Anaerobic Digestion Performance: Separate Collected vs. Mechanical Segregated Organic Fractions of Municipal Solid Waste as Feedstock

Abstract

The replacement of fossil fuel with renewable energy sources seems as though it will be crucial in the future. On the other hand, waste generation increases year by year. Thus, waste-to-energy technologies fit in with the actual trends, such as the circular economy. The crucial type of generated waste is municipal solid waste, which is in the research area. Regarding the organic fraction of municipal solid waste (OFMSW), anaerobic digestion (AD) allows the recovery of biogas and energy. Furthermore, if it is supported by source segregation, it should allow the recovery of material as fertilizer. The AD process performance (biogas yield and stability) comparison of source-segregated OFMSW (ss-OFMWS) and mechanically sorted OFMSW (ms-OFMSW) as feedstocks was performed in full-scale conditions. The daily biogas volume and methane content were measured to assess AD efficiency. To verify the process stability, the volatile fatty acid (VFA) content, pH value, acidity, alkalinity, and dry matter were determined. The obtained biogas yield per ton was slightly higher in the case of ss-OFMSW (111.1 m3/ton), compared to ms-OFMSW (105.3 m3/ton), together with a higher methane concentration: 58–60% and 51–53%, respectively, and followed by a higher electricity production capacity of almost 700 MWh for ss-OFMSW digestion. The obtained VFA concentrations, at levels around 1.1 g/kg, pH values (slightly above 8.0), acidity, and alkalinity indicate the possibilities of the digester feeding and no-risk exploitation of either as feedstock.

Separate Collected Versus Mechanical Segregated Organic Fractions in Terms of Fertilizers Suitability

“…The AD input materials characteristics are presented in Table 1. The fraction contents were similar to the results obtained in our previous study [13]. It was noticed that the organic content was higher in biowaste (67.2%) compared to OFMSW (46.3%), while the wood quantity was at a similar level (7.4 and 6.2%, respectively).…”

“…The effluents examined in this study were characterized by 21.6% and 13.6% of DM for ms-and ss-effluents, respectively (Table 3). The reason for this might be higher mineral and fine fraction contents in the mechanical sorted organic fraction of municipal solid waste [13]. The DM content affects the stickiness and viscosity.…”

“…Then, the daily samples collected over a week were mixed and averaged to get one weekly sample of OFMSW and Both waste streams are processed via anaerobic digestion (AD) at the plant. The AD facility consists of two Kompogas ® chambers, operating in thermophilic conditions (54 • C) [13]. After the fermentation, waste was removed from the chamber using a piston pump.…”

“…Source segregation fits the circular economy concept and is regarded as a landfilling problem solution [12]. Source-segregated biowaste provides higher recovery potential and treatment process performance compared to OFMSW [13]. Nevertheless, the biological treatment of OFMSW still has to be verified, mainly in full-scale, considering that also generated byproducts.…”

Prospects of Fuel Cell Combined Heat and Power Systems

“…The quest for a paradigm shift from the high dependence of fossil fuel due to its harmful effect on the environment has increased in the last couple of years [1][2][3][4][5][6]. Factors like unstable fossil commodities prices and the depletion of the ozone layer are key factors encouraging the research community to consider and alternative energy generation medium.…”