Revealing the correlation of biomethane generation, DOM fluorescence, and microbial community in the mesophilic co-digestion of chicken manure and sheep manure at different mixture ratio

Metataxonomic characterization of the microbial present in the anaerobic digestion of turkey litter waste with the addition of two inocula: allochthonous and commercial

Turkey litter waste is lignocellulosic waste that can be sustainably used as an energy source through anaerobic digestion (AD). The 16S ribosomal RNA technique helps to unravel microbial diversity and predominant metabolic pathways. The assays were performed in 600-mL-glass bottles with 400 mL volume, for 60 days at 37 °C. The study evaluated the physicochemical parameters, the composition of the microbiota, and the functional inference in AD of different concentrations of turkey litter (T) using two inocula: granular inoculum (S) and commercial inoculum (B). The highest accumulated methane production (633 mL CH4·L-1) was observed in the test containing 25.5 g VS·L-1 of turkey litter with the addition of the two inocula (T3BS). In tests without inoculum (T3) and with commercial inoculum (T3B), there was an accumulation of acids and consequent inhibition of methane production 239 mL CH4·L-1 and 389 mL CH4·L-1, respectively. Bacteroidota, Firmicutes, and Actinobacteria were the main phyla identified. The presence of archaea Methanobacterium, Methanocorpusculum, and Methanolinea highlighted the hydrogenotrophic metabolic pathway in T3BS. Functional prediction showed enzymes involved in three metabolic pathways in turkey litter biodigestion: acetotrophic, hydrogenotrophic, and methylotrophic methanogenesis. The predominant hydrogenotrophic pathway can be observed by analyzing the microbiota, archaea involved in this specific pathway, genes involved, and relative acid consumption for T3S and T3BS samples with higher methane production. Molecular tools help to understand the main groups of microorganisms and metabolic pathways involved in turkey litter AD, such as the use of different inocula, allowing the development of strategies for the sustainable disposal of turkey litter.

Low maintenance anammox enrichment and nitrogen removal with an anaerobic baffled reactor

The stringent growth requirements of anammox bacteria may be a challenge for employing the anammox process for nutrient removal at household or decentralized scales, where low maintenance systems are more successful. Enrichment of anammox bacteria was achieved by 100 d using a lab-scale (32 L) anaerobic baffled reactor (ABR). Even though strict anaerobic conditions were not imposed, NH4-N and NO2-N removals of >90% were maintained after ∼100 d, with greatest removals observed in the first two chambers of the four-chamber ABR. Batch anammox activity tests and results of qPCR analyses confirmed the presence of anammox bacteria in all four ABR chambers. Changes in fluorescent peaks and indices supported that intracellular compounds from reactor biomass evolved along the ABR. The presence of denitrifiers, confirmed by qPCR, and lower NO2/NH4 ratios than predicted by stoichiometry indicated that nitrification-denitrification processes also may have contributed to the high N removal in the anammox ABR.

Overview of pretreatment technologies on vegetable, fruit and flower market wastes disintegration and bioenergy potential: Indian scenario

Disposal of segregated organic fractions of centralized wholesale market wastes (i.e. vegetable, fruit and flower markets waste) in dumpsites/landfills are not only a serious issue but also underutilizes the huge potency of these organic wastes. Anaerobic digestion (AD) is a promising technology for converting organic wastes into methane, as a carbon-neutral alternative to conventional fuels. The major challenges related to the AD process are poor biodegradation of wastes and buffering capacity within the anaerobic digester that lowers the biogas yield. To accelerate biodegradation and to enhance the process efficacy of anaerobic digestion, several pretreatment technologies (mechanical, thermal, biological, chemical and combined pre-treatments) for organic wastes prior to the AD process were developed. This review article presents a comprehensive analysis of research updates in pretreatment techniques for vegetable, fruit and flower markets wastes for enhancing biogas yields during the AD process. The technological aspects of the pretreatment process are described and their efficiency comparison with the resultant process yields and environmental benefits are also discussed. The challenges and technical issues associated with each pretreatment and future research directions for overcoming the field implementation issues are also proposed.

