Food Waste Content Research Articles

Characterizing the variability of food waste quality: A need for efficient valorisation through anaerobic digestion

In order to determine the variability of food waste (FW) characteristics and the influence of these variable values on the anaerobic digestion (AD) process, FW characteristics from 70 papers were compiled and analysed statistically. Results indicated that FW characteristics values are effectively very variable and that 24% of these variations may be explained by the geographical origin, the type of collection source and the season of the collection. Considering the whole range of values for physicochemical characteristics (especially volatile solids (VS), chemical oxygen demand (COD) and biomethane potential (BMP)), FW show good potential for AD treatment. However, the high carbohydrates contents (36.4%VS) and the low pH (5.1) might cause inhibitions by the rapid acidification of the digesters. As regards the variation of FW characteristics, FW categories were proposed. Moreover, the adequacy of FW characteristics with AD treatment was discussed. Four FW categories were identified with critical characteristics values for AD performance: (1) the high dry matter (DM) and total ammonia nitrogen (TAN) content of FW collected with green waste, (2) the high cellulose (CEL) content of FW from the organic fraction of municipal solid waste, (3) the low carbon-to-nitrogen (C/N) ratio of FW collected during summer, (4) the high value of TAN and Na of FW from Asia. For these cases, an aerobic pre-treatment or a corrective treatment seems to be advised to avoid instabilities along the digestion. Finally, the results of this review-paper provide a data basis of values for FW characteristics that could be used for AD process design and environmental assessment.

Opportunities and challenges of environmental geotechnics in China

Environmental problems in waste management and soil contamination are serious in China. The Chinese government has paid great attention to these problems, and environmental geotechnics has become a new and promising direction for both research and industry. The opportunities and challenges of environmental geotechnics in China are presented from two aspects, that is, solid waste management and soil contamination control/remediation. New methods and technologies are required for the design and management of Chinese sanitary landfills, which contain high food waste content municipal solid wastes and commonly have high leachate mounds. The market of contaminated site remediation is developing rapidly in China as a result of growing reuse of brownfields left by relocation of old and polluting industries. The valuable experience and mature technologies of the developed countries in contaminated land remediation are helpful to promote technological advancement in China.

Research on the drying kinetics of household food waste for the development and optimization of domestic waste drying technique

ABSTRACTDomestic food waste drying foresees the significant reduction of household food waste mass through the hygienic removal of its moisture content at source. In this manuscript, a new approach for the development and optimization of an innovative household waste dryer for the effective dehydration of food waste at source is presented. Food waste samples were dehydrated with the use of the heated air-drying technique under different air-drying conditions, namely air temperature and air velocity, in order to investigate their drying kinetics. Different thin-layer drying models have been applied, in which the drying constant is a function of the process variables. The Midilli model demonstrated the best performance in fitting the experimental data in all tested samples, whereas it was found that food waste drying is greatly affected by temperature and to a smaller scale by air velocity. Due to the increased moisture content of food waste, an appropriate configuration of the drying process variables can lead to a total reduction of its mass by 87% w/w, thus achieving a sustainable residence time and energy consumption level. Thus, the development of a domestic waste dryer can be proved to be economically and environmentally viable in the future.

Source segregation of food waste in office areas: Factors affecting waste generation rates and quality

Existing legislation mandates that the amount of waste being recycled should be increased. Among others, in its Resource Strategy Plan, the Danish Government decided that at least 60% of food waste generated by the service sector, including in office areas, should be source-sorted and collected separately by 2018. To assess the achievability of these targets, source-sorted food waste and residual waste from office areas was collected and weighed on a daily basis during 133 working days. Waste composition analyses were conducted every week to investigate the efficiency of the source-sorting campaign and the purity of the source-sorted food waste. The moisture content of source-sorted food waste and residual waste fractions, and potential methane production from source-sorted food waste, was also investigated.Food waste generation equated to 23±5kg/employee/year, of which 20±5kg/employee/year was source-sorted, with a considerably high purity of 99%. Residual waste amounted to 10±5kg/employee/year and consisted mainly of paper (29±13%), plastic (23±9%) and missorted food waste (24±16%). The moisture content of source-sorted food waste was significantly higher (8%) than missorted food waste, and the methane potential of source-sorted food waste was 463±42mLCH4/g VS. These results show that food waste in office areas offers promising potential for relatively easily collectable and pure source-sorted food waste, suggesting that recycling targets for food waste could be achieved with reasonable logistical ease in office areas.

