Food Waste Storage Research Articles

Deeper insight into the storage time of food waste on black soldier fly larvae growth and nutritive value: Interactions of substrate and gut microorganisms

Biological treatment of food waste (FW) by black soldier fly larvae (BSFL) is considered as an effective management strategy. The composition and concentrations of nutrients in FW change during its storage and transport period, which potentially affect the FW conversion and BSFL growth. The present study systematically investigated the effect of different storage times (i.e., 0–15 d) on FW characteristics and its substantial influence on the BSFL growth. Results showed that the highest larvae weight of 282 mg and the shortest growth time of 14 days were achieved at the group of FW stored for 15 days, but shorter storage time (i.e., 2–7 d) had adverse effect on BSFL growth. Short storage time (i.e., 2–4 d) improved protein content of BSFL biomass and prolonged storage time (i.e., 7–10 d) led to the accumulation of fat content. The changes of substrate characteristics and indigenous microorganisms via FW storage time were the main reasons for BSFL growth difference. Lactic acid (LA) accumulation (i.e., 19.84 g/L) in FW storage for 7 days significantly limited the BSFL growth, leading to lowest larvae weight. Both the substrate and BSFL gut contained same bacterial communities (e.g., Klebsiella and Proteus), which exhibited similar change trend with the prolonged storage time. The transfer of Clostridioides from substrate to BSFL gut promoted nutrients digestion and intestinal flora balance with the FW stored for 15 days. Pathogens (e.g., Acinetobacter) in BSFL gut feeding with FW storage time of 7 days led to the decreased digestive function, consistent with the lowest larvae weight. Overall, shorter storage time (i.e., 2–7 d) inhibited the BSFL digestive function and growth performance, while the balance of the substrate nutrients and intestinal flora promoted the BSFL growth when using the FW stored for 15 days.

Biotic and abiotic insights into the storage of food waste and its effect on biohydrogen and methane production potential

The present study investigated the physicochemical and microbiological changes occurring during the storage of simulated restaurant food waste (FW) and how such changes affected its biohydrogen and biogas production potential. FW was stored for 72 h in a closed atmosphere under two different scenarios: i) without and ii) with inoculation of a mixed microbial culture harboring lactic acid bacteria (LAB). Both storage scenarios resulted in similar biotic and abiotic changes in FW. Particularly, FW was pre-acidified and pre-hydrolyzed to some extent during the storage, resulting in a feedstock enriched in LAB (≈ 95 % total relative abundance) and lactate (10.5–12.3 g/L, 87.0–90.5 % selectivity). Biochemical hydrogen potential tests revealed that the use of stored FW resulted in similar or even higher hydrogen production efficiencies compared to that of non-stored FW, achieving up to 60 NmL H2/g VS added and a maximum volumetric hydrogen production rate of 9.7 NL H2/L-d. Metabolically, the conversion of lactate into hydrogen was crucial regardless of the use of non-stored or stored FW, albeit the presence of fermentable carbohydrates in the substrate was also essential either to produce lactate or to co-produce extra hydrogen. On the contrary, biochemical methane potential tests showed that the biogas production potential of FW was not affected by storage, yielding on average 400 NmL CH4/g VS added and revealing that lactate oxidation to methane precursors represented an important step in FW biomethanization.

Decentralised system for demand-oriented collection of food waste – Assessment of biomethane potential, pathogen development and microbial community structure

Enormous amounts of food waste (FW) are produced worldwide, requiring efficient disposal strategies, both economically and ecologically. Anaerobic digestion to produce biomethane is among the most promising strategies, but requires proper solutions for storage and delivery of the waste material. Here, a decentralized system for demand-oriented FW storage and its practical usability was assessed. FW was stored under batch and fed-batch strategies at 5 °C, 20 °C and 30 °C for 28 days. The results showed that FW can be stored without cooling since bacterially produced lactic acid rapidly stabilized the material and inactivated pathogens. While FW storage worked well under all storage conditions and strategies, 16S analysis revealed a distinct microbiota, which was highly characteristic for each storage temperature. Moreover, FW storage had no negative impact on methane yield and stored FW contained readily degradable substances for demand-oriented biogas production.

The Assessment of Indoor Formaldehyde and Bioaerosol Removal by Using Negative Discharge Electrostatic Air Cleaners.