Anaerobic Co-Digestion of Sheep Manure and Waste from a Potato Processing Factory: Techno-Economic Analysis

Anaerobic co-digestion of sheep manure and potato waste was studied under batch and semi-continuous conditions. Biochemical methane potential tests were carried out for the different substrates before evaluating co-digestion at high-solid content. The reactors presented stable performance under mesophilic conditions, at an organic loading rate (OLR) of 3.5–4.0 kg VS/m3 and a hydraulic retention time (HRT) of approximately 20 days. Increasing the OLR of semi-continuous reactors decreased the methane yield and degradation efficiency of the digestion. Methane-specific production was in the range of 196 and 467 mL CH4/g vs. (sheep manure system and co-digestion, respectively). Based on the experimental data obtained, a techno-economic study was performed for wet and solid-state fermentation systems, with the first configuration presenting better results. The economic feasibility of the hypothetical plant was analyzed considering the variability in electricity and compost selling prices. The economic feasibility of the plant was determined with an electricity selling price of EUR 0.25/kWh, and assuming a centralized plant serving several farmers. Still, this price was considered excessive, given the current electricity market values.

Bio-reserves inventory-improving substrate management for anaerobic waste treatment in a fast-growing Indian urban city, Chennai

India is one among the Asia's newly industrialized countries, in which urban centres generate large amount of municipal solid wastes due to the rapid urbanization. To demonstrate urban waste potentials for biogas production by anaerobic digestion, a comprehensive analysis on the availability of organic waste hotspots and its biogas potential for the exemplary case of Chennai, India, was undertaken. The identified hotspots and their biogas potential were plotted with Geographical Information System as thematic maps. The results of biogas potential tests revealed strong variations in the biogas potentials of individual waste streams from 240.2 to 514.2 mL_N/g oDM (organic dry matter) with oDM reduction in the range of 36.4-61.5 wt.-%. Major waste generation hotspots were identified from the surveyed urban bio-reserves and the biogas potentials within an effective area of 5 km radius surrounding the hotspot were estimated. It was found that the biogas potential of individual hotspots ranged between 38.0-5938.7 m³/day. Further results revealed that the biogas potential during anaerobic co-digestion, by considering nearby bio-reserves in the effective areas of major hotspots, with and without residential organic waste, ranged between 4110.4-18-106.1 m³/day and 253.2-5969.5 m³/day, originating from 144.0-620.0 tons and 3.1-170.5 tons, respectively. Despite variations in the composition of the wastes, the Carbon/Nitrogen ratio, oDM reduction, biogas production and substrate availability were improved during co-digestion of nearby bio-reserves within the major hotspots, thereby improving the prevailing barriers in substrate management during anaerobic digestion of wastes.

Enhancement methane fermentation of Enteromorpha prolifera waste by Saccharomyces cerevisiae: batch kinetic investigation, dissolved organic matter characterization, and synergistic mechanism

With the invasion of green tide, there were millions of tons of Enteromorpha prolifera (Enteromorpha) that need to be disposed of. An efficient microecological system for Enteromorpha fermentation was constructed using Saccharomyces cerevisiae (S. cerevisiae) and granular sludge at mesophilic condition (35 °C). In order to investigate the influence of S. cerevisiae dosage on fermentation, biomethane production and variations in dissolved organic matter (DOM) were investigated. The results indicated that the microecosystem with added S. cerevisiae exhibited improved fermentation capacity. Specifically, biomethane production was improved by 18%, with a maximum methane yield of 331 mL/g VS, and the time required to reach 90% methane yield was reduced by 41%. There were positive linear relationships between S. cerevisiae dosage and the efficiency of hydrolysis, acidogenesis, acetogenesis, and methanogenesis (R² > 0.9). According to theoretical calculations, there was a positive effect of lower S. cerevisiae dosage (less than 0.93 g/g TS) on biomethane production, and excess dosage (more than 0.93 g/g TS) led to a negative effect due to volatile fatty acid (VFA) accumulation. The excitation-emission matrix (EEM) indicated that the humification index (HIX) and fulvic acid (FA) percentage of fluorescence regional integration in the system were decreased because the quinone and ketone groups of the FA accepted electrons from S. cerevisiae. These findings suggested that this microecosystem can accelerate fermentation speed (41%) and increase biomethane output (18.2%). The synergistic effect of Enteromorpha fermentation with Saccharomyces cerevisiae addition.