Conversion of lipid from food waste to biodiesel

Advanced anaerobic digestion of household food waste pretreated by in situ-produced mixed enzymes via solid-state fermentation: Feasibility and application perspectives

Enzymatic pretreatment is an effective method which can improve the anaerobic digestion (AD) efficiency of household food waste (HFW). As an alternative to expensive commercial enzymes, mixed enzymes (MEs) produced in situ from HFW by solid-state fermentation (SSF) can greatly promote the hydrolysis rate of HFW and achieve advanced anaerobic digestion (AAD) economically sustainable. In this paper, strategies for improving the efficiency of the enzyme-production process and the abundance of MEs are briefly discussed, including SSF, fungal co-cultivation, and stepwise fermentation. The feasibility of using HFW as an applicable substrate for producing MEs (amylase, protease, and lignocellulose-degrading enzymes) and its potential advantages in HFW anaerobic digestion are comprehensively illustrated. Based on the findings, an integrated AAD process of HFW pretreated with MEs produced in situ was proposed to maximise bioenergy recovery. The mass balance results showed that the total volatile solids removal rate could reach 98.56%. Moreover, the net energy output could reach 2168.62 MJ/t HFW, which is 9.79% higher than that without in situ-produced MEs and pretreatment. Finally, perspectives for further study are presented.

Moving towards the Application of Biocatalysis in Food Waste Biorefinery

Waste valorization is an important strategy to reduce environmental pollution and dependency on petroleum-based fuels. In this regard, utilization of food waste as a versatile and low-cost resource is important. Several advanced catalytic methods for the valorization of food waste have been widely investigated for the production of liquid biofuels. Along this line, chemical catalysts have been explored for the synthesis of liquid biofuels. Chemo-catalysis is mainly metal based, which requires harsh process conditions. Alternatively, biocatalysts are currently being investigated as a result of several advantages such as mild reaction conditions, recyclability, selectivity and biodegradability. In this work, recent biocatalytic technologies for the preparation of liquid biofuels through food waste valorization are discussed thoroughly. Lipases are employed for the synthesis of biodiesel and the upgradation of bio-oil, whereas methane mono-oxygenases could be explored for the production of methanol via the oxidation of methane generated from food wastes. Industrial production of ethanol from food waste using bioconversion technologies is a success story. To date, there has been no specific report on the use of food waste for propanol preparation using enzymes. The ABE process (Acetone–Butanol–Ethanol) (using suitable microorganisms) is used for butanol preparation, where the vacuum stripping system is integrated to remove butanol from the broth and circumvent inhibition. The synthesis of hydrocarbon fuels from fatty acids and triglycerides can be carried out using enzymes, such as carboxylic acid reductase and fatty acid photodecarboxylase (an algal photoenzyme). Both carboxylic acid reductase and fatty acid photodecarboxylase have not yet been applied in the direct valorization of food wastes. Furthermore, limitations of the reported methods, societal and economic aspects and a fresh perspective on the subject, along with important examples, are described.

Effect of hydrothermal pretreatment and compound microbial agents on compost maturity and gaseous emissions during aerobic composting of kitchen waste

Though aerobic composting is commonly used in kitchen waste (KW) disposal, the high-oil and high-salt characteristics of KW could affect composting efficiency and lead to the land using risk of produced fertilizer. The impact of hydrothermal pretreatment (HTP) and addition of compound microbial agent (CMA) on compost maturity, greenhouse gas (GHGs) emissions and bacterial community during the kitchen waste composting were evaluated in the present work. Results indicated that N2O, CH4 and CO2 emissions from treatment by HTP and CMA addition were reduced by 82.72%, 13.77% and 20.78 %, respectively, comparing with the control (without HTP and without CMA addition). The seed germination index (GI) value of the HTP and CMA addition treatment was 1.03 and had the highest maturity in all treatments. Furthermore, the bacterial community analysis indicated that CMA inoculation could increase the relative abundance of genus Bacillus at the thermophilic stage of composting to accelerate organic biodegradation. This work provided important insight into mitigating GHGs emissions and improving compost quality in kitchen waste composting.

