Towards a standardization of biomethane potential tests

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.info:eu-repo/semantics/publishedVersio

Biomethane production from starch and lignocellulosic crops : a comparative review

The methane produced from the anaerobic digestion of organic wastes and energy crops represents an elegant and economical means of generating renewable biofuel. Anaerobic digestion is a mature technology and is already used for the conversion of the organic fraction of municipal solid wastes and excess primary and secondary sludge from waste-water treatment plants. High methane yield up to 0.45 m3 STP CH4/kg volatile solids (VS) or 12 390 m3 STP CH4/ ha can be achieved with sugar and starch crops, although these cultures are competing with food and feed crops for high-quality land. The cultivation of lignocellulosic crops on marginal and set-aside lands is a more environmentally sound and sustainable option for renewable energy production. The methane yield obtained from these crops is lower, 0.17-0.39 m3 STP CH4/kg VS or 5400 m3 STP CH4/ha, as its conversion into methane is facing the same initial barrier as for the production of ethanol, for example, hydrolysis of the crops. Intensive research and development on efficient pre-treatments is ongoing to optimize the net energy production, which is potentially greater than for liquid biofuels, since the whole substrate excepted lignin is convertible into methane.La production de m\ue9thane \ue0 partir de la digestion ana\ue9robie de d\ue9chets organiques et de plantes \ue9nerg\ue9tiques repr\ue9sente un moyen \ue9l\ue9gant et \ue9conomique d\u2019obtenir du biocarburant renouvelable. La digestion ana\ue9robie est une technologie \ue9prouv\ue9e que l\u2019on utilise d\ue9j\ue0 pour la conversion de la fraction organique des d\ue9chets urbains solides et de l\u2019exc\ue9dent de boues primaires et secondaires provenant des stations d\u2019\ue9puration des eaux us\ue9es. Il est possible d\u2019obtenir un rendement de m\ue9thane \ue9lev\ue9 qui peut atteindre 0,45 m3 de CH4 (TPN)/kg de solides volatils (SV) ou 12 390 m3 de CH4 (TPN)/ha en utilisant des cultures riches en sucre et en amidon, bien que ces cultures se disputent les terres de premi\ue8re qualit\ue9 avec les cultures alimentaires et fourrag\ue8res. La culture des plantes lignocellulosiques sur des terres marginales ou retir\ue9es de la culture constitue une option plus \ue9cologique et durable pour la production d\u2019\ue9nergie renouvelable. Le rendement de m\ue9thane obtenu \ue0 partir de ces cultures est moins \ue9lev\ue9, \ue0 savoir, de 0,17 \ue0 0,39 m3 de CH4 (TPN)/kg de SV ou 5400 m3 de CH4 (TPN)/ha, car sa conversion en m\ue9thane se heurte au m\ueame obstacle initial que dans le cas de la production d\u2019\ue9thanol qui est de proc\ue9der \ue0 une hydrolyse de la plante. Des travaux de recherche et de d\ue9veloppement intensifs sur des pr\ue9traitements efficaces sont en cours pour optimiser la production nette d\u2019\ue9nergie, qui est potentiellement plus \ue9lev\ue9e que dans le cas des biocarburants liquides, car le substrat en entier, sauf la lignine, se convertit en m\ue9thane.Peer reviewed: YesNRC publication: Ye

Anaerobic digestion as an effective biofuel production technology

The methane produced from the anaerobic digestion of organic wastes and energy crops represents an elegant and economical mean of generating renewable biofuel. Anaerobic digestion is a mature technology and is already used for the conversion of the organic fraction of municipal solid wastes and primary and secondary sludge from wastewater treatment plant. High methane yield up to 0.45 Nm3 CH<inf>4</inf>/kg volatile solids (VS) or 12,390 Nm3 CH<inf>4</inf>/ha can be achieved with sugar and starch crops, although these cultures are competing for high quality land with food and feed crops. The cultivation of lignocellulosic crops on marginal and set-aside lands is a more environmentally sound and sustainable option for renewable energy production. The methane yield obtained from these crops is lower, 0.17-0.39 Nm3 CH<inf>4</inf>/kg VS or 5,400 Nm3 CH<inf>4</inf>/ha, as its conversion into methane is facing the same initial barrier as for the production of ethanol, e.g., hydrolysis of the crops. Intensive research and development on efficient pretreatments is ongoing to optimize the net energy production, which is potentially greater than for liquid biofuels, since the whole substrate excepted lignin is convertible into methane. Algal biomass is another alternative to food and feed crops. Their relatively high methane potential (up to 0.45 Nm3 CH<inf>4</inf>/kg VS fed) combined with their higher areal biomass productivity make them particularly attractive as a feedstock for an anaerobic digestion-based biorefinery concept.Peer reviewed: YesNRC publication: Ye

Anaerobic co-digestion of dairy manure with mulched switchgrass for improvement of the methane yield

