Co-digestion Of Kitchen Waste Research Articles

Comparison of anaerobic co-digestion of vacuum toilet blackwater and kitchen waste under mesophilic and thermophilic conditions: Reactor performance, microbial response and metabolic pathway

Co-digestion of kitchen waste (KW) and black water (BW) can be considered as an attractive method to efficiently achieve the clean energy from waste. To find the optimal operation parameters for the co-digestion, the effects of different temperatures (35 and 55 °C) and BW:KW ratios on the reactor performances, microbial communities and metabolic pathways were studied. The results showed that the optimum BW:KW ratio was 1:3.6 and 1:4.5 for mesophilic and thermophilic optimal reactors, with methane production of 449.04 mL/g VS and 411.90 mL/g VS, respectively. Microbial communities showed significant differences between the reactors under different temperatures. For bacteria, increasing BW:KW ratio significantly promoted Defluviitoga enrichment (1.1%–9.5%) under thermophilic condition. For Archaea, the increase in BW:KW ratio promoted the enrichment of Methanosaeta (8.6%–56.4%) in the mesophilic reactor and Methanothermobacter (62.0%–89.2%) in the thermophilic reactor. The analysis of the key enzymes showed that, acetoclastic methanogenic pathway performed as the dominant under mesophilic condition, with high abundance of Acetate-CoA ligase (EC:6.2.1.1) and Pyruvate synthase (EC:1.2.7.1). Hydrogenotrophic methanogenic pathway was the main pathway in the thermophilic reactors, with high abundance of Formylmethanofuran dehydrogenase (EC:1.2.99.5).

Anaerobic Co Digestion of Kitchen Waste With Cattle Dung and Poultry Manure A Means to Overcome The Problems of Anaerobic Mono Digestion and Improve The Production of Biogas

Anaerobic Co Digestion of Kitchen Waste With Cattle Dung and Poultry Manure A Means to Overcome The Problems of Anaerobic Mono Digestion and Improve The Production of Biogas

Hydrogen and Methane Production in a Two-Stage Thermophilic Anaerobic Digestion System by Co-Digestion of Kitchen Waste and Municipal Sewage Sludge with a High Solid Content

The thermophilic anaerobic fermentation of mixed materials for simultaneously producing biohydrogen and methane has become a research hotspot. In this study, thermally treated kitchen waste (KW) and municipal sewage sludge (MSS) were used as substrates for a thermophilic two-stage anaerobic digestion process. The effects on gas production performance were investigated in both the hydrogen-producing stage and methane-producing stage under different organic load rates (OLRs). The production rates, volume, removal rates, and energy yields of volatile solids (VS) were optimal under higher OLRs for both the hydrogen (OLR = 12.5 g VS/L·day) and methane stages (OLR = 5 g VS/L·day). These conditions also provided the optimal average removal rate and total energy yield of VS for the entire anaerobic fermentation system (65.4% and 30.9 kJ/g VS, respectively). Overall, the results demonstrate the superior efficiency of VS removal and hydrogen and methane production in a two-stage thermophilic anaerobic co-digestion of KW and MSS with a high solid content under proper material mix ratio and higher OLRs. This study provides the basis for material mass ratio, mixtures' pretreatment, and operation control for future pilot tests.

Enhancement mechanisms of iron powder on co-digestion of kitchen waste and Pennisetum hybrid

To investigate iron enhanced anaerobic digestion performance, a survey was conducted to examine how iron powder (IP) affected the stability of a co-digestion reactor for kitchen waste and Pennisetum hybrid in a semi-continuous mode. In addition, the mechanisms underlying this process were analyzed according to various parameters and microbial communities. The results showed that the maximum stable operational organic loading rate (OLR) for the IP reactor increased by 50% compared to that of the control reactor, while the specific methane yields and volumetric methane yields increased by 4.8%− 106.8% and 6.3%− 105.9%, respectively, when OLRs were 1.0–3.0 g VS/(L·d). Meanwhile, selective enrichment of propionate-utilizing bacteria and hydrogenotrophic methanogens may have promoted the conversion of volatile fatty acids while increasing gene abundance via a methane-forming pathway. The addition of IP changed the dominant microorganisms related to the methanogenesis pathway. Additionally, the occurrence of interspecies formate transfer promoted anaerobic digestion stability in the IP reactor.

