Towards a standardization of biomethane potential tests

8 PáginasProduction 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. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.The workshop in Leysin, Switzerland, has been financed by the Swiss Federal Office for Energy, and co-sponsored by Bioprocess Control Sweden AB, Lund, Sweden. The authors thank Alexandra Maria Murray for editing the English

16s rRNA gene sequencing and radioisotopic analysis reveal the composition of ammonia acclimatized methanogenic consortia

Different mesophilic and thermophilic methanogenic consortia were acclimatised and enriched to extreme total ammonia (9.0 and 5.0 g NH4+-N L−1, respectively) and free ammonia (1.0 and 1.4 g NH3-N L−1, respectively) levels in this study. [2-14C] acetate radioisotopic analyses showed the dominance of aceticlastic methanogenesis in all enriched consortia. According to 16S rRNA gene sequencing result, in mesophilic consortia, methylotrophic Methanomassiliicoccus luminyensis was predominant, followed by aceticlastic Methanosarcina soligelidi. A possible scenario explaining the dominance of M. luminyensis includes the use of methylamine produced by Tissierella spp. and biomass build-up by metabolizing acetate. Nevertheless, further studies are needed to pinpoint the exact metabolic pathway of M. luminyensis. In thermophilic consortia, aceticlastic Methanosarcina thermophila was the sole dominant methanogen. Overall, results derived from this study demonstrated the efficient biomethanation ability of these ammonia-tolerant methanogenic consortia, indicating a potential application of these consortia to solve ammonia toxicity problems in future full-scale reactors

Bioaugmentation strategy for overcoming ammonia inhibition during biomethanation of a protein-rich substrate

High ammonia levels inhibit anaerobic digestion (AD) process and bioaugmentation with ammonia tolerant methanogenic culture is proposed to alleviate ammonia inhibition. In the current study, hydrogenotrophic Methanoculleus bourgensis was bioaugmented in an ammonia-inhibited continuous reactor fed mainly with microalgae (a protein-rich biomass), at extreme ammonia levels (i.e. 11 g NH4+-N L−1). The results showed 28% increase in methane production immediately after bioaugmentation. Moreover, volatile fatty acids decreased rapidly from more than 5 g L−1 to around 1 g L−1, with a fast reduction in propionate concentration. High throughput 16s rRNA gene sequencing demonstrated that the bioaugmented M. bourgensis doubled its relative abundance after bioaugmentation. “Microbiological domino effect”, triggered by the bioaugmented M. bourgensis establishing a newly efficient community, was proposed as the working mechanism of the successful bioaugmentation. Additionally, a strong aceticlastic methanogenesis was found at the end of the experiment evidenced by the dominant presence of Methanosarcina soligelidi and the low abundance of syntrophic acetate oxidising bacteria at the final period. Overall, for the first time, this study proved the positive effect of bioaugmentation on ammonia inhibition alleviation of the microalgae-dominating fed reactor, paving the way of efficient utilization of other protein-rich substrates in the future

BIOAUGMENTATION STRATEGY FOR OVERCOMING AMMONIA INHIBITION DURING BIOMETHANATION OF A PROTEIN-RICH SUBSTRATE

10.1016/j.chemosphere.2019.05.140231415-42

Long-term preserved and rapidly revived methanogenic cultures: Microbial dynamics and preservation mechanisms

Bioaugmentation with specialized inocula has been proven a feasible way to remediate under-performing anaerobic digestion (AD) processes. However, a major bottleneck for successful and cost-effective bioaugmentation is the lack of ready-to-use, specialized methanogenic cultures when required. The reason is the slow growth of the anaerobic consortia and the high cost of maintaining them active in the necessary amounts for successful bioaugmentation applications. This study offers an effective procedure where customized AD inocula could be preserved and used on-demand for remediation of ammonia inhibited AD reactors. Additionally, it introduces the biological and physicochemical mechanisms that render the long-term preservation of the AD inocula possible. Specifically, two different preservation carriers (i.e. agar gel and liquid basic anaerobic medium) were assessed at two different temperatures (i.e. 4 \ub0C and 24 \ub0C) using an ammonia tolerant methanogenic consortium. The results from methane production, lag-phase, maximum methane production rate and cell viability indicate that the consortium preserved for 168 days in agar gel at 24 \ub0C performed best compared to the other tested preservation conditions. Meanwhile, 16S rRNA sequencing analysis indicated that Methanosarcina soligelidi and Methanoculleus palmolei shown a high revival rate and metabolic activity after long-term preservation. Thus, this successful long-term preservation method of ready-to-use AD consortia could render the successful bioaugmentation in full-scale biogas reactors economically possible in the near future