Effect of hydrothermal pretreatment on the degrease performance and liquid substances transformation of kitchen waste

Hydrothermal treatment (HT) is a pragmatic approach for pretreatment of kitchen waste (KW). This work investigated the effect of hydrothermal pretreatment (HTP) on the deoiling, desalting and liquid substances transformation of KW. The orthogonal test method was used to study the effects of three factors at five levels, including solid to liquid ratio (A_1-5), heating time (B_1-5) and hydrothermal temperature (C_1-5). The results indicated that the floatable oil content was improved significantly after HTP. The highest floatable oil content was 84.54 mL/kg at the hydrothermal condition of 1/1.5, 20 min and 100 °C, which was 2.42 times higher than the control. The maximum desalination ratio (92.66%) was at A₅B₁C₅ (1/2.5, 5 min, 100 °C), which was 4.48 times higher than control group (No.0) (20.67%). The VFAs concentration was the highest (11441.05 mg/kg) at 1/2.5, 5 min and 100 °C, which increased by 711.03% compared to the No.0 (1410.78 mg/kg). In addition, the maximum TOC value was obtained at 53530.84 mg/kg. After HTP, the acetic acid and butyric acid concentrations of the liquid phase increased, while the ethanol concentration decreased. The contents of T,NH₄⁺-N and organic nitrogen in the liquid phase of the HTP system increased, while NO₃^--N remained at a low level (4.96-20.48 mg/kg). The range and variance analysis showed that the temperature had the greatest effect on the deoiling and the liquid substances transformation of KW among these three factors, followed by solid to liquid ratio and heating time. Based on the orthogonal experiment, the optimal parameters for KW deoiling were A₃ (1/1.5), B₄ (25 min) and C₅ (100 °C). This work provided a reference for the KW deoiling and hence improve the efficient utilization of KW.

Integrated polylactic acid and biodiesel production from food waste: Process synthesis and economics

In this study, techno-economic analysis of the sustainable production of polylactic acid (PLA) and biodiesel from Food Waste (FW), with a plant capacity of 50 tons/day, was investigated. In addition, FW of four countries (China, India, Brazil, and the USA) with different compositions of water, protein, lipid and carbohydrate were proposed. Each country has different PLA production rates based on carbohydrate and biodiesel production based on fat. In this study, the FW composition of the USA shows better economic feasibility than other countries. The actual minimum selling price is 6.53 (China), 5.35 (India), 4.75 (Brazil), and 4.29 (US) $/kg. The uncertainty of the MSP was analyzed based on various input limits. The sensitivity analysis was conducted based on biodiesel-selling price, PLA-selling price, income tax, and project lifetime on techno-economic analysis parameters, such as ROI, payback period, IRR and NPV were investigated.

Critical Factors and Emerging Opportunities in Food Waste Utilization and Treatment Technologies

Globally, approximately one-third of food produced for human consumption is lost or discarded, comprising 1. 3 billion tons annually. Factors contributing to food waste from the food manufacturer to the consumer level are numerous. Events that may result in food waste include, but are not limited to, manufacturing food by-products, improper handling within the supply chain (e.g., cold chain deviations), misunderstood food date labels, over-purchasing, and consumer-level temperature abuse. From the manufacturer to consumer, each node in the food supply requires concerted efforts to divert food waste from entering municipal landfills. Depending on the state of the food waste, it is diverted to various outlets, from food donation for consumption to composting for soil amendment. To better understand the opportunities in the United States to divert food waste from landfills, current and emerging federal policies as well as the causes of food waste generation must be understood. Unfortunately, information on both the composition of food waste in the U.S. and how it impacts critical factors in food waste treatment, especially in food waste composting, is limited. Specifically, this review aims to: (1) discuss and compare critical factors that impact the fate of food waste and (2) examine emerging opportunities to advance the processing and products of food waste.

Hydrothermal carbonization of simulated food waste for recovery of fatty acids and nutrients

We conducted Hydrothermal carbonization (HTC) of simulated food waste under different reaction conditions (180 to 220 °C, 15 and 30 min), with the aim of recovering both fatty acids from the hydrochar and nutrients from the aqueous-phase products. HTC of the simulated food waste produced hydrochar that retained up to 78% of the original fatty acids. These retained fatty acids were extracted from the hydrochar using ethanol, a food-grade solvent, and gave a net recovery of fatty acid of ∼ 50%. The HTC process partitioned more than 50 wt% of the phosphorus and around 38 wt% of the nitrogen into the aqueous-phase products. A reaction path consistent with decarboxylation predominated during HTC under all of the reaction conditions investigated. A path consistent with dehydration was also observed, but only for the more severe reaction conditions. This work illustrates the potential that HTC has for valorization of food waste.