This study investigated the single-pass performance of a negative corona electrostatic precipitators (ESP) in removing suspended particulates (PM2.5 and PM10), formaldehyde (HCHO), and bioaerosols (bacteria and fungi) and measured the ozone (O3) concentration generated by ESP. The experimental results revealed that if the operational conditions for the ESP were set to high voltage (−10.5 kV) and low air flow rate (2.4 m3/min), ESP had optimal air pollutant removal efficiency. In the laboratory system, its PM2.5 and PM10 removal rates both reached 99% at optimal conditions, and its HCHO removal rate was 55%. In field tests, its PM2.5, PM10, HCHO, bacteria, and fungi removal rates reached 89%, 90%, 46%, 69%, and 85% respectively. The ESP in the laboratory system (−10.5 kV and 2.4 m3/min) generated 7.374 ppm of O3 under optimal conditions. Under the same operational conditions, O3 generated by ESP in the food waste storage room and the meeting room were 1.347 ppm and 1.749 ppm, respectively. The removal of HCHO and bioaerosols was primarily attributed to their destruction in the corona, as well as ozone oxidation, and collection on the dust collection plate.

Improving the energetic utilization of household food waste: Impact of temperature and atmosphere during storage

Food waste (FW) from households represents a major fraction of municipal waste and it is often collected in separate biowaste bins. Until waste collection is carried out, storage conditions in the biowaste bin influence FW properties. To draw conclusions for an optimized waste utilization in anaerobic digestion (AD), the aim of this study was to evaluate the impact of storage duration (20 to 40 days) and temperature (5 °C and 20 °C) on inherent energy potentials of household FW during aerobic and anaerobic storage. Therefore, physico-chemical parameters of recipe-based FW samples with reproducible initial compositions were monitored.After 20 days of aerobic storage, water contents (WC) were reduced from 61.9% to 39.5% (20 °C) and from 63.9% to 50.3% (5 °C) while organic dry matter (oDM) concentrations were lowered by 4.3% (20 °C) and 1.1% (5 °C). Increased pH-values of 6.6 (initially 5.5) were only measured for FW stored aerobically at 20 °C. In total, the energy potential was decreased by 31% (20 °C) and by 16% (5 °C). Thus, storage temperature and duration are crucial parameters for optimized aerobic FW storage leading to higher energy yields in AD.Instead, anaerobic storage of FW decreased pH-values to <5 while increasing WC in all samples (up to 67% at 20 °C). As oDM concentrations were preserved almost completely, the energy potential losses were only marginal proving that energy contents of FW could be preserved at household level. Consequently, energy yields in AD of FW could be increased through anaerobic storage conditions.

Impact of storage duration and micro-aerobic conditions on lactic acid production from food waste

Food waste (FW) is an abundant resource with great potential for lactic acid (LA) production. In the present study, the effect of storage time on FW characteristics and its potential for LA production was investigated. The largest part of sugars was consumed during 7 to 15 days of FW storage and the sugar consumption reached 68.0% after 15 days. To enhance the LA production, micro-aerobic conditions (13 mL air/g VS) and addition of β-glucosidase were applied to improve polysaccharides hydrolysis, resulting to increase of monosaccharides content to 76.6%. Regarding fermentative LA production, the highest LA titer and yield of hydrolyzed FW was 32.1 ± 0.5 g/L and 0.76 ± 0.01 g/g-sugar, respectively. Furthermore, L-LA isomer was higher than 70% when FW was stored for up to 7 days. However, attention should be paid on controlling the FW storage to approximately one week.

Prediction of Volatile Organic Compounds (VOCs) From Decomposition of Local Household Food Waste Using the Artificial Neural Network

This study examines the potential of artificial neural network (ANN) to predict Total Volatile Organic Compounds (TVOCs) released via decomposition of local food wastes. To mimic the decomposition process, a bioreactor was designed to stimulate the food waste storage condition. The food waste was modeled based on the waste composition from a residential area. A feed forward multilayer back propagation (Levenberg – Marquardt training algorithm) was then developed to predict the TVOCs. The findings indicate that a two-layer artificial neuron network (ANN) with six input variables and these include (outside and inside temperature, pH, moisture content, oxygen level, relative humidity) with a total of eighty eight (88) data are used for the modeling purpose. The network with the highest regression coefficient (R) is 0.9967 and the lowest Mean Square Error (MSE) is 0.00012 (nearest to the value of zero) has been selected as the Optimum ANN model. The findings of this study suggest the most suitable ANN model that befits the research objective is ANN model with one (1) hidden layer with fifteen (15) hidden neurons. Additionally, it is critical to note that the results from the experiment and predicted model are in good agreement.