A simple method for predicting the lower heating value of municipal solid waste in China based on wet physical composition

A rapid and cost-effective prediction method based on wet physical composition has been developed to determine the lower heating value (LHV) of municipal solid waste (MSW) for practical applications in China. The heating values (HVs) of clean combustibles were measured in detail, and the effect of combustibles, food waste, and ash content on HV was studied to develop the model. The weighted average HV can be used to predict the MSW HV with high accuracy. Based on the moisture measurements of each major real combustible and the HV of clean solid waste, a predictive model of the LHV of real MSW was developed. To assess the prediction performance, information was collected on 103 MSW samples from 31 major cities in China from 1994 to 2012. Compared with five predictive models based on the wet physical composition from different regions in the world, the predictive result of the developed model is the most accurate. The prediction performance can be improved further if the MSW is sorted better and if more information is collected on the individual moisture contents of the waste.

High-solid Anaerobic Co-digestion of Food Waste and Rice Straw for Biogas Production

Anaerobic co-digestion of food waste (FW) and rice straw (RS) in continuously stirred tank reactor (CSTR) at high organic loading rate (OLR) was investigated. Co-digestion studies of FW and RS with six different mixing ratios were conducted at an initial volatile solid (VS) concentration of more than 3 gVS · L−1. The biogas production, methane contents, degradation efficiency of VS, chemical oxygen demand (COD) and volatile fatty acids (VFAs) were determined to evaluate the stability and performance of the system. The results showed that the co-digestion process had higher system stability and higher volumetric biogas production than mono-digestions. Increase in FW content in the feedstock could increase the methane yield and shorten retention time. The efficiency of co-digestion systems mainly relied on the mixing ratios of FW and RS to some extent. The highest methane yield was 60.55 mL·gV·S−1 · d−1 at a mass ratio (FW/RS) of 3 : 1, which was 178% and 70% higher than that of mono-digestions of FW and RS, respectively. Consequently, the anaerobic co-digestion of FW and RS could have superior stability and better performance than mono-digestions in higher organic loading system.

The influence of food waste on dioxin formation during incineration of refuse-derived fuels

We report a preliminary characterization of three refuse-derived fuels (RDFs) produced from recovered wood (RW) and two municipal solid wastes (MSWs) with different food waste contents. The fuels were characterized with respect to elemental composition and emissions of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) during combustion in a full-scale incinerator. The first RDF (RDF 1) had a low food waste content because it was based on MSW collected from a region where extensive separation of kitchen waste in the household is common. RDF 2 was based on MSW from a region with no organized separation of kitchen waste and therefore had a higher food waste content. A RW fuel with no added MSW was combusted to provide reference data.RDF 1 had very favourable fuel quality and PCDD/F emissions. In particular, its combustion generated lower PCDD/F concentrations (14.6ng/m3) than that of RDF2 (23.9ng/m3) or RW (22.6ng/m3). This may have been because its relatively high heating value increased its combustion efficiency and the relatively high Cl and Fe contents of RDF 2 promoted PCDD/F formation and chlorination. Both RDF materials had lower moisture contents and higher heating values than the RW fuel.