Bi-level multi-objective programming approach for bioenergy production optimization towards co-digestion of kitchen waste and rice straw

The increase in kitchen waste (KW) generation and irresponsible rice straw (RS) disposal has accentuated problems regarding environmental pollution and resource wasting. Although anaerobic co-digestion has been shown to be a more efficient strategy for bioenergy production than single digestion, there is still significant resistance to its application and diffusion owing to RS collection and many related factors in practice. Therefore, this study proposes a cooperative scheme for the cross-regional problem involving authorities and disposal plants. Subsequently, a bi-level multi-objective programming is developed to express the complexity of conflicts relationship in a multi-hierarchical problem and to achieve economic development, environmental protection and societal satisfaction in the bioenergy optimization process. A practical case study is then investigated to demonstrate the applicability of methodology in co-digestion deployment and resource recovery improvement, whereby scenario analyses are conducted by adjusting associated parameters. The practical application observed that (1) RS purchase was positively correlated with carbon reduction and social satisfaction targets, while excessive pursuit of social satisfaction resulted in a rebounding of carbon emissions; (2) the most popular mix ratios in disposal plants were 4:1 and 3:1, but they favor the latter when RS is readily available in sufficient quantities. Finally, some targeted suggestions are proposed for all stakeholders, which are expected to be a reference for potential users in other areas.

Co-Digestion of Kitchen Waste with Grass and Leaves after Hyperthermophilic Pretreatment for Methane and Hydrogen Production

The study investigated co-digestion batch experiments using kitchen waste (KW) and garden waste (GW) collected from individual households. Grass and leaves were first subjected to a 3-day hyperthermophilic pretreatment at 70 °C and 80 °C and then co-digested with kitchen waste at 35 °C and 55 °C. The hyperthermophilic pretreatment resulted in the solubilization of organic material with the release of fatty acids, whereas the biogas yield was negligible. In the second stage, the greatest methane yield of 387 NmL/gVS was achieved for the mono-digestion of leaves, whereas the co-digestion of grass with 50% KW gave the highest hydrogen production of 88 NmL/gVS. Considering the overall process performance, the best operating conditions were established using a 3-day hyperthermophilic pretreatment at 70 °C, followed by co-digestion at 55 °C in the second stage for the mixture of 25% garden waste with 75% KW.

Biogas production from anaerobic co-digestion using kitchen waste and poultry manure as substrate-part 1: substrate ratio and effect of temperature.

The rapidly declining fossil fuels are no longer able to meet the ever-increasing energy demand. Moreover, they are considered responsible for greenhouse gas (GHG) emission, contributing to the global warming. On the other hand, organic wastes, such as kitchen waste (KW) and poultry manure (PM), represent considerable pollution threat to the environment, if not properly managed. Therefore, anaerobic co-digestion of KW and PM could be a sustainable way of producing clean and renewable energy in the form of biogas while minimizing environmental impact. In this study, the anaerobic co-digestion of KW with PM was studied to assess the rate of cumulative biogas (CBG) production and methane percentage in four digester setups (D1, D2, D3, and D4) operated in batch mode. Each digester setup consisted of five parallelly connected laboratory-scale digesters having a capacity of 1 L each. The digester setups were fed with KW and PM at ratios of 1:0 (D1), 1:1 (D2), 2:1 (D3), and 3:1 (D4) at a constant loading rate of 300 mg/L with 50 gm cow manure (CM) as inoculum and were studied at both room temperature (28 °C) and mesophilic temperature (37 °C) over 24 days. The co-digestion of KW with PM demonstrated a synergistic effect which was evidenced by a 16% and 74% increase in CBG production and methane content, respectively, in D2 over D1. The D3 with 66.7% KW and 33.3% PM produced the highest CBG and methane percentage (396 ± 8 mL and 36%) at room temperature. At mesophilic condition, all the digesters showed better performance, and the highest CBG (920 ± 11 mL) and methane content (48%) were observed in D3. The study suggests that co-digestion of KW and PM at mesophilic condition might be a promising way to increase the production of biogas with better methane composition by ensuring nutrient balance, buffering capacity, and stability of the digester.

Application of the single-stage anaerobic membrane bioreactor (1S-AnMBR) for the co-digestion of organic kitchen waste and sewage

In the scenario of sustainable technology application, the minimization of waste and resource consumption are more fundamental compared to effluent quality. In recent years, many kinds of researches related to green technology in wastewater treatment have been conducted, such as constructed wetland, membrane bioreactor, etc. With the same perception, the co-digestion of kitchen waste and sewage study was carried out. The principle of this environmentally friendly technology is to create a low-cost pretreatment for domestic wastewater, by taking advantage of the organic carbon available in the leftovers to remove contaminants in the wastewater, improve water quality, reduce excess sludge and save money. The study is aimed to evaluate the carbon and nutrient recovery of a laboratory single-stage anaerobic membrane bioreactor (1S-AnMBR), which included an Up-flow Anaerobic Sludge Blanket (UASB) continuous with an UF membrane bioreactor. The result shown that the obtained COD removals were above 80% at all organic loading rates (OLRs). The effluent COD concentrations were 160±21, 227±45, 340±78, 563±104 and 886±96 mg.L-1 at OLRs of 0.9 to 1.5; 2.0; 3.5; 5.0 and 7.0 kg COD.m-3.day-1, respectively. The biogas yields collected were 1119±76, 1550±68, 2155±80, 3610±86 and 5989±88 mL.day-1 at OLRs of 0.9; 1.5; 2.0; 3.5; 5.0 and 7.0 kg COD.m-3.day-1. High performance of ammonia conversion from organic nitrogen was obtained in the AnMBR. Total nitrogen and phosphorus losses were 12% and 15%, respectively. Transmembrane pressure (TMP) increased to the pressure limit of 45kPa after 11 days of operation at OLR of 5 kg COD.m-3.d-1. Thus membrane fouling is a big challenge for AnMBR. Besides these promising research outcomes, the technology is expected to bring convincing results into practice in the co-digestion of solid wastes and sewage that may be suitable for rural or remote areas, in which solid waste and sewage collection systems are not available.

Methane production from anaerobic mono- and co-digestion of kitchen waste and sewage sludge: synergy study on cumulative methane production and biodegradability

Globally, kitchen waste (KW) and sewage sludge (SS) are two important forms of organic wastes that need immense attention during handling and management. As the characteristics and components of KW vary significantly with respect to location and season, it is often difficult to understand the behavior of KW during the (co-)digestion process. Therefore, this study aimed to investigate the synergistic influence of KW over SS and vice versa during anaerobic (co-)digestion. Anaerobic mono-digestion and co-digestion of SS and KW, considering three different mixing ratios SS:KW; (SK1–25:75, SK2–50:50, SK3–75:25), was conducted to investigate their specific methane yields (SMY) and biodegradability (BD). The modified Gompertz equation was used to estimate the theoretical methane potential and used as a reference for experimental data assessment. The results demonstrated that SMYs were 212 and 368 L kg−1 VSadded for SS, and KW, respectively. Under the category of co-digestion, sample SK2 (SS:KW; 50:50) had the highest BD of 91% as compared to digestion of SS (61%) and KW (74.9%) separately. A synergistic effect on methane production was witnessed with all ratios and the maximum was noticed with SK2, ca. 40%, which can be ascribed to the enhanced hydrolysis because of the addition of KW, which is readily degradable by nature. Further, this study could be used as guidelines to the design and optimization of the co-digestion process.

