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Objective: to produce bioethanol from the alcoholic fermentation of agri-food waste.Design/methodology/approach: food waste was collected for one month and separated into fruit and fabaceous waste; its size was reduced and then washed with hot acetone. A batch of 100 g of residue underwent acid hydrolysis with 5 %H 2 SO 4 at 125 °C, the hydrolysate was fermented with Saccharomyces cerevisiae at 30 °C for 48 h; the ferment was then distilled at 78 °C. The sugar content was determined following the phenol-sulfuric method. Brix degrees, density andpercentage w/w ethanol were measured with a densimeter.Results: from the fruit residues, an organic fraction was obtained with a total sugar content of 53.3 g/100 g of residue and 9.6 °Brix, generating 45 mL of distillate with 3.8 % w/w of bioethanol. From the fabaceae residues, an organic fraction was obtained with a total sugar content of 19.4 g and 4.140 °Brix, generating 30 mL of distillate with 2.54 % w/w of bioethanol.Study limitations/implications: Rapid decomposition of waste due to bacterial and fungal decomposition complicates long-term storage.Findings/conclusions: fermentable sugars can be obtained from the evaluated agri-food waste to obtain bioethanol. In this way, they can be integrated into the value chain as raw materials, reducing their accumulation and the environmental impact generated by their final disposal.

Hypericum perforatum residue waste, which is obtained after the extraction of a traditional Chinese herbal medicine, contained a high concentration of cellulose that can be used for ethanol production. The addition of other wastes with high nitrogen content and the effect of residual medical components on ethanol fermentation were investigated. Among inorganic nitrogen compounds, such as (NH4)2SO4, certain organic solid waste dregs including bean dregs and Salviae miltiorrhiza dregs (another Chinese traditional herb), and ethanol fermentation residue from food waste, S. miltiorrhiza dregs can effectively improve ethanol production. Ethanol concentration after 72 h with added S. miltiorrhiza dregs was 6.0 g/L, which was 44.8% of the theoretical yield. The remaining medical components on ethanol fermentation did not show any inhibitory effect. The bioconversion of traditional Chinese medicine dregs to ethanol can be a new approach for medicine waste utilization.

In the present study the bioconversion of dried household food waste (FORBI) to energy carriers was investigated aiming to its sustainable management and valorization. FORBI was either directly fermented towards ethanol and hydrogen or was previously subjected to extraction with water resulting to a liquid fraction (extract) rich in sugars and a solid residue, which were then fermented separately. Subsequently, the effluents were assessed as substrates for methane production via anaerobic digestion (AD). Mono-cultures and co-cultures of C5 and C6 yeasts were used for the alcoholic fermentation whereas for the production of hydrogen, mixed acidogenic consortia were used. Taking into account the optimum yields of biofuels, the amount of recoverable energy was estimated based for each different approach. The maximum ethanol yield was 0.16 g ethanol per kg of FORBI and it was achieved for separate fermentation of liquid and solid fractions of the waste. The highest hydrogen yield that was observed was 210.44 L ± 4.02 H2/kg TS FORBI for 1% solids loading and supplementation with cellulolytic enzymes. Direct AD of either the whole FORBI or its individual fractions led to lower overall energy recovery, compared to that obtained when fermentation and subsequent AD were applied. The recoverable energy was estimated for the different exploitation approaches of the waste. The maximum achieved recoverable energy was 21.49 ± 0.57 MJ/kg.

In this study, the effectiveness of the ethanol fermentation pretreatment for biomethanation was examined. A sequential batch biomethanation experiment was performed for 130 days using artificial food waste, which was saccharized and ethanol fermented without any evaporation of ethanol. This is compared with a control experiment without pretreatment. Methane yields of the control and pretreatment series were 420 and 460 mL/g of the added volatile solids (VS) with 53% and 68% of methane content, 0.082 and 0.014 g of volatile suspended solids/g VS added for sludge yield, and 87% and 94% for VS biodegradability, respectively. In terms of material balance, the generation of carbon dioxide during biomethanation from an ethanol fermented substrate is lower in volume than that without it, because carbon dioxide is released during ethanol fermentation. The lower sludge generation of the ethanol fermented substrate results from the biomass yield of ethanol and free energy obtained from the biomethanation of ethanol, which is lower than that obtained from the biomethanation of starch.