Recent advances in valorization of organic municipal waste into energy using biorefinery approach, environment and economic analysis

Researcher's all around works on a copious technique to lessen waste production and superintend the waste management for long-term socio-economic and environmental benefits. Value-added products can be produced from municipal waste by using holistic and integrated approaches. In this review, a detail about the superiority of the different methods like anaerobic digestion, biofuel production, incineration, pyrolysis and gasification were used for the conversion of municipal waste to feedstock for alternate energy and its economic- environmental impacts were consolidated. Most conversion techniques were environmentally friendly to manage municipal waste. The biological process was more economically feasible compare to the thermal process, for the reason thermal process required a large amount of capital investment and energy utilization. In the thermal process, gasification shows low emission, and pyrolysis shows low capital investment and economically feasible compare to other thermal processes. Waste to energy technology significantly reduced the emission and energy demand.

Effect of pH on the Economic Potential of Dark Fermentation Products from Used Disposable Nappies and Expired Food Products

Used disposable nappies constitute a waste stream that has no established treatment method. The purpose of this study was the assessment of the dark fermentation of used disposable nappies and expired food products under different pH values. The biodegradable part of the used disposable nappies was recovered and co-fermented with expired food products originating from supermarkets. The recoverable economic potential of the process was examined for different volatile fatty acids exploitation schemes and process pH values. The process pH strongly affected the products, with optimum hydrogen production at pH 6 (4.05 NLH2/Lreactor), while the amount of produced volatile fatty acids was maximized at pH 7 (13.44 g/L). Hydrogen production was observed at pH as low as pH 4.5 (2.66 NLH2/Lreactor). The recoverable economic potential was maximized at two different pH values, with the first being pH 4.5 with minimum NaOH addition requirements (181, 138, and 296 EUR/ton VS of substrate for valorization of volatile fatty acids through microbial fuel cell, biodiesel production, and anaerobic digestion, respectively) and the second being pH 6, where the hydrogen production was maximized with the simultaneous production of high amounts of volatile fatty acids (191, 142, and 339 EUR/ton VS of substrate respectively).

Sustainable processing of food waste for production of bio-based products for circular bioeconomy

Sustainable development of circular bioeconomy concept is only possible upon adopting potential advanced technologies for food waste valorization. This approach can simultaneously answer resources and environmental challenges incurred due to capital loss and greenhouse gases accumulation. Food waste valorization opens new horizons of economical growth, bringing waste as an opportunity feedstock for bio processes to synthesize biobased products from biological source in a circular loop. Advanced technologies like Ultrasound assisted extraction, Microwave assisted extraction, bioreactors, enzyme immobilization assisted extraction and their combination mitigates the global concern caused due to mismanagement of food waste. Food waste decomposition to sub-zero level using advanced techniques fabricates food waste into bio-based products like bioactive compounds (antioxidants, pigments, polysaccharides, polyphenols, etc.); biofuels (biodiesel, biomethane, biohydrogen); and bioplastics. This review abridges merits and demerits of various advanced techniques extended for food waste valorization and contribution of food waste in revenue generation as value added products.

Food waste valorization: Energy production using novel integrated systems

Management of food waste (FW) is a global challenge due to increasing population and economic activities. Presently, landfill and incineration are the keyways of FW management, while economical and environmental sustainability have been an issue. Therefore, the biological processes have been investigated for resource and energy recovery from FW. However, these biological approaches have certain drawbacks and cannot be a complete solution for FW management. Therefore, this review aims to offer a detailed and complete analysis of current available technologies to achieve environmental and economical sustainability. In this context, zero solid waste discharge for resource and energy recovery has been put into view. Corresponding to which several innovative technologies using integrated biological methods for resource and energy recovery from FW have been elucidated.