The owners of farm-scale anaerobic digesters are relying on off-farm wastes or energy crops as a co-digestion feedstock with animal manure in order to increase their production of methane and thus revenues. Switchgrass represents an interesting feedstock for Canadian digesters owners as it is a high-yielding low-maintenance perennial crop, well adapted to northern climate. Methane potential assays in batch tests showed methane production of 19.4 \ub1 3.6, 28.3 \ub1 1.7, 37.3 \ub1 7.1 and 45.7 \ub1 0.8 L kg -1, for raw manure, blended manure, manure and mulched switchgrass, manure and pretreated switchgrass, respectively. Two 6-L lab-scale anaerobic digesters were operated for 130 days in order to assess the benefit of co-digesting switchgrass with bovine manure (digester #2), at a 20% wet mass fraction, compared with a manure-only operation (digester #1) The digesters were operated at an hydraulic retention time of 37 \ub1 6 days and at loads of 2.4 \ub1 0.6 and 2.6 \ub1 0.6 kg total volatile solids (TVS) L\u207b\ub9 day\u207b\ub9 for digesters #1 (D1) and #2 (D2), respectively. The TVS degradation reached 25 and 39%, which resulted in a methane production of 1.18 \ub1 0.18 and 2.19 \ub1 0.31 L day\u207b\ub9 for D1 and D2, respectively. The addition of 20% on a wet mass ratio of switchgrass to a manure digester increased its methane production by 86%. The co-digestion of switchgrass in a 500 m\ub3 manure digester could yield up to 10.2 GJ day\u207b\ub9 of purified methane or 1.1 MWh day\u207b\ub9 of electricity.Peer reviewed: YesNRC publication: Ye

Anaerobic treatment of a municipal landfill leachate

NRC publication: Ye

Acidogenic fermentation of Scenedesmus sp.-AMDD: comparison of volatile fatty acids yields between mesophilic and thermophilic conditions

This study compared the acidogenic fermentation of Scenedesmus sp.-AMDD at laboratory-scale, under mesophilic (35 \ub0C) and thermophilic conditions (55 \ub0C). Preliminary batch tests were performed to evaluate best conditions for volatile fatty acid (VFA) production from microalgal biomass, with respect to the inoculum, pH and nutrients. The use of bovine manure as inoculum, the operating pH of 4.5 and the addition of a nutrient mix, resulted in a high VFA production of up to 222 mg g-1 total volatile solid (TVS), with a butyrate share of 27%. Both digesters displayed similar hydrolytic activity with 0.38\ub10.02 and 0.42\ub10.03 g soluble chemical oxygen demand (COD) g-1 TVS for the digesters operated at 35 and 55 \ub0C, respectively. Mesophilic conditions were more favourable for VFA production, which reached 171\ub15, compared to 88\ub112 mg soluble COD g-1 TVS added under thermophilic conditions (94% more). It was shown that in both digesters, butyrate was the predominant VFA.Peer reviewed: YesNRC publication: Ye

Impact of mechanical, chemical and enzymatic pre-treatments on the methane yield from the anaerobic digestion of switchgrass

The conversion of cellulosic crops into biofuels, including methane, is receiving a lot of attention lately. Panicum vergatum, or switchgrass, is a warm season perennial grass well adapted to grow in North America. Different pre-treatments were tested in 0.5 l batch reactors, at 35 \ub0C, in order to enhance the methane production from switchgrass, including temperature, sonication, alkalinization and autoclaving. The methane production on the basis of volatile solids (VS) added to the fermentation were 112.4 \ub1 8.4, 132.5 \ub1 9.7 and 139.8 ml g-1 after 38 days of incubation for winter harvested switchgrass (WHS) after grinding, grinding with alkalinization, and grinding with alkalinization and autoclaving, respectively. The methane production was higher for fresh summer harvested switchgrass (SHS), with a production of 256.6 \ub1 8.2 ml g-1 VS after mulching, alkalinization and autoclaving. The methane production from SHS was improved by 29 and 42% when applying lignin (LiP) or manganese peroxidase (MnP), at 202.1 \ub1 9.8 and 222.9 \ub1 22.5 ml g-1 VS, respectively. The combination of an alkali pre-treatment with the MnP increased the methane production furthermore at 297.7 ml g-1 VS. The use of pectinases without chemical pre-treatment showed promising yields at 287.4 and 239.5 ml g-1 VS for pectate-lyase and poly-galacturonase, respectively. An estimation of the methane yield per hectare of crop harvested resulted in net energy production of 29.8, 49.7 and 78.1 GJ for winter harvested switchgrass, mulched and pretreated summer harvested switchgrass, respectively. Switchgrass represents an interesting candidate as a lignocellulosic crop for methane production.Peer reviewed: YesNRC publication: Ye

Digestion ana\ue9robie de boues municipales : op\ue9ration d'une unit\ue9 mobile

Peer reviewed: YesNRC publication: Ye

Advances in oil producing crops and algae based feedstocks

NRC publication: Ye

Combining photolysis and bioprocesses for mineralization of high molecular weight polyacrylamides

The influence of ultraviolet photolysis as a pretreatment to the aerobic and anaerobic biological mineralization of a 14C-polyacrylamide was assessed using a series of radiorespirometry bioassays. The polyacrylamide studied was non-ionic with molecular weights ranging between 100,000 and 1 million. Aerobic and anaerobic biomineralization of the unphotolysed (raw) polyacrylamide was found to be only 0.60% and 0.70%, respectively, after 6 weeks of incubation, and hence indicative of the natural recalcitrance of polyacrylamide to microbial degradation. The effectiveness of UV irradiation in the physical breakdown of the polyacrylamide chain into oligomers was demonstrated by the shift in the molecular weight distribution and the positive correlation between the time of irradiation and the degree of its biological mineralization. The molecular weight fraction below 3 kD, which represents only 2% of the raw polyacrylamide, was increased to 41, 60 and 80% after 12, 24 and 48 hours of photolysis, respectively. This in turn, yielded, after 6 weeks of incubation, an aerobic mineralization of 5, 17 and 29% of 150 mg/L polyacrylamide, respectively, and an anaerobic mineralization of 3, 5 and 17%, respectively. Biomass acclimation substantially improved the specific initial rate of biomineralization of the photolysed polyacrylamides, but not the overall percentage of polyacrylamides mineralized.NRC publication: Ye