Co-digestion Of Food Waste Research Articles

Temperature Effect on Biogas Production from Co-digestion of Food Waste, Potash and Cow Dung

Temperature influence on biogas production from co-digestion of substrate (food waste, potash and cow dung) was investigated. Different concentrations of the substrate (4% to 12%) were mixed and loaded into the anaerobic digesters to produce biogas. Results of temperature effects on the biogas volume indicated that as the days of production increased, the temperature in the digesters increases and the volume of the biogas produced also increased. For digester B1 to B5, the temperature increase ranged from 10.1 to 44.5oC while the volume of the biogas produced increased from 11.3 to 25.9; 15.3 to 30.9; 10.1 to 34.5; 18.5 to 36.0 and 18.8 to 36m3/day for digesters B1, B2, B3, B4 and B5 respectively. For digesters B6 to B9, the temperature increase ranged from 20.6 to 48.4oC while the volume of the biogas produced increased from 22.1 to 40.2; 20.6 to 41.5; 24.9 to 42.0 and 24.2 to 42.5m3/day for digesters B6, B7, B8 and B9 respectively. A total 17859.6m3 of biogas was generated for a period of 90 days. Average temperature ranges from 29.30 ± 3.00oC for digester B1 (4% concentration of sample) to 41.46 ± 4.33oC of digester B8 (11% concentration of sample). This result was further clarified from the Analysis of variance and multiple comparisons of the temperature which revealed that digesters B5, B8 and B9 had no significant difference among them. The correlation of temperature and volume of biogas generated by each digester revealed that temperature significantly influenced the quantity of biogas generated at P= 0.01 and r = 0.760 (B2G), r = 0.740(B3G), r = 0.721(B6G) and r = 0.650(B8G) showing relationship were significant and had a high relationship between temperature and the substrates.

High-solid co-digestion performance of lipids and food waste by mesophilic hollow fiber anaerobic membrane bioreactor

The co-digestion performance of mesophilic (37℃) hollow fiber anaerobic membrane bioreactor (HF-AnMBR) in treating high-solid lipids and food waste (FW) for 180 days was investigated. The organic loading rate (OLR) was increased from 2.33 to 14.64 g-chemical oxygen demand (COD) /L/d by increasing the lipids/FW from 10%, 30%, and 50% on dry based. The COD conversion efficiency for methane was 83.13%, 84.85%, 82.63%, and 84.30%, and the sludge growth rate was 0.001, 0.097, 0.065, 0.016 g TS/g COD at OLR of 2.33, 9.36, 12.76 and 14.64 g-COD/L/d, respectively. The COD, proteins, and carbohydrates concentrations in permeate were stable, with an average of 2.25, 0.50, and 0.18 g/L, respectively. The long-term stable performance of the HF-AnMBR indicated that this study will help guide application of the co-digestion of lipids and food waste.

Biochar-promoted methane production and mitigation of acidification during thermophilic anaerobic co-digestion of food waste with crude glycerol: comparison with re-inoculation

Food waste and crude glycerol were anaerobically co-digested for 100 days at 52 ± 1 °C with an organic loading rate of 1.0 g L−1 d−1. This long-term thermophilic anaerobic digestion (AD) system encountered severe inhibition from volatile fatty acids (VFAs). The study investigated the impacts of re-inoculation (RI) and biochar addition (BA) on this AD process, and monitored the variation of pH, VFAs, total alkalinity and total ammonia nitrogen during treatment. RI treatment was effective in the short term by recovering reactivity after inhibited sludge was mixed 1:1 with active inoculant. In the long term, RI could not reverse process imbalance and finally failed on day 56. Superior performance in methane production and process stability was observed in BA reactors when compared with control and RI reactors. Overall, the biochar contributed to alkalinity and facilitated the activation of methanogenesis and stimulated the conversion of VFAs.

Anaerobic co-digestion of yard waste, food waste, and pig slurry in a batch experiment: An investigation on methane potential, performance, and microbial community

Anaerobic co-digestion (ACoD) of organic fraction of municipal solid waste (OFMSW) appears to be an efficient approach for biomethane production. This study conducted ACoD of yard waste (YW), food waste (FW), and pig slurry at varying percentages of YW, and the corresponding evolution of microbial community structure was observed. The results demonstrated that methane productivity increased with decreasing YW content. After 45 days, the system with 20%YW feedstock had the highest productivity with a maximum cumulative methane yield of 368.6 ± 21.6 mL/gVS. Interestingly, our findings revealed important cellulose-degrading bacteria like Ruminofilibacter, Pantoea, and Blvii28 wastewater-sludge group, along with acetoclastic and hydrogenotrophic methane producers like Methanosaeta and Methanoculleus, respectively. The microbial community profile is a potential guideline for microbial enrichment to produce high-efficiency inoculum for biomethane production from yard, agriculture, and livestock waste.

