Digestate, residual organic matter produced as byproducts during the anaerobic digestion process, needs to be utilized because of its potential greenhouse gas emissions. An alternative solution is to valorize digestate for biogas production. The current study investigates feasibility of simultaneous thermal post-treatment of digestate and in-situ biogas upgrading in the trickling filter bed (TFB) reactor. Thermal post-treatment improved the solubilization of food waste-based digestate for biogas production. It was reported that the TFB reactor are efficient to facilitate gas-liquid mass transfer during production of methane (CH4) from carbon dioxide (CO2) and hydrogen (H2). The exogenous H2 injection in in-situ biogas upgrading decreased CO2 content from 51.35 to 16.72% and upgrade CH4 content from 48.65 to 81% in the output gas. The reactor CH4 production rate reached 0.89 L/LR•d and the H2 utilization efficiency of 98% was accomplished. Furthermore, the results showed that chemical oxygen demand removal efficiency of digestate reached to a maximum of 64% in 10 days hydraulic retention time. The microbial analysis indicated hydrogenotrophic Methanobacterium ferruginis was highly abundant in the liquid and biofilm phase, while acetoclastic Methanosarcina flavescens localized in the biofilm phase. The findings from this work showed that digestate can be simultaneously exploited for improving effluent quality and biogas upgrading.

In-situ biogas upgrading in an anaerobic trickling filter bed reactor treating a thermal post-treated digestate

Presently, fossil fuels are extensively employed as major sources of energy, and their uses are considered unsustainable due to emissions of obnoxious gases on the burning of fossil fuels, which can lead to severe environmental complications, including human health. To tackle these issues, various processes are developing to waste as a feed to generate eco-friendly fuels. The biological production of fuels is considered to be more beneficial than physicochemical methods due to their environmentally friendly nature, high rate of conversion at ambient physiological conditions, and less energy-intensive. Among various biofuels, hydrogen (H2) is considered as a wonderful due to high calorific value and generate water molecule as end product on the burning. The H2 production from biowaste is demonstrated, and agri-food waste can be potentially used as a feedstock due to their high biodegradability over lignocellulosic-based biomass. Still, the H2 production is uneconomical from biowaste in fuel competing market because of low yields and increased capital and operational expenses. Anaerobic digestion is widely used for waste management and the generation of value-added products. This article is highlighting the valorization of agri-food waste to biofuels in single (H2) and two-stage bioprocesses of H2 and CH4 production.

Anaerobic Digestion of Agri-Food Wastes for Generating Biofuels.

Abstract Microbial community development within an anaerobic trickle bed reactor (TBR) during methanation of syngas (56% H 2 , 30% CO, 14% CO 2 ) was investigated using three different nutrient media: defined nutrient medium (241 days), diluted digestate from a thermophilic co-digestion plant operating with food waste (200 days) and reject water from dewatered digested sewage sludge at a wastewater treatment plant (220 days). Different TBR operating periods showed slightly different performance that was not clearly linked to the nutrient medium, as all proved suitable for the methanation process. During operation, maximum syngas load was 5.33 L per L packed bed volume (pbv) &amp; day and methane (CH 4 ) production was 1.26 L CH 4 /L pbv /d. Microbial community analysis with Illumina Miseq targeting 16S rDNA revealed high relative abundance (20–40%) of several potential syngas and acetate consumers within the genera Sporomusa , Spirochaetaceae , Rikenellaceae and Acetobacterium during the process. These were the dominant taxa except in a period with high flow rate of digestate from the food waste plant. The dominant methanogen in all periods was a member of the genus Methanobacterium , while Methanosarcina was also observed in the carrier community. As in reactor effluent, the dominant bacterial genus in the carrier was Sporomusa . These results show that syngas methanation in TBR can proceed well with different nutrient sources, including undefined medium of different origins. Moreover, the dominant syngas community remained the same over time even when non-sterilised digestates were used as nutrient medium. Key points • Independent of nutrient source, syngas methanation above 1 L/L pbv /D was achieved. • Methanobacterium and Sporomusa were dominant genera throughout the process. • Acetate conversion proceeded via both methanogenesis and syntrophic acetate oxidation. Graphical abstract 

/pdf/microbial-community-development-during-syngas-methanation-in-2aiyalp0.pdf

Microbial community development during syngas methanation in a trickle bed reactor with various nutrient sources

The United Kingdom (UK) has a decarbonisation strategy that includes energy from both hydrogen and biomethane. The latter comes from the growing anaerobic digestion (AD) market, which in 2020 produced 23.3 TWh of energy in the form of biogas. According to the strategy, this must be upgraded to biomethane by removal of carbon dioxide (CO2): a goal that could also be fulfilled through CO2 biomethanisation, alleviating the need for carbon capture and storage. Results are presented from a survey of publicly available datasets coupled with modelling to identify potential scale and knowledge gaps. Literature data were used to estimate maximum biomethane concentrations by feedstock type: these ranged from 79% for food wastes to 93% for livestock manures. Data from various government sources were used to estimate the overall potential for CO2 biomethanisation with current AD infrastructure. Values for the uplift in biomethane production ranged from 57% to 61%, but the need for more consistent data collection methodologies was highlighted. On average, however, if CO2 biomethanisation was applied in all currently operating UK AD plants an energy production uplift of 12,954 GWh could be achieved based on 2020 figures. This is sufficient to justify the inclusion of CO2 biomethanisation in decarbonisation strategies, in the UK and worldwide.

https://www.mdpi.com/2227-9717/10/6/1202/pdf?version=1655382625

Potential for Biomethanisation of CO2 from Anaerobic Digestion of Organic Wastes in the United Kingdom

Elucidation of microbial interactions, dynamics, and keystone microbes in high pressure anaerobic digestion.

Nanoparticle-associated single step hydrogen fermentation for the conversion of starch potato waste biomass by thermophilic Parageobacillus thermoglucosidasius

Ajay Thapa

Papers

In-situ biogas upgrading in an anaerobic trickling filter bed reactor treating a thermal post-treated digestate

Nanoparticle-associated single step hydrogen fermentation for the conversion of starch potato waste biomass by thermophilic Parageobacillus thermoglucosidasius