Storage of Food Waste: Variations of Physical\u2013Chemical Characteristics and Consequences on Biomethane Potential

Food waste (FW) storage influences its physical–chemical characteristics and anaerobic digestion (AD) performance. In this work we present the results of two weeks long experiment where two types of FW were stored in dedicated cells (10 L and 300 L). Air was evenly flushed on the top surface of the substrates and then analyzed to identify and quantify possible gaseous emissions. Solid and liquid fractions were also periodically sampled and analyzed for total solid, volatile solid, ammonia and VFA contents. Results showed that storage initiated a hydrolysis process that modified the physical structure of FW, leading to the production of gases (CH4, CO2 and ethanol) and a partly liquefied FW. Depending on experimental conditions, a fraction between 61 and 70% of the initial substrate remained solid at the end of the storage period. In the liquid phase, a large proportion of lactic acid was measured with maximum contents of 5.9 and 14.8 g/kgvs for the small-scale experiments with two different FW types and 3.0 g/kgvs for the large-scale experiment, leading to inhibition of the biomethane potential (BMP) tests. In conclusion, this work showed that when storage of FW is needed before AD, the optimal time recommended to keep a high methane yield is one week.

Demand-oriented energy supply by the anaerobic digestion of organic waste

The share of renewable energy is steadily increasing globally. Nevertheless, power generation from renewable energy sources, such as solar and wind energy, is highly dependent on suitable weather conditions and therefore highly fluctuating. Thus, alternatives to compensate fluctuations in the energy production are necessary. Biogas plants have the potential to balance energy generation fluctuations and work independently from unstable weather. Experiments on laboratory scale showed that the storage of food waste had only a marginal impact on its energy content. A rapid acidification due to a lactic acid fermentation leads to a pH decrease and concomitant organic acids increase, preserving the stored organic waste. The pH dropped from initially 4.8 to 4 within the first 2 days of storage. It declined until day 10 to 3.6 and stayed at this level until the end of the experiment. Due to a low pH and a high VFA concentration, only minor amounts of gas were produced during storage. No formation of explosive gas mixtures was detected during the storage. Therefore, no safety precautions are necessary to avoid danger from explosion. The results obtained in laboratory were confirmed by experiments on real scale. Thus, pre-condition of organic waste for a flexible feeding and demand-oriented energy supply is feasible to balance energy generation fluctuations.

Understanding the anaerobic biodegradability of food waste: Relationship between the typological, biochemical and microbial characteristics

In this study, an extensive characterisation of food waste (FW) was performed with the aim of studying the relation between FW characteristics and FW treatability through an anaerobic digestion process. In addition to the typological composition (paper, meat, fruits, vegetables contents, etc) and the physicochemical characteristics, this study provides an original characterisation of microbial populations present in FW. These intrinsic populations can actively participate to aerobic and anaerobic degradation with the presence of Proteobacteria and Firmicutes species for the bacteria and of Ascomycota phylum for the fungi. However, the characterisation of FW bacterial and fungi community shows to be a challenge because of the biases generated by the non-microbial DNA coming from plant and by the presence of mushrooms in the food. In terms of relations, it was demonstrated that some FW characteristics as the density, the volatile solids and the fibres content vary as a function of the typological composition. No direct relationship was demonstrated between the typological composition and the anaerobic biodegradability. However, the Pearson's matrix results reveal that the anaerobic biodegradation potential of FW was highly related to the total chemical oxygen demand (tCOD), the total solid content (TS), the high weight organic matter molecules soluble in water (SOLW>1.5 kDa) and the C/N ratio content. These relations may help predicting FW behaviour through anaerobic digestion process. Finally, this study also showed that the storage of FW before collection, that could induce pre-biodegradation, seems to impact several biochemical characteristics and could improve the biodegradability of FW.