Application of life cycle assessment for municipal solid waste management options in Hohhot, People's Republic of China

With increasing population and urbanization levels in the People's Republic of China, environmental problems related to the management of municipal solid waste (MSW) are inevitable. This study aimed to determine the environmental impact of the current MSW management system in Hohhot City and to establish an optimum future strategy for it by applying life cycle assessment (LCA) methodology. Four scenarios were compared using the CML-IA impact characterization method, which took into account their potential contribution to global warming, ozone depletion, human toxicity, photochemical ozone creation, acidification, and eutrophication potentials. The system boundaries included the collection and recycling, transfer and transportation of MSW, and its disposal by incineration, landfilling, and carbon dioxide (CO₂) capture methods. The results showed that the scenario involving landfill and incineration in a ratio of 1:5 was the optimal waste management option; however, increasing the proportion of waste incinerated led to a significant increase in global warming potential. Additional technologies are thus required to overcome this problem, and it was found that the use of CO₂ capture technology resulted in a 30% reduction in the total environmental impact potential. This study's results indicate that LCA is a valuable and practical tool to support decision-making that can be used to suggest problematic areas in current waste management strategies and to determine an optimal alternative to the solid waste management option.

Estimation and analysis of municipal food waste and resource utilization potential in China

With rapid urbanization, municipal food waste (MFW), which is an important part of municipal solid waste, has attracted considerable attention owing to its environmental impact and polluting nature. There has been little research on the quantity and distribution of food waste (FW) produced in China. This study focused on a systematic estimation and analysis of MFW produced in administrative divisions at the prefecture-level and above in China for the first time. From the national level to the prefectural level, with the shrinking of the research units, more intuitive support was obtained for relevant decisions. On the basis of the estimated results, suggestions are provided for proper FW treatment technologies and operational scale of the facilities, and the resource utilization potential has also been estimated. The distribution results indicated that FW characteristics have great variability in the different economic regions of China. Furthermore, it was found that the available FW has a resource utilization potential that is equivalent to 4669.1 million m³ of biogas, 3.6 million tons of biodiesel, and 1.5 million tons of organic fertilizer (dry weight). It is worth mentioning that this amount of biogas can replace 7.5 million tons of standard coal. However, only a small part of the generated MFW can be treated in the existing treatment plants in China. Finally, current key bottlenecks of FW treatment in China have been discussed, and detailed suggestions are presented for further improvement of MFW management.

A review on valorization of spent coffee grounds (SCG) towards biopolymers and biocatalysts production

Spent coffee grounds (SCG) are an important waste product millions of tons generated from coffee consumption and could be effectively utilized for various applications due to their high organic content. SCG can be used as a potential feedstock to develop coffee-based biorefinery towards value-added products generation through various biotechnological processes. Considerable developments have been reported on emerging SCG-based processes/products in various environmental fields such as removal of heavy metals and cationic dyes and in wastewater treatment. In addition, SCG are also utilized to produce biochar and biofuels. This review addressed the details of innovative processes used to produce polymers and catalysts from SCG. Moreover, the application of these developed products is provided and future directions of the circular economy for SCG utilization.

Electricity generation from food wastes and spent animal beddings with nutrients recirculation in catalytic fuel cell

A biochemical system was used for electricity generation from food waste (FW) and spent animal beddings (SAB). The wastes were blended and fermented anaerobically to produce fermentation liquids used as fuels for running a catalytic fuel cell. The fermentation liquids were analyzed for their components. The results show the organic contents i.e. volatile solids of both FW and SAB to be 23.4 and 20.9 g/L while the carbon contents were 6.5 and 6.1 g/L respectively. The media were however very rich in volatile fatty acids (VFAs). When used, the fermentation liquids from FW and SAB generated mean open-circuit voltages of 0.64 and 0.53 V and mean maximum power densities (P_mean) of 1.6 and 1.3 mW/cm² respectively. The fuel cell showed very high efficiency in the conversion of all VFAs especially butyric acid with the highest been 97% for FW and 96% for SAB.

Microbial strategies for bio-transforming food waste into resources

With the changing life-style and rapid urbanization of global population, there is increased generation of food waste from various industrial, agricultural, and household sources. According to Food and Agriculture Organization (FAO), almost one-third of the total food produced annually is wasted. This poses serious concern as not only there is loss of rich resources; their disposal in environment causes concern too. Food waste is rich in organic, thus traditional approaches of land-filling and incineration could cause severe environmental and human health hazard by generating toxic gases. Thus, employing biological methods for the treatment of such waste offers a sustainable way for valorization. This review comprehensively discusses state-of-art knowledge about various sources of food waste generation, their utilization, and valorization by exploiting microorganisms. The use of microorganisms either aerobically or anaerobically could be a sustainable and eco-friendly solution for food waste management by generating biofuels, electrical energy, biosurfactants, bioplastics, biofertilizers, etc.