The development of sustainable bioethanol fuel production from food waste has increasingly become an attractive topic. Food waste is recognized as the most available and costless feedstock. Therefore, ethanol production has been adopted as cost-efficient and an ecological way for FW disposal. This paper reviewed the microorganisms utilized for ethanol fermentation, the effect of enzymatic hydrolysis on ethanol concentration, optimization of accurate process parameters, and recycling of huge volumes of stillage for ethanol production towards reducing any incurred environmental burdens and minimizing the cost. The statistical tools which may enhance the process efficiency had been presented. Also, the perspective and the future development were introduced. All these aimed to fully utilize the food waste and also reduce the cost for side-product in this process; proper operation conditions and the control methods for stillage recycling were considered as the methods to improve ethanol fermentation from food waste.

Anaerobic digestion (AD) of food waste (FW) tends to result in the accumulation of volatile fatty acids (VFA), especially a large quantity of propionic acid that is inevitably produced. Propionic acid has a significant inhibitory effect on AD at a concentration far lower than acetic acid. Therefore, anaerobic digestion cannot be operated at an excessively high load. We proposed an AD system that used a considerable amount of starch-rich food waste for ethanol fermentation as a pretreatment and reported that it improved methane concentration in biogas with a low propionic acid accumulation even under high-load operation. This study examined whether ethanol fermentation pretreatment (EP) of food waste can contribute to high-load operation on AD using an anaerobic membrane bioreactor (AnMBR). This involved a sequential bath experiment using FW that was saccharized before fermentation to ethanol. The results are compared with those for FW without pretreatment. The organic loading rate (OLR) was stepwise increased to 43.5 g COD/L/d by increasing the feed OLR, the hydraulic retention time (HRT) was six days and methane content was 71%–74%, which is thrice the capability of the control series and the highest load in the reports of medium temperature AD of FW. Furthermore, the primary methanogens were tolerant to ammonia inhibition. Correspondingly, the ammonium produced improved the buffering capacity of AD at high load. Functional archaeal and bacterial communities in the two reactors were examined. The abundance of hydrogenotrophic methanogens in AnMBR are determined to highlight the impact of the EP for FW disposal through 16S rRNA sequence analysis. Because there were multiple methanogens that use hydrogen, the higher decomposition of the substrate was attributable to the maintenance of a lower hydrogen partial pressure. It contributed to create a virtuous cycle with the EP. This study demonstrates the performance of the EP during high loading and long-term AD operation using an AnMBR; moreover, ultra-high load is achieved by changing the metabolic pathway.

A three-stage process that consisted of saccharification, ethanol fermentation of the saccharified liquid, and anaerobic treatment of the saccharified residue to convert food waste (FW) to ethanol and CH4 was developed. Results revealed that high sugar recovery (i.e., 61.7%) from FW could be achieved after saccharification and 15.2% saccharified sugar was retained in saccharified residue after solid–liquid separation. A high ethanol yield was obtained during ethanol fermentation of the saccharified liquid. This high yield indicates the superiority of the system. The ethanol productivity in the ethanol fermentation stage was 0.9 g L–1 h–1. A CH4 yield of 248.4 mL/g of volatile solid (VS) was achieved in the CH4 fermentation stage, whereas that in the single-stage fermentation system was 252.6 mL/g of VS. A comparison of the two fermentation systems based on material balance and energy outcome demonstrated that the three-stage process achieved a 27.5% increase in the FW decomposition rate, a 51.8% reduction...

Ethanol fermentation from food waste could reduce the solid waste pollution and realize energy utilization. In order to decrease distillation waste, the recycle of such waste was adopted in ethanol fermentation. It demonstrated that such treatment could only last for four times due to the existence of side products. The distillation waste would gradually reduce ethanol concentration and sugar utilization ratio, lactic acid would be accumulated to 8 g/L, and salinity would be accumulated to 10 g/L, pH decreased to less than 3.5. Three-dimensional fluorescence analysis showed protein-type substances, microbial metabolism type substances, and humic substances were accumulated during the recycling. In order to resolve such problems, addition of protease was chosen in this research. The recycling time could enhance to seven times and the highest ethanol concentration was 35 g/L, the lowest ethanol concentration was 20 g/L. The recycling of distillation waste could save water resource, reduce wastewater dischar...