The anaerobic co-digestion of fruit and vegetable waste and horse manure mixtures in a bench-scale, two-phase anaerobic digestion system

In this study, the anaerobic digestion of mixtures of food waste (FW) and horse manure was investigated using a bench-scale two-phase reactor system. Both phases were maintained at 35°C for the duration of the 30-day study period. The first phase reactors were prepared with biomass mixtures in deionized water such that each mixture had an initial total solids (TS) concentration of 6 wt%. The second phase reactors were inoculated with cow manure in water two weeks prior to the study period at 3 wt% TS. The biogas from all second phase reactors contained greater than 60 vol% methane in the biogas before they were used in the study, thus indicating the presence of active methanogens. Filtrate (5 mL) from the first phase was used as feed to the second phase reactor. The chemical oxygen demand (COD), total organic carbon, and volatile solids (VS) of the feed from Phase 1 increased with FW content in the biomass mixture, and so the organic loading rates (OLRs) to the Phase 2 reactors also increased. Accordingly, the volume of biogas and methane generated from Phase 2 also increased with FW content. The low OLR (<0.2 g VS/L/day), the use of a two-phase system, and the use of filtrate from Phase 1as feed to Phase 2 allowed for high utilization of the feed; the observed specific methane yields (mL/g COD) were greater than 80% of the theoretical yields for all mixtures. The methane yields were statistically similar to within a 95% confidence interval.

Greenhouse gas emissions during MSW landfilling in China: Influence of waste characteristics and LFG treatment measures

Reducing greenhouse gas (GHG) emissions from municipal solid waste (MSW) treatment can be highly cost-effective in terms of GHG mitigation. This study investigated GHG emissions during MSW landfilling in China under four existing scenarios and in terms of seven different categories: waste collection and transportation, landfill management, leachate treatment, fugitive CH4 (FM) emissions, substitution of electricity production, carbon sequestration and N2O and CO emissions. GHG emissions from simple sanitary landfilling technology where no landfill gas (LFG) extraction took place (Scenario 1) were higher (641−998 kg CO2-eq·t−1ww) than those from open dump (Scenario 0, 480−734 kg CO2-eq·t−1ww). This was due to the strictly anaerobic conditions in Scenario 1. LFG collection and treatment reduced GHG emissions to 448−684 kg CO2-eq·t−1ww in Scenario 2 (with LFG flare) and 214−277 kg CO2-eq·t−1ww in Scenario 3 (using LFG for electricity production). Amongst the seven categories, FM was the predominant contributor to GHG emissions. Global sensitivity analysis demonstrated that the parameters associated with waste characteristics (i.e. CH4 potential and carbon sequestered faction) and LFG management (i.e. LFG collection efficiency and CH4 oxidation efficiency) were of great importance. A further learning on the MSW in China indicated that water content and dry matter content of food waste were the basic factors affecting GHG emissions. Source separation of food waste, as well as increasing the incineration ratio of mixed collected MSW, could effectively mitigate the overall GHG emissions from landfilling in a specific city. To increase the LFG collection and CH4 oxidation efficiencies could considerably reduce GHG emissions on the landfill site level. While, the improvement in the LFG utilization measures had an insignificant impact as long as the LFG is recovered for energy generation.

Greenhouse gas emissions from biogenic waste treatment: options and uncertainty

A simplified life cycle assessment was conducted to estimate greenhouse gas (GHG) emissions and energy production from each component of biogenic waste treated in an open dumping site, and by composting, anaerobic digestion, and incineration employed with additional options. The impact of uncertainties and sensitivities of the parameters in the treatment methods were investigated. We conducted a sensitivity analysis to identify the most sensitive parameters, and we discussed the relationship between uncertainty and sensitivity. Our results revealed that the moisture content of food waste and the biomass-derived carbon and methane concentration of the landfill gas of biogenic waste subjected to open dumping are the most sensitive parameters across all the treatment methods. The net GHG emissions from food waste treated in an open dumping site ranged over ten times (0.30 − 3.67 Gg CO2 eq/Gg). In addition, by employing additional options for the open dumping site, including soil cover, a landfill gas collection system, shifting to a semi-aerobic condition, and energy conservation by using a gas engine, we found that the net GHG emissions could be reduced by 10, 27.9, 37.4 %, and up to 56.7 %, respectively. Shifting to a semi-aerobic system is the most effective method for reducing GHG emissions, followed by landfill gas collection.

Greenhouse gas emissions from MSW incineration in China: Impacts of waste characteristics and energy recovery

Determination of the amount of greenhouse gas (GHG) emitted during municipal solid waste incineration (MSWI) is complex because both contributions and savings of GHGs exist in the process. To identify the critical factors influencing GHG emissions from MSWI in China, a GHG accounting model was established and applied to six Chinese cities located in different regions. The results showed that MSWI in most of the cities was the source of GHGs, with emissions of 25–207kgCO2-eqt−1rw. Within all process stages, the emission of fossil CO2 from the combustion of MSW was the main contributor (111–254kgCO2-eqt−1rw), while the substitution of electricity reduced the GHG emissions by 150–247kgCO2-eqt−1rw. By affecting the fossil carbon content and the lower heating value of the waste, the contents of plastic and food waste in the MSW were the critical factors influencing GHG emissions of MSWI. Decreasing food waste content in MSW by half will significantly reduce the GHG emissions from MSWI, and such a reduction will convert MSWI in Urumqi and Tianjin from GHG sources to GHG sinks. Comparison of the GHG emissions in the six Chinese cities with those in European countries revealed that higher energy recovery efficiency in Europe induced much greater reductions in GHG emissions. Recovering the excess heat after generation of electricity would be a good measure to convert MSWI in all the six cities evaluated herein into sinks of GHGs.

Effects of mixture ratio on anaerobic co-digestion with fruit and vegetable waste and food waste of China

The biochemical methane potentials for typical fruit and vegetable waste (FVW) and food waste (FW) from a northern China city were investigated, which were 0.30, 0.56 m 3 CH 4/kgVS (volatile solids) with biodegradabilities of 59.3% and 83.6%, respectively. Individual anaerobic digestion testes of FVW and FW were conducted at the organic loading rate (OLR) of 3 kg VS/(m 3·day) using a lab-scale continuous stirred-tank reactor at 35°C. FVW could be digested stably with the biogas production rate of 2.17 m 3/(m 3·day) and methane production yield of 0.42 m 3 CH 4/kg VS. However, anaerobic digestion process for FW was failed due to acids accumulation. The effects of FVW: FW ratio on co-digestion stability and performance were further investigated at the same OLR. At FVW and FW mixing ratios of 2:1 and 1:1, the performance and operation of the digester were maintained stable, with no accumulation of volatile fatty acids (VFA) and ammonia. Changing the feed to a higher FW content in a ratio of FVW to FW 1:2, resulted in an increase in VFAs concentration to 1100–1200 mg/L, and the methanogenesis was slightly inhibited. At the optimum mixture ratio 1:1 for co-digestion of FVW with FW, the methane production yield was 0.49 m 3 CH 4/kg VS, and the volatile solids and soluble chemical oxygen demand (sCOD) removal efficiencies were 74.9% and 96.1%, respectively.

Food waste impact on municipal solid waste angle of internal friction

The impact of food waste content on the municipal solid waste (MSW) friction angle was studied. Using reconstituted fresh MSW specimens with different food waste content (0%, 40%, 58%, and 80%), 48 small-scale (100-mm-diameter) direct shear tests and 12 large-scale (430 mm × 430 mm) direct shear tests were performed. A stress-controlled large-scale direct shear test device allowing approximately 170-mm sample horizontal displacement was designed and used. At both testing scales, the mobilized internal friction angle of MSW decreased considerably as food waste content increased. As food waste content increased from 0% to 40% and from 40% to 80%, the mobilized internal friction angles (estimated using the mobilized peak (ultimate) shear strengths of the small-scale direct shear tests) decreased from 39° to 31° and from 31° to 7°, respectively, while those of large-scale tests decreased from 36° to 26° and from 26° to 15°, respectively. Most friction angle measurements produced in this study fell within the range of those previously reported for MSW.

Effect of mixing ratio of woody waste and food waste on the characteristics of carbonization residue

Biomass such as woody waste and food waste can be converted to a renewable energy source by means of carbonization processes. The basic characteristics of woody waste and food waste, such as proximate analysis and heating value, were evaluated before carrying out carbonization tests. Carbonization tests were carried out to obtain the basic characteristics of carbonization residue on changing the proportion of food waste from 0% to 30% in the mixture of woody waste and food waste. The effect of the food waste was estimated by basic characteristics of the residue such as the heating value, yield, and fuel ratio. As increased the food waste content, the bulk density, yield and chlorine content of the carbonization residue increased, but fuel ratio, the carbon content and heating value of the residue decreased. From the results of the basic characteristics of the residue, the optimum food waste content in carbonization tests was found to be 20%. Even if food waste is combined with woody waste at levels up to 30%, the sulfur and chlorine concentrations in the residue were much lower than the regulatory standard levels. From the results for the fuel ratio and heating value of the residue, the carbonization residue is suitable for use as a renewable energy source and can be categorized by the second grade level of solid fuel products.

The Progressive Increase of Food Waste in America and Its Environmental Impact

Food waste contributes to excess consumption of freshwater and fossil fuels which, along with methane and CO2 emissions from decomposing food, impacts global climate change. Here, we calculate the energy content of nationwide food waste from the difference between the US food supply and the food consumed by the population. The latter was estimated using a validated mathematical model of metabolism relating body weight to the amount of food eaten. We found that US per capita food waste has progressively increased by ∼50% since 1974 reaching more than 1400 kcal per person per day or 150 trillion kcal per year. Food waste now accounts for more than one quarter of the total freshwater consumption and ∼300 million barrels of oil per year.

Source separation of household waste: A case study in China

A pilot program concerning source separation of household waste was launched in Hangzhou, capital city of Zhejiang province, China. Detailed investigations on the composition and properties of household waste in the experimental communities revealed that high water content and high percentage of food waste are the main limiting factors in the recovery of recyclables, especially paper from household waste, and the main contributors to the high cost and low efficiency of waste disposal. On the basis of the investigation, a novel source separation method, according to which household waste was classified as food waste, dry waste and harmful waste, was proposed and performed in four selected communities. In addition, a corresponding household waste management system that involves all stakeholders, a recovery system and a mechanical dehydration system for food waste were constituted to promote source separation activity. Performances and the questionnaire survey results showed that the active support and investment of a real estate company and a community residential committee play important roles in enhancing public participation and awareness of the importance of waste source separation. In comparison with the conventional mixed collection and transportation system of household waste, the established source separation and management system is cost-effective. It could be extended to the entire city and used by other cities in China as a source of reference.

Leachate pretreatment for enhancing organic matter conversion in landfill bioreactor

Direct recycling of leachate from refuse of high food waste content was shown to ineffectively stabilize the refuse. This work aims at evaluating the effects of three pretreatments of leachate on the refuse stabilization efficiency were investigated. Pretreatment of leachate using an anaerobic upflow filtration bioreactor (UFB) or a well-decomposed waste layer could reduce the COD and provide methanogens, both were beneficial to establish early methanogenesis status. Using an aerobic sequential batch reactor (SBR) to pretreat the leachate could reduce its COD to 1000 mg l −1, but the fully developed methanogenesis phase would be built up in a later stage. The organic matters in the effluent leachate inhibited both the hydrolysis/acidogenesis and the methanogenesis steps in the refuse. With the dilution and acid neutralization effects by the recycled leachate, a favorable methanogenetic environment could be produced from the column's top, which moved downward along, and finally made the breakthrough of the column.

Strategies for the anaerobic digestion of the organic fraction of municipal solid waste: an overview

Different process strategies for anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) are reviewed weighing high-solids versus low-solids, mesophilic versus thermophilic and single-stage versus multi-stage processes. The influence of different waste characteristics such as composition of biodegradable fractions, C:N ratio and particle size is described. Generally, source sorting of OFMSW and a high content of food waste leads to higher biogas yields than the use of mechanically sorted OFMSW. Thermophilic processes are more efficient than mesophilic processes in terms of higher biogas yields at different organic loading rates (OLR). Highest biogas yields are achieved by means of wet thermophilic processes at OLRs lower than 6 kg-VS x m(-3) d(-1). High-solids processes appear to be relatively more efficient when OLRs higher than 6 kg-VS x m(-3)d(-1) are applied. Multi-stage systems show in some investigations a higher reduction of recalcitrant organic matter compared to single-stage systems, but they are seldom applied in full-scale. An extended cost-benefit calculation shows that the highest overall benefit of the process is achieved at an OLR that is lower and a hydraulic retention time (HRT) that is longer than those values of OLR and HRT, at which the highest biogas production is achieved.

Comparison of a Corn/Soybean Diet Versus a Dried, Recycled Food Waste Product in Swine1, 21Supported by New Jersey Agricultural Experiment Station Sustainable Agriculture Research and Education Program.2Recycled food waste obtained from Nutra-Feed Corporation (Clermont, FL).

<h2>Abstract</h2> Recycled food waste (FW) may provide a nutritious, alternate feed for swine. However, the high water content of FW makes it difficult to manage, suggesting that a dry, processed product may be more suitable. Pigs will readily consume wet FW, but little research has addressed the use of dried or processed FW as animal feed. The preference and digestibility of a dry FW product were determined in two research trials. The preference trial measured food intake and growth rates during a 14-d adaptation phase and an 8-d choice phase. Barrows (n = 20; 26.3 ± 1.3 kg) were adapted to either a corn and soybean meal (CS) or FW diet for 14 d. Both diets in this and the following experiment were fed in a meal form. During this adaptation phase, pigs fed CS ate more than the FW group (CS, 2.92 kg/d; FW, 2.39 kg/d; P<0.05), and also grew faster than the FW group (CS, 0.66 kg/d; FW, 0.43 kg/d; P<0.001). During the following 8-d phase, all pigs were offered both diets for 1h (1300 to1400 h) to determine preference. From 1400 to 1130h of the following day, pigs received their usual diet. During the 1-h choice period, all pigs preferred the CS diet over the FW; the pigs fed FW originally consumed significantly more CS than did the pigs fed CS originally (CS-CS, 0.43 kg; CS-FW, 0.13 kg; FW-CS, 0.86 kg, FW-FW, 0.10 kg/d; SEM=0.16 g). During the nonchoice time (21.5 h/d), pigs assigned to the CS group consumed significantly more feed than did the pigs assigned to the FW diet (CS, 3.37 kg/d; FW, 2.36 kg/d; P=0.02). During this 8-d phase, both groups of pigs grew at the same rates (CS, 1.08 kg/d; FW, 0.99 kg/d; P=0.23); this was probably due to the increased intake by the pigs assigned to the FW group during the preference period. Digestibility was determined using six barrows (29.5 ± 3.3 kg) in an experiment consisting of a 13-d adaptation and a 5-d collection. Dry matter and ADF digestibilities were significantly higher in pigs assigned to the CS diet, but there were no differences in either CP or EE (fat) digestibility. These data suggest that, when diets were formulated for protein and not amino acids, pigs given a choice prefer a standard CS diet to the dry FW product used in this study. Confounding was evident because of the low levels of lysine in both treatment groups, especially the FW treatment (lysine: FW=0.65%, CS=0.82%). Data also showed that when pigs assigned to the FW diet were offered CS for only 1 h/d, they grew at rates similar to the pigs assigned to the CS diet, suggesting that FW supplemented with some CS would be an adequate diet for growing pigs.

Proximate Analysis of Food Service Wastes

Association of Official Analytical Chemists (AOAC) methods of analysis were used to determine the protein, fat, ash, carbohydrate, moisture, and energy contents of food wastes from a large university dining center and two military facilities. Food waste from the service area of the university dining center contained (on a dry weight basis): 14.86% protein, 17.46% fat, 3.23% ash, and 64.50% carbohydrate, and 1.97 MJ/100 g of sample. The average nutrient content of food waste from the service area for the two military facilities was: 17.53% protein, 21.69% fat, 3.99% ash, and 56.79% carbohydrate and 2.06 MJ/100 g of sample. The moisture was 65.29% and 70.81% from the university and military facilities, respectively. Findings from this study can be used in evaluating usage of food waste, such as animal feeding, composting, and bioconversion.