•Temperature-phased anaerobic digestion (TPAD) of food waste were evaluated.•The biogas and methane yields of FW in TPAD were lower than those in TAD and MAD.•The TPAD had a lower FAN inhibition ...factor than MAD and TAD.•The energy conversion efficiency in TPAD was higher than that in TAD.
The temperature-phased anaerobic digestion (TPAD) of food waste was studied for the purpose of comparing with single-stage mesophilic and thermophilic anaerobic digestion. The biogas and methane yields in the TPAD during the steady period were 0.759 ± 0.115 L/g added VS and 0.454 ± 0.201 L/g added VS, which were lower than those in the two single-stage anaerobic digestion. The improper sludge retention time may be the reason for the lower biogas and methane production in TPAD. The removal of volatile solids in the TPAD was 78.55 ± 4.59% and the lowest among the three anaerobic digestion processes. The reaction ratios of the four anaerobic digestion steps in the TPAD were all lower than those in the two single-stage anaerobic digestion. The energy conversion efficiency of the degraded substrate in the TPAD was similar with those in single-stage mesophilic and thermophilic anaerobic digestion systems.
The increasing volume of sewage sludge from wastewater treatment facilities is becoming a prominent concern globally. The disposal of this sludge is particularly challenging and poses severe ...environmental hazards due to the high content of organic, toxic and heavy metal pollutants among its constituents. This study presents a simple review of four sewage to energy recovery routes (anaerobic digestion, combustion, pyrolysis and gasification) with emphasis on recent developments in research, as well as benefits and limitations of the technology for ensuring cost and environmentally viable sewage to energy pathway. This study focusses on the review of various commercially viable sludge conversion processes and technologies used for energy recovery from sewage sludge. This was done via in-depth process descriptions gathered from literatures and simplified schematic depiction of such energy recovery processes when utilised for sludge. Specifically, the impact of fuel properties and its effect on the recovery process were discussed to indicate the current challenges and recent scientific research undertaken to resolve these challenges and improve the operational, environmental and cost competitiveness of these technologies.
Sugarcane straw is not effectively used in the industry currently. However, sugarcane straw hemicellulose hydrolyzate (HH) application as raw material for H2 and CH4 production is a promising ...alternative. In this work, the two-stage anaerobic digestion (TS-AD) approach led to 37.86 mLH2/L.h and 40.12 mLCH4/L.d, while the single-stage anaerobic digestion (SS-AD) generated 46.11 mLCH4/L.d. Hence, the two-stage process was energetically favorable than the single-stage by approximately 33%. Additionally, the comparison with standard medium (composed of glucose, xylose, and arabinose) applied as raw material indicated that although hydroxymethylfurfural and furfural from HH were not responsible for the decrease in H2 production, they extended the adaptive phase of methanogenic archaea during the methanogenesis. Hemicellulose hydrolysate is an attractive raw material for two-stage anaerobic digestion.
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•Hemicellulose hydrolysate is an attractive raw material for H2 and CH4 production.•1363.08 mLH2/L were obtained at the initial sugar concentration of 30 mM.•Furfural and HMF affected the adaptive phase of archaea in methanogenesis.•Higher productivity (40 mL-CH4/L.d) and COD removal (91%) in two-stage AD.•The overall energy potential in two steps was 33% higher.
•Performances and methanogenic pathway of SADB and wet AD of organic waste were analyzed.•Liquid digestate recirculation improved AD even at TS>30%.•Methane yields were SADB=252 NLCH4/kgVS wet AD=320 ...NLCH4/kgVS.•Large syntrophic metabolism was detected in the liquid phase of SADB.