Influence of pH controlling on fermentation performance in kitchen waste and cow manure

ABSTRACT In order to make the process more sustainability and more efficient in co-digestion of kitchen waste (KW) and cow manure (CM), the effect of pH controlling at initial fermentation time (I), first gas stagnation time (A), and combination of both times (C) were investigated. Five pH values (6.5, 7.0, 7.5, 8.0 and 8.5) were set in each case to find out the optimal way of pH regulation with the consideration of changes in biogas and methane production, volatile solid (VS) reduction, and lag-phase time. The results show that adjusting pH of the co-digestion system could significantly improve biogas production except when pH was set to 6.5 in groups I and A. Adjusting pH twice (group C) could increase the system stability. When pH value was set to 7.5 twice, highest methane production (16501.10 mL), the highest methane yield of 287.64 mL/g VSadded, and a relatively short lag-phase time (27.3d) were obtained by C7.5.

Performance Evaluation of Biogas Yields Potential from Co-Digestion of Water Hyacinth and Kitchen Waste

Solid wastes are generated and dump indiscriminately in Nigeria due to poor implementation of standards, thus causing environmental and public health hazards. Nigeria generates more than 32 million tons of solid waste annually, out of which only 20-30% is collected and disposed in an open dump site. Different researchers have reported that organic waste fraction of solid waste generated in Nigeria has the highest percentage which is over 50%. However, this fraction of organic waste is yet to be properly utilized for biogas production. This research work is focused on the performance evaluation of biogas potential yields from co-digestion of kitchen wastes and water hyacinth. A 0.030m3 anaerobic mild steel digester was fabricated and used to digest the composition of water hyacinth and kitchen wastes. The experiment was conducted under mesophilic temperature range and a pH range of 6.0-7.4. The results obtained show that a cumulative biogas yield of 0.0499m3 was obtained from 30kg of substrates composition of kitchen waste and water hyacinth. Besides, optimum biogas yields were obtained at optimum mesophilic temperature.

Performance Evaluation of Biogas Yields Potential from Co-Digestion of Water Hyacinth and Kitchen Waste

Solid wastes are generated and dump indiscriminately in Nigeria due to poor implementation of standards, thus causing environmental and public health hazards. Nigeria generates more than 32 million tons of solid waste annually, out of which only 20-30% is collected and disposed in an open dump site. Different researchers have reported that organic waste fraction of solid waste generated in Nigeria has the highest percentage which is over 50%. However, this fraction of organic waste is yet to be properly utilized for biogas production. This research work is focused on the performance evaluation of biogas potential yields from co-digestion of kitchen wastes and water hyacinth. A 0.030m3 anaerobic mild steel digester was fabricated and used to digest the composition of water hyacinth and kitchen wastes. The experiment was conducted under mesophilic temperature range and a pH range of 6.0-7.4. The results obtained show that a cumulative biogas yield of 0.0499m3 was obtained from 30kg of substrates composition of kitchen waste and water hyacinth. Besides, optimum biogas yields were obtained at optimum mesophilic temperature.