Valorizing kitchen waste through bacterial cellulose production towards a more sustainable biorefinery

In this work, water washing pretreatment was employed on kitchen waste (KW) to integrate a multi-product biorefinery process for producing biogas, biodiesel, bacterial cellulose (BC) and biofertilizer. As a crucial stream in this biorefinery process, BC production were investigated to clarify the effects of residual salt and cooked oil. Meanwhile, glycerol, a by-product in biodiesel stream, as carbon source was attempted to produce BC. Results indicated that BC yield was significantly promoted from 0.11 g L^-1 to 2.07 g L^-1 as NaCl content decreased from 0.44% to 0.04%. Correspondingly, the BC crystallinity increased from 30.1% to 57.4% and the tensile strength increased from 3.30 MPa to 21.64 MPa. In addition, the residual cooked oil didn't affect the BC yield significantly, however, the crystallinity was greatly decreased from 57.4% to 34.5% as more cooked oil was remained in the medium of KW, and the tensile strength was decreased from 21.64 MPa to 4.30 MPa, correspondingly. Obviously, reducing the salt and cooked oil content in the starch fraction of KW by intensifying the water washing pretreatment will greatly benefit the BC yield and qualities. When the glycerol from biodiesel stream was employed for BC production with content of 10 g L^-1-25 g L^-1, 34.2%-44.0% increase on BC yield can be achieved. By contrast, extra higher glycerol content (50 g L^-1) reduced the BC yield by 41%. However, the crystallinity and the tensile strength were increased by 18% and 2.2-folds, respectively. Therefore, the biodiesel stream can be well integrated in the process via producing BC with by-product of glycerol as a replaceable carbon source. Based on the results above, a more sustainable biorefinery process of KW via BC production can be achieved, which will potentially offer a new path to valorize the daily-released KW.

Investigation of the archeological remains using ultrahigh resolution mass spectrometry

Investigation of the archeological material at the molecular level can reveal the composition of ancient paint, balsamic material, reveal cooking recipes, etc. High-resolution mass spectrometry is a powerful technique with underestimated potential for archeology. Here, we present the investigation of the 3000-year-old archeological remains, identified as parts of internal organs of an Egyptian mummy, using high-resolution Orbitrap mass spectrometry. We observed a diverse number of oxidized classes of compounds: O, O₂, O₃, O₄, O₅, N, NO, NO₂, NO₃, NO₄, NO₅, N₂O, N₂O₂. Such chemical composition is unusual and we never observed it in our previous studies of petroleum, humic substances, products of wood pyrolysis or other natural complex mixtures. It is possible that such compounds are formed via biodegradation of lipids and other organic material used for funeral rites. We did not observe evidence of the presence of mineral bitumen, although there are many historical records of the use of mineral bitumen for mummification.

Valorization of food-waste hydrolysate by Lentibacillus salarius NS12IITR for the production of branched chain fatty acid enriched lipid with potential application as a feedstock for improved biodiesel

Oxidation stability and cold flow properties of biodiesel can be improved by using lipid with enriched branched-chain fatty acid (BCFA) as a feedstock. A halophilic bacterium was utilized for the production of BCFA enriched lipid from acid hydrolysate of food-waste. The maximum reducing sugar obtained by hydrolysis of wheat bran, rice bran, mango peel, and orange peel were 64.52 ± 0.57, 38.7 ± 0.58, 55.64 ± 1.14, 36.29 ± 0.54 g/L, respectively. On assessing these hydrolysates as feedstock for growth of halophilic bacterium Lentibacillus salarius NS12IITR at 10 g/L reducing sugar concentration, wheat bran hydrolysate was found to be best in-terms of sugar consumption (92%), lipid production (0.70 ± 0.029 g/L) and maximum branched-chain fatty acid methyl ester (FAME) (81 ± 4.72% of total FAME). At 20 g/L of reducing sugar concentration of wheat bran hydrolysate, the biomass and lipid yields were almost doubled. Efficient lipid extraction from cell, involving thermolysis at 85 °C and pH 2 along with osmotic shock resulted in isolation of 69% of total lipid.