Solid anaerobic digestion batch (SADB) with liquid digestate recirculation and wet anaerobic digestion of organic waste were experimentally investigated. SADB was operated at an organic loading rate (OLR) of 4.55kgVS/m3day, generating about 252NL CH4/kgVS, whereas the wet digester was operated at an OLR of 0.9kgVS/m3day, generating about 320NL CH4/kgVS. The initial total volatile fatty acids concentrations for SADB and wet digestion were about 12,500mg/L and 4500mg/L, respectively. There were higher concentrations of ammonium and COD for the SADB compared to the wet one. The genomic analysis performed by high throughput sequencing returned a number of sequences for each sample ranging from 110,619 to 373,307. More than 93% were assigned to the Bacteria domain. Seven and nine major phyla were sequenced for the SADB and wet digestion, respectively, with Bacteroidetes, Firmicutes and Proteobacteria being the dominant phyla in both digesters. Taxonomic profiles suggested a methanogenic pathway characterized by a relevant syntrophic acetate-oxidizing metabolism mainly in the liquid digestate of the SADB. This result also confirms the benefits of liquid digestate recirculation for improving the efficiency of AD performed with high solids (>30%w/w) content.
With the implementation of zero-waste city and waste classification in China, a large amount of food waste (FW) began to appear in concentration, and there was an urgent requirement for appropriate ...and efficient treatment technology. Traditional FW disposal methods (landfill and incineration) could cause several environmental problems, so resource recycling has become the main development trend of FW in China. In recent years, anaerobic digestion (AD) technology for FW resource treatment has attracted much attention due to its advantages such as the ability to obtain clean energy, low carbon emissions, and suitability for large-scale treatment compared with other recycling technologies (composting, feed, and breeding insects). Chinese policy is conducive to the development of AD for FW, which has the potential to produce methane and achieve economic and environmental benefits. This paper presents an overview of the researches, application situations, and perspectives for the AD of FW resource treatment in China. The bibliometric analysis shows that China has the most interest in the AD of FW compared to other countries, and the amount and characteristics analysis of FW indicates that FW is suitable for treatment by AD. At the same time, this review analyzes the influence factors, methods to promote AD, working mechanism, secondary pollution of AD. Besides, the article introduces and analyzes the current policies, application status, economic and environmental benefits, and problems of AD for FW resource treatment in China. AD is considered as an alternative resource treatment technology for FW, although there are still several problems such as odors, digestate, etc. In the future, China should focus on the reform of management policy, the implementation of the AD circular economy model, and the research of the biorefinery model based on AD technology.
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•The amount and characteristics of food waste in China were analyzed.•The research progress of anaerobic digestion for food waste was reviewed.•Summarizing the status of anaerobic digestion for food waste in China•The carbon reduction from biogas generation is 46.68 kg CO2/t food waste.•Future perspectives of anaerobic digestion industry were suggested.
Up-flow anaerobic sludge blanket (UASB) reactor belongs to high-rate systems, able to perform anaerobic reaction at reduced hydraulic retention time, if compared to traditional digesters. In this ...review, the most recent advances in UASB reactor applications are critically summarized and discussed, with outline on the most critical aspects for further possible future developments. Beside traditional anaerobic treatment of soluble and biodegradable substrates, research is actually focusing on the treatment of refractory and slowly degradable matrices, thanks to an improved understanding of microbial community composition and reactor hydrodynamics, together with utilization of powerful modeling tools. Innovative approaches include the use of UASB reactor for nitrogen removal, as well as for hydrogen and volatile fatty acid production. Co-digestion of complementary substrates available in the same territory is being extensively studied to increase biogas yield and provide smooth continuous operations in a circular economy perspective. Particular importance is being given to decentralized treatment, able to provide electricity and heat to local users with possible integration with other renewable energies. Proper pre-treatment application increases biogas yield, while a successive post-treatment is needed to meet required effluent standards, also from a toxicological perspective. An increased full-scale application of UASB technology is desirable to achieve circular economy and sustainability scopes, with efficient biogas exploitation, fulfilling renewable energy targets and green-house gases emission reduction, in particular in tropical countries, where limited reactor heating is required.
It is clear that renewable resources will play a crucial role in limiting the CO2 emissions. Energy from biomass and waste is regarded as one of the most dominant future renewable energy sources, ...since it can provide a continuous power generation. In this regard, the application of anaerobic digestion is emerging spectacularly. This manuscript lists and discusses the main beneficial properties of anaerobic digestion. Different types of biomass and waste are suitable for anaerobic digestion: the organic fraction of municipal solid waste, waste oils and animal fat, energy crops and agricultural waste, manure and sewage sludge. The potential, opportunities and challenges of these biomasses are discussed. Typical biogas yield and points of attention are included. The manuscript concludes with an overview and discussion of the major research trends in anaerobic digestion, including the analysis of microbial community development, the extension of anaerobic digestion models, the development of pre-treatment techniques and upgrading of the biogas produced.