Anaerobic Mono- and Co-digestion of Primary Sludge, Secondary Sludge and Food Waste: Biogas Production at Different Mixture Ratio

Anaerobic Mono- and Co-digestion of Primary Sludge, Secondary Sludge and Food Waste: Biogas Production at Different Mixture Ratio

Stoichiometry and energy assessment comparison between thermophilic and mesophilic high-solid anaerobic co-digestion of lipids and food waste

High-solid anaerobic co-digestion of lipids and food waste at different lipid/TS ratios was investigated with an HRT of 30 days under thermophilic and mesophilic conditions. By co-digestion with food waste with thermophilic and mesophilic anaerobic digestion systems, the organic loading rate of lipids achieved 2.33 g/L/d and 1.67 g/L/d and the degradation efficiency of lipids reached 87 % and 85 %, respectively. As the lipid/TS ratio increased from 10 % to 50 %, the methane content in the biogas significantly increased from 60 % to 65 %, and the average methane yield of thermophilic and mesophilic anaerobic co-digestion was 288 mL-CH4/g-COD and 275 mL-CH4/g-COD, respectively. Meanwhile, the COD removal (80 % and 79 %) and lipids degradation (87 % and 85 %) kept high efficiencies with both thermophilic and mesophilic systems. The difference performance was attributed to the different microbial yield coefficients under different temperatures. Furthermore, an increase in lipid/TS ratio in the substrate inevitably resulted in lower microbial yield coefficients due to the low cell synthesis efficiency of lipids. In order to clarify the distribution of organic elements, stoichiometric equations were also illustrated. From the aspect of energy assessment, it was suggested that the energy surplus of mesophilic anaerobic co-digestion was 9 % higher than that of thermophilic anaerobic co-digestion when the lipid/TS ratio was less than 50 %, although the anaerobic system was energy and economy positive under both thermophilic and mesophilic conditions.

Mitigation of the Toxicity of Capsaicin on Anaerobic Codigestion of Food Waste and Waste Activated Sludge Using Calcium Peroxide: A Comprehensive Analysis Using Computational and Biological Approaches

Increasing amounts of food waste with high concentrations of capsaicin are generated globally. Capsaicin concentration has been proven to inhibit methane production in the anaerobic codigestion process; thus, strategies to alleviate this toxicity are urgently needed. This study focuses on the use of calcium peroxide for alleviating the inhibitory effect of capsaicin and methane production promotion in anaerobic codigestion for the first time. Results show that calcium peroxide increases the rate of capsaicin degradation significantly. Based on active site prediction, degradation product identification, and density functional theory calculations, the main pathways of capsaicin degradation are verified to be O-demethylation and hydrogen abstraction. According to the quantitative structure–activity relationship, the main degradation products are less toxic than capsaicin. With an increase of calcium peroxide addition from 0 to 0.10 g/g VS (volatile solid), the methane yield and production rate are promoted from 174.92 ± 7.12 mg/g VS and 10.54 ± 0.32 mL/(g VS·d) to 307.56 ± 10.43 mg/g VS and 23.15 ± 0.72 mL/(g VS·d), respectively. This study provides insights into calcium peroxide-enhanced capsaicin degradation and demonstrates an effective niche to mitigate the capsaicin toxicity toward anaerobic codigestion.

A bi-level optimized approach for promoting the mixed treatment of municipal sludge and food waste.

The mixed treatment of municipal sludge and food waste can generate renewable energy, solve the environmental and economic challenges caused by this waste, and has attracted significant research attention. Using environmentally friendly anaerobic co-digestion of municipal sludge and food waste can improve the effects of anaerobic mono-digestion and produce more biogas. However, as the municipal sludge and food waste managers are different, balancing the interests of both managers is needed to encourage anaerobic co-digestion development. By fully considering the interests of the local authority, the waste water treatment plants, and the food waste anaerobic digestion treatment plants, this paper developed a bi-level optimization approach based on Stackelberg equilibrium theory to resolve the conflicts between the different stakeholders, in which uncertain parameters were used to describe the uncertainties. The proposed model was then applied to a real case in Chongqing, China, to test its practicality, and scenario analyses under different policy parameter values were conducted to provide guidance for local authorities, waste water treatment plants, and food waste treatment plants. The proposed approach was found to provide balanced strategies for all three stakeholders, increase the renewable energy output of municipal sludge and food waste treatment 14.2 times, and reduce carbon emissions by 50%, thereby protecting the environment and achieving a circular economy.