Recently, research on the alcoholic fermentation of kitchen waste has been accelerating for both ecological and economical reasons, primarily for ethanol use as renewable biofuel. Present work deals with the fermentative production of ethanol from different starch based kitchen waste. Kitchen waste from local students restaurant was separated by basic component as: peas, green beans, beans, rice, potato, wheat bread and corn. Thermo-acidic pretreatment of these raw materials was conducted by the addition of HCl up to pH of 1, and by autoclaving at 120 oC for 30 min. From the experimental result, maximum ethanol yield was obtained from wheat bread (0.11 g/g). The highest ethanol yield per starch of 0.36 g/g, which equals to 64% of the theoretical value, was obtained for peas. From the overall analysis, the examined thermo-acid pretreatment was the most efficient for hydrolysis of wheat bread, while it was least efficient for green beans. In order to enhance the efficiency of conversion of starch from kitchen waste into ethanol, pH lower than 1 is highly recommended. The results demonstrated the potential of different food waste as a promising biomass resource for the production of ethanol.

Resource technology for food waste has become the research hot recently. To perform ethanol fermentation from food waste could realize energy recovery and pollution prevention. This study investigated the effects of two kinds of immobilization carriers, loofa sponge and fiber ball on ethanol fermentation from food waste. The seven runs of fermentation experiments demonstrated that the fermentation broth with fiber ball showed an increase of residue sugar concentration (31.98g/l) and a decrease of sugar utilization ratio (60.02%) in the fourth run. When it came to the seventh run of experiment, the sugar utilization ratio was only 49.04%, which showed that the fermentation yield by the yeast decreased significantly. While the fermentation by loofa sponge revealed stable fermentation efficiency, the sugar utilization ratio were all above 80%. The effect of size and inoculum for loofa sponge showed that 3 gram dry loofa sponge in 100 ml saccharification liquid was suitable. While the size had little effect on the fermentation.

Stillage reflux fermentation in food waste ethanol fermentation could reduce sewage discharge but exert a harmful effect because of side-product accumulation. In this study, regulation methods based on metabolic regulation and side-product alleviation were conducted. Result demonstrated that controlling the proper oxidation-reduction potential value (-150mV to -250mV) could reduce the harmful effect, improve ethanol yield by 21%, and reduce fermentation time by 20%. The methods of adding calcium carbonate to adjust the accumulated lactic acid showed that ethanol yield increased by 17.3%, and fermentation time decreased by 20%. The accumulated glyceal also shows that these two methods can reduce the harmful effect. Fermentation time lasted for seven times without effect, and metabolic regulation had a better effect than side-product regulation.

In this study, a lab-scale biological anaerobic/anaerobic/anoxic/membrane bioreactor (A3-MBR) was designed to treat wastewater from the ethanol fermentation of food waste, a promising way for the disposal of food waste and reclamation of resources. The 454 pyrosequencing technique was used to investigate the composition of the microbial community in the treatment system. The system yielded a stable effluent concentration of chemical oxygen demand (202±23mg/L), total nitrogen (62.1±7.1mg/L), ammonia (0.3±0.13mg/L) and total phosphorus (8.3±0.9mg/L), and the reactors played different roles in specific pollutant removal. The exploration of the microbial community in the system revealed that: (1) the microbial diversity of anaerobic reactors A1 and A2, in which organic pollutants were massively degraded, was much higher than that in anoxic A3 and aerobic MBR; (2) although the community composition in each reactor was quite different, bacteria assigned to the classes Clostridia, Bacteroidia, and Synergistia were important and common microorganisms for organic pollutant degradation in the anaerobic units, and bacteria from Alphaproteobacteria and Betaproteobacteria were the dominant microbial population in A3 and MBR; (3) the taxon identification indicated that Arcobacter in the anaerobic reactors and Thauera in the anoxic reactor were two representative genera in the biological process. Our results proved that the biological A3-MBR process is an alternative technique for treating wastewater from food waste.

