A Review on the Challenges and Choices for Food Waste Valorization: Environmental and Economic Impacts

Abstract

Valorization of food waste (FW) is instrumental for reducing the environmental and economic burden of FW and transitioning to a circular economy. The FW valorization process has widely been studied to produce various end-use products and summarize them; however, their economic, environmental, and social aspects are limited. This study synthesizes some of the valorization methods used for FW management and produces value-added products for various applications, and also discusses the technological advances and their environmental, economic, and social aspects. Globally, 1.3 billion tonnes of edible food is lost or wasted each year, during which about 3.3 billion tonnes of greenhouse gas is emitted. The environmental (−347 to 2969 kg CO₂ equiv/tonne FW) and economic (−100 to $138/tonne FW) impacts of FW depend on the multiple parameters of food chains and waste management systems. Although enormous efforts are underway to reduce FW as well as valorize unavoidable FW to reduce environmental and economic loss, it seems the transdisciplinary approach/initiative would be essential to minimize FW as well as abate the environmental impacts of FW. A joint effort from stakeholders is the key to reducing FW and the efficient and effective valorization of FW to improve its sustainability. However, any initiative in reducing food waste should consider a broader sustainability check to avoid risks to investment and the environment.

Introduction

The food industry generates a vast amount of food waste (FW, either dry or wet), which is attracting a lot of attention not only because of the environmental and economic impacts but also because of the growing concerns for food due to the ever-increasing population on the earth, the changing population demographics, and the effect of climate change on food production.^1,2 Feeding people recovered food from scrapings and waste behavior is challenging. Moreover, food rescue is incredibly expensive. The current model for food waste disposition is not based upon economically sustainable practices. In addition, food loss or waste generation depends on the type of food. For example, loss and waste are greater in the case of perishable food such as fruits and vegetables. The Food and Agriculture Organization (FAO) of the United Nations noted that agricultural, industrial processing, retail, and the final consumption stages are responsible for 11–23, 17–19, 8–17, and >50% of FW, respectively.^1,2 In addition, the generation of FW also depends on the recovery of byproducts. For example, in the United States of America, carcass yield for cattle-meat processing is around 40%, which consists of hides, bone, and paunch of about 10%, 40%, and 5%, respectively; however, much of these are considered waste.^3,4 In the case of poultry, the carcass yield is reported to be 40% and 80% for deboned and whole birds, respectively.⁴ However, the carcass yield is noted to be 40–50% in the case of fish.⁴ The recovery rate of sweet corn, processing tomatoes, potatoes, peppers, grain and soy processing, and fresh-cut produce processing is 25–30% (90% of that is used for animal feed), 90–95%, 90%, 40–80%, 90–96%, and 20–50% (squash, 50% hull and seed; apples, 30%), respectively.⁴

In Canada, food loss and waste in primary processing, secondary processing (further processing), and distribution stages were 34%, 13%, and 4%, respectively. Fruit industries generate approximately 30–35% of whole fruits as FW;^5,6 however, the reported FW was 60% in the case of durian. In Canada, 58% of all food supply is lost or wasted;⁷ however, one-third of wasted food could be recovered,⁷ a portion of which could be sent to communities across the country. If food recovery is excluded, the ultimate FW would be lower than the reported amount.⁴ In 2017, Canadian consumers threw away the vast majority of 63% of foods that could have been eaten, and about $49.5 billion of FW is avoidable.^7,8 In 2019, avoidable food loss and waste in production, manufacturing, processing, distribution, retail store, hotel and restaurants, and consumer levels were 6%, 23%, 20%, 5%, 12%, 13%, and 21%, respectively.⁹ However, the production, processing, distribution, and consumption sector contributed 28%, 17%, 9%, and 46% to the total food waste in the United Kingdom, respectively.¹⁰ Globally, on average, fruits and vegetables contributed about 45% to the total FW (Figure 1). Usually, unavoidable FW, especially peel, skin, and twigs of fruits, contains a greater amount of bioactive compounds than do the edible portions.^11,12 In addition, it is also reported that food processing waste is rich in protein, lipid, and carbohydrates, thus exhibiting valorization (conversion of FW into value-added products) potential¹³ in producing animal feed, cosmetics, chemicals, as well as prebiotics,^14,15 and it can play an important role in reducing problems associated with FW.¹⁶

Figure 1.

Share of various global food waste.²³ [Fruits and vegetables are the major contributors to the total FW in different jurisdictions followed by cereals, root and tubers, milk, meat, and others. However, the generation of FW depends on the types of food, processing stages, and food supply chains, as well as the jurisdictions.]

On average, annually, a Canadian family spends $1766.0 on food that is wasted.¹⁷ Annually, wasted or lost food weighed 35.5 million tonnes,¹⁸ which emits 56.5 million tonnes of greenhouse gas (GHG) (CO₂ equiv) in Canada.⁷ Annually, FW costs about $100 billion, and $49 billion is sent to landfills or composted,⁹ which leads to environmental, economic, and societal implications.¹⁹ However, in the United Kingdom (UK), FW was 13.1 million tonnes of food, which emits 27.0 million tonnes of GHG.¹⁰ We noted that cereals and vegetables contributed 31% and 28%, respectively, to the total FW; however, meat and fish were the major contributors to total emissions even though they contributed only 10% to the total FW. In the U.S., more than $10 billion annual net economic value is identified from FW prevention and recovery initiatives.²⁰ FW and loss is a major concern of the environment, economy, society, and health; thus, it is considered as one of the 10 circular economy (circular economy refers to an economy that involves industrial processes and economic activities to restore or regenerate products eliminating waste while maintaining their highest value²¹) indicators.²² Valorizing the vast amount of FW can provide economic benefits and reduce GHG emissions.