Effect of ammonia on anaerobic digestion of municipal solid waste: Inhibitory performance, bioaugmentation and microbiome functional reconstruction

The bioaugmentation is crucial to improve the energy-efficient process for anaerobic digestion of organic wastes at high ammonia levels. Genomic insights into the intricate microbial networks at a high ammonia level remain underexplored. The present study showed that the addition of Methanoculleus sp. DTU887 remarkably enhanced the methane production yield of organic fraction of municipal solid waste by 21% and decreased the volatile fatty acids by 10% when compared to the period before bioaugmentation. Genome-centric metagenomics reports the functional contribution of microbial members during organic waste degradation under the extremely high level of 13.5 g NH4+-N/L. Specifically, metabolic reconstruction revealed that these organisms have the potential to perform fermentative and acetogenic catabolism, a process facilitated by energy conservation-related with H2/CO2 metabolism. Peptococcaceae spp. (DTU903, DTU900, and DTU895). and Tissierellales sp. DTU879 could degrade the organic waste hydrolysis product, i.e., glucose to acetate and H2. Tissierellales sp. DTU879 and Syntrophaceticus sp. DTU783 could degrade the derived acetate. The H2 scavenging Methanoculleus sp. DTU887 performs complementary metabolic reactions with Peptococcaceae spp., Tissierellales sp. and Syntrophaceticus sp., indicating syntrophic glucose and acetate degradation. This research offers the first insight that the key organisms form a syntrophy-supported food web in response to the bioaugmentation with ammonia tolerant methanogens performed in an AD system subjected to severe ammonia inhibition

Acclimation to extremely high ammonia levels in continuous biomethanation process and the associated microbial community dynamics

Acclimatized anaerobic communities to high ammonia levels can offer a solution to the ammonia toxicity problem in biogas reactors. In the current study, a stepwise acclimation strategy up to 10 g NH4+-N L 121, was performed in mesophilic (37 \ub1 1 \ub0C) continuously stirred tank reactors. The reactors were co-digesting (20/80 based on volatile solid) cattle slurry and microalgae, a protein-rich, 3rd generation biomass. Throughout the acclimation period, methane production was stable with more than 95% of the uninhibited yield. Next generation 16S rRNA gene sequencing revealed a dramatic microbiome change throughout the ammonia acclimation process. Clostridium ultunense, a syntrophic acetate oxidizing bacteria, increased significantly alongside with hydrogenotrophic methanogen Methanoculleus spp., indicating strong hydrogenotrophic methanogenic activity at extreme ammonia levels (>7 g NH4+-N L 121). Overall, this study demonstrated for the first time that acclimation of methanogenic communities to extreme ammonia levels in continuous AD process is possible, by developing a specialised acclimation AD microbiome

CYanoTech: A sustainable and innovative management system for toxic cyanobacteria blooming of surface waters with combined energy production, sustainable agriculture, and food safety

The blooming of toxic cyanobacteria in surface waters worldwide has become more persistent and prevalent, thus affecting a number of economic sectors including the tourism industry, fishery and food industry, water treatment and monitoring industry, and health sector with annual loses in the range of millions of dollars. With so many diverse sectors of modern living being affected by the same problem, it is crucial to develop and apply innovative and sustainable management systems for toxic cyanobacteria that can be easily adapted into current infrastructures. CYanoTech is a two-year project that proposes a novel, sustainable, and innovative management system for mitigating the effects of toxic cyanobacteria blooming in surface waters while combining energy production and promoting sustainable agriculture, and food safety. The CYanoTech system comprises of removal of the excess aquatic biomass (cyanobacteria cells and algae) from water with a low energy non-mechanical separation technology, the treatment of the aquatic biomass for the production of energy and marketable products (fertilizers), and the application of treated and untreated surface water in hydroponic cultures that produces safe for consumptions crops (cyanotoxins-free crops). The energy produced will compensate the total energy needs of the applied treatment processes, further reducing the system’s overall carbon footprint, making it self-sustainable. Life-Cycle-Analysis will be used to prove the system’s sustainability and market accessibility. To achieve all the project aims, the Water Treatment Laboratory- Aqua of the Cyprus University of Technology has partnered up with research groups from the Ionian University in Greece and the University of Gdansk in Poland