Ratio Of Food Waste Research Articles

Synergistic effects of rice straw and rice bran on enhanced methane production and process stability of anaerobic digestion of food waste

This study investigated the synergistic effects of rice straw (RS) and rice bran (RB) addition on methane production and process stability of anaerobic digestion of food waste (FW). Positive synergistic effect (Synergy index (SI) = 1.03–1.24 > 1) was noticed in all the co-digestion reactors. The optimum mixing ratio of FW:RS:RB (volatile solid (VS) basis) was 60:10:30 with the maximum SI (1.24), achieving 27.4% increase in methane yield (235.4 mL/g-VS) and around 5 days shorter of λ (3.7 days) compared to the mono-digestion of FW (184.8 mL/g-VS and 8.2 days). Remarkably high concentration of volatile fatty acids (VFAs) was also accumulated in the mono-digestion of FW, especially propionic acid, which to a great extent caused the methane production to stagnate. Results from this study demonstrate that co-digestion of FW and RS with RB has high potentials for energy recovery from AD of the mixed feedstocks and its stable operation.

Effect of co-digestion of food waste and cow dung on biogas yield

This paper aims at finding the effect of co-digestion of cow dung and food waste on total biogas yield. Biogas production was improved through co-digestion of cow dung and food waste (FW) containing a small fraction of inoculum under mesophilic temperature (37ºC) over a retention time of 24 days. Co-digestion ratios of 1:1, 2:1 and 3:1 for cowdung/foodwaste were used for the study on anaerobic digestion on the co digested matter. Tests were carried out starting with the preparation of substrates, substrate characterization to determine the moisture content (MC), total solids (TS), volatile solids (VS) and ultimately batch anaerobic digestion experiments under thermophilic conditions (370C). The moisture content, volatile solids and total solids for food waste were 78, 22 and 90.7% respectively while the characteristics for cow dung were 67.2, 32.8 and 96.0 % respectively. From the study, a mixing ratio of cow dung: food waste of 1:2 was found to be the optimum substrate mixture for biogas production at 25595.7 Nml. The accumulated gas volumes of 18756.6, 14042.5, 13940.8 and 13839.1 Nml were recorded for cow dung: food waste ratios of 2:1, 1:1, 1:3 and 3:1 respectively. For a co-digestion containing more of the food waste than cow dung, a higher volume of biogas is produce.

Enhanced biomethane recovery from fat, oil, and grease through co-digestion with food waste and addition of conductive materials

In this study, the effect of conductive additives on co-digestion of fat, oil, and grease (FOG) and food waste (FW) was evaluated. Initially, biochemical methane potential (BMP) test was conducted for optimization of mixing ratio of FW and FOG. The optimal methane production (800 L (kg VS)−1) was obtained from co-digestion of 70% FW + 30% FOG (w/w), which was 1.2 times and 12 times of that obtained from mono-digestion of FW and FOG, respectively. This optimal mixing ratio was used for subsequent fed-batch studies with the addition of two conductive additives, granular activated carbon (GAC) and magnetite. The addition of GAC significantly shortened the lag phase (from 7 to 3 d), reduced accumulation of various volatile fatty acids (VFAs), and enhanced methane production rate (50–80% increase) compared to the control and magnetite-amended bioreactor. Fourier transformation infrared (FTIR) analysis suggested that the degradation of lipids, protein and carbohydrates was the highest in GAC amended reactor, followed by magnetite and control reactors. GAC addition also enriched more abundant and diverse bacteria and methanogens than control. Magnetite addition also showed similar trends but to a lesser degree. The substantial enrichment of syntrophic LCFA β-oxidizing bacteria (e.g. Syntrophomonas) and methanogenic archaea in the GAC-amended bioreactor likely attributed to the superior methanogenesis kinetics in GAC amended bioreactor. Our findings suggest that the addition of GAC could provide a sustainable strategy to enrich kinetically efficient syntrophic microbiome to favor methanogenesis kinetics in co-digestion of FW and FOG.