High-Resolution Mass Spectrometry Study of the Bio-Oil Samples Produced by Thermal Liquefaction of Microalgae in Different Solvents

We have performed a comparative analysis of the bio-oil produced by thermal liquefaction of microalgae in different solvents using high-resolution Orbitrap mass spectrometry and GC-MS approach. Water, methanol, ethanol, butanol, isopropanol, acetonitrile, toluene, and hexane were used as solvents in which the liquefaction was performed. It was observed that all resulting oils demonstrate a considerable degree of similarity. For all samples, compounds containing 1 and 2 nitrogen atoms dominated in the positive ESI spectra, while a relative contribution of other compounds was small. In negative ESI mode, compounds having 2 to 7 oxygens were observed. Statistical analysis revealed that products can be combined in two groups depending on the solvent used for the liquefaction. To the first group, we can attribute the products obtained by using protic (alcohols) and to the second by using aprotic (acetonitrile, toluene) solvents. Nevertheless, based on our results, we concluded that solvent possesses a minor impact on molecular composition of bio-oil. We suggested that the driving force of the liquefaction reaction is the thermal dehydration of the carbohydrate in algae, resulting in water formation, which could be the trigger of the producing of bio-oil. To prove this hypothesis, we performed the reaction with the dry algae in the absence of the solvent and observed the formation of bio-oil. Graphical Abstract.

Characterization of food waste from different sources in Hong Kong

Food waste from different sources or at different generation stages may have different compositional characteristics and is therefore suitable for recycling into different products. To have a better understanding of their chemical composition, five food waste types were collected, namely, household kitchen waste (HH), preconsumption and postconsumption food waste from a hotel (Hpr and Hpo), wet market food waste (WM) and kitchen waste from a Chinese restaurant (CR), and their compositions were assessed monthly for 1 year. They served as suitable feedstock for various conversion technologies according to their chemical profiles. HH and CR had higher crude protein content (26%) and considerable amounts of minerals, making them nutritionally suitable for feeding animals. Preconsumption food wastes Hpr and WM had more favorable C:N ratios (16.5-17.4) and crude fat contents (4.6-6.5%) as feedstock for composting. Postconsumption food wastes were potential feedstock for the production of biogas and biodiesel because of the higher dry matter (>26%) and fat content (>13%). The coefficients of variation (CV) in all nutrients analyzed except Ca for postconsumption food wastes ranged from 5% to 37%, which showed lower temporal variability than preconsumption food wastes (CVs 10-131%). This implies that the composition of postconsumption food waste was relatively less fluctuating and can be considered a more reliable feedstock for food waste conversion. Implications: Characterization of food waste composition from different sources and determination of their temporal variation were performed to understand their characteristics and facilitate sound food waste management. Separating food wastes according to their sources and types helps reduce their composition variability, and thus increases the consistence in food-waste-derived products and recycling success. Study on temporal variation indicates that postconsumption food wastes varied less with time and could serve as reliable feedstocks for food waste conversion.

Physicochemical property enhancement of biodiesel synthesis from hybrid feedstocks of waste cooking vegetable oil and Beauty leaf oil through optimized alkaline-catalysed transesterification

Recycling waste cooking vegetable oils by reclaiming and using these oils as biodiesel feedstocks is one of the promising solutions to address global energy demands. However, producing these biodiesels poses a significant challenge because of their poor physicochemical properties due the high free fatty acid content and impurities present in the feedstock, which will reduce the biodiesel yields. Hence, this study implemented the following strategy in order to address this issue: (1) 70 vol% of waste cooking vegetable oil blended with 30 vol% of Calophyllum inophyllum oil named as WC70CI30 used to alter its properties, (2) a three-stage process (degumming, esterification, and transesterification) was conducted which reduces the free fatty acid content and presence of impurities, and (3) the transesterification process parameters (methanol/oil ratio, reaction temperature, reaction time, and catalyst concentration) were optimized using response surface methodology in order to increase the biodiesel conversion yield. The results show that the WC70CI30 biodiesel has favourable physicochemical properties, good cold flow properties, and high oxidation stability (22.4 h), which fulfil the fuel specifications stated in the ASTM D6751 and EN 14214 standards. It found that the WC70CI30 biodiesel has great potential as a diesel substitute without the need for antioxidants and pour point depressants.