The higher is the food loss, the greater is the life cycle inventory.²⁴ It is also worth mentioning that globally about $1 trillion and 26 × 10⁹ GJ of energy is wasted every year.²⁵ Therefore, it is important to reduce FW as well as valorize them to reduce food^26,27 and energy insecurity and abate GHG gas emissions from the wasted food as well as to enhance the profitability of farms/food industries (Box 1: Food Waste Generation and Valorization). It is also argued that the effective valorization of FW would improve the sustainability of food chains.²⁸ In 2016, Ontario enacted Bill 151 to address rising waste generation and promote the circular economy including organic waste.²⁹

FW can be valorized in several ways for generating heat and power, solid or liquid fuels, biomaterials, or chemicals (biofertilizer, biocarbon, activated carbon, graphene, additives, volatile acids, etc.) for various applications depending on their characteristics. For example, processed FW was used as a filler material for producing biocomposite,^6,30 bioplastics,³¹ and generating heat and power^32,33 in the valorization process. However, a biodegradable composite film has also been produced from carrot processing waste via bench casting for food packaging applications.³⁴ An enormous environmental and socio-economic burden is associated with FW, which needs to be addressed for the sustainability of FW as a resource in the circular food economy. The policy initiatives in FW management have been summarized to evaluate the benefits of circular economy and bioeconomy concepts as compared to the existing management systems.³⁵ Although several authors have compiled the FW valorization process for biomaterials,³⁶ biocomposite,³⁷ biofuels,³⁸ or animal feed,³⁷ the economic and environmental implications are yet to be discussed. This study summarized the potential valorization processes of FW, some of the recent developments in FW valorization processes, and their potential implications on the economy and environment to discuss the challenges and choices in the valorization processes of FWs for their sustainability.

Box 1: Food Waste Generation and Valorization

Food Waste and Hunger

Globally, 1.3 billion tonnes of food is wasted or lost every year.³⁹⁻⁴¹ The developed (population 1.4 billion) and developing countries (population 6.2 billion) discarded 670 and 630 million tonnes of edible foods, respectively,^2,42 while globally about 690–829 million people remain hungry⁴³⁻⁴⁶ and 3 billion can not afford a healthy diet.^43,44 In America, 38 million people are food insecure and have already faced hunger.⁴⁷

Food Waste Valorization

Food waste is generated in different stages of the food life cycle: preharvest and postharvest (preindustrial, industrial, and postindustrial), which consists of both edible and inedible food. The food waste composition also widely varies in different jurisdictions and sources of food waste.⁴⁸ Usually, animal-based food waste is energy-rich as compared to watery plant-based food waste such as fruits and vegetables.⁴⁹ Thus, the selection of food waste valorization technologies depends on the moisture content and the composition of food waste to avoid energy-intensive processes in producing value-added end-use products for various applications.

Food Waste

Usually, FW occurs in every step of food supply chains such as in industrial (postharvest, processing, and distribution), retailers, households, and food services sectors because of contamination or decreased quality.⁵⁰ It generates both edible and inedible FW. The nonedible portions of food and the discarded food are defined as food waste (FW). Food is also wasted due to insufficient skills, lack of technology, poor infrastructure, logistics, and management capacity as well as lack of markets.⁵¹ The generation of FW depends on the type of food, technological advancement, economy, marketing, and consumption,⁵² as well as the purchasing patterns.⁵³ In addition, the sociodemographic of households also plays an important role in FW generation.⁵⁴⁻⁵⁶ For example, bread is the most wasted food product among young consumers.^53,57

Figure 2 shows annual FW generation at the household level in selected countries.^44,58 Globally, FW generation was 931 million tonnes in 2019, where the household level generated 569 million tonnes, while a section of the population is starving.^43,44 The food service and retail sectors contributed 244 and 118 million tonnes to the total FW, respectively.⁴⁴ Food services are the key source of FW in the postconsumer stages. For example, 50% of food displayed in buffet services is wasted.⁵⁹ Because of food safety regulations, only 10–15% of leftover food can be safely donated.⁶⁰ Therefore, the effective and innovative use of FW could serve a double purpose such as diverting FW, which is usually sent to landfills, and producing value-added products that either the food sector or other sectors can use, which would help in reducing waste management cost of the food industry and greenhouse gas (GHG) emissions.

Figure 2.

Household-level food waste generation in selected countries⁵⁸ and in the world.⁴⁴ [The generation of household-level FW depends on technological advancement, and socioeconomic, logistics, infrastructure, and management,⁵² as well as the purchasing capacity.⁵³ FW is greater in developed countries as compared to the developing countries.]

