CeO 2 and Side-Stream Hydrogenation Domestication Synergistically Mitigate Ammonia Inhibition in Food Waste Anaerobic Digestion: Insights into Microbial Metabolism and System Stability

Elucidating interactive effects of sulfidated nanoscale zero-valent iron and ammonia on anaerobic digestion of food waste

Effects of disposable plastics and wooden chopsticks on the anaerobic digestion of food waste

Particle size reduction is a commonly used pretreatment technique to promote methane production from anaerobic digestion (AD) of food waste (FW). However, limited research has focused on the effect of micron-sized particles on AD of FW. This research presented an ultrafine wet milling (UFWM) pretreatment method to reduce the particle size of FW particles. After four hours of milling, D90 was reduced to 73 μm and cumulative methane production boosted from 307.98 mL/g vs. to 406.75 mL/g vs. without ammonia inhibition. We evaluated the performance of the AD systems and explored their facilitation mechanisms. Kinetic analysis showed that the modified Gompertz model predicted experimental values most accurately. UFWM pretreatment increased the maximum methane production rate by 44.4% and reduced the lag time by 0.65 days. The mechanical stress and collisions of milling resulted in a scaly surface of the particles, which greatly increased the voids and surface area. A rise in the XPS peak area of the C–N and C=O bonds proved the promotion of the liberation of carbohydrates and fats. Further microbial community analysis revealed that the relative abundance of Bacteroidota and Methanosarcina were enriched by UFWM. Meanwhile, methane metabolism pathway analysis confirmed that module M00567, module M00357, and related enzymes were stimulated. This study provided a theoretical basis for UFWM pretreatment applications and improvements in AD of FW.

Biohydrogen generation from anaerobic digestion of food waste

At present, most studies have been focused on anaerobic digestion (AD) of food waste (FW) at temperatures above 35 °C. While AD of FW at psychrophilic temperature has been rarely reported, this may be a more economical procedure for municipal solid waste (MSW) management by reducing the organic fraction content and the corresponding environmental impact from its disposal. FW and inoculum have been characterized and AD of FW assays have been run for 12 weeks in accordance with VDI 4630. The effect of FW to inoculum ratio (FWIR) has been assessed in batch assays and the organic load rate (OLR) has been tested in semi-continuous operation mode. In addition, soluble chemical oxygen demand (SCOD) evolution has been periodically measured during all tests. Results showed an important reduction of specific methane yield (SMY) (up to 65%) when FWIR is increased (from 0.5 to 1.5) in batch tests while SCOD removal remains quite constant (approx. 90%). On the other hand, during semi-continuous operation SMY and SCOD removal have been highly reduced (up to approx. 70 and 73%) when OLR is increased (from 1 to 3 g_VS L−1 d−1). Despite the low SMY, the AD of FW at psychrophilic temperature is a feasible solution, especially at low organic loads. Therefore, it may be used in decentralized strategies for improving the MSW management. This operation mode reduces installation costs and reactor operation complexity at the same time decreases the SCOD of municipal waste stream.

In this study, the impact of cobalt iron oxide(CoFe2O4) on the anaerobic digestion (AD) of food waste (FW) was investigated including the variations in pH, VFAs, ORP, Fe2+/Fe3+ concentrations, SCOD, dehydrogenase activity, methane production and microbial community structure. The results showed that CoFe2O4 had a positive effect on the anaerobic digestion of food waste. CoFe2O4 could promote the release of SCOD, increase the dehydrogenase concentration and reduce ORP resulting in an increase of methane production. At a CoFe2O4 concentration of 200 mg/L, the cumulative methane production reached to 414.75 mL/(gVS) which was increased by 79.1% compared to the control group(231.59 mL/(gVS)). Meanwhile, the variation of microbial community showed that CoFe2O4 could increase the relative abundance of Methanobacterium and the methane production pathway in the AD was shifted from acetoclastic to hydrogenotrophic.