Valorisation of food and beverage waste via saccharification for sugars recovery

Valorisation of mixed food and beverage (F&B) waste was studied for the recovery of sugars via saccharification. Glucoamylase and sucrase were employed to hydrolyse the starch and sucrose present in the mixed F&B waste because of the high cost-effectiveness for such recovery. The Michaelis-Menten kinetics model suggests that preservatives and additives in beverages did not inhibit glucoamylase and sucrase during saccharification. High levels of glucose (228.1 g L^-1) and fructose (55.7 g L^-1) were efficiently produced within 12 h at a solid-to-liquid ratio of 37.5% (w/v) in 2.5 L bioreactors. An overall conversion yield of 0.17 g sugars per g of mixed F&B waste was obtained in mass balance analysis. Lastly, possible industrial applications of the sugar-rich hydrolysate and by-products are discussed. This study is believed to cast insights into F&B waste recycling via biotechnology to produce high-value added products to promote the establishment of a circular bio-economy.

A spent coffee grounds based biorefinery for the production of biofuels, biopolymers, antioxidants and biocomposites

Spent coffee grounds are composed of lipid, carbohydrates, carbonaceous, and nitrogen containing compounds among others. Using n-hexane and n-hexane/isopropanol mixture highest oil yield was achived during soxhlet extraction of oil from spent coffee grounds. Alternatively, supercritical carbon dioxide can be employed as a green solvent for the extraction of oil. Using advanced chemical and biotechnological methods, spent coffee grounds are converted to various biofuels such as, biodiesel, renewable diesel, bioethanol, bioethers, bio-oil, biochar, and biogas. The in-situ transesterification of spent coffee grounds was carried out in a large scale (4 kg), which led to 80-83% biodiesel yield. In addition, a large number of value added and diversified products viz. polyhydroxyalkanoates, biosorbent, activated carbon, polyol, polyurethane foam, carotenoid, phenolic antioxidants, and green composite are obtained from spent coffee grounds. The principles of circular economy are applied to develop a sustanaible biorefinery based on valorisation of spent coffee grounds.

Utilization of organic residues using heterotrophic microalgae and insects

Various organic residues occur globally in the form of straw, wood, green biomass, food waste, feces, manure etc. Other utilization strategies apart from anaerobic digestion, composting and incineration are needed to make use of the whole potential of organic residues as sources of various value added compounds. This review compares the cultivation of heterotrophic microalgae and insects using organic residues as nutrient sources and illuminates their potential with regard to biomass production, productivity and yield, and utilization strategies of produced biomasses. Furthermore, cultivation processes as well as advantages and disadvantages of utilization processes are identified and discussed. It was shown that both heterotrophic algae and insects are able to reduce a sufficient amount of organic residues by converting it into biomass. The biomass composition of both organisms is similar which allows similar utilization strategies in food and feed, chemicals and materials productions. Even though insect is the more complex organism, biomass production can be carried out using simple equipment without sterilization and hydrolysis of organic residues. Contrarily, heterotrophic microalgae require a pretreatment of organic residues in form of sterilization and in most cases hydrolysis. Interestingly, the volumetric productivity of insect biomass exceeds the productivity of algal biomass. Despite legal restrictions, it is expected that microalgae and insects will find application as alternative food and feed sources in the future.

Investigation of bio-oil produced by hydrothermal liquefaction of food waste using ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry

Recent research has revealed that more than 1.3 billion tons of food is wasted globally every year. The disposal of such huge biomass has become a challenge. In the present paper, we report the production of the bio-oil by hydrothermal liquefaction of three classes of food waste: meat, cheese and fruits. The highest yield of the bio-oil was observed for meat (∼60%) and cheese (∼75%), while for fruits, it was considerably low (∼10%). The molecular composition of the obtained bio-oil was investigated using ultrahigh resolution Fourier Transform Ion Cyclotron Resonance mass spectrometry and was found to be similar to that obtained from algae. Several thousand heteroatom compounds (N, N₂, ON₂, etc. classes) were reliably identified from each sample. It was found that bio-oils produced from meat and cheese have many compounds (∼90%) with common molecular formulas, while bio-oil produced from fruits differs considerably (∼30% of compounds are unique).