Food Waste Reduction Initiatives

Enormous efforts are underway in reducing FW, such as upgrading storage systems, improving process efficiencies, improving packaging and distribution, and developing stress tolerance food, especially fruits and vegetables, to extend their shelf life, as well as policy. An extended shelf life can reduce FW at the retail and household levels. Active and intelligent packaging has also been developed integrating digital tools (intelligent tools and traceability) such as sensors/indicators (thermal, leak, freshness, and pH) in the package. The intelligent tools monitor various quality aspects and share the quality status of products with the stakeholders involved in food chains (producers to consumers),⁶¹ which are noted to be effective in reducing food spoilage.⁵⁰ For example, gas sensors can reveal the status of spoilage by indicating the gas concentrations.⁶² Consequently, the application of intelligent packaging in food systems can also play a vital role to minimize spoilage and to alert consumers of spoilage, food quality, and safety,^50,61,63 as well help in reducing FW.^64,65 In addition, producing biodegradable polymers from FW and then applying for sustainable food packaging can be a more resilient way to reduce FW and minimize their environmental impacts.⁶⁶ Various apps have also been developed to divert excess food to local communities or foodbanks to reduce FW and environmental impacts. For example, in Canada, the Second Harvest Food Rescue App connects businesses with surplus food to social organizations (about 2300 organizations) distributing surplus food to reduce FW.⁶⁷ Consumers could play a key role in lowering FW at household levels by well-planned purchases and adopting adequate storage.^68,69 In addition, sorting of FW at sources is known to be an effective way to divert some of the wasted food either for redistribution or for use as animal feed, which thus can be useful in reducing the generation of FW. Various policy initiatives have also been deployed to reduce FW from the food chain. For example, Canada has enacted a food donation law and policy to protect food donors and reduce FW.⁷⁰ In the United States of America, restaurant and grocery stores need to donate excess wholesome food to charitable organizations that are working on hunger relief, instead of dumping them in landfills.⁷¹ The United Nations also urged countries to halve FW throughout the food chain by 2030.⁷²

Food Waste Valorization

Conversion of FW or byproducts or undervalued biomass into valued products and their effective applications is known as the valorization of that waste or undervalued product. Various conversion techniques are used to produce value-added products for different applications. Figure 3 represents some of the commonly used conversion technologies, products, and potential valorization process applications. Usually, FW is high in moisture content, which provides beneficial effects in some of the conversion processes such as anaerobic digestion (AD), fermentation, hydrolysis, hydrothermal carbonization (HTC), etc.; however, it sometimes needs size reduction or pretreatment (ultrasound, microwave, pulsed electric field, etc.) to improve the conversion process and extract more value-added products. FW is high in carbohydrates,⁷³ proteins, nutrients, oils, water, and natural acids;^74,75 thus, it poses the potential of fermentative products.^73,75 Various value-added products along with bioenergy have also been developed from FW, and the yield is dependent on the components of FW. Table 1 shows the compositions of different FW, which seem to vary depending on the FW sources. Pulsed electric field pretreatment is superior and produces better quality products.^76,77 Dried and ground food waste/byproducts such as wheat bran, potato fiber, and pea fiber were also used with polymeric matrixes producing a biocomposite for sustainable pots, containers, nonwoven tissues, and films.⁷⁸ Fritsch et al. have summarized various extraction methods that have been used at optimal conditions for maximum phenolic compound yields from different potato peels, which varied 10.3–593.3 mg/100 g (dry basis) depending on the potato cultivars and the methods of extractions.⁷⁹ The yield of value-added products from FW was also observed to widely vary depending on the type of FW and conversion technologies (Table 2). It has also been noted that organic compounds extracted from various FW (especially fruits and vegetable byproducts) can be revalorized and used to inhibit corrosion in corrosive media.⁸⁰

Figure 3.

Schematic of the food waste valorization processes, products, and applications (AD, anaerobic digestion; HTC, hydrothermal carbonization). [This figure shows the potential sources of food waste, valorization technologies, and value-added products generated from FW and their applications in different areas, which can play a determinant role in the sustainability of the FW valorization processes. The product yields also depend on the valorization techniques (stage 1 and/or stage 2), pretreatments, and types of FW.⁷⁹]

Table 1. Components in Some of the Food Waste^a.

	composition, % (based on dry weight)
source of food waste (FW)	protein	starch	carbohydrates	fat	cellulose	hemicellulose	lignin	ash	source
canteen	21.02	31.87		17.56	23.21				(83)
canteen	18.72	35.61		19.11	20.82				(83)
*animal kitchen waste	54.4		9.9	35.7	3.9				(84)
*vegetable kitchen waste	21.6		59.0	19.4	21.6	9.0			(84)
*other kitchen waste	23.1		57.6	19.2	7.5	2.7			(84)
kitchen waste (student restaurant)	16.21–17.59	22.94–25.06	53.96–56.04		16.54–17.26	7.69–7.71	16.43–17.57	5.88–5.92	(85,86)
FW (catering service)	18.3–23.5	16.2–29.4						3.4–5.2	(87)
kitchen waste	10.1–22.5	35.8–44.6							(88)
kitchen waste	13.8	44.0							(89)
household	10.39–17.01	10.61–10.75			10.24–10.38	11.30–11.34			(90)
cafeteria	7.93–9.57	33.47–36.53	52.57–59.69	5.85–7.29#	15.4–20.8	3.31–3.75			(91)
retail store	13.9	63.5							(92)
source separated food waste (UK: Eastleigh)	19.7		45.8		6.61	8.86	2.17		(41)
FW	7.0		67.0	10.0#					(93)
FW	27.8		35.1	22.4#					(94)
FW	15.0		55.2–61.9	23.0–24.0					(95)
spend coffee ground	14.39		14.09						(96)
spend coffee ground	13.7–13.9		51.9–56.3					1.6–1.8	(97)
hard shell of Brazil nut	3.3–3.8	3.3–3.5		7.3#				3.3–4.1	(98)
FW	15.0	19.0		14.0				2.0	(99)
FW	3.9–21.9		35.5–69.0					1.0–2.0	(100)

^a*, % of volatile solid; MSW, municipal solid waste; #, lipids.