Importance of storage time in mesophilic anaerobic digestion of food waste

Storage was used as a pretreatment to enhance the methanization performance of mesophilic anaerobic digestion of food waste. Food wastes were separately stored for 0, 1, 2, 3, 4, 5, 7, and 12days, and then fed into a methanogenic reactor for a biochemical methane potential (BMP) test lasting up to 60days. Relative to the methane production of food waste stored for 0–1day (285–308mL/g-added volatile solids (VSadded)), that after 2–4days and after 5–12days of storage increased to 418–530 and 618–696mL/g-VSadded, respectively. The efficiency of hydrolysis and acidification of pre-stored food waste in the methanization reactors increased with storage time. The characteristics of stored waste suggest that methane production was not correlated with the total hydrolysis efficiency of organics in pre-stored food waste but was positively correlated with the storage time and acidification level of the waste. From the results, we recommend 5–7days of storage of food waste in anaerobic digestion treatment plants.

Feasibility of converting lactic acid to ethanol in food waste fermentation by immobilized lactate oxidase

Adoption of lactic acid bacteria (LAB) into ethanol fermentation from food waste can replace the sterilization process. However, LAB inoculation will convert part of the substrate into lactic acid (LA), not ethanol. This study adopted lactate oxidase to convert the produced LA to pyruvate, and then ethanol fermentation was carried out. The immobilization enzyme was utilized, and corresponding optimum conditions were determined. Results showed that calcium alginate could successfully immobilize the enzyme and improve pH and thermal stability. The optimum pH and temperature were 6.2 and 55°C, respectively. The utilization of immobilized enzyme with catalytic time of 5h could convert 70% LA to pyruvate, and the addition of enzyme increased the ethanol yield by 20% more than that of the control. The process could be applied in food waste storage and can help in reducing carbon source consumption.

Research on the Adoption of Lactic Acid Bacteria in Food Waste Storage and Ethanol Production

The preservation and de-odorization of food waste are very important for its utilization in fuel ethanol production as raw materials. In this paper, the inoculation of lactic acid bacteria (LAB) was carried out for food waste storage and its further fermentation for ethanol. Four contamination prevention methods, anaerobic storage, autoclaving, acid usage, the inoculation of LAB, were compared in this study. The optimum conditions for inoculation of LAB into food waste as well as the fermentation characteristic were studied. The optimum inoculum size and storage time of LAB for food waste were 0.5% (V/V) and 2 days, respectively. The quantities of microorganisms such as Escherichia coliform (E. coli) and Methicillin Resistant Staphylococcus aureu (MRSA) could not be detected in the final phase of fermentation. It proved that the inoculation of LAB in food waste could prevent the growth of putrefying bacteria. The low pH or metabolic product by lactic acid (LA) fermentation was the reason for contamination prevention.

HEAT AND MASS TRANSFER IN REACTIVE POROUS MEDIA WITH LOCAL NONEQUILIBRIUM CONDITIONS

A two-dimensional mathematical model is developed to simulate the coupled heat and mass transfer in porous media involving strong exothermic chemical reaction. This type of problem has received great attention due to its relevance to a wide range of engineering applications, such as storage of food waste and other products, chemical reactors, drying technologies, catalytic reactors and many others. The flow in our problem is governed by the Darcy-Brinkman-Forchheimer model, which is solved numerically with the finite volume method. The effect of pertinent parameters such as Darcy number, Biot interstitial number, Reynolds number, solid-to-fluid conductivity ratio, and Frank-Kamenetskii number are analyzed. The influence of the exothermic chemical reaction on both heat and mass transfers is discussed. Both quantitative and qualitative results are presented.

Use of starter culture of Lactobacillus plantarum BP04 in the preservation of dining-hall food waste

In this work, Lactobacillus plantarum BP04 was employed as starter culture in dining-hall food waste storage with different inoculant levels at 0, 2 and 10% (v/w) to suppress the outgrowth of pathogenic and spoilage bacteria. Inoculation by Lactobacillus plantarum BP04 was effective in accelerating pH drop and reducing the growth period of enterobacteria to 9, 7 and 2 days, corresponding to inoculant levels at 0, 2 and 10% (v/w). Increasing inoculum levels were found to inhibit the growth of Lactobacillus brevis and Leuconostoc lactis. HPLC analysis revealed that lactic acid was the predominant organic acid during the treatment of dining-hall food waste. Its concentration varied among the fermented processes reflecting variations of microbial activity in the fermented media.