A bioaugmentation approach was used to enhance the performance of anaerobic digestion (AD) using cow manure (CM) as the substrate in a continuous system. To obtain the desirable microbial culture for bioaugmentation, a biochemical methane potential test (BMP) was used to evaluate three commonly used inocula namely (1) municipal solid waste (MSW), (2) wastewater treatment plant (WWTP), and (3) cow manure digester (CMMD) for their hydrolytic capacity. The highest lignocellulose removal (56% for cellulose and 50% for hemicellulose) and the most profusion of cellulolytic bacteria were obtained when CM was inoculated with CMMD. CMMD was thus used as the seed inoculum in a continuously operated reactor (Ra) with the fiber fraction of CM as the substrate to further enrich cellulolytic microbes. After 100 days (HRT: 30 days), the Bacteria fraction mainly contained Ruminofilibacter, norank_o_SBR1031, Treponema, Acetivibrio. Surprisingly, the Archaea fraction contained 97% ‘cellulolytic archaea’ norank_c_Bathyarchaeia (Phylum Bathyarchaeota). This enriched consortium was used in the bioaugmentation experiment. A positive effect of bioaugmentation was verified, with a substantial daily methane yield (DMY) enhancement (24.3%) obtained in the bioaugmented reactor (Rb) (179 mL CH4/gVS/d) than that of the control reactor (Rc) (144 mL CH4/gVS/d) (P < 0.05). Meanwhile, the effluent of Rb enjoyed an improved cellulose reduction (14.7%) than that of Rc, whereas the amount of hemicellulose remained similar in both reactors' effluent. When bioaugmentation stopped, its influence on the hydrolysis and methanogenesis sustained, reflected by an improved DMY (160 mL CH4/gVS/d) and lower cellulose content (53 mg/g TS) in Rb than those in Rc (DMY 144 mL/CH4/gVS/d and cellulose content 63 mg/g TS, respectively). The increased DMY of the continuous reactor seeded with a specifically enriched consortium able to degrade the fiber fraction in CM shows the feasibility of applying bioaugmentation in AD of CM.
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In Europe, green hydrogen and biogas/green gas are considered important renewable energy carriers, besides renewable electricity and heat. Still, incentives proceed slowly, and the feasibility of local green gas is questioned. A supply chain of decentralised green hydrogen production from locally generated electricity (PV or wind) and decentralised green gas production from locally collected biomass and biological power-to-methane technology was analysed and compared to a green hydrogen scenario. We developed a novel method for assessing local options. Meeting the heating demand of households was constrained by the current EU law (RED II) to reduce greenhouse gas (GHG) emissions by 80% relative to fossil (natural) gas. Levelised cost of energy (LCOE) analyses at 80% GHG emission savings indicate that locally produced green gas (LCOE = 24.0 €ct kWh−1) is more attractive for individual citizens than locally produced green hydrogen (LCOE = 43.5 €ct kWh−1). In case higher GHG emission savings are desired, both LCOEs go up. Data indicate an apparent mismatch between heat demand in winter and PV electricity generation in summer. Besides, at the current state of technology, local onshore wind turbines have less GHG emissions than PV panels. Wind turbines may therefore have advantages over PV fields despite the various concerns in society. Our study confirms that biomass availability in a dedicated region is a challenge.
Reclasseringsorganisaties richten zich op het verminderen van de kans op recidive. Ze letten op risicogedrag en spannen zich in om plegers van een delict een nieuwe kans te geven in de maatschappij. Ook onderzoek laat zien dat deze benadering aantoonbaar effectiever is dan hoge straffen. In de media lijkt echter de roep om strengere straffen toe te nemen. Wat is de publieke opinie?
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