This study focuses on the use of restaurant waste for production of ethanol. Food wastes (corn, potatoes, and pasta) were converted to ethanol in a two-step process: a two-part enzymatic digestion of starch using α-amylase and glucoamylase and then fermentation of the resulting sugars to ethanol using yeast. Because of the low initial composition of starch in the food waste, low ethanol concentrations were achieved: at best 8 mg/mL ethanol (0.8% by mass). Ethanol concentration increased with increasing enzyme dosage levels. Calculations were conducted to evaluate whether waste heat from restaurant waste could be used to drive flash vaporization to purify ethanol. If the solution produced by fermenting food waste is flashed at a temperature of 99.7°C, 77% of the ethanol is recovered in a vapor stream with 1.14 mol % ethanol (2.87 mass %). Waste heat could provide over a third of the energy for this vaporization process. If 4 mol % ethanol could be produced in the fermentation step by increasing the initial starch content in the waste solution and improving the fermentation process, then a single flash at 98.9°C will recover nearly 99% of the ethanol, giving a mass concentration of ethanol of 10.3%, which is similar to that achieved in industrial grain fermentation. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1280–1283, 2013

Ethanol fermentation from food waste decreases pollution and optimizes waste utilization. However, the high-energy consumption involved in the distilling process hinders the industrial application of ethanol fermentation. In the present study, pervaporation was adopted to resolve such a shortcoming. A flocculation–filtration unit was used for the treatment of the fermentation broth. The purpose was to decrease the amount of suspended solids (SS) and oil, which affected the pervaporation membrane used for ethanol separation from food waste broth. Seven kinds of flocculants at three pH levels were adopted to screen the best type and corresponding dosage. Then, a mixture of fiber-ball and quartz sand was used to treat the residue oil and SS. Considering the higher flux of the filtration process, 500 mg/L sodium alginate in a raw fermentation broth was considered the best choice. After treatment, 94.74% of SS and 98.60% of oil in the fermentation liquid were removed. The effluent quality contained the desirable qualities of the inlet water in the pervaporation step.

In order to reduce and re-utilize the ethanol fermentation residue from food waste, this study utilized residues to produce solid biomass fuel and carried out burning test by thermal gravity (TG) analysis. The results demonstrated that the residue from food waste shared the characteristic of high volatile content, high heat potential, low fixed carbon and low ash content. The burnable content was about 86.99% based on dry mass, while the heat potential was 23.06 MJ•kg-1. Lignitous coal or blind coal was adopted as the additive to improve the burning characteristic of the fermentation residue. The result for a mixture of lignitous coal and residue was better than those of blind coal with the increase of complex burning index S from 2.38E-07°C-3•min-2 to 7.99E-08°C-3•min-2, decrease of ignition point, enhancement of average burning ratio and amelioration of burning characteristic. All these provided theoretical guidance for fermentation residue utilization as the solid fuel.

BACKGROUND: Continuous ethanol fermentation of concentrated food waste hydrolysates has been studied. The process was carried out in an immobilized cell reactor with beads of calcium-alginate containing immobilized Saccharomyces cerevisiae H058 at temperature 30 °C and pH 5.0. RESULTS: The total residual sugar decreased with increase of hydraulic retention time (HRT) under various reducing sugar concentrations. Ethanol production by immobilized cells increased with increase in HRT, regardless of the substrate concentrations employed. The highest ethanol concentration of 89.28 g L−1 was achieved at an HRT of 5.87 h and reducing sugar concentration of 200 g L−1. At an HRT of 1.47 h, the maximum volumetric ethanol productivity of 49.88 g L−1 h−1 and the highest ethanol yield of 0.48 g g−1 were achieved at reducing sugar concentration of 160 and 200 g L−1, respectively. The difference between the fresh and the 30-day Ca–alginate immobilized cell was also shown by scanning electronic micrographs of beads taken from their outer and inner surfaces. CONCLUSIONS: Continuous ethanol production from concentrated food waste hydrolysates using immobilized yeast cells is promising in view of the high ethanol productivity obtained at relatively high conversion and excellent reactor stability. Copyright © 2011 Society of Chemical Industry

A single-chamber microbial fuel cell (MFC) was used in this study to treat recycled stillage obtained from food waste ethanol fermentation. Corresponding substrates inside the system were evaluated by fluorescence spectra, and microbial communities were also investigated. Results demonstrated that output voltage and current, respectively, reached 0.29 V and 1.4 mA with an external resistance of 200 Ω. Corresponding total organic carbon and chemical oxygen demand removal efficiency reached more than 50% and 70%, respectively. Results of fluorescence spectra demonstrated that tryptophan-like aromatic, soluble microbial by-product-like and humic acid-like substances accumulated and were not easily degraded. Microbial community analysis by high-throughput sequence indicated that Advenella and Moheibacter occupied the highest proportion among all genera at the anode instead of Geobacter . These results may be due to complicated accumulated stillage, and potential tetracyclines possibly influenced microbial communities. Details on how stillage affects MFC operation should be further studied, and a solution on relieving effects should be established.