Synergistic effect and biodegradation kinetics of sewage sludge and food waste mesophilic anaerobic co-digestion and the underlying stimulation mechanisms

Anaerobic co-digestion has attracted much attention due to its unique advantages compared with the anaerobic mono-digestion. In this work, the synergistic effect and biodegradation kinetics of sewage sludge (SS) and food waste (FW) were studied during anaerobic co-digestion. Biochemical methane potential (BMP) assay and three kinetic models were used to detect and analyze methane production potential during co-digestion under different ratios of SS and FW. The SS:FW ratios of 0.5:0.5 showed very high methane recovery, with the methane productivity increasing by 4.59 times (50.30 ± 10.37 mL/g-VS/day), the lag-phase shortening by 11.53 times (0.182 day) and the hydrolysis rate increasing by 3.88 times (0.334/day) compared with the SS mono-digestion. Moreover, correlation model parameter analysis indicated the Cone model has the best fitness to the experimental data. These results confirmed the superiority of co-digestion and the existence of synergy, which can greatly accelerate the biodegradation process and more effectively recover bioenergy.

Effects of food waste addition on biofilm formation and sulfide production in a gravity sewer

The conversion of food waste (FW) into the sewage system is regarded as a promising method of relieving the burden of solid waste management. However, knowledge about its effects on sewer processes is limited, particularly in terms of biofilm formation and sulfide production. In this study, a gravity sewer system was set up to investigate the effects of the addition of FW on biofilm formation, the sulfate-reducing bacteria (SRB) population, and the sulfide production potential. The sewer biofilm characteristics changed with long-term FW addition, and a greater thickness (by 32%), an increased dry density (by 13%), and more extracellular polymeric substance (by 141%) were observed. The thicker and denser biofilm limited oxygen diffusion, enlarged the anaerobic area in the sewer biofilm, promoted an increase in the SRB population, and enhanced the sulfide production potential in the gravity sewer. Substantial differences in the H2S profiles in the biofilm samples with and without the addition of FW were observed via microelectrode analysis. A model-based investigation of sewer biofilm formation with and without the addition of FW was conducted with a dynamic sewer biofilm model to gain further insights into sewer biofilm processes. The results suggest that the addition of FW can promote sulfide production and SRB growth in a sewer biofilm, which can be significantly affected by the ratio of FW to sewage. It is worth further investigations of the impacts of FW addition on the potential sulfide production in pressure sewers.

Electrically regulating co-fermentation of sewage sludge and food waste towards promoting biomethane production and mass reduction

Microbial electrolysis cell (MEC) was integrated into conventional anaerobic digestion (AD) system (i.e. MEC-AD) to electrochemically regulate the co-fermentation of food waste (FW) and sewage sludge (SS). Two anaerobic systems (i.e. MEC-AD, and single AD) were operated in parallel to explore the potential stimulation of electrical regulation in metabolic behaviors of FW and SS and subsequent biomethane production. The highest accumulative methane yield was achieved at an applied voltage of 0.4 V and the FW and SS ratio of 0.2:0.8, increasing by 2.8-fold than those in AD. The combined MEC-AD system mitigated N2O emission and considerably improved ammonia removal and the dewaterability of digestate, in contrast to AD. Scanning electron microscope (SEM) visualized the presence of a large number of rod-like and cocci-like electroactive microbes on the electrode surface. Electrical regulation stimulated the self-growth and proliferation of typical Methanobacterium and Methanosaeta, accordingly contributing to biomethane production greatly.

Biogas Production by Co-Digestion of Canteen Food Waste and Domestic Wastewater under Organic Loading Rate and Temperature Optimization

The objective of this study was to characterize biogas production performance from the co-digestion of food waste and domestic wastewater under mesophilic (35 ± 1 °C) and thermophilic (55 ± 1 °C) conditions. The food waste used as a co-substrate in this study was collected from a main canteen at the Hatyai campus of Prince of Songkla University, Songkhla Province, Thailand. The optimum co-digestion ratio and temperature conditions in a batch experiment were selected for a semi-continuous experiment. Organic loading rates (OLRs) of 0.66, 0.33, and 0.22 g volatile solid (VS) L−1 d−1 were investigated in a semi-continuous experiment by continuously stirring a tank reactor (CSTR) for biogas production. The highest biomethane potential (BMP, 0.78 ml CH4 mg−1 VS removal) was achieved with a ratio of food waste to domestic wastewater of 10:90 w/v at a mesophilic temperature. An OLR of 0.22 g VS L−1 d−1 of co-digestion yielded positive biogas production and organic removal. The findings of this study illustrate how biogas production can be used for operating feed conditions and control for anaerobic co-digestion of domestic wastewater and food waste from a university canteen.