Valorisation of food waste via fungal hydrolysis and lactic acid fermentation with Lactobacillus casei Shirota

Food waste recycling via fungal hydrolysis and lactic acid (LA) fermentation has been investigated. Hydrolysates derived from mixed food waste and bakery waste were rich in glucose (80.0-100.2gL(-1)), fructose (7.6gL(-1)) and free amino nitrogen (947-1081mgL(-1)). In the fermentation with Lactobacillus casei Shirota, 94.0gL(-1) and 82.6gL(-1) of LA were produced with productivity of 2.61gL(-1)h(-1) and 2.50gL(-1)h(-1) for mixed food waste and bakery waste hydrolysate, respectively. The yield was 0.94gg(-1) for both hydrolysates. Similar results were obtained using food waste powder hydrolysate, in which 90.1gL(-1) of LA was produced with a yield and productivity of 0.92gg(-1) and 2.50gL(-1)h(-1). The results demonstrate the feasibility of an efficient bioconversion of food waste to LA and a decentralized approach of food waste recycling in urban area.

Optimization and kinetic modeling of esterification of the oil obtained from waste plum stones as a pretreatment step in biodiesel production

This study reports on the use of oil obtained from waste plum stones as a low-cost feedstock for biodiesel production. Because of high free fatty acid (FFA) level (15.8%), the oil was processed through the two-step process including esterification of FFA and methanolysis of the esterified oil catalyzed by H2SO4 and CaO, respectively. Esterification was optimized by response surface methodology combined with a central composite design. The second-order polynomial equation predicted the lowest acid value of 0.53mgKOH/g under the following optimal reaction conditions: the methanol:oil molar ratio of 8.5:1, the catalyst amount of 2% and the reaction temperature of 45°C. The predicted acid value agreed with the experimental acid value (0.47mgKOH/g). The kinetics of FFA esterification was described by the irreversible pseudo first-order reaction rate law. The apparent kinetic constant was correlated with the initial methanol and catalyst concentrations and reaction temperature. The activation energy of the esterification reaction slightly decreased from 13.23 to 11.55kJ/mol with increasing the catalyst concentration from 0.049 to 0.172mol/dm(3). In the second step, the esterified oil reacted with methanol (methanol:oil molar ratio of 9:1) in the presence of CaO (5% to the oil mass) at 60°C. The properties of the obtained biodiesel were within the EN 14214 standard limits. Hence, waste plum stones might be valuable raw material for obtaining fatty oil for the use as alternative feedstock in biodiesel production.

Extraction of medium chain fatty acids from organic municipal waste and subsequent production of bio-based fuels

This paper provides an overview on investigations for a new technology to generate bio-based fuel additives from bio-waste. The investigations are taking place at the composting plant in Darmstadt-Kranichstein (Germany). The aim is to explore the potential of bio-waste as feedstock in producing different bio-based products (or bio-based fuels). For this investigation, a facultative anaerobic process is to be integrated into the normal aerobic waste treatment process for composting. The bio-waste is to be treated in four steps to produce biofuels. The first step is the facultative anaerobic treatment of the waste in a rotting box namely percolate to generate a fatty-acid rich liquid fraction. The Hydrolysis takes place in the rotting box during the waste treatment. The organic compounds are then dissolved and transferred into the waste liquid phase. Browne et al. (2013) describes the hydrolysis as an enzymatically degradation of high solid substrates to soluble products which are further degraded to volatile fatty acids (VFA). This is confirmed by analytical tests done on the liquid fraction. After the percolation, volatile and medium chain fatty acids are found in the liquid phase. Concentrations of fatty acids between 8.0 and 31.5 were detected depending on the nature of the input material. In the second step, a fermentation process will be initiated to produce additional fatty acids. Existing microorganism mass is activated to degrade the organic components that are still remaining in the percolate. After fermentation the quantity of fatty acids in four investigated reactors increased 3-5 times. While fermentation mainly non-polar fatty acids (pentanoic to octanoic acid) are build. Next to the fermentation process, a chain-elongation step is arranged by adding ethanol to the fatty acid rich percolate. While these investigations a chain-elongation of mainly fatty acids with pair numbers of carbon atoms (acetate, butanoic and hexanoic acid) are demonstrated. After these three pre-treatments, the percolate is brought to a refinery to extract the non-polar fatty acids using bio-diesel, which was generated from used kitchen oil at the refinery. The extraction tests in the lab have proved that the efficiency of the liquid-liquid-extraction is directly linked with the chain length and polarity of the fatty acids. By using a non-polar bio-diesel mainly the non-polar fatty acids, like pentanoic to octanoic acid, are extracted. After extraction, the bio-diesel enriched with the fatty acids is esterified. As a result bio-diesel with a lower viscosity than usual is produced. The fatty acids remaining in the percolate after the extraction can be used in another fermentation process to generate biogas.