Korean Food Waste Research Articles

Korean Food Waste Reduction Policies and the Strategies for Food Waste Index in SDGs

Korean Food Waste Reduction Policies and the Strategies for Food Waste Index in SDGs

Dilute sulfuric acid fractionation of Korean food waste for ethanol and lactic acid production by yeast

Fermentation of food waste biomass can be used to produce biochemicals such as lactic acid and ethanol in a cost-effective manner. Korean food waste (KFW) dewatered by a screw press contains 23.1% glucan on a dry basis and is a potential raw material for the production of ethanol and lactic acid through fermentation. This study was conducted to optimize the dilute acid fractionation conditions for KFW fermentation with respect to the H2SO4 concentration (0–0.8% w/v), temperature (130–190 °C), and residence time (1–128 min) using response surface methodology. Dilute sulfuric acid fractionation was carried out using a 30-mL stainless steel reactor under conditions, and then the dilute acid fractionation was scaled-up in 1-L and 7-L stainless steel reactors under the optimal conditions. The hydrolysate was concentrated, liquid-liquid extracted and neutralized for lactic acid and ethanol production. The highest concentration of glucose obtained from the KFW was 26.4 g/L using fractionation with 0.37% w/v H2SO4 at 156 °C for 123.6 min. Using recombinant Saccharomyces cerevisiae containing a codon-optimized lactate dehydrogenase, the yield of lactic acid and ethanol was 77% of the theoretical yield for 17.4 g/L of fermentable sugar at pH 5.5. Additionally, the yield of ethanol produced by Issatchenkia orientalis was 89% of the theoretical yield for 25 g/L of fermentable sugar at pH 3.

A new approach for concurrently improving performance of South Korean food waste valorization and renewable energy recovery via dry anaerobic digestion under mesophilic and thermophilic conditions

Dry semicontinuous anaerobic digestion (AD) of South Korean food waste (FW) under four solid loading rates (SLRs) (2.30–9.21kg total solids (TS)/m3day) and at a fixed TS content was compared between two digesters, one each under mesophilic and thermophilic conditions. Biogas production and organic matter reduction in both digesters followed similar trends, increasing with rising SLR. Inhibitor (intermediate products of the anaerobic fermentation process) effects on the digesters’ performance were not observed under the studied conditions. In all cases tested, the digesters’ best performance was achieved at the SLR of 9.21kg TS/m3day, with 74.02% and 80.98% reduction of volatile solids (VS), 0.87 and 0.90m3 biogas/kg VSremoved, and 0.65 (65% CH4) and 0.73 (60.02% CH4) m3 biogas/kg VSfed, under mesophilic and thermophilic conditions, respectively. Thermophilic dry AD is recommended for FW treatment in South Korea because it is more efficient and has higher energy recovery potential when compared to mesophilic dry AD.

Continuous electrochemical removal of salts from Korean food wastes

In this study, we developed a new electrochemical process to remove the salts from food wastes. The primary removal mechanisms are washing and electromigration. The screw speed and current were selected as the primary factors influencing the removal of salts. An experimental design was applied in order to determine the optimum conditions for the removal of salts and 82.7% of the salts were removed under some of these conditions. Based on the continuous operation of the apparatus, the criteria for the removal of salts in the food composts could be achieved.

Potential methane yield of food waste/food waste leachate from the biogasification facilities in South Korea

This study was to find out potential of methane yield on food waste and food waste leachate as biomass in Korea. The seven biogasification facilities were selected for comparison of theoretical methane yield and actual methane yield. The theoretical methane yield was calculated based on organic constituents (carbohydrate, protein, fat) and based on element analysis. The actual methane yield was investigated based on volatile solids and CODcr. Theoretical methane yields by organic constituents were 0.52 Sm3CH4/kg VS and 0.35 Sm3CH4/kg CODcr and these by element analysis were 0.53 Sm3CH4/kg VS and 0.36 Sm3CH4/kg CODcr. Actual methane yields were 0.36 Sm3CH4/kg VSin and 0.26 Sm3CH4/kg CODcrin. Considering the average removal efficiency of organic materials of seven FWL biogasification facilities, actual methane yields were 0.48 Sm3CH4/kg VSrem and 0.33 Sm3CH4/kg CODcrrem. Methane yield by organic constituents is very similar to that by element analysis and actual methane yields of volatile solids and CODcr were similar to theoretical value. The actual methane yield in this study showed approximated boundary values with previous other references which conducted in lab-scale or biochemical methane potential (BMP) tests. In conclusion, Korean food waste and food waste leachate have sufficient potential of methane yield in the ongoing biogasification facilities.

Characteristics of MSWI Ash and its Application to Zeolite Synthesis

In this study, composition for bottom ash and fly ash of MSWI was analyzed and zeolite was synthesized in order to expand its recycling on high quality and mass consumption. Analysis of ash its characteristics was performed by XRF, XRD, SEM, EDX, TG/DTA. Bottom/fly ash was fired for elimination of unburned carbon at 750°C/12 hr, crushed and synthesized to zeolite in 1, 2, 3, 4, 5 M NaOH solutions under 105°C/24hr by hydrothermal method. Calcite and calcium-silicate compound was mainly contained in bottom ash and CaCl2∙4H2O, Ca (OH)2, NaCl, and calcite and KCl in fly ash. Especially amount of Cl was much contained in fly ash due to Korean food waste characteristics. Bottom ash could synthesize Zeolites in form of sodalite under 3~4 M NaOH and fly ash could synthesize Zeolite A under 1~2 M NaOH. In addition, zeolite synthesized with bottom ash had higher specific surface area and zeolite from fly ash had higher CEC value. Accordingly, ash from MSWI could be recycled for further valuable uses such as non-point pollutant control and/or soil amendment.

Anaerobic co-digestion of food waste and piggery wastewater: Focusing on the role of trace elements

The objective of this study was to evaluate the feasibility of anaerobic co-digestion of food waste and piggery wastewater, and to identify the key factors governing the co-digestion performance. The analytical results indicated that the food waste contained higher energy potential and lower concentrations of trace elements than the piggery wastewater. Anaerobic co-digestion showed a significantly improved biogas productivity and process stability. The results of co-digestion of the food waste with the different fractions of the piggery wastewater suggested that trace element might be the reason for enhancing the co-digestion performance. By supplementing the trace elements, a long-term anaerobic digestion of the food waste only resulted in a high methane yield of 0.396m3/kg VSadded and 75.6% of VS destruction with no significant volatile fatty acid accumulation. These results suggested that the typical Korean food waste was deficient with some trace elements required for anaerobic digestion.

Optimization of operational parameters for ethanol production from Korean food waste leachate

Recently, research on the production of ethanol from waste has been accelerating for both ecological and economical reasons, primarily for its use as an alternative to petroleum based fuels. In this study, response surface methodology based 2 3 -full factorial central composite design was employed to optimize the parameters of ethanol production from Korean food waste leachate. The reducing sugar concentration of the food waste leachate determined by the dinitrosalicylic acid method was 75 g/L. A second order polynomial model was developed to evaluate the quantitative effects of temperature, pH and reducing sugar concentration in order to find an optimum condition for the ethanol production from food waste leachate. From the experimental result, maximum ethanol concentration of 24.17 g/L was obtained at the optimum condition of temperature (38 oC), pH (5.45) and reducing sugar concentration (75 g/L). The experimental value (24.17 g/L) agreed very well with the predicted one (23.66 g/L), indicating the suitability of the model employed and the success of response surface methodology in optimizing the conditions of ethanol production from food waste leachate. Canonical analysis indicated that the stationary point was a saddle point for the ethanol yield. Despite being a waste, an ethanol yield of 0.32 g ethanol/g reducing sugar demonstrated the potential of food waste leachate as a promising biomass resource for the production of ethanol.

Methane production potential of leachate generated from Korean food waste recycling facilities: A lab-scale study

This paper examines the applicability of food waste leachate (FWL) in bioreactor landfills or anaerobic digesters to produce methane as a sustainable solution to the persisting leachate management problem in Korea. Taking into account the climatic conditions in Korea and FWL characteristics, the effect of key parameters, viz., temperature, alkalinity and salinity on methane yield was investigated. The monthly average moisture content and the ratio of volatile solids to total solids of the FWL were found to be 84% and 91%, respectively. The biochemical methane potential experiment under standard digestion conditions showed the methane yield of FWL to be 358 and 478 ml/g VS after 10 and 28 days of digestion, respectively, with an average methane content of 70%. Elemental analysis showed the chemical composition of FWL to be C(13.02)H(23.01)O(5.93)N(1). The highest methane yield of 403 ml/g VS was obtained at 35 degrees C due to the adaptation of seed microorganisms to mesophilic atmosphere, while methane yields at 25, 45 and 55 degrees C were 370, 351 and 275 ml/g VS, respectively, at the end of 20 days. Addition of alkalinity had a favorable effect on the methane yield. Dilution of FWL with salinity of 2g/l NaCl resulted in 561 ml CH(4)/g VS at the end of 30 days. Considering its high biodegradability (82.6%) and methane production potential, anaerobic digestion of FWL in bioreactor landfills or anaerobic digesters with a preferred control of alkalinity and salinity can be considered as a sustainable solution to the present emergent problem.

Osmoprotectants enhance methane production from the anaerobic digestion of food wastes containing a high content of salt

AbstractBACKGROUND: Treatment and disposal of Korean food waste encounter technical difficulties due to a high‐salt problem. In order to increase methane production from food waste by using osmoprotectants, which are known to overcome osmotic stresses in many plants and other organisms, osmoprotectants including glycine betaine, choline, carnitine and trehalose were added to salt‐containing food wastes for anaerobic digestion.RESULTS: For NaCl‐amended food wastes containing 10 and 35 g L−1 NaCl, glycine betaine and choline increased methane production by about twofold compared to food waste without any osmoprotectants. For non‐washed food waste containing 11.6 g L−1 NaCl, glycine betaine increased methane production by about sixfold. Among these osmoprotectants, glycine betaine was the most effective for increasing methane productivity in anaerobic digestion of food waste with salinity. Analysis of glycine betaine in cell extracts using high‐performance liquid chromatography showed that glycine betaine accumulated in the cells of anaerobic sludge.CONCLUSION: Osmoprotectants significantly enhanced methanization of high‐salt food wastes by alleviating the salt‐induced physiological stresses in microorganisms. The application of osmoprotectants provided an effective substitute for other conventional methods to reduce inhibitory effects of high salt, such as dilution and co‐digestion. Copyright © 2008 Society of Chemical Industry

Effect of vermiculite addition on compost produced from Korean food wastes

To evaluate the effect of vermiculite addition on composting food wastes from Korean households, food wastes were composted in three small bins to which different additives were added. The following three bins were employed: in Case I, only recycled compost was composted; in Case II, food wastes with recycled compost; and in Case III, food wastes with recycled compost and vermiculite. In the experiment performed for 30 days, it was confirmed that the supplementary addition of vermiculite to the composting mixture did not significantly improve the weight loss rate and the decomposition rate of food wastes. Due to dilution through the use of inorganic vermiculite, the vermiculite addition reduced the organic matter concentration of the composting mixtures. Vermiculite addition did not raise the pH value. Weight losses of roughly 70% were observed based on calculating moisture loss as well as dry food waste loss and not considering additives, while dry food waste loss was 29.4% and 35.8% with and without the addition of vermiculite, respectively. For these experiments, the major portion of the weight loss was the loss of water. The results indicate a need to differentiate between weight loss percentages and decomposition percentages, and a need to indicate if either of these percentages includes or excludes the mass of additives.

Evaluation of Korean food waste composting with fed-batch operations II: using properties of exhaust gas condensate

Abstract An evaluation of Korean food waste composting, with a fed-batch operation, was conducted using the properties of the exhaust gas condensate. The traditional indices, as well as condensate properties, showed the same patterns of variation over each reaction time in the batch cycles during fed-batch composting. Trends for the variation in the pH of the condensate (pHcn) corresponded to those of the traditional indices, such as pH of the compost (pHcm) and CO2 evolution in the exhaust gas. In addition, the carbon chemical forms in the condensate would indirectly represent the gaseous metabolites, such as CO2, NH3, and VFA, which are generally emitted from aerobic composting processes. The patterns and quantities of NH3 gas evolution in the exhaust gas, especially, could be effectively estimated by their correlations with the NH4 and NH3 concentrations in the condensate or the pHcn in each cycle of fed-batch composting. Therefore, it was considered that the measurement of the condensate properties might serve as more useful and convenient operating indices than the analysis of solid and gas samples, during the composting process.

Evaluation of Korean food waste composting with fed-batch operations I: using water extractable total organic carbon contents (TOCw)

Evaluation of fed-batch composing, with three different moisture conditions, for Korean food wastes was conducted using the water extractable total organic carbon content (TOCw) of mixed materials. Composting with about 50% initial moisture content was slightly more effective than composting with about 60% initial moisture content and of that where the moisture content was constantly controlled at about 50%. These different efficiencies were shown well by various indices of the composting rates, especially those based on variations of the TOCw in the mixed materials. The TOCw content represents the easily biodegradable components of organic waste, rather than the volatile or dry solids contents. The rates of the TOCw degradation showed relatively good correlations with the rates of the total wet weight reduction, as well as the rate of CO 2 evolution, during the composting process. Therefore, it could also be used as a more appropriate index for the evaluation of this kind of high-rate composting process. Additionally, variations in the TOCw clearly followed the Arrhenius equation and its degradation could be estimated quantitatively using a first order reaction model. Moreover, the percentage of TOCw degradation in each cycle could be predicted based on the similarity of variations in the TOCw of each cycle in a fed-batch composting process.

Simulation on long-term operation of an anaerobic bioreactor for Korean food wastes

A mathematical model was formulated to simulate the long-term performance of an anaerobic bioreactor designed to digest Korean food wastes. The system variables of various decomposition steps were built into the model, which predicts the temporal characters of solid waste, and volatile fatty acid (VFA) in the reactor, and gas production in response to various input loadings and temperatures. The predicted values of VFA and gas production were found to be in good agreement with experimental observations in batch and repeated-input systems. Finally, long-term reactor performance was simulated with respect to the seasonal temperature changes from 5°C in winter to 25°C in summer at different food waste input loadings. The simulation results provided us with information concerning the success or failure of a process during long-term operation.

Single-stage anaerobic codigestion for mixture wastes of simulated Korean food waste and waste activated sludge.

Korean food waste was treated with a single-stage anaerobic codigester (SSAD) using waste activated sludge (WAS) generated from a municipal wastewater treatment plant. The stability and performance of the system was analyzed. The C/N ratio was improved with increasing food waste fraction of feed mixture. The pH, alkalinity, and free ammonia nitrogen concentration were the parameters used to evaluate the digester's stability. The experimentally determined values of the parameters indicated that there were no methane inhibitions in the digester. Digester performance was determined by measuring the total chemical oxygen demand TCOD), volate solids (VS) removal, methane content in biogas, methane production rate (MPR), and specific methane productivity. Methane content in biogas and MPR were significantly dependent on hydraulic retention time (HRT) and ratio of food waste to WAS. The methane content in biogas decreased at shorter HRT or higher organic loading rate (OLR) with increased food waste fraction. Concerning the performance of the codigester, the optimum operating condition of the SSAD was found to be at an HRT of 10 d with a feed mixture ratio of 50% food waste and 50% WAS. A TCOD removal efficiency of 53.6% and a VS removal efficiency of 53.7% were obtained at an OLR of 5.96 kg of TCOD/(m3 d) and 3.14 kg of VS/(m3 d), respectively. A maximum MPR of 1.15 m3 CH4/(m3 d) and an SMP of 0.37 m3 CH4/kg of VSfeed were obtained at an HRT of 10 d with a methane content of 63%.

Evaluation of stability of compost prepared with Korean food wastes

Food wastes were composted with saw dust, dried paper mill sludge, and decayed wood dust to reduce the volume of wastes and to produce a stable organic soil amendment. To determine the stability for agricultural utilization, the compost maturity was evaluated using physical, chemical, and biological parameters. Temperature of the inner compost heap remained high at over 50°C during the 80 d of composting, but the chemical and physical parameters apparently changed between 30 and 50 piling d: pH was a weakly acidic of the initial stage and neutral after 30 d of composting. The C / N ratio decreased to less than 12 after 65 d of composting, but the C / N ratio of the products was less than 0.5 time that of the initial value after 35 d of composting. Reducing sugar contents changed significantly between 40 and 45 d of composting, and the Y value that indicated color changes of the water extracts decreased and became stabilized at around 3 after 50 d of composting. Ring types and color on circular paper chromatograms showed an apparent difference before and after 40 d of composting. The content of sodium (Na), which might be one of the most harmful elements in Korean food wastes for agricultural utilization, increased from 12 to 17 g kg−1 with time and Na mostly occurred in a water-soluble form. Acetic acid was the main component of volatile organic acids, and total organic acids were produced at a very high rate (500–700 mg kg−1) during the first 5–30 d of composting and then the rate decreased rapidly to below 300 mg kg−1 after 35 d of compo sting. Germination index of Chinese cabbage in water extracts fluctuated with compost pile turning to a value below 50 by 40 d of composting, due to the effects of high contents of organic acids and Na. The value exceeded 50 after 45 d of compo sting but did not increase further with continuous composting, which might be due to the high content of Na. Lettuce, a sensitive species, was scarcely germinated in water extracts of the food compost. Consequently, the high content of Na in Korean food waste compost, in spite of maturity, could be a limiting factor for agricultural utilization. The effects of Korean food waste compost on plant growth and soil conditions should be evaluated further at the field level.

Volatile fatty acids production from food wastes and its application to biological nutrient removal

Korean food wastes were anaerobically digested to produce volatile fatty acids (VFA) that can be used as a carbon source in biological nutrient removal in a sequential batch reactor (SBR). Acetate, propionate and butyrate were produced at a yield of 379–400 g VFA/kg VS0 (initial volatile solids). The ratio of SCOD (Soluble Chemical Oxygen Demand) of VFA to ammonia nitrogen (N) was in the range of 36.2–36.5 and the ratio of SCOD to phosphorus was between 151 and 162. The removal rate of nitrogen and phosphorus improved from 44% and 37% to 92% and 73%, respectively when the VFA were added to the influent of the Taejon municipal wastewater plant. The concentration of nitrogen and phosphorus were maintained below 3 mg/l and 1 mg/l, respectively. The N- and P-content of the food waste was low enough not to influence the final N- and P-concentrations of the wastewater.

Two-phase methanization of food wastes in pilot scale.

A 5 ton/d pilot scale two-phase anaerobic digester was constructed and tested to treat Korean food wastes in Anyang city near Seoul. The easily degradable presorted food waste was efficiently treated in the two-phase anaerobic digestion process. The waste contained in plastic bags was shredded and then screened for the removal of inert materials such as fabrics and plastics, and subsequently put into the two-stage reactors. Heavy and light inerts such as bones, shells, spoons, and plastic pieces were again removed by gravity differences. The residual organic component was effectively hydrolyzed and acidified in the first reactor with 5 d space time at pH of about 6.5. The second, methanization reactor converted the acids into methane with pH between 7.4 and 7.8. The space time for the second reactor was 15 d. The effluent from the second reactor was recycled to the first reactor to provide alkalinities. The process showed stable steady-state operation with the maximum organic loading rate of 7.9 kg volatile solid (VS)/m3/d and the volatile solid reduction efficiency of about 70%. The total of 3.6 tons presorted MSW containing 2.9 tons of food organic was treated to produce about 230 m3 of biogas with 70% (v/v) of methane and 80 kg of humus. This process is extended to full-scale treating 15 tons of food waste a day in Euiwang city and the produced biogas is utilized for the heating/cooling of adjacent buildings.

Catalytic and thermal degradation of Korean food sludge

Korean food waste sludge was degraded by using a new thermal degradation method. In this system, radish contained waste food sludge as main portion was selected as a standard material. Products of thermal degradation were mainly composed of carbonized solid, small amounts of oil and methane. Total energy production was dependent on the reaction temperature. About 25–32% of solid in the radish was converted to carbonized solid in the thermal degradation of radish at 200°C. The heating values of the carbonized solid and the liquefied heavy oil were 4000–6000 cal/g and about 8000 cal/g respectively. Various catalysts were also examined to improve the carbonized solid used as energy source. Acid clay and MontmorilloniteKSF catalysts showed the best results among the catalysts tested. From the energy balance, this thermal degradation process operated at 200°C was a net energy producer.

95/04848 Biochemical methane potential and solid state anaerobic digestion of Korean food wastes

95/04848 Biochemical methane potential and solid state anaerobic digestion of Korean food wastes