Co-digestion of food waste and hydrothermal liquid digestate: Promotion effect of self-generated hydrochars

Hydrothermal treatment (HTT) can efficiently valorize the digestate after anaerobic digestion. However, the disposal of the HTT liquid is challenging. This paper proposes a method to recover energy through the anaerobic co-digestion of food waste and HTT liquid fraction. The effect of HTT liquid recirculation on anaerobic co-digestion performance was investigated. This study focused on the self-generated hydrochars that remained in the HTT supernatant after centrifugation. The effect of the self-generated hydrochars on the methane (CH4) yield and microbial communities were discussed. After adding HTT liquids treated at 140 and 180 °C, the maximum CH4 production increased to 309.36 and 331.61 mL per g COD, respectively. The HTT liquid exhibited a pH buffering effect and kept a favorable pH for the anaerobic co-digestion. In addition, the self-generated hydrochars with higher carbon content and large oxygen-containing functional groups remained in HTT liquid. They increased the electron transferring rate of the anaerobic co-digestion. The increased relative abundance of Methanosarcina, Syntrophomonadaceae, and Synergistota was observed with adding HTT liquid. The results of the principal component analysis indicate that the electron transferring rate constant had positive correlationships with the relative abundance of Methanosarcina, Syntrophomonadaceae, and Synergistota. This study can provide a good reference for the disposal of the HTT liquid and a novel insight regarding the mechanism for the anaerobic co-digestion.

Impacts of organic loading rate and hydraulic retention time on organics degradation, interspecies interactions and functional traits in thermophilic anaerobic co-digestion of food waste and sewage sludge

This study provided novel insights into the effects of organic loading rate (OLR) and hydraulic retention time (HRT) on thermophilic anaerobic co-digestion of food waste and sewage sludge. The obtained maximum methane (CH4) yield of 328 ± 4 mL CH4/g CODfed at HRT of 15 days (OLR = 5.8 g VS/L/d) was partly attributable to the enhanced acidogenesis, acetogenesis, and methanogenesis phases. The increased key enzyme activities, particularly acetate kinase (improved by 5.2-fold), providing substantial methanogenic substrates for efficient CH4 production. The functional syntrophs that were related to syntrophic decarboxylation, novel acetate oxidation & reductive acetyl-CoA, and β-oxidation pathways could drive trophic interactions with methanogens. This markedly stimulated hydrogenotrophic Methanoculleus thermophilus metabolism and concomitantly enriched mixotrophic Methanosarcina thermophila. The distinctive cross-feeding interspecies interactions significantly affected the assembly and dynamics of thermophilic consortia. These findings shed light on the physicochemical and microbial mechanisms of HRT- and OLR-dependent enhancement of methanogenesis.

Intermittent energization improves microbial electrolysis cell-assisted thermophilic anaerobic co-digestion of food waste and spent mushroom substance

Microbial electrolysis cell-assisted thermophilic anaerobic digestion (MEC-TAD) is a promising method to improve anaerobic co-digestion efficiency; however, its application is restricted by high energy consumption. To improve the energy use efficiency of MEC-TAD, this study investigated the effect of different intermittent energization strategies on thermophilic co-digestion performance. Results revealed that an 18 h-ON/6h-OFF energization schedule resulted in the fastest electron transfer rate and the highest methane yield (364.3 mL/g VS). Mechanistic analysis revealed that 18 h-ON/6h-OFF resulted in the enrichment of electroactive microorganisms and increased abundance of enzyme-coding genes associated with energy metabolism (ntp, nuo, atp), electron transfer (pilA, nfrA2, ssuE), and the hydrogenotrophic methanogenic pathway. Finally, energy balance analysis revealed that 18 h-ON/6h-OFF had the highest net energy benefit (2.52 kJ) and energy conversion efficiency (110.76 %). Therefore, intermittent energization of MEC-TAD using an 18 h-ON/6h-OFF schedule can provide improved performance and more energy savings.

Co-digestion of food waste with cow dung by anaerobic digestion for biogas production.