Toward a Generic Analytical Framework for Sustainable Nitrogen Management: Application for China.

Managing reactive nitrogen (Nr) to achieve a sustainable balance between production of food, feed and fiber, and environmental protection is a grand challenge in the context of an increasingly affluent society. Here, we propose a novel framework for national nitrogen (N) assessments enabling a more consistent comparison of the uses, losses and impacts of Nr between countries, and improvement of Nr management for sustainable development at national and regional scales. This framework includes four key components: national scale N budgets, validation of N fluxes, cost-benefit analysis and Nr management strategies. We identify four critical factors for Nr management to achieve the sustainable development goals: N use efficiency (NUE), Nr recycling ratio (e.g., ratio of livestock excretion applied to cropland), human dietary patterns and food waste ratio. This framework was partly adopted from the European Nitrogen Assessment and now is successfully applied to China, where it contributed to trigger policy interventions toward improvements for future sustainable use of Nr. We demonstrate how other countries can also benefit from the application our framework, in order to include sustainable Nr management under future challenges of growing population, hence contributing to the achievement of some key sustainable development goals (SDGs).

Multi-hydrolytic enzyme accumulation and microbial community structure of anaerobic co-digestion of food waste and waste-activated sludge

ABSTRACTThe accumulation of multi-hydrolytic enzyme through anaerobic co-digestion of waste-activated sludge (WAS) and food waste (FW) was studied by regulating temperature, pH and the mass ratio of FW to WAS (F/W). Experimental results showed that temperature had a profound effect on the activity of the enzyme and the most suitable temperatures for the accumulation of amylase and protease were 37°C and 50°C, respectively. The highest activity of amylase and protease accumulated reached 10.29 and 19.23 U/mL at an F/W ratio of 2:1. The addition of anaerobic co-digestion solution enriching protease and amylase had positive effects on the hydrolysis of WAS. In addition, the Illumina high-throughput sequencing demonstrated that the bacterial diversity decreased, but the bacterial abundance increased during the co-digestion process of WAS and FW. The predominant strains for secreting amylase were Lactobacillus and Clostridium-sensu-strito-1, and Aeromonas was the dominant strain for secreting protease.

Impact of organic waste composition on life cycle energy production, global warming and Water use for treatment by anaerobic digestion followed by composting

In response to significant organic waste generation, environmental policies are increasingly mandating diversion of organic waste from landfills and promoting alternative management practices to produce energy and reduce greenhouse gas emissions (GHG). Anaerobic digestion and composting are organic waste treatment alternatives, however, both practices require careful management to prevent similar environmental impacts as landfills. A model was developed to assess the impact of anaerobic digestion followed by composting of food waste and green waste mixtures on net energy production, global warming potential and scarce water use. The model included the ability to vary the initial organic waste composition, decomposition kinetics and treatment time. Energy needs for composting aeration and water pumping, and water use decreased as anaerobic digestion time increased. Composting water use savings for an organic waste anaerobically digested for 90 days prior to composting compared to zero days prior to composting ranged between 25%–53% for different organic waste compositions (from 1:0 to 0:1 green waste to food waste ratios), and energy use savings for composting aeration and water pumping ranged between 15%–17% and 24%–54%, respectively, for the same conditions. For an anaerobic digestion pretreatment time of 30 days prior to composting, the analysis predicted scarce water use to be 0.31–1.09 m3 swe/Mg waste, primary energy use to be −168.5–298.3 MJ/Mg waste, and global warming potential to be 8.1–26.4 kg CO2e/Mg waste. The results will help inform the design and maintenance of waste treatment in resource-limited environments.

Effect of food to vegetable waste ratio on acidogenesis and methanogenesis during two-stage integration

The mixing ratio of food waste (FW) to vegetable waste (VW) (2:3 FW:VW ∼ 152.51 g VS and 2:1 FW:VW ∼ 137.03 gVS) was optimized using two-stage (LBR-UASB) experimental process depending upon volatile solid (VS) load. The effect of FW to VW ratio was studied in Leach Bed Reactor (LBR) towards leachate production. Results revealed that hydrolysis rate (73.11%), sCOD (3294.3 g/KgVS) and tVFA (2664 g/KgVS) yield was higher in 2:1 FW:VW ratio. Acetate, propionate, lactate and methane yield for 2:3 FW:VW (420 g/KgVS, 87 g/KgVS, 180 g/KgVS and 226.86 ml/gVS respectively) was different from 2:1 FW:VW (340 g/KgVS, 247 g/KgVS, 340 g/KgVS and 218.54 ml/gVS respectively). 2:3 FW:VW ratio depicted higher VS (53.96%) and COD (54.1%) removal than 2:1 FW:VW ratio 46.34% and 41.8% respectively. VW addition regulated pH, restricted propionate and lactate production with enhanced methanogenesis by improving acetate production in two-stage AD process which further boosted process stability and efficiency.

Decomposition of food waste using bulking agent and bio-drying technology

Technology to process food waste should be easy maintenance, fast, economical, affordable, environmentally friendly, and socially acceptable. Processing food waste according to the principle is biological decomposition. Biological processes usually take quite a long time (30 days). This study aims to accelerate the process of decomposition of food waste and produce a quality fertilizer products. Bulking agent (biofilm), bio activator (microorganism from cassava), and bio-drying technology are used to accelerate the decomposition process. The ratio of food waste and bulking agent is 7:3 (v/v). Mature product serves as a bulking agent and additive microorganisms. Additive microorganisms are also done by adding microorganism derived from cassava with a ratio of 10ml/500 g (Ml); 20 ml/500 g (M2); and 10ml/500 g of food waste (M3). The results showed the temperature of the food waste reached 50 ? at first. The addition of bulking agent and Additive microorganisms causes the thermophilic phase to occur early. This shows the thermophilic phase being achieved in a short period. Based on testing of compost maturity parameters, food waste has matured within 3 days. The C-Organic Concentration was 27.57%, N-total 1.98%, C/N ratio of 13.92, P-Total 0.23% and K-total 0.83%. In conclusion of this study, mature compost can be used as bulking agent with mature compost ratio and 7: 3 (v/v) bulking agent. Processing food waste is quite effective using a combination of bulking agent (mature compost), additive microorganisms and bio-drying technology.

Potential of biogas production from anaerobic co-digestion of fat, oil and grease waste and food waste

The generation of fat, oil and grease (FOG) waste can be a nuisance hazard, but also a potential for resource recovery. FOG waste can be utilized as nutrient and energy source through anaerobic digestion which may increase methane yield but also increase presence of inhibitors. Using the biochemical methane potential method, this research is aimed to determine the effect of FOG waste in the co-digestion process of food waste (FW) to produce biogas. The research was conducted for 42 days at 37°C using FOG waste codigested with FW of 3 different volatile solid (VS) rasio which are 0.125, 0.3, and 0.5. The results showed that FOG waste combined with FW has a methane yield that may reach up to 485 ± 36.8 mL CH4/gr VS, the highest one produced by the 0.125 VS rasio mix. While the ratio of FOG waste with FW at 0.3 and 0.5 only produce 128 ± 195 and 4 ± 1.45 mL CH4/gr VS, respectively. The ratio of 0.125 also demonstrates the highest COD reduction of 56% compared to the other ratio which indicates the 0.125 FOG and FW ratio can be implemented to utilize FOG waste and increase methane yield during anaerobic digestion process.

Biohydrogen Production from Co-Digestion of High Carbohydrate Containing Food Waste and Combined Primary and Secondary Sewage Sludge

In this paper, FW (Food Waste) and SS (Sewage Sludge) were co-digested for biohydrogen production. After characterization both FW and SS were found as better option forbiohydrogen production. FW was rich in carbohydrate containing specially rice, which was added as more than 50% and easily hydrolyzable waste. FW is considered as an auxiliary substrate for biohydrogen production and high availability of carbohydrate in FW makes it an important substrate for the production of biohydrogen. On the contrary, SS was rich in protein and has a high pH buffering capacity, which makes it appropriate for co-digestion. Adequate supplementation of inorganic salts, the addition of hydrogen producing inoculums, protein enrichment and pH buffering capacity of SS and carbohydrate content in FW increases the hydrogen production potential. Various experiments were performed by considering different mixing ratios like 90:10, 80:20, 70:30, 60:40 and 50:50 of FW and SS. The 50:50 and 90:10 mixing ratio of FW and SS were found as best among all other co-digested ratios. The maximum specific hydrogenyield 106.7 mL/gVS_(added) was obtained at a waste composition of 50:50 followed by 92.35 mL/gVS_(added) from 90:10 of FW to SS. The optimum pH and temperature for operating this process werein the range of 5.5-6.5 and 35°C. The production of clean energy and waste utilization in anaerobic co-digestion process makes biohydrogen generation a promising and novel approach to fulfilling the increasing energy needs as a substitute for fossil fuels.