The role of the total solids (TS) content on anaerobic digestion was investigated in batch reactors. A range of TS contents from 10% to 35% was evaluated, four replicates were performed. The total ...methane production slightly decreased with TS concentrations increasing from 10% to 25% TS. Two behaviors were observed at 30% TS: two replicates had similar performances to that at 25% TS; for the two other replicates, the methane production was inhibited as observed at 35% TS. This difference suggested that 30% TS content corresponded to a threshold of the solids content, above which methanogenesis was strongly inhibited. The Anaerobic Digestion Model No. 1 (ADM1) was used to describe the experimental data. The effects of hydrolysis step and liquid/gas mass transfer were particularly investigated. The simulations showed that mass transfer limitation could explain the low methane production at high TS, and that hydrolysis rate constants slightly decreased with increasing TS.
•Solid AD is the most appropriate process to valorize waste with high TS content.•Few industrial solid AD processes available, technological hurdles must be solved.•Scientific and technological ...hurdles must be studied at adapted scale.•Solid AD is mainly used in Europe, where French AD differs from the German model.
In this paper, a state-of-art about solid anaerobic digestion (AD), focused on recent progress and trends of research is proposed. Solid anaerobic digestion should be the most appropriate process for degradation of by-products with high total solid (TS) content, especially lignocellulosic materials like agricultural waste (straw, manure), household waste and food waste. Solid AD is already widely used in waste water treatment plant for treating plant for sewage sludge but could be more developed for lignocellulosic materials with high TS content. Many research works were carried out in Europe on solid AD, focused on current hurdles (BMP, codigestion, inhibition, microbial population, rheology, water transfers, inoculum, etc.) in order to optimize the solid AD process. In conclusion, hurdles of solid AD process should and must be solved in order to propose better productivity and profitability of such system operating with high TS content (>15%), favouring reliable industrial processes.
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•The biochar prepared at high temperature presented high stability and low biotoxicity.•ADSBCs/PDS systems were effective for degradation of diverse organic contaminants.•Persulfate ...was activated via an electron-transfer regime.•The nonradical pathway can effectively inactivate diverse bacteria in wastewater.
The peroxydisulfate (PDS) -based advanced oxidation processes (AOPs) is a promising technology for wastewater treatment and the efficiency primarily depends on the high-performance catalysts. Therefore, it is necessary to develop a green and low-cost biomaterial for PDS activation to drive such a process. In this study, biochar catalysts were produced via pyrolysis of anaerobic digestion sludge (ADS) as effective PDS activators. The biochar derived from ADS (ADSBC) yielded large specific surface areas, a high degree of graphitization and good conductivity, which can be used for effectively oxidizing various pollutants including dyes, estrogens and sulfonamides with PDS in broad pH and temperature ranges. It is showed that PDS activated by ADSBC 1000 can completely remove sulfathiazole in 90 min much higher than that of ADSBC 400 (20.25%). Moreover, the biochar produced under high pyrolysis temperature shows great stability and low biotoxicity due to the limited metals leaching and eliminated persistent free radicals as well as dissolved organic matter. The mechanism of the ADSBCs/PDS system was critically discussed via selectively radical screening tests, solvent exchange (H2O to D2O), selectivity to pollutants and electrochemical analysis. These results revealed that the organics were decomposed by a nonradical pathway via electron transfer rather than relying on free radicals or singlet oxygen. More importantly, the biochar-based nonradical oxidation system can leveraged for inactivation of Escherichia coli (E. coli) and diverse bacteria in both simulated and real wastewater. Therefore, this work not only provides an approach to reuse the sludge residue to prepare graphitic biochar catalysts as PDS activators for decontamination of emerging micropollutants, but also expands the practical application of advanced carbocatalysis for bacteria inactivation by nonradical oxidation in real wastewater.
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