LAB-SCALE STUDY ON CO-DIGESTION OF KITCHEN WASTE, SLUDGE AND SEWAGE

Anaerobic digestion is widely used for biodegradable solid organic wastes in order to recover bio-energy in the form of biogas. Some previous studies presented that co-digestion of various substrates can improve biogas yields as well as enhanceperformance of organic wastes digestion, in comparison with digestion of sole solid waste. This study aimed to evaluate the performance of anaerobic mono-digestion and anaerobic co-digestion of the following mixtures: (a) sole kitchen waste (KW), (b) KW and sewage (SW), (c) sole sludge (SL)and (d) KW and SL. This study was conductedby four lab-scale anaerobic complete mixing reactors (numbered MH1 – MH4) in 4,5 liters working volume atorganic loading rate (OLR) 2,0 g(VS).L-1.d-1. The KW was collected from canteen B4 and SW was collected from effluent from septic tank C6 Building in Ho Chi Minh University of Technology (HCMUT). The results show that the reactor of sole KW obtained average total chemical oxygen demand (tCOD), soluble chemical oxygen demand (sCOD), total solid (TS), volatile solid (VS), total phosphorus (TP) and total Kjeldahl nitrogen (TKN) of 62 %, 62 %, 71 %, 72 %, 73 % and 45 %, respectively, whereas reactor of KW and SW co-digestion had were tCOD, sCOD, TS, VS, TP and TKN removal of 73 %, 78 %, 75 %, 79 %, 59 % and 57 %, respectively. Thus co-digestion of KW and SW revealed an efficient enhancement of digestion, instead of sole KW digestion. Similarly, TS (74 %) and VS removals (75 %) of co-digesting mixtures of SL and KW were higher than those of sole SL digestion (67 %). Furthermore, co-digestion of SL and KW obtained better performance in tCOD and sCOD removals (70 % and 76 %, respectively).

Anaerobic co-digestion of kitchen waste and wastewater sludge: biogas-based power generation

ABSTRACTAnaerobic co-digestion of kitchen waste (KW) and wastewater sludge (WS) at different total solids ratios of 1:0, 1:1, 0:1 was conducted under mesophilic temperature conditions (35 ± 1 °C). The co-digestion of kitchen waste and wastewater sludge showed enriched methane gas generation when compared with individual anaerobic digestion of kitchen waste and wastewater sludge individually. The optimum ratio of kitchen waste to wastewater sludge was 1:1. The methane gas yield at 1:1 loading of kitchen waste to wastewater sludge was 43.6%. The total nitrogen content for sludge was 1820 mg/kg. The total nitrogen content of blended was 2180 mg/kg. Cr, Cd, Pb, Mg and Zn were in the kitchen waste and wastewater sludge.

Effect of initial pH on anaerobic co-digestion of kitchen waste and cow manure

This study investigated the effects of different initial pH (6.0, 6.5, 7.0, 7.5 and 8.0) and uncontrolled initial pH (CK) on the lab-scale anaerobic co-digestion of kitchen waste (KW) with cow manure (CM). The variations of pH, alkalinity, volatile fatty acids (VFAs) and total ammonia nitrogen (NH4+–N) were analyzed. The modified Gompertz equation was used for selecting the optimal initial pH through comprehensive evaluation of methane production potential, degradation of volatile solids (VS), and lag-phase time. The results showed that CK and the fermentation with initial pH of 6.0 failed. The pH values of the rest treatments reached 7.7–7.9 with significantly increased methane production. The predicted lag-phase times of treatments with initial pH of 6.5 and 7.5 were 21 and 22days, which were 10days shorter than the treatments with initial pH of 7.0 and 8.0, respectively. The maximum methane production potential (8579mL) and VS degradation rate (179.8mL/g VS) were obtained when the initial pH was 7.5, which is recommended for co-digestion of KW and CM.

Anaerobic co-digestion of kitchen waste and pig manure with different mixing ratios

Anaerobic co-digestion of kitchen waste (KW) and pig manure (PM) with seven different PM to KW total solids (TS) ratios of 1:0, 5:1, 3:1, 1:1, 1:3, 1:5 and 0:1 was conducted at mesophilic temperature (35 ± 1 °C) to investigate the feasibility and process performance. The co-digestion of PM and KW was found to be an available way to enhance methane production compared with solo-digestion of PM or KW. The ratio of PM to KW of 1:1 got the highest biodegradability (BDA) of 85.03% and a methane yield of 409.5 mL/gVS. For the co-digestion of KW and PM, there was no obvious inhibition of ammonia nitrogen because it was in an acceptable range from 1380 mg/L to 2020 mg/L in the whole process. However, severe methane inhibition and long lag phase due to the accumulation of volatile fatty acids (VFAs) was observed while the KW content was over 50%, and in the lag phase, propionic acid and butyric acid made up the major constituents of the total VFAs. The technical digestion time (T80: the time it takes to produce 80% of the digester's maximum gas production) of the above 7 ratios was 15, 21, 22, 27, 49, 62 and 61 days, respectively. In this study, a mixing ratio of 1:1 for PM and KW was found to maximize BDA and methane yield, provided a short digestion time and stable digestion performance and was therefore recommended for further study and engineering application.