Published national and state reports have revealed that Australia deposits an average of 16 million Mg of solid waste into landfills yearly, of which approximately 12.6% is comprised of food. Being highly biodegradable and possessing high energy content, anaerobic digestion offers an attractive treatment option alternative to landfilling. The present study attempted to identify the theoretical maximum benefit of food waste digestion in Australia with regard to energy recovery and waste diversion from landfills. The study also assessed the scope for anaerobic process to utilize waste for energy projects through various case study scenarios. Results indicated anaerobic digestion of total food waste generated across multiple sites in Australia could generate 558 453 dam(3) of methane which translated to 20.3 PJ of heating potential or 1915 GWe in electricity generation annually. This would contribute to 3.5% of total current energy supply from renewable sources. Energy contribution from anaerobic digestion of food waste to the total energy requirement in Australia remains low, partially due to the high energy consumption of the country. However its appropriateness in low density regions, which are prevalent in Australia, may allow digesters to have a niche application in the country.

Evaluating the role of salinity in enhanced biogas production from two-stage anaerobic digestion of food waste by zero-valent iron

Unveiling the bioaugmentation mechanism of Clostridium thermopalmarium HK1 enhancing methane production in thermophilic anaerobic digestion of food waste

Insights into high-solids anaerobic digestion of food waste concomitant with sorbate: Performance and mechanisms

Enhanced mitigation of antibiotic resistance genes in anaerobic digestion of food waste using biochar-supported nanoscale zero-valent iron.

Improving the stability and efficiency of anaerobic digestion of food waste using additives: A critical review

The anaerobic digestion (AD) of food waste (FW) was augmented with ammonia-tolerant anaerobic sludge (ATAS). Different inoculum substrate ratios (ISR) under an initial ammonia stress of 4220 mg N/L were investigated. Results showed that the average specific methane production (SMP) of FW in the ATAS system increased by 36% compared with that in un-acclimated anaerobic sludge. SMP with ISR of 1:2.5 increased by approximately 6 times. Volatile fatty acids (VFAs) accumulation and sharp pH decline were not detected. These results revealed the high performance of ATAS in simultaneously relieving ammonia and acid stress. This improvement was attributed to multiple factors. ATAS had high ammonia tolerance and ability in conversion of acetate into methane. The equilibrium of NH3/NH4+, CO2/H2CO3/HCO3-, and CxHyCOOH/CxHyCOO- could promote VFAs and ammonia ionization, reduce the levels of free VFAs and ammonia, neutralize pH, and thus enhance the system's buffering capacity to be less susceptible to fluctuations. These results demonstrated that employing ATAS in improving AD performance and resilience from acid and ammonia inhibition is feasible and effective.

Enhanced energy recovery via separate hydrogen and methane production from two-stage anaerobic digestion of food waste with nanobubble water supplementation

Day by day as the population increases, food waste keeps on growing. This waste needs to be managed in order to reduce the number of landfills and to use food waste efficiently. Among the various processes available, Anaerobic Digestion (AD) of food waste is one of the alternatives for processing food waste. The two biggest obstacles to anaerobic digestion of food waste are high biodegradability and high C/N ratio. The C/N ratio determines the ratio between substrate and nutrients; the latter is essential for microbial synthesis and for providing alkalinity through ammonia metabolism. Biogas, a product of the anaerobic digestion process, is a clean and renewable form of energy that can replace conventional energy sources that cause ecological-environmental problems and at the same time are depleted more quickly. The aim of this work was to increase the nitrogen content to enhance the production of biogas from canteen waste. During the process, two digesters of the same capacity were operated. Anaerobic digestion of canteen waste along with addition of ammonium chloride was carried out in Digester 1 while AD of only canteen waste was carried out in Digester 2. The amount of biogas produced in Digester 1 was in the range of 0.04 m3/kg–0.075 m3/kg, while in Digester 2 the volume range was 0.02 m3/kg–0.04 m3/kg. The average biogas produced in digester 1 consisting of canteen waste and nitrogen source was 0.053 m3/kg while biogas production in digester 2 with only canteen waste was 0.030 m3/kg. So, biogas produced by addition of nitrogen source was 77 % higher than that of only canteen waste. From this study we obtained a higher amount of biogas by addition of ammonium chloride as an external nitrogen source. Nitrogen demand of methanogens was fulfilled by additional supply of nitrogen resulting in increased quantity of biogas. Therefore, in anaerobic digestion addition of ammonium chloride was beneficial for food waste digestion. Hence, nitrogen content in canteen waste turned out to be the main parameter affecting anaerobic digestion of canteen waste which is justified in this research.