Table 2. Food Waste Conversion Technology and Value-Added Product Yield.

type of food waste	conversion process and conditions	products and yield	source
Biochemical Conversion
soy waste	solid-state fermentation (substrate: 7 g/100 mL; 35 °C)	single cell protein, 56.42%; crude protein and nucleic acid, 5.28%	(101)
bread waste	solid-state fermentation (substrate to inoculum ratio 5% v/v; 37 °C)	succinic acid; 0.55 g per bread waste	(102)
MSW (organic fraction)	acidogenic fermentation/sequencing; 37 °C	biopolymer (polyhydroxyalkanoates), 76 g/kg-VS, and biogas, 0.44–0.51 m3/kg VS	(103)
MSW (organic fraction)	acidogenic fermentation/sequencing; 37 °C	biopolymer (polyhydroxyalkanoates), 114.4 ± 14.5 g/kg total solids	(104)
yam peel	solid-state fermentation, 27 °C, 96 h	single cell protein, 15.54%	(105)
fruit waste	anaerobic digestion, 38 °C; biochar (350–550 °C, 15 min) was used as an additive	methane, 285.7 mL/g substrate	(106)
food waste	anaerobic digestion, 37 °C; biochar (450–550 °C, 15 min) was used as an additive	methane, 465–540.4 mL CH4/g-VS	(107)
food waste (canteen)	hydrolysis and transesterification	methyl esters 135.8 and 13.8 g of crude glycerol per kg of food waste	(108)
food waste	two-stage enzymatic hydrolysis	reducing sugar, 204.2 g/L	(109)
spent coffee ground	autohydrolysis, polysaccharides extraction, 160 °C	polysaccharides, 29.29%, phenolics, 234 mg/g	(110)
food waste	fermentation (leach be reactor), neutral pH, room temperature	volatile fatty acids 649 g COD/kg volatile solids	(111)
spend coffee ground	solvent extractions, 30 °C	oil, 11.8%; hexane 22.5 g/g dry spend coffee ground	(96)
Thermochemical Conversion
food waste	microwave pyrolysis, 400 °C, 30 min	biooil, 32.2%	(112)
fish waste	pyrolysis, fixed bed reactor, 500 °C, 60 min	biooil, 57.1%	(113)
banana peel	pyrolysis, 500 °C, 20 min	biooil, 18–28%	(114)
banana pseudostems	pyrolysis, 500 °C, 60 min, fixed bed reactor	biooil, 18–50%	(115)
hydro-mechanically pretreated municipal food waste	anaerobic digestion	methane, 511.92 L/kg-volatile solid (VS) and nutrient-rich liquid digestate (4.61% N, 3.33% P, 0.39% K)	(116)
Biochemical–Thermochemical
food waste	AD-integrated with gasification, AD, 35–55 °C	methane, 557–680 mL/g volatile solid	(109)
food waste	AD, 500 kg FW/day, combined heat and power	heat, 175.9 kW h; electricity, 163.9 W h	(32)

In addition, FW has also been used for animal feeding,⁸¹ which is usually considered a cost-efficient valorization method for FW from food supply chains; however, due to regulatory concerns, it is sometimes restricted.¹³ Although using FW as animal feed is the most cost-effective management option, in practice, only 2.9% of FW is fed to animals in the U.S., while 55.9% is sent to landfills.⁸² Bioconversion of wasted food into insect-based protein development for either food or feed is a potential way to achieve a circular economy.³⁴ The effective sorting of FW at sources of FW can reduce incineration and landfilling, providing economic, environmental, and social benefits.⁶⁹ The diversion of FW to feed hungry people provides the highest environmental benefits regardless of food types.⁴⁹

Animal/Fish Feed

Usually, food waste (FW) contains various bioactive compounds, which thus can be converted into health-beneficial animal feed.³⁷ In the EU, 3.5 million tonnes of FW annually is converted into animal feed and is predicted to expand to 7 million tonnes by 2025.¹¹⁷ Conversion of FW into protein-rich fish feed by using black soldier fly (BSF) is an emerging bioconversion technology. FW is fed to BSF larvae in this emerging technology, and the highest larvae growth was observed with 80% moisture in FW.¹¹⁸ Although the quality attributes of dehydrated FW slightly vary depending upon their sources, it can be applied in fish or cattle farming as the nutrient levels of most of the dehydrated FW are well matched to fish- and cattle-feed.¹¹⁹ However, FW needs to be handled and processed appropriately before being used as animal feed to reduce the risk of diseases.

Biochemical Conversion

Landfilling

Food waste is an integral part of MSW and is usually sent to landfills. Depending on the jurisdictions, MSW consists of 25–65% FW.⁴¹ In Canada, 95% of municipal solid waste (MSW) is sent to landfills.¹²⁰ A recent study revealed that the primary destination of FW in Canada is either landfills or animal feed or composting or AD.¹⁸ For example, FW contributes about 26.5%¹²¹ and 24.1%⁸² to the total MSW in Canada and the U.S., respectively. However, FW contains both lignin and lignocellulosic materials, which are recalcitrant in anaerobic conditions,¹²² thus inhibiting the bioavailability of these materials and resulting in a low methane yield without pretreatments, and the landfilling of FW is not the optimum process for the production of biogas.¹²³

Anaerobic Digestion (AD)

Anaerobic digestion (AD) of organic waste is one of the attractive and effective valorization technologies for both resource and energy recovery.^109,124 Banks et al. noted that FW consists of carbohydrates, fats, proteins, and essential elements, thus exhibiting a high potential for biogas production. Consequently, AD or industrial application in a biorefinery offers the greatest opportunities for resource and energy recovery and would be considered as the first option for FW management.⁴¹ The methane yield from thermally treated (mild) kitchen waste was 342–398 mL/g volatile solid (VS); however, H₂ production improved significantly (reached up to 113 mL/g VS) because the thermal treatment facilitated the transformation of soluble sugars.¹²⁵

Abbas et al. studied the anaerobic digestion of FW and cattle manure in a carbon steel reactor at mesophilic conditions (30 ± 1 °C) with animal intestine as an inoculum and noted the optimal biogas yield with 30% inoculum for both cases; however, FW produced biogas at a faster rate than did the cattle manure as well as yielded more biogas than the latter.¹²⁶ Biogas and methane yield were also improved from the AD of FW when biochar and trace metal were used.¹²⁷ For example, biogas and methane yield improved from 11.2 ± 6.5% to 27.3 ± 9.5% and from 8.3 ± 6.8 to 33.2 ± 2.8% for a biochar dose of 2.0 and 5.0 g/L, respectively.¹²⁷ In addition, codigestion reduces the toxicity potential, stabilizes the digestate, and improves the methane yield because of synergies (the combined effect of two or more active ingredients is greater than the sum of the effects that the ingredients generate individually¹²⁸) of cotreatment.¹²² The nutrient-rich digestate has the potential to be used for soil amendment.

Yu et al. used a model to evaluate the methane yield from the FW AD process. The simulated results revealed that the yield from the AD process varied from 528.22 mL/g-total solids to 545.29 mL/g-total solid (TS), which might be because of the composition of FW.⁸³ Methane production was 446 and 242 mL/g-volatile solids (VS) of cheese whey and hemp residues, respectively; however, the yield increased by 10.7% when (cheese whey:hemp residue = 70:30) codigested.¹²⁹ However, in a two-stage AD process, the methane yield varied from 180–732 mL/g-VS depending on the conversion rate of VS.¹³⁰ A high nitrogen removal (89%) has been achieved in a two-stage AD process of FW where partially nitrated wastewater of the AD process was fed, thus enhancing the environmental sustainability of the AD process of FW.¹³¹ In addition, codigestion for the condensate of the FW drying process and sludge from wastewater treatment plant increased the methane yield (72.5%) of activated sludge because of the increased carbon–nitrogen ratio, which resulted from the higher carbon–nitrogen ratio in the condensate.¹³²

Fermentation

Fermentation is one of the potential technologies for FW valorization. The expensive enzymes required in the fermentation process of FW is one of the main obstacles for this process; however, the incorporation of onsite enzyme production with fermentation plants can be a possible option to minimize this obstacle.⁹⁰ The product yield in the fermentation process of FW also depends on the inoculation methods. A two-step process has also been employed to produce biodiesel from potato peels. Initially, a fungal strain (Aspergillus awamori) was used in the solid-state fermentation of potato peels to create glucoamylase and protease. The crude hydrolysates’ produced from restaurant FW then were fermented in a shake flask with yeast (Rhodosporidium toruloides) to extract the microbial oil, which was transesterified into biodiesel.¹³³ Hydrolysate produced from FW solid-state fermentation was used in biohydrogen production, and the best hydrogen production rate was 39.14 mL/g FW.¹³⁴ In addition, hydrolysate produced by the enzymatic hydrolysis of FW has been used as a culture medium in microalgae cultivation, and hydrolysate enhanced the quality of microalgae suitable for biodiesel.¹³⁵ Although the production of flavoring compounds from FW through solid-state fermentation can minimize FW, the processing cost is high; however, a high capital cost is associated with scaling-up of this process.¹³⁶

Composting

Composting creates a product that can be used for soil amendment to improve soil nutrients at farming and household levels, thus reducing FW in landfills,¹²⁶ and may result in improved farm income through the sale of compost.¹³⁷ Zeolite was added with oil-degrading and multibacterial consortium in a composting experiment and revealed that oil-degrading bacterium degraded the oil-rich postconsumption food waste (PCFW) better than the multifunctional bacterium consortium or without inoculum as well as shortened the decomposition time by 20 days.¹³⁸ The compost from FW is nutrient-rich as compared to vermicompost¹³⁹ and thus would be a potential material for soil amendment.

Thermochemical Conversion

Pyrolysis/Copyrolysis

Pyrolysis is an emerging technology used to valorize FW to novel products with or without catalysts.¹⁴⁰ Low-temperature pyrolysis of FW compost facilitates the carbon fixation as compared to high-temperature pyrolysis (400–500 °C).¹⁴¹ Catalytic pyrolysis of FW improves product yield and quality. FW has also been coparalyzed with herbal medicine byproducts, and we noted that the pyrolysis process parameters (such as temperature, treatment duration, and reactor design; for example, low temperature pyrolysis produces a greater amount of biocarbon and a lower amount of bio-oil as compared to high temperature pyrolysis¹⁴²) affect the product yield and quality.¹⁴³ The study revealed that the synergetic effect between FW and herbal medicine byproducts resulted in a higher H₂ yield. Similarly, Park et al. also confirmed that the pyrolysis parameters affect the product yields in the copyrolysis of FW and wood bark. The copyrolysis of FW and wood bark reduces harmful chemicals and increases H₂ yield.¹⁴⁴

Incineration

The incineration of FW is energy-intensive because FW is usually high in moisture content.¹²² However, various pretreatment methods are being used to reduce moisture content in FW, and then pretreated FW is incinerated for power generation.¹⁴⁵ The incineration process reduces 80–85% volume of the waste while producing heat and energy and reduces the amount of waste to landfills;^146,147 however, it emits harmful gases such as dioxin and heavy metals when combusted at temperatures under 1000 °C¹⁴⁸ and fly ash.

Hydrothermal Carbonization (HTC)

HTC is known to be a more suitable technology for producing value-added products from high moisture feedstock such as food waste (FW). In addition, biogenic steam reformation has also been used at high temperature to convert mixed waste streams (organic and nonorganic) into biogas/syngas, water, nutrients, CO₂, and aggregates. For example, formate, an excellent hydrogen carrier, was produced from hydrothermally treated FW.¹⁴⁹ Hydrothermal liquefaction (HTL) is another potential method of producing ethanol from potato peels because peels are rich in starch.¹⁵⁰ HTL is also recognized as a potential path for energy and nutrient recovery from FW. High temperature and pressure liquefaction (600 °C, 35.3 MPa) transferred 50% and 68% of nitrogen and phosphorus in FW to the process water, respectively, and produced biocrude (30 wt %) high in energy content (36.5 MJ/kg); however, the process performance depended on the process parameters.¹⁵¹

Integrated Valorization Process (Biochemical–Thermochemical Conversion)

In an integrated biorefinery approach, thermal hydrolysis, AD, and photofermentation were tied to produce bioenergy as well as value-added products (such as polyhydroxyalkanoates) from FW.^25,152,153 Thermal hydrolysis solubilized about 40.4% of solids in FW, facilitated the extraction of rich hydrolysate and improved the AD process, and reduced about 78.6% volume of the disposal.¹⁵⁴ The phototrophic treatment with purple bacteria enhanced protein-rich biomass growth. The authors also noted that the composition of FW played a vital role in producing value-added products from the integrated biorefinery approach. Microbial electrolysis cell (MEC) treatment coupled with AD became an efficient process for making hydrogen from FW. The hydrogen recovery of 511.0 mL and 49.4 mL/g-VS was achieved from integrated (AD-MEC) and AD, respectively, because of the higher removal rates of carbohydrates, and volatile fatty acids, which indicated that the AD-MEC process improved the organic component utilization efficiency in the soluble phase.¹⁵⁵ Hydrothermal carbonization coupled with AD is also noted to be an acceptable option.¹⁵⁶

The energy recovery from FW varied depending on the recovery approaches.^2,157 For example, energy recovery from an integrated approach such as fermentation and AD (H₂ and CH₄/ethanol and CH₄ production approach) produced 19.92 ± 0.46 and 21.49 ± 0.57 MJ/kg-TS, respectively. In contrast, only the AD approach produced 17.47 ± 0.17/kg-TS.¹⁵² However, the authors did not report the energy input in the processes. Gasification coupled with AD of sorted FW produced hydrogen-rich syngas and methane-rich biogas.¹⁰⁹ The integrated biorefinery approach also provided greater revenue to the energy input ratio in the case of producing multiple products from potato waste.²⁵ In addition, the authors argued that producing multiple bioproducts from potato peel waste in an integrated approach can transform the linear economy platform into a circular economy.

It is also important to note that the decomposition rate of food waste depends on the technologies used as well as the composition of food waste. The decomposition also depends on the types of waste¹⁵⁸ as well as the decomposition parameters.^159,160 For example, most vegetable waste decomposes within 5–30 days; however, a banana peel or an apple core requires more than 30 days.¹⁵⁸

Applications of Treated Food Waste or Products from Food Waste

A wide range of applications of biochar/biocarbon have been reported, which include cement mortar,¹⁶¹ soil amendment to improve crop growth,^162,163 water purification,^164,165 as well as a catalytic material to support the catalytic conversion process,¹⁶⁶ as an additive in AD of FW for enhancing the biogas production,^36,106 as well as for energy storage.¹⁶⁷ For example, biochar-based composite was used for contaminant removal from water.^168,169 Biochar is also being used as a soil amendment in wheat cultivation, which confirmed better crop growth.¹⁶³ Refined carbon from tea waste attains better electrochemical properties and a greater capacitance, which is used in a porous carbon nanosheet, and thus can be an alternative material for carbon-based electrical devices.¹⁶⁷ However, FW hydrothermally converted into formate is an excellent hydrogen carrier that can be used as a fuel cell material.¹⁴⁹

Value-added products such as antioxidant compounds and anthocyanins have various industrial applications including in the food industries. For example, anthocyanins are sensible to storage temperature¹⁷⁰ and can be used as natural dyes in French meringue.¹⁷¹ The application of colorant extracted from coffee waste in bioenergy production and dental health has also been reported.¹⁷²

Impacts of Valorization Methods

Enormous efforts are underway to reduce or reuse food waste (FW) as well as in the recovery or disposal to reduce the environmental and socio-economic impacts. Box 2: Food Waste Management Impacts represents an overview of the FW, mitigation, and management pathways for reducing the impacts associated with them.

Box 2: Food Waste Management Impacts

GHG Emissions

Annually, wasted or lost food released 3.3 billion tonnes of GHGs (CO₂ equiv) on the earth.⁴⁰ Reuse of the edible portion for human consumption is more preferable than reuse in animal industries because of the greater avoided emissions’ benefit¹⁷³ or use in a biorefinery for value-added products. The environmental impacts also depend on the types of food and waste valorization processes, which also depend on the embodied carbon emissions and potential energy/material recovery.⁴⁹ However, for the inedible portion, materials’ recovery is environmentally preferable followed by nutrient and energy recovery, and the least preferable option is a landfill.^173,174

Food Waste Reduction

Various approaches are in place to reduce food waste from every stage of the food supply chain. Forecasting optimized production, marketing, and management are the key in reducing the generation of food waste.¹⁷⁵ Prevention or reduction would be the primary target followed by the valorization stages as strategies for food waste management policies.

Valorization

A suitable valorization approach is critical to reducing the cost of food waste management and conserving resources because the economic impact of FW depends on the valorization processes. The economic benefits also depend on the end used products produced from food waste.¹⁵⁷ Consequently, careful consideration needs be placed in selecting a valorization process on the basis of the types and composition of food waste. Food waste reduction and reuse initiative not only provide environmental benefits but also lead to several social benefits as the loss of about $1.0 trillion²⁵ associated with waste or lost food can be reduced.

Environmental Impacts

The environmental impact from FW greatly depended on the valorization methods. The highest impact reported was in the case of a landfill, which is dependent on the biogas captured followed by composting, incineration, and AD, and the least was in the case of animal feeding. A wide variation among various studies might be because of methodological choices, system boundary, geographical location, and assumptions of studies (Table 3). The per capita climate change impact of FW in the U.S., Canada, UAE, KSA, and Japan was reported to be 0.53, 0.45, 0.48, 0.58, and 0.14 tonne CO₂ equiv, respectively.¹⁷⁶ However, effective valorization of wasted food can alleviate emissions from FW in different countries. For example, in the United States, conversion of industrial higher-value products could abate about 1.9 × 10⁸ tonnes of emissions (CO₂ equiv) every year.¹⁷⁷ Kim et al. noted that energy generated from each tonne of the FW incineration process could provide −315 kg CO₂-equiv of environmental credit where the benefits came from both MSW and dried food waste; however, the authors cautioned that energy recovery only from FW would not be feasible because of the high energy demand of high moisture FW.¹⁷⁸ However, net energy output from the FW AD process was 186.01 MJ/tonne, while the net input was 167.47 MJ/tonne. The environmental burden of the process was 96.97 kg CO₂-equiv/tonne of FW where methane was used in a cogeneration process of heat and electricity.¹⁷⁹ The author also noted that the FW contained 8% nonfood components (glass and plastic bags), which has contributed to the total environmental burden of the AD process because of GHG emissions from the incineration of nonfood components. In situ composting of solid digestate from the AD of FW had the least environmental impact as compared to incineration and landfill; however, in terms of energy consumption, coprocessing with MSW landfill or incineration was noted to be an acceptable option.¹⁸⁰ The environmental benefit of an AD plant that processed 200 tonne FW a day was 16.09 tonne of CO₂/day.¹⁸¹ However, the decentralized AD provided the highest environmental benefit (−238.4 kg CO₂ equiv/tonne) when biogas was used as a cooking fuel as compared to centralized AD and biogas used as a transportation fuel.¹⁸² Similarly, AD has the least environmental impacts as compared to composting, incineration, and landfill, while in-vessel composting was reported to be the least sustainable.¹⁸³

Table 3. Environmental Impacts of the Food Waste Management Process^a.

conversion technology	feedstock	application	product yield	GWP (kg-CO2 equiv/tonne)	AP (kg SO2 equiv)/tonne	EP (kg PO4 equiv)/tonne	source
Biochemical Conversion
HTC (batch experiment at 225–275 °C)	food waste	energy	dry char 57.87–74.06% (28.19 GJ/tonne)	–32.6–190.0			(194)
HTC (55000–81361 tonne/year)	green waste (leaves, grass)	energy		51.2–372.0			(191)
AD (hydrolysis, acidification, and methane fermentation)	food waste	steam and electricity, fertilizer		211.0			(178)
codigestion (anaerobic)	food waste and sludge	energy, fertilizer	biogas: 13.32 m3/tonne	259.0			(178)
AD	food waste	heat and electricity		96.97	–0.3	0.02	(179)
AD (biogas and digestate produced at a digestion facility)	food waste	biogas, electricity replacement		–314.0			(49)
composting (open-window system in a commercial facility; optimal temperature and concentration of carbon)	food waste	compost, fertilizer replacement		–31.0			(49)
landfill with CH4 capture (anoxic conditions)	food waste	biogas, electricity replacement		573.0			(49)
landfill without CH4 capture (anoxic conoditions)	food waste			2969.0			(49)
AD (250 tonne/day; pretreatment: 1 h at 120–180 °C)	food waste	biogas to energy, solid digestate incineration/composting/landfilling	1100.8–1186.5 MJ/tonne FW	100.8–2018.2	–0.17–0.33	0.3–0.9	(180)
AD (decentralized: 2 tonne/day)	food waste	biogas as cooking fuel		–238.4			(182)
AD (centralized: 300 tonne/day)	food waste	biogas, CHP		29.3–77.9	1.2–2.6	0.2–0.4	(182)
Thermochemical Conversion
incineration (850–1100 °C)	dried food waste	electricity, ash landfilled		342.0			(178)
incineration (MSW incinerator)	food waste	energy, electricity replacement		–58.0			(49)

^aNote: The negative value indicates the avoided emission; MSW, municipal solid waste.

A comparative study among AD, thermal treatment (incineration), and coprocessing with municipal wastewater and landfilling also confirmed that the environmental performance of thermal treatment was the best for most of the impact categories (climate change, acidification, human toxicity, ecotoxicity, and fossil depletion). At the same time, landfilling was the worst option.¹⁸⁴ The authors noted that the thermal treatment emerged as the best option because of the effective implementation of waste-to-energy measures where the energy generation efficiency was considered to be 22% and 60% for electrical and heat, respectively. In contrast, FW incineration was reported to be environmentally adverse because of the high moisture content in FW and thus became an energy-intensive treatment process, and AD was identified as the preferable option as compared to incineration.¹⁸⁵ However, the use of FW as animal feed provided more environmental benefit (−347.0 kg-CO₂ equiv/tonne)⁴⁹ as compared to the biochemical or thermochemical conversion of FW.

Economic Impacts

The annual cost of lost and wasted food is estimated to be U.S. $680 and U.S. $310 billion in developed and developing countries,⁴² which has attracted a lot of attention. However, the economic impact of FW is dependent on the valorization processes; thus, a suitable valorization approach is critical to reduce the cost of FW management and conserve the resources. For example, the economic evaluation of methane production from the AD process noted that the FW AD process might not be economically beneficial if only the methane yield is taken into consideration and used for heat (57%) and electricity (43%) generation.¹⁷⁹ The authors also argued that high value-added applications (used in vehicles, on-grid electricity, etc.) of biogas from the FW AD process would increase the economic benefit of the process. In contrast, Guo and Yang confirmed the economic feasibility of the AD process of FW. The daily economic and environmental benefit of the AD plant was $10 582 (66 888 yuan) and 43 350 kW h, respectively, which processed 200 tonnes of FW/day.¹⁸¹ However, the authors noted that the subsidies from the government were instrumental for economic benefit. The codigestion of hemp residues and cheese whey enhanced economic benefits.¹²⁹ Similarly, AD is also noted to be economically preferable as compared to FW’s incineration.¹⁸⁵ It was estimated that each year $5,600 or $900 million could be generated by converting the industrial FW to lactic acids via fermentation or biogas through AD in the United States.¹⁷⁷ In addition, the simulated minimum selling price of ethanol produced from FW was noted to be $0.64/L, which can be competitive with its counterparts and confirmed the economic feasibility of a commercial FW valorization plant.⁹⁹

In contrast, incineration had the least life cycle cost as compared to other waste management options such as AD, composting, and landfilling.^183,186 For example, on-site incineration of FW a the Honk Kong International Airport was identified to be the most sustainable option as compared to landfill or composting, which provided the lowest life-cycle cost (HKD 461.73/tonne) and the highest energy recovery (707 k Wh/tonne) and thus resulted in both economic (HKD 697.81/tonne) and environmental (HKD 470.96/tonne) savings because of energy recovery from the incineration process and pollution control systems integrated with the incinerator.¹⁸⁶ However, the decentralized composting of FW was noted to be economically beneficial and provided an economic benefit of $100/tonne.¹⁸⁷ At the same time, centralized/community composting often faces operational challenges and requires considerable investment.¹⁸⁷ The life cycle cost of FW incineration, composting, AD, and landfill was reported to be €71, €80, €110, and €124 per tonne ($79–138/tonne FW), respectively.¹⁸³ In Canada, the municipal solid waste disposal cost is $90–242/tonne.¹⁸⁸ The operating cost of the organic waste management plant in Guelph was $117/tonne in 2019.¹⁸⁹

Lactic acid and biogas produced from FW in an integrated biorefinery (sequential fermentation) are noted to be profitable, while the FW can be collected for an area of 20 000–50 000 inhabitants because of the combination of multiple process flows, enhanced yield of valuable products, as well as minimized waste generation and management costs.¹⁹⁰ The study also revealed that optimal energy use is achieved in the case of an integrated approach rather than a single process. However, the carbon abatement cost of hydrothermal carbonization of organic waste (leaves and grass cutting) depends on the study’s scