Raw Food Waste Research Articles

Effect of high concentration of ammonium on production of n-caproate: Recovery of a high-value biochemical from food waste via lactate-driven chain elongation.

Ammonium accumulation is inevitable during the fermentation of food waste (FW), challenging the application of chain elongation process upgrading FW into the high-value biochemical n-caproate, which is a medium chain carboxylate. This study is the first to investigate ammonium inhibition of lactate-driven chain elongation process. The short-term exposure of a Clostridium IV-dominated chain elongating reactor microbiome at an ammonium concentration of 1-4g L-1 linearly decreased n-caproate production by 25-80%. High levels of ammonium (≥5g L-1) could cause failure of chain elongation, shifting the product from n-caproate to propionate. The involved mechanisms revealed that ammonium reshaped the microbial community from Clostridium IV domination to Clostridium IV and Propionibacterium co-domination (based on 16S rRNA sequencing) and reduced the activities of key enzymes involved in the reversed β-oxidization pathway. We propose an effective strategy from our study, which is the first one to do in our knowledge, to upgrade raw FW without dilution to n-caproate: lowering the ammonium accumulation to 1.0g L-1 at the setup phase for adaptation and prolonging the hydraulic retention time (10days) during the operation phase for the colonization of chain-elongation bacteria. These findings lay a foundation for the implementation of the LCE process on FW, providing an alternative way to alleviate the global FW crisis.

Food waste valorization by purple phototrophic bacteria and anaerobic digestion after thermal hydrolysis

Increased demand for effective waste management strategies, along with the need for a transition from a fossil fuel-based economy to a bio-based economy sharpens the need for synergies and scientific innovations. Food waste (FW) is an essential component of municipal solid waste, and its accumulation has become a global concern. This work discusses a closed-loop integrated biorefinery. It couples thermal hydrolysis with anaerobic digestion and photofermentation for the recovery of bioenergy resources and the production of value-added products. Thermal hydrolysis yielded up to 40.4% solids solubilization, allowing the separation of an organic-rich hydrolysate. This pre-treatment also improves anaerobic digestibility of the solid fraction, thus increasing biogas production, which can feed a combined heat and power plant. This approach makes the process sustainable and energy-efficient while decreasing the total volume of the disposal waste by 78.6%. Phototrophic treatment of the hydrolysate through a purple phototrophic bacteria-based mixed culture resulted in biomass growth with high protein content (65% wt.). The system also produced polyhydroxyalkanoates (PHA) and hydrogen, accounting for a total valorization of 16.9% of the initial total solids of the raw food waste. This variety of possible products allows setting a seasonal production in a biorefinery, depending on the composition of the debris and the market demand. Modulation of the nitrogen composition of the food waste can help to choose the best option, where low Nitrogen drives PHA and hydrogen production. In contrast, high Nitrogen leads to increased protein production.

Mesophilic anaerobic digestion of food waste: Effect of thermal pretreatment on improvement of anaerobic digestion process

The treatment of food waste (FW) is an important challenge in developed and undeveloped countries due to the rapid disintegration of this waste. Hence biogas technology is used to produce energy and to reduce the volume of waste. This technology has disadvantages in terms of sensitivity to nutritional imbalance and low biodegradability. In this case, several pretreatments have been applied to improve biogas production such as thermal pretreatment (TP). This study investigated the effects of TP on physico-chemical properties and methane yield (MY) improvement. With the effect of temperature and time treatment, soluble COD was increased and reaching 68.54 ± 2,4 mg/L recorded at (100 °C, 30 min), which was 43. 41% higher than control. In contrast, TP decreased the percentage of VS compared to the raw FW. Furthermore, anaerobic digestion (AD) of FW pretreated at 100 °C during 30min was tested, the MY was (382.82 mLSTP CH4/ g VS) which 23.68 % higher than untreated food waste. Biodegradability was increased from 83.2 ± 3 % to 91.4 ± 4.1 % showing an increase of 9.8 %.

Evaluation of the physico-chemical development of kitchen food wastes through torrefaction - a biodiversity case study

This study evaluated the change in physical and chemical properties of sun-dried food waste, during torrefaction in a fixed bed reactor. Torrefaction was carried out at different temperatures 230 °C, 260 °C, and 290 °C, for different residence times of 15, 30, 45, 60, 75, and 90 min in a fixed bed reactor. The solid torrefied products were analyzed by elemental analysis, proximate analysis, compositional analysis, and thermogravimetric analysis (TGA), and it was found that most suitable residence time for torrefaction was 60 min as torrefaction beyond 60 min did not yield much improvement in changing the properties of kitchen food waste. Carbon content increased from 46.0 to 58.5%, consecutively increasing higher heating value (HHV) from 16.1 to 21.9%. Compositional analysis demonstrated that there was not much hemicellulose left in the raw food waste after cooking; however, it had cellulose in significant proportion which went through decomposition during torrefaction. Lignin was not affected much. Various process parameters such as mass yield, energy yield, and energy density were also studied, and it was found the mass and energy yield decreased by 65.0% and 47.5%, respectively, and energy density increased by 35%. Van Krevelen indicated clearly that torrefied char had achieved coal characteristics.

Anaerobic-aerobic sequential treatment: Temperature optimization and cost implications

ABSTRACTTraditionally, aeration units, used as a polishing stage after anaerobic digestion (AD) of wastes, are operated at ambient temperature. Yet, when effluent quality is the main design criterion, raising the temperature of the aeration stage can be justified by improved removal efficiencies. In this study, an anaerobic-aerobic sequential system (AASS) was operated to co-digest raw wastewater and food waste. The aerobic compartment was tested under psychrophilic and mesophilic temperatures. At the design loading rate of 2 gVS L−1 d−1, the anaerobic digester achieved removal efficiencies of 85 ± 2% of volatile solids (VS), 84 ± 3% of total chemical oxygen demand (CODT) and a biogas yield of 1,035 ± 30 mL gVSfed−1 (50% methane). The aerobic reactor achieved additional removal of 8% CODT and 7 % VS. By raising the temperature of the aerobic reactor to the mesophilic range, COD and solids concentrations of the effluent dropped to approximately half their values. This was accompanied by an increase in nitrification (from 68% to 91%) and denitrification (from 10% to 16%). The energy analysis showed that total energy consumption slightly increases (from 0.45 to 0.49 kWh kgCODfed−1) by raising the temperature of the aerobic reactor to mesophilic range. A preliminary evaluation of the sludge disposal cost, revealed a saving increase of 5–6% under mesophilic operation with respect to psychrophilic conditions.Implications: In order to cope with the globally increasing constraints on the disposal of urban wastes, efficient post-processing of effluents becomes a crucial requirement for the anaerobic digestion industry. In this context, the submitted manuscript shows that the quality of the effluent, of an anaerobic digester, treating food waste with raw wastewater, can be substantially improved by optimizing the aerobic polishing stage. Raising the temperature of the aerobic reactor to the mesophilic range resulted in a drop of solids and COD concentrations to approximately half their values. Equally important, the implications on operational costs were found to be favorable, compared to traditional psychrophilic aerobic post-treatment, when taking into consideration indirect sludge treatment costs and energy selling revenues.

Combining Wet Rendering with Torrefaction to Improve the Fuel Characteristics of Biochar from Food Waste

Food waste is a potential source of renewable carbon that can be utilized as a feedstock for biofuel production. Instead of disposing it in the landfills, food waste can be processed through thermochemical process known as torrefaction, which is conducted between 200°C and 300°C under inert atmosphere, to produce energy-dense biochar. Due to high oil content in the food waste, wet rendering process is introduced as a pre-treatment step to remove the oil from food waste. In this study, the potential of food waste as a renewable energy source is studied, where the biochar produced from direct torrefaction (DT) is compared with the biochar produced from torrefaction process that is preceded with wet rendering (WR) process. Food waste was torrefied in the fixed bed reactor at temperatures 220°C, 240°C and 260°C, with various residence times (15 min, 30 min and 45 min). The produced biochars were characterized in terms of its elemental composition, High Heating Value (HHV) and proximate analysis which includes moisture content, fixed carbon, ash content and volatile matter. It was found that the torrefied food waste shows improved physical properties when compared to raw food waste. The moisture content showed significant reduction while the fixed carbon increased with increasing torrefaction and residence time. This effects were further improved with WR, especially HHV which indicates that the WR process followed by torrefaction may be able to further improve the produced biochar.

Whole genome sequencing confirms source of pathogens associated with bacterial foodborne illness in pets fed raw pet food.

Reports of raw meat pet food containing zoonotic foodborne bacteria, including Salmonella, Escherichia coli, and Listeria monocytogenes, are increasing. Contaminated raw pet food and biological waste from pets consuming those diets may pose a public health risk. The U.S. Food and Drug Administration Veterinary Laboratory Investigation and Response Network conducted 2 case investigations, involving 3 households with animal illnesses, which included medical record review, dietary and environmental exposure interviews, animal sample testing, and whole genome sequencing (WGS) of bacteria isolated from the pets and the raw pet food. For each case investigation, WGS with core genome multi-locus sequence typing analysis showed that the animal clinical isolates were closely related to one or more raw pet food bacterial isolates. WGS and genomic analysis of paired animal clinical and animal food isolates can confirm suspected outbreaks of animal foodborne illness.

Torrefaction of landfill food waste for possible application in biomass co-firing

Greenhouse gas emissions and municipal solid waste management have presented challenges globally. This study aims to produce a high-quality biochar with properties close to bituminous coal from landfill food waste (FW). FW was analyzed by proximate and ultimate analyses to determine its fuel properties and elemental composition before torrefaction. Temperature was varied from 200 to 300 °C at a constant residence time of 40 min and 10 °C/min heating rate. Calorific value, mass yield, energy yield and energy density were computed and used to determine the quality of the resulting biochar. Quality of raw food waste was also determined by elemental analysis. Thermal evolution was then investigated using hyphenated Thermogravimetric Analysis (TGA) and Fourier Transform Infra-Red Spectrometry (FTIR). Torrefaction was done at 225 °C, 275 °C and 300 °C. The calorific value was upgraded from 19.76 MJ/kg for dried raw food waste to 26.15 MJ/kg for torrefied food waste at the appropriate conditions which were 275 °C, 40 min and 10 °C/min. The higher heating value was comparable to that of bituminous coal from Anglo Mafube in South Africa. Elemental analysis of biochar showed an increase in carbon content with temperature due to loss of oxygen containing volatiles. This agreed with TG curves and FTIR spectra which confirmed release of H2O, CO and CO2. This resulted in a more hydrophobic solid fuel with high energy density. Food waste can therefore be upgraded to a biochar with similar fuel properties as pulverized coal used in coal fired boilers.

Hydrothermal carbonization of food waste: simplified process simulation model based on experimental results

Hydrothermal carbonization (HTC) was performed on homogenized food waste (FW) in a batch reactor at 200, 230, and 260 °C for 30 min. Solid product, called hydrochar, was characterized by means of ultimate analysis, proximate analysis, higher heating value (HHV), and ash content. On the other hand, liquid products were analyzed by inductively coupled plasma (ICP), total carbon, and pH. HHV of FW was increased from 25.1 to 33.1 MJ kg−1 by HTC. Ash content is less than 3% for hydrochars as well as the raw FW. Fixed carbon increased from 18.8 to 22.4% with the increase of HTC temperature. Fuel characteristics indicate hydrochar as a potential solid fuel and carbon storage. Therefore, a simplified simulation model was created for a continuous process that performs HTC of 1 t of FW per day. It was determined that HTC of food waste has potential to be a viable process for the production of solid fuel, primarily due to ease of drying product char.

Evaluation of physical, chemical and heavy metal concentration of food waste composting

In this study, food waste composting with rice husk and coconut fibre as compost medium were carried out. Two types of different fermentation liquids were prepared which were fermented liquid (banana peel) and fermented liquid from fermented soybeans. During the composting process, a compost samples for a twenty week duration at an interval time of two weeks. Among the physico-chemical parameters that were tested were temperature, moisture content, pH value, Total Nitrogen, Total Phosphorous, Potassium and Total Organic Carbon and Carbon Nitrogen ratio. Heavy metals such as copper, cadmium, lead, nickel and arsenic were observed and analysed. From this study, it was found that, the temperature increased during the thermophilic phase while there was gradually increase of Total Nitrogen, Total Phosphorous and Potassium from the beginning till the end of the composting process. It was also found that the total organic carbon (TOC) and the carbon nitrogen ratio decreased significantly during the decomposition process. Traces amounts of heavy metals were also detected and remains below the standard Malaysian Environmental regulations. It was concluded that, the composting process was faster with processed food waste followed by combination of processed food waste and raw. Raw food waste were demonstrated the lowest degradation rate.

Study on Composition and Generation of Food Waste in Makanan Ringan Mas Industry

Food waste management is a major problem for most food premises in Malaysia. This study was conducted at one of the Small Medium Industries (SMIs) called Makanan Ringan Mas Industry that is located in Parit Kuari Darat, Parit Raja, Johor. This premise generates food waste almost every day including processed food waste (chips and coconut candy) and raw food waste (banana peels, tapioca peels, breadfruit peels and grated coconut). The objective of the study was to determine the waste generation and composition of food waste generated by the premise. Food waste collected from the premise once a week and tested for moisture content and density. The results demonstrated that Makanan Ringan Mas Industry generated more raw food waste compared to processed food waste. Banana peels recorded the highest amount at 27.15kg per month compared to other food waste. To conclude, banana peels were found to be the highest component in the food waste composition by Makanan Ringan Mas Industry whereas breadfruit peels were found to be the lowest.

Food Waste Composting Study from Makanan Ringan Mas

The poor management of municipal solid waste in Malaysia has worsened over the years especially on food waste. Food waste represents almost 60% of the total municipal solid waste disposed in the landfill. Composting is one of low cost alternative method to dispose the food waste. This study is conducted to compost the food waste generation in Makanan Ringan Mas, which is a medium scale industry in Parit Kuari Darat due to the lack knowledge and exposure of food waste recycling practice. The aim of this study is to identify the physical and chemical parameters of composting food waste from Makanan Ringan Mas. The physical parameters were tested for temperature and pH value and the chemical parameter are Nitrogen, Phosphorus and Potassium. In this study, backyard composting was conducted with 6 reactors. Tapioca peel was used as fermentation liquid and soil and coconut grated were used as the fermentation bed. Backyard composting was conducted with six reactors. The overall results from the study showed that the temperature of the reactors were within the range which are from 30° to 50°C. The result of this study revealed that all the reactors which contain processed food waste tend to produce pH value within the range of 5 to 6 which can be categorized as slightly acidic. Meanwhile, the reactors which contained raw food waste tend to produce pH value within the range of 7 to 8 which can be categorized as neutral. The highest NPK obtained is from Reactor B that process only raw food waste. The average value of Nitrogen is 48540 mg/L, Phosphorus is 410 mg/L and Potassium is 1550 mg/L. From the comparison with common chemical fertilizer, it shows that NPK value from the composting are much lower than NPK of the common chemical fertilizer. However, comparison with NPK of organic fertilizer shown only slightly difference value in NPK.

Lactic acid fermentation from food waste with indigenous microbiota: Effects of pH, temperature and high OLR

The effects of pH, temperature and high organic loading rate (OLR) on lactic acid production from food waste without extra inoculum addition were investigated in this study. Using batch experiments, the results showed that although the hydrolysis rate increased with pH adjustment, the lactic acid concentration and productivity were highest at pH 6. High temperatures were suitable for solubilization but seriously restricted the acidification processes. The highest lactic acid yield (0.46g/g-TS) and productivity (278.1mg/Lh) were obtained at 37°C and pH 6. In addition, the lactic acid concentration gradually increased with the increase in OLR, and the semi-continuous reactor could be stably operated at an OLR of 18g-TS/Ld. However, system instability, low lactic acid yield and a decrease in VS removal were noticed at high OLRs (22g-TS/Ld). The concentrations of volatile fatty acids (VFAs) in the fermentation mixture were relatively low but slightly increased with OLR, and acetate was the predominant VFA component. Using high-throughput pyrosequencing, Lactobacillus from the raw food waste was found to selectively accumulate and become dominant in the semi-continuous reactor.

Effect of rice bran on the quality of vermicompost produced from food waste

Aims: The present study was carried out to evaluate the production of eco-friendly and environmentally bio-fertilizer from a mixture of food waste (FW) and rice bran (RB). Materials and Methods: The various mixtures of RB and FW (1:1, 1:2, 1:3, and 1:5) were prepared and spread in Diy beds for 20 days. After that, the raw compost was poured in four containers beds contains 100 adult earthworms Eisenia foetida for 30 days. Physical and chemical parameters including temperature, humidity, carbon to nitrogen (C/N) ratio, and pH were monitored. Results: The obtained results showed that at the first of composting process, the temperature was sharply increased and after that dropped and reached to the ambient temperature. The C/N ratio was decreased in studied Diy beds during preparing and vermicompost processes. The averages of C/N ratios in the raw FW and RB at mixing ratios of 1:1, 1:2, 1:3, and 1:5 were 45.35, 38.43, 35.3, and 32.11, respectively. The C/N ratios in the vermicompost were reduced to 20.85, 18.3, 16.86, and 15.16, respectively. Conclusion: The results of this study showed that composting and vermicomposting process can be used as a potential tool for bio convert rice bran and food waste. However, it is suggested that the rice bran can be amended with food waste to ensure better quality of vermicompost.

Characterization of Food Waste and Its Digestate as Feedstock for Thermochemical Processing

The products of a commercial one-stage anaerobic digestion and a laboratory-scale pyrolysis of raw food waste (RFW) and digestated food waste (DFW) were characterized to evaluate the treatment effect, product yield, and physicochemical properties. The pyrolysis of the RFW and DFW resulted in generation of 7.4 and 5.3 wt % of gas and 60.3 and 52.2 wt % of bio-oil, while biochar yields decreased with an increase in the pyrolysis temperature. Differential thermogravimetric tests of RFW and DFW show 20% in both solid residues produced at a temperature of 550 °C, indicating a relatively low impact of the digestion process on the RFW. The mineral matter content was found to be lower for RFW compared to DFW. The variation in the content of fixed carbon and volatile matter reflected the effect of anaerobic degradation of the food waste. The bio-oils showed a low concentration of phenols, esters, and derivatives of hydrocarbons for DFW compared to RFW. The specific heat capacities were determined for RFW and DFW, ...

Examination of food waste co-digestion to manage the peak in energy demand at wastewater treatment plants.

Many digesters in Germany are not operated at full capacity; this offers the opportunity for co-digestion. Within this research the potentials and limits of a flexible and adapted sludge treatment are examined with a focus on the digestion process with added food waste as co-substrate. In parallel, energy data from a municipal wastewater treatment plant (WWTP) are analysed and lab-scale semi-continuous and batch digestion tests are conducted. Within the digestion tests, the ratio of sewage sludge to co-substrate was varied. The final methane yields show the high potential of food waste: the higher the amount of food waste the higher the final yield. However, the conversion rates directly after charging demonstrate better results by charging 10% food waste instead of 20%. Finally, these results are merged with the energy data from the WWTP. As an illustration, the load required to cover base loads as well as peak loads for typical daily variations of the plant's energy demand are calculated. It was found that 735 m³ raw sludge and 73 m³ of a mixture of raw sludge and food waste is required to cover 100% of the base load and 95% of the peak load.

