• Energy Research

Source Segregation (SS) is a novel strategy in dairy housing that can reduce emissions and separate organic matter and nutrients more efficiently than traditional slurry solid-liquid separation. The anaerobic digestion (AD) methane yield of the SS fractions, however, is unknown. We aimed at unveiling the biomethane yield of these fractions by conducting AD experiments under different configurations: batch, continuous feeding, and fed-batch. In the batch test, the solid (SF) and liquid fraction (LF) from the SS system, a slurry collected from the pit (CS), and a self-made slurry (MF) were used as substrates. The results showed that the specific CH4 yields of the SF and MF were in same range and both higher than the CS. We concluded that SS can increase the CH4 yield of dairy excreta mainly by reducing losses in the animal house. The SF and MF were then compared in a continuously-fed thermophilic test, where SF had a higher specific (174 compared to 105 NL kg−1 VS) and volumetric (12.2 compared to 9.9 NL CH4 kg−1 excreta) yields. We concluded that the SF can effectively substitute slurry in AD without compromising the yield, possibly increasing economic viability by reducing transport costs and reactor size. Further, SF produced 356 NL CH4 kg−1 VS and a digestate with 1.8% lower dry matter in the fed-batch as compared to continuous feeding. Continuously stirred fed-batch can thus increase the CH4 yield of the SF and reduce the DM of its digestate potentially contributing to lower emissions in storage and field application.

In vier (semi-)continu bedreven laboratorium reactoren is onderzoek gedaan naar het effect van het verkorten van de verblijftijd op de biogasproductie van varkens- en rundveemest en het gehalte aan vluchtige vetzuren in de vergister. Tevens is onderzocht wat het effect is van het toevoegen van een kleine hoeveelheid glycerine op de verblijftijd en gehalte aan vluchtige vetzuren in de vergister. In four CSTR laboratory reactors research has been conducted into the effect of reduction of the retention time on the biogas production from pig and cattle slurry and the volatile fatty acid content in the digester. Further, the effect of adding a small amount of glycerine on the retention time and the volatile fatty acid content in the digester has been researched.

Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from 30 laboratories around the world, to agree on common solutions to the conundrum of inconsistent BMP test results. This paper presents the consensus of the intense roundtable discussions and cross-comparison of methodologies used in respective laboratories. Compulsory elements for the validation of BMP results were defined. They include the minimal number of replicates, the request to carry out blank and positive control assays, a criterion for the test duration, details on BMP calculation, and last but not least criteria for rejection of the BMP tests. Finally, recommendations on items that strongly influence the outcome of BMP tests such as inoculum characteristics, substrate preparation, test setup, and data analysis are presented to increase the probability of obtaining validated and reproducible results.

Source separated toilet water is a valuable resource for energy and fertilizers as it has a high concentration of organics and nutrients, which can be reused in agriculture. Recovery of nutrients such as nitrogen, phosphorous, and potassium (NPK) decreases the dependency on energy-intensive processes or processes that rely on depleting natural resources. In new sanitation systems, concentrated black water (BW) is obtained by source-separated collection of toilet water. BW-derived products are often associated with safety issues, amongst which pathogens and antibiotic-resistant pathogens. This study presents results showing that thermophilic (55–60 °C) and hyperthermophilic (70 °C) anaerobic treatments had higher (antibiotic-resistant) culturable pathogen indicators removal than mesophilic anaerobic treatment. Hyperthermophilic and thermophilic anaerobic treatment successfully removed Escherichia coli and extended-spectrum β-lactamases producing E. coli from source-separated vacuum collected BW at retention times of 6–11 days and reached significantly higher removal rates than mesophilic (35 °C) anaerobic treatment (p < 0.05). The difference between thermophilic and hyperthermophilic treatment was insignificant, which justifies operation at 55 °C rather than 70 °C. This study is the first to quantify (antibiotic-resistant) E. coli in concentrated BW (10–40 gCOD/L) and to show that both thermophilic and hyperthermophilic anaerobic treatment can adequately remove these pathogen indicators.