Biogas from anaerobic co-digestion of food waste and primary sludge for cogeneration of power and heat

The anaerobic digestion (AD) process is being increasingly recognised as a technology for clean energy generation. However, in Ecuador, there is a little application of this technology due to lack of adequate research, economic incentives and the current relatively low price of electricity. This study examined the feasibility of biogas production using anaerobic co-digestion of food waste (FW) and primary sludge (PS) under thermophilic (55 ⁰C) and mesophilic (35 ⁰C) conditions. The biogas is then used for power and heat generation. Using case study approach, data were collected from Riobamba vegetable market and Penipe waste treatment plant in Ecuador. Three different mixing ratios of FW: PS were used (1:2, 1:1 and 2:1) with volatile solids (VS) content of 84.53%, 86.99%, and 89.6% respectively. Furthermore, the organic loading rates (OLR) used were 2.08, 2.49 and 3.34 gvs 1-1 day-1 for the above mixing ratios with a hydraulic retention time (HRT) of 21 days.Computational models of biogas production and a combined heat and power (CHP) system were developed using Aspen Plus software. Results indicated that a mixing ratio of 1:2 and mass flow of 132.42 tonnes/day, the maximum specific methane production obtained was 270 and 205 ml CH4/ gVS at thermophilic and mesophilic conditions respectively. The power production with the aforementioned values were 188.42 and 137.79 kW for both thermal conditions. Finally, an economic analysis for both scenarios was carried out using Ecuadorian renewable energy tariffs. A positive NPV values of £147,580 and £186,307 with a discounted payback period of 20.97 and 17.33 years were obtained for both scenarios respectively, assuming that the interest rate was 4.89% and a lifetime of 25 years.

Evaluating analytical methods for the characterization of lipids, proteins and carbohydrates in organic substrates for anaerobic co-digestion

This study provides insights into the characterization of lipids, proteins and carbohydrate content in substrates for codigestion, and evaluates their effects on biogas yield. Among the analytical methods evaluated, the Bligh and Dyer, Hach Total Nitrogen and the Anthrone method were found to be most suitable for lipids, proteins and carbohydrates analysis, respectively. The co-digestibility of ten co-substrate mixes prepared using various volume-to-volume ratios of foodwaste (FW), fats, oils and grease (FOG), and waste activated sludge (WAS) were tested using biomethane potential assays. The three main substrates were mono-digested as well. WAS mono-digestion yielded the lowest methane yield of 118mL CH4/g VS, while a 50:50 mix of WAS and FOG, containing 85% lipid and 15% protein produced the highest methane yield of 1040mL CH4/g VS. In general, lipid-rich samples yielded more biogas than samples rich in proteins and carbohydrates. However, samples rich in proteins and carbohydrates had faster biogas production rates.

Co-Composting of Sewage Sludge with Food Waste Using Bin Composter

Optimization of sludge composting has been analysed by co-composting of sewage sludge with food waste by using a bin composter with regular aeration. Two bin composting experiments were set up to study the effect of different mixing ratios of food waste from the wet market to sewage sludge from Al Hadhbah waste water treatment plant which is located in Tripoli on some physical and chemical characteristics of the resulted compost. The selected ratios were 1:2 (A) and 1:3 (B) of food waste to sewage sludge respectively. Composting was conducted for 100 days and the sampling from the mixtures was performed each five days. Temperature (T), pH, electrical conductivity (EC), total organic carbon contents (TOC %) and total nitrogen contents (TN %) were monitored during the composting. The ratio of C/N, inorganic residual material (ash content) and nutrient changes as represented by potassium (K %) and phosphorus (P %) contents was also determined. The compost produced in this study has a favorable ratio of C/N (13.43 for compost A and 14. 32 for compost B). With significant amount of nutrients (TN %, K%, P%) The results of analysis of variance (ANOVA) revealed a significant effect of elapsed composting time (at the probability level of 0.05) on T, pH, TOC%, K% and P%. The effect of composting ratio was insignificant (at the probability level of 0.05) on T, TOC %, TN %, C/N and P%. The multiple comparison results using Tukey’s test showed significance difference between the mean values of EC and K% among the composting ratio at the confidence level of 95%. Generally, the compost ratio of 1:2 was found to be the most suitable for use as organic fertilizer