Effect of co-managing organic waste using municipal wastewater and solid waste treatment systems in megacities

A model was developed to calculate the mass and heat balances of wastewater and municipal solid waste treatment plants when these plants operate either separately or together with a mutual dependence on mass and energy. Then the energy consumption, life cycle costs (LCCs), greenhouse gas (GHG) emissions and effluent quality were evaluated under various scenarios to identify the most effective co-management and treatment system. The results indicated that co-digestion of kitchen waste and sewage sludge, and their co-combustion reduced LCCs by 30%, energy consumption by 54% and GHG emissions by 41% compared to the base case. However, co-digestion increased the total nitrogen load in the wastewater treatment plant effluent. Even if an advanced wastewater treatment system was applied to improve total nitrogen concentration, the above indicators were affected but still reduced compared to the base case. Therefore, it was confirmed that the integrated system was beneficial for megacities.

Evaluating Methane Production from Anaerobic Mono- and Co-digestion of Kitchen Waste, Corn Stover, and Chicken Manure

Anaerobic mono- and co-digestion of kitchen waste (KW), corn stover (CS), and chicken manure (CM) under mesophilic (37 °C) conditions were conducted in batch mode with the aim of investigating the biomethane potential (BMP), biodegradability, methane production performance, and stability of the process. An initial volatile solid concentration of 3 g VS L–1 with a substrate-to-inoculum (S/I) ratio of 0.5 was first tested, and two S/I ratios of 1.5 and 3.0 were evaluated subsequently. The modified Gompertz equation was used to assist in the interpretation of the conclusions. The results showed that BMP and specific methane yields were 725 and 683 mL g–1 VSadded for KW, 470 and 214 mL g–1 VSadded for CS, and 617 and 291 mL g–1 VSadded for CM, respectively. Therefore, KW had the highest biodegradability of 94% as compared with CS (45%) or CM (47%). For KW mono- and co-digestion with CS, CM, or their mixture, methane production performance was better at an S/I ratio of 1.5 than that of 3.0. For CS, CM, and their mixture, S/I ratios of both 1.5 and 3.0 were suitable. A synergistic effect was found in the co-digestion process, which was mainly attributed to a proper carbon-to-nitrogen ratio and the reduced total volatile fatty acids-to-total alkalinity ratio, thus providing better buffering capacity and supporting more microorganisms for efficient digestion.

Co-digestion of kitchen waste and fruit–vegetable waste by two-phase anaerobic digestion

The high salinity and fat contents of kitchen waste (KW) inhibits the effect of two-phase anaerobic digestion system. This research introduces fruit-vegetable waste (FVW) to alleviate the inhibition effect caused by salinity and fat concentrations, and tries to achieve an optimal addition ratio of FVW, an optimal hydraulic remain time (HRT) of acidogenic-phase reactor and methanogenic-phase reactor. A two-phase anaerobic digestion (AD) system was developed to co-dispose KW and FVW. Four sets of experiments were run with different mass proportions between KW and FVW (25-75, 50-50, 75-25, and 100-0% m/m). Considering the biodegradation rate and the acidification degree, the system with 25% KW had the best performance during the acidogenic phase. When the system was run with 50% KW, it not only had the best stability performance but also had a bigger capacity to treat KW than the system with 25% KW. The system with 50% KW was the best ratio in this two-phase AD system. Co-digestion of KW and FVW by two-phase AD is feasible. The addition of FVW can reduce the inhibition effect caused by salinity and fat concentrations, reduce the HRT, and lead to a higher degree of acidification.