mill industrial waste with urban sewage sludge from wastewater treatment plants (WWTP). These wastes include olive mill solid waste (OMSW) and olive mill effluent (OME). This co-digestion process enables the energetic exploitation of OMSW and/or OME and introduces an environmental solution for their highly pollutant compounds. The behaviour of both co-substrates was studied using biochemical methane potential assays. To determine the optimal proportions of each co-substrate, different quantities of OME and OMSW were added to a constant quantity of substrate (urban sewage sludge) and put to test. A small amount of digested sludge from WWTP was used as an inoculum to accelerate the pace of the reactions. Thus, the optimal proportions between substrate and co-substrate were defined. The samples containing OMSW showed a biodegradability around 23%, slightly above that of the substrate on its own (21.3%). Moreover, biogas production in samples containing OMSW was significantly superior to samples containing substrate only. Nevertheless, the samples containing OME as a co-substrate presented an inferior biodegradability (20.3%) to that of the substrate on its own. Similarly, biogas production in OME co-digestion remained within the usual values of urban sewage sludge biogas production. In all cases, the system remained stable and the energetic efficiency of the process was improved in comparison to the digestion of substrate only. Therefore, co-digestion with urban sewage sludge proves to be a cost-effective method for OMSW and OME environmental management.

Characterisation and cleaning of biogas from sewage sludge for biomethane production

This study investigates the conversion of sewage sludge from wastewater treatment plants (WWTP) into biomethane for automotive fuel or grid injection. A prototype plant was monitored in Northern Italy, based on vacuum swing adsorption (VSA) on synthetic zeolite 13×: this biogas upgrading method is similar to pressure swing adsorption (PSA) and commonly used for other kinds of biomass. Measurements of biogas inlet, biomethane outlet and off-gas were performed including CH4, CO2, CO, H2, O2, N2, HCl, HF, NH3, H2S and volatile organic compounds (VOCs). Critical levels were observed in the biogas for of H2S and HCl, whose concentrations were 1570 and 26.8 mg m−3, respectively. On the other hand, the concentration of halogenated VOCs (including tetrachloroethylene and traces of perfluoroalkilated substances, PFAS) and mercaptans were relatively low. A simultaneous and reversible adsorption on 13× zeolite was achieved for H2S and CO2, and carbon filters played a minor role in desulfurisation. The presence of HCl is due to clarifying agents, and its removal is necessary in order to meet the required biomethane characteristics: an additional carbon-supported basic adsorbent was successfully used to remove this contaminant. This study also highlights the interference of CO2 towards HCl if sampling is performed in compliance with the new EU standard for biomethane. High total volatile silicon (TVS) was confirmed in sewage sludge biogas, with a major contribution of siloxane D5: the suitability of this compound as an indicator of total siloxanes is discussed. Results demonstrate that volatile methyl siloxanes (VMS) do not represent a critical issue for the VSA upgrading methodology.

Activated Carbon As A Support In Biotrickling Filters For The Removal Of Siloxanes In Sewage Sludge Biogas

Activated Carbon As A Support In Biotrickling Filters For The Removal Of Siloxanes In Sewage Sludge Biogas

Behaviour and adsorptive removal of siloxanes in sewage sludge biogas

We investigated the behaviour of siloxanes, which adversely affect biogas engines, as well as their concentration levels in sewage sludge biogas in Japan. We also performed experiments on the absorptive removal of siloxanes using various adsorbents and determined the main adsorbent characteristics required for the removal of siloxanes. The results of our study on the concentration and composition of siloxanes in biogas were similar to previous reports. Moreover, we found that the concentration of siloxanes changes in relation to the outside air temperature based on real-time measurements of siloxanes using a continuous analyser. We further speculated that the continuous analyser would accurately indicate the siloxane concentration in model biogas but overestimate the siloxane concentration in actual biogas because of positive interference by VOCs and other biogas components. In the siloxane adsorption experiment, the equilibrium uptake of both cyclic siloxanes, D4 and D5, was positively related to the BET-specific surface area of the adsorbents and the fraction of the external surface area taken up by relatively large diameter pores. We attributed the adsorption results to the fact that the siloxane molecules are generally larger than micropores; therefore, they are less susceptible to adsorption to micropores. Based on these results, we concluded that adsorbents with large BET-specific surface areas, especially those with a high external specific surface area and pores of relatively large diameters, are desired for the removal of siloxanes.

Exploiting the Medium Term Biomass Energy Potentials in Austria: A Comparison of Costs and Macroeconomic Impact

The transition to an implicitly solar-basedenergy system can make use of various specificbiomass energy systems. This paper provideseconomic and environmental indicators forevaluating alternative options.The paper proceeds in three empirical steps.First, an expert survey supplies the primarybiomass potentials available for non-food usein Austria and their respective costs. Second,an inquiry into investment, operating andfinancing costs of 30 different biomass energyuse systems allows a standardized comparisonamong them and their relationship to fossilreference technologies. Third, a computablegeneral equilibrium model of the Austrianeconomy is employed to quantify the impacts offostering the use of distinct biomass energytechnologies.The results allow us to distinguish betweenthose technologies that tend to lead to anincrease in both GDP and employment (e.g.,combined heat and power production from sewagesludge biogas), to an increase only inemployment, while GDP tends to diminish (e.g.,district heating based on agricultural pellets)or to a decline in both (e.g., co-firing basedon wood-chips, bark or industrial pellets).Individual technologies could account for up toone third of Austrias Kyoto obligation, whilecombinations of technologies, triggered by acombined CO2 tax and biomass energysubsidy for example, could almost fully lead toAustrian Kyoto-compliance.