Enhancing anaerobic digestion of food waste through biochemical methane potential assays at different substrate: inoculum ratios

Food waste has a high energy potential that can be converted into useful energy in the form of methane via anaerobic digestion. Biochemical Methane Potential assays (BMPs) were conducted to quantify the impacts on methane production of different ratios of food waste. Anaerobic digester sludge (ADS) was used as the inoculum, and BMPs were performed at food waste:inoculum ratios of 0.42, 1.42, and 3.0g chemical oxygen demand/g volatile solids (VS). The 1.42 ratio had the highest CH4-COD recovery: 90% of the initial total chemical oxygen demand (TCOD) was from food waste, followed by ratios 0.42 and 3.0 at 69% and 57%, respectively. Addition of food waste above 0.42 caused a lag time for CH4 production that increased with higher ratios, which highlighted the negative impacts of overloading with food waste. The Gompertz equation was able to represent the results well, and it gave lag times of 0, 3.6 and 30days and maximum methane productions of 370, 910, and 1950mL for ratios 0.42, 1.42 and 3.0, respectively. While ratio 3.0 endured a long lag phase and low VSS destruction, ratio 1.42 achieved satisfactory results for all performance criteria. These results provide practical guidance on food-waste-to-inoculum ratios that can lead to optimizing methanogenic yield.

Technical evaluation of a tank-connected food waste disposer system for biogas production and nutrient recovery

In this study, a tank-connected food waste disposer system with the objective to optimise biogas production and nutrient recovery from food waste in Malmö was evaluated. The project investigated the source-separation ratio of food waste through waste composition analyses, determined the potential biogas production in ground food waste, analysed the organic matter content and the limiting components in ground food waste and analysed outlet samples to calculate food waste losses from the separation tank.It can be concluded that the tank-connected food waste disposer system in Malmö can be used for energy recovery and optimisation of biogas production. The organic content of the collected waste is very high and contains a lot of energy rich fat and protein, and the methane potential is high.The results showed that approximately 38% of the food waste dry matter is collected in the tank. The remaining food waste is either found in residual waste (34% of the dry matter) or passes the tank and goes through the outlet to the sewer (28%). The relatively high dry matter content in the collected fraction (3–5% DM) indicates that the separation tank can thicken the waste substantially.The potential for nutrient recovery is rather limited considering the tank content. Only small fractions of the phosphorus (15%) and nitrogen (21%) are recyclable by the collected waste in the tank. The quality of the outlet indicates a satisfactory separation of particulate organic matter and fat. The organic content and nutrients, which are in dissolved form, cannot be retained in the tank and are rather led to the sewage via the outlet.

Tracing source and migration of Pb during waste incineration using stable Pb isotopes

Emission of Pb is a significant environmental concern during solid waste incineration. To target Pb emission control strategies effectively, the major sources of Pb in the waste incineration byproducts must be traced and quantified. However, identifying the migration of Pb in each waste component is difficult because of the heterogeneity of the waste. This study used a laboratory-scale incinerator to simulate the incineration of municipal solid waste (MSW). The Pb isotope ratios of the major waste components (207Pb/206Pb=0.8550–0.8627 and 208Pb/206Pb=2.0957–2.1131) and their incineration byproducts were measured to trace sources and quantify the Pb contribution of each component to incineration byproducts. As the proportions of food waste (FW), newspaper (NP), and polyethylene bag (PE) in the artificial MSW changed, the contribution ratios of FW and PE to Pb in fly ash changed accordingly, ranging from 31.2% to 50.6% and from 35.0% to 41.8%, respectively. The replacement of PE by PVC significantly increased the partitioning and migration ratio of Pb. The use of Pb isotope ratios as a quantitative tool for tracing Pb from raw waste to incineration byproducts is a feasible means for improving Pb pollution control.