Food waste is categorized under household waste which were produce in large amount every day and it can be a good potential to generate biogas production via anaerobic digestion. In this research, the characteristics of co-digestion process are measured to determine the biogas production between food waste and cow dung. The food waste is co-digest with two different type of cow dung are collected depends on their food consuming (grass:bran); 100% grass and 95% grass : 5% bran. The digester is maintained at 35°C of temperature for mesophilic condition. pH values and C/N ratio are noted until 35 days. The biogas production is analysed by using biogas analyzer. The highest biogas production in this study is 67.2% which are co-digest between food waste and cow dung (100%) compared cow dung (95%) is 53.9% on day 26. This shows that the cow dung (100%) produces more biogas than cow dung (95%). Anaerobic digestion process will best suits for biogas production and for the best utilization of food waste.

Enzyme pretreatments for anaerobic co-digestion of food waste blended with bioplastics: effects on methane production and microbial community structure

Bioplastic bags mixed with food waste seem inevitable with the growth of waste classification and the banning of non-biodegradable polymers in China.

Influence of inoculum-to-substrate ratio on biogas enhancement during biochar-assisted co-digestion of food waste and sludge

ABSTRACT High accumulation of volatile fatty acids (VFAs) is one of the major concerns during mesophilic anaerobic co-digestion of food waste (FW) and sewage sludge (SS). Therefore, improving the stability of the anaerobic digestion process could surpass quick acidification while accelerating methanogenesis. In this study, the suitability of biochar-assisted co-digestion was evaluated at different inoculum and substrate ratios (I/S ratios: 0.1, 0.3, 0.6, and 0.9). The maximum methane yield of 256.85 mL/gVSadd was observed at an I/S ratio of 0.6. The results indicated fast volatile solid removal (∼ 47.17% to 73%) and a critical role of biochar addition in alleviating the underlying inhibitions. Substantial changes in the microbial community composition including Methanosata, Methanobrevibacter, and Methanosarcina were also observed which predominated and stabilised the methanogenesis process at higher I/S ratios. These results emphasised that the anaerobic co-digestion of FW/sludge is a promising approach, wherein the biochar amendment at different I/S ratios should be well maintained to avoid inhibitions from excess microbial VFA acidification of organic waste feedstocks.

Co-digestion of food waste recycling wastewater with thermally hydrolized sewage sludge for the improvement of anaerobic treatment efficiency

Co-digestion of food waste recycling wastewater with thermally hydrolized sewage sludge for the improvement of anaerobic treatment efficiency

Assessment of Microbial Diversity during Thermophilic Anaerobic Co-Digestion for an Effective Valorization of Food Waste and Wheat Straw

In this study, predominant bacterial and archaeal populations and their roles during anaerobic mono-digestion of food waste (FW) and co-digestion of FW with straw pellets (SP) at thermophilic temperature (53 ± 1 °C) were assessed by Next Generation Sequencing (NGS) analysis at organic loading rates (OLRs) of 3.0 and 7.0 gVS/L/d. Depending on the seed; results revealed that Firmicutes, Bacteroidetes, and Proteobacteria were, respectively the most prevalent bacterial phyla at both OLRs investigated. On the other hand, Euryarchaeota was dominated by methanogens playing crucial role in biogas production and correlated mainly with the activities of Methanobacteria and Methanomicrobia at class level. Acetoclastic Methanosaetae was the predominant genus at OLR = 3.0 gVS/L/d; however, shared the same predominance with hydrogenotrophic methanogens Methanospirillium at the highest OLR. Although no clear effect in response to straw addition at OLR of 3.0 gVS/L/d could be seen in terms of methanogenic archaea at genus level, hydrogenotrophic methanogens revealed some shift from Methanobacterium to Methanospirillium at higher OLR. Nevertheless, no prominent microbial shift in the presence of wheat straw at increased OLR was likely due to adapted inoculation at start-up which was also demonstrated by relatively stable biogas yields during co-digestion.

Co-digestion of domestic kitchen food waste and palm oil mill effluent for biohydrogen production

Biohydrogen production from organic waste not only provides a sustainable way to produce biofuel but it also resolves the growing environmental concerns associated with agro-industrial waste. This research study investigated the biological hydrogen production potential in batch mode through co-digestion of domestic kitchen food waste (DKFW) and palm oil mill effluent (POME) under mesophilic conditions by immobilized Bacillus anthracis bacterial strain. The results showed that hydrogen production from co-digestion of DKFW and POME with an equal proportion of the combination is pH and temperature-dependent. Where, the elevated pH from 4.0 to 5.0 increases hydrogen production significantly; however, increasing the pH > 5.0 reduces productivity. Similarly, by raising the operating temperature from 25 °C to 35 °C the hydrogen production rate (HPR) increases up to 67 mL/h. Apart from hydrogen production, a reduction in chemical oxygen demand (COD) was observed by up to 72 % in this study. The improvement observed for HPR and a significant reduction in COD, suggests that the co-digestion of POME and DKFW is an ideal substrate for hydrogen production at operational temperatures and initial pH of 35 °C and 5.0, respectively. The strategy for utilizing the different organic waste together as a substrate provides a new avenue for the complex substrate for bioenergy production.

Co-digestion of food waste and cellulose-based bioplastic: From batch to semi-continuous scale investigation

Only few studies on the behaviour of bioplastics in anaerobic co-digestion could be found in literature and most of them are conducted in batch mode. Despite the fact that continuous experiments confirm or add new insight to the findings acquired from batch ones, there is still lack of such studies. This work aims to cover this gap, carrying out a semi-continuous anaerobic co-digestion of food waste and cellulose acetate (which its behaviour under anaerobic environment is also quite unexplored). After a first evaluation of the potential methane production from each substrate at batch scale, the semi-continuous co-digestion of food waste and cellulose acetate was carried out in three configurations. During the semi-continuous process, a methane yield of 331 NmlCH4/gVS was generated from the co-digestion of food waste and cellulose acetate while bioplastics specimens achieved a weight loss of about 45 %. The results were both lower than the one obtained from batch co-digestion, although methane production rates were comparable regardless of being fed with or without bioplastics. An increase was registered after 65 days of semi-continuous process, due to the accumulation of CA specimens. This confirms the different degradation trends between bioplastics and food waste.

Performance Comparison of CSTR and CSFBR in Anaerobic Co-Digestion of Food Waste with Grease Trap Waste

In this study, a newly established bench-scale thermophilic continuously stirred fluidized bed reactor (CSFBR) was applied for anaerobic co-digestion of food waste (FW) with grease trap waste (GTW). The performance of CSFBR regarding stability and treatment efficiency was inspected through a laboratory contrast experiment with two traditional continuous stirred tank reactors (CSTRs). In the OLR range of 3.19–7.41 g COD/L/d, the methane production rate of the thermophilic CSFBR was about as high as that of the thermophilic CSTR. Nevertheless, the thermophilic CSFBR had much lower VFAs (<1000 mg/L) and LCFA concentrations (<100 mg/L) as compared with the thermophilic CSTR. Unlike the mesophilic CSTR, there was no foaming that occurred in the CSFBR during the whole experimental period. The results all suggested that CSFBR simultaneously provided high treatment capacity and process stability in anaerobic digestion with high-lipid loading.

Anaerobic Co-Digestion of Bioplastics and Food Waste under Mesophilic and Thermophilic Conditions: Synergistic Effect and Biodegradation

To mitigate the various problems caused by using conventional plastics, bioplastic (BP) has emerged as a substitute for plastics. BP wastes after use are commonly treated using composting, causing many environmental problems. Anaerobic digestion (AD) has become prominent as an alternative method of producing renewable energy. The aim of this study was to estimate the methane production yield (MPY) of BPs (polylactic acid (PLA) and polyhydroxyalkanoate (PHA)) with mechanical pretreatment (particle size < 0.5 cm) and investigate the effect of co-digestion of BPs and food waste (FW). Batch experiments were conducted under mesophilic and thermophilic conditions at various mixing ratios (FW/PLA or PHA = 95:5 and 90:10 on a weight basis). During 20 d of digestion at temperatures of 37 and 55 °C, MPYs of PHA were 153.8–172.0 mL CH4/g chemical oxygen demand (COD), but that of PLA was significantly low (<25.6 mL CH4/g COD). Higher MPYs were attained at 55 °C than at 37 °C. The synergistic effects of FW addition on BP AD were observed at both temperatures, especially at 55 °C. By comparing theoretical (based on mono-digestion results) and actual (based on co-digestion results) MPYs, the synergistic effect of FW addition on MPY of co-digestion reached 8.5–26.6% and 12.7–25.5% for PLA- and PHA-fed tests, respectively. The biodegradation rates (on a volatile solids (VS) basis) of PLA and PHA were 6.0–13.7% and 49.1–52.3% and increased by 1.8–4.3 and 1.2–1.5 times in the PLA- and PHA-fed co-digestion tests, respectively. Co-digestion of FW might be a feasible treatment option for BPs combined with simple mechanical pretreatment.