Ethanol production from food wastes does not only solve environmental issues but also provides renewable biofuels. This study investigated the feasibility of producing ethanol from food wastes at high solids content (35%, w/w). A vacuum recovery system was developed and applied to remove ethanol from fermentation broth to reduce yeast ethanol inhibition. A high concentration of ethanol (144 g/L) was produced by the conventional fermentation of food waste without a vacuum recovery system. When the vacuum recovery is applied to the fermentation process, the ethanol concentration in the fermentation broth was controlled below 100 g/L, thus reducing yeast ethanol inhibition. At the end of the conventional fermentation, the residual glucose in the fermentation broth was 5.7 g/L, indicating incomplete utilization of glucose, while the vacuum fermentation allowed for complete utilization of glucose. The ethanol yield for the vacuum fermentation was found to be 358 g/kg of food waste (dry basis), higher than that for the conventional fermentation at 327 g/kg of food waste (dry basis).

The utility of the juice of rotten or discarded pineapples and the waste material of the production of pineapple juice as low-cost substrates for ethanol production by Zymomonas mobilis was investigated. Z. mobilis ATCC 10988 produced 59.0g·l −1 ethanol in undiluted pineapple juice without nutritional supplementation and without the regulation of the pH while 42.5g·l −1 ethanol was obtained using a125g·l −1 sucrose medium supplemented with 10g·l −1 yeast extract and mineral salts. Ethanol fermentation using unhydrolyzed and enzymatically hydrolyzed pineapple waste material was also investigated under various culture conditions. When a 15% (v/v) dilution of unhydrolyzed waste material without nutritional supplementation was used, more than 3.5g·l −1 ethanol was produced. When the media containing 15, 30, and 40% (v/v) of the hydrolyzate consisting of a 60% (v/v) suspension of pineapple waste material were used, final concentrations of ethanol were 5.0g·l −1 , 7.6g·l −1 , and 9.3g·l −1 , respectively. These results suggest that pineapple juice and the waste material can be useful low-cost substrates for ethanol production by Z. mobilis without supplementation with expensive organic nitrogen complexes such as yeast extract and without the regulation of the pH during cultivation, leading to the reduction in the production costs.

The enzymatic hydrolysis of food waste by commercially available enzymes and the subsequent ethanol fermentation of the hydrolysates by Saccharomyces cerecisiae H058 were studied in this work. The optimum batch enzymatic conditions were found to be saccharification pH of 4.5, temperature of 55!, glucoamylase concentration of 120 u/g, α-amylase concentration of 10 u/g, solid-liquid ratio of 1: 0.75 (w/w). Fed batch hydrolysis process was started with a solid-liquid ratio of 1: 1 (w/w), with solid food waste added at time lapse of 2 h to get a final solid-liquid ratio of 1: 0.5 (w/w). After 4 h of reaction, the reducing sugar concentration reached 194.43 g/L with a enzymatic digestibility of 93.12%. Further fermentation of the batch and fed batch enzymatic hydrolysates, which contained reducing sugar concentration of 131.41 and 194.43 g/L respectively, was performed using Saccharomyces cerevisiae H058, 62.93 and 90.72 g/L ethanol was obtained within 48 h.

Lower efficiency serves as limiting factor in the enzymatic saccharification of food waste (FW) for ethanol fermentation. We investigated the effects of temperature, tetracycline; the optimization of dual enzymatic inoculation using simplex lattice design; as well as batch ethanol fermentation based on optimized FW saccharification. The moderate temperature (50 °C) was proper to balance the saccharification efficiency and reducing sugar loss. The tetracycline inoculation (80 mg/L) dramatically prevented the reducing sugar loss of saccharification by inhibiting the microbial contaminants. The optimized ratio of α-amylase and amyloglucosidase was 0.5:0.5, which indicated that the experimental results under the optimum conditions agreed well with the model predictions. The ethanol yield reached 0.25 g/g dry FW under optimum conditions of saccharification indicating this strategy could be promising to utilize FW.