Product based evaluation of pyrolysis of food waste and its digestate

The aim of this work was to assess the energy potential of food waste energy harvesting system (digestion followed by pyrolysis of digestate). Digestate (DFW) with increased calorific content was produced after a commercial one stage anaerobic digestion of the raw food waste (RFW). Separate pyrolysis of RFW and DFW (digestated food waste) distributed 15.7 MJ/kg and 17.2 MJ/kg respectively, among the gas, char and bio-oil, while energy of pyrolysis at 0.72 MJ/kg for RFW and 0.87 MJ/kg for DFW at the heating rate of 10 °C/min to 500 °C. Increase in the digestate specific heat to 2.5 MJ/m3 and its significant ash difference reflects the substrate (RFW) transformation due to biochemical treatment. The thermogravimetric analysis indicated the substrates mass dynamics and stability extent of the treatment products (DFW, RFW500 and DFW500). Generally, transitional energy base products (biogas and bio-oil) are generated through the energy harvesting system (EHS) of food waste, while energy rich solid fuels can be produced through pyrolysis at 500 °C. Thus, the sustainable potential of EHS to widen and broaden recycling capacity of biomass and smartly appropriate its resources are demonstrated to be dependent and pivoted on the adopted treatment method.

Bioethanol Production from the Raw Corn Starch and Food Waste Employing Simultaneous Saccharification and Fermentation Approach

Response surface methodology based on the 24 factorial central composite design (CCD) was applied to optimize the liquefaction and saccharification process for the enhancement of sugar production from raw corn starch. Optimum level of the pre and post-cooking α-amylase and glucoamylase dose were found to be 3.0 and 1.5 U/ml, respectively, while saccharification temperature for the maximum sugar production was found to be 50 °C. The quadratic model predicted that maximum conversion efficiency for the enhanced sugar production from raw corn starch was 93.65 % under the above mentioned optimum level of variables. Additional experiments performed in triplicate with the optimized level of variables showed maximum conversion efficiency of 94.12 %, in close agreement between the predicted and experimental results. The generated sugar was subjected for the bioethanol production in separate fermentation system using yeast while simultaneous saccharification and fermentation system was also evaluated.

Co-digestion of food waste in municipal wastewater treatment plants: Effect of different mixtures on methane yield and hydrolysis rate constant

Batch trials for co-digestion of raw sludge and food waste using eleven different mass-based mixtures were performed ranging from 5% to 30%. In contrast to conducting digestion trials as replicates in parallel as commonly done in previous studies, replications were performed successively in each trial to capture the variability in yield caused by a changing composition of the substrates. Trials were conducted four times with the same mixture ratios, but always using a fresh charge of inoculum, raw sludge and food waste. Data fitting was applied to assess the effect of the different mixtures on both the ultimate methane yield and the hydrolysis rate constant. The results revealed that with increasing contributions of food waste, the methane yield of the mixtures increased just due to its higher methane potential. The hydrolysis rate constant in the mixtures with a low contribution of food waste (up to 12.5% mass-based or 35% based on volatile solids) derived in batch experiments were higher than the one observed during the mono-digestion. Hence, co-digestion of food waste holds promise not only due to a higher methane yield, but in particular due to the accelerated methane production rate.

Evaluation of hydrogen producing cultures using pretreated food waste

In order to enhance bio-hydrogen production from food waste, pretreatment methods are widely used. The influence of the initial pH and autoclaving were investigated in batch experiments. Fermentative studies showed that pure cultures like Clostridium beijerinckii could directly utilize raw food waste to produce hydrogen, while other cultures (Clostridium butyricum and Clostridium pasteurianum) could produce hydrogen only after pH adjustment. In this case, the optimal starting pH of the culture was found to be 7. Autoclaving could further enhance hydrogen yields due to increased hydrolysis of food waste. The maximum hydrogen yield was achieved by C. butyricum (38.9 mL-H2/g-VSadded) after autoclaving food waste with pH adjustment at 7. In addition, the ratio acetic to butyric acid was decreased by autoclaving pretreatment, because butyrate metabolic pathway was favored in the fermentation process. However, suitable pH for bacteria growth and the low ammonia production could be achieved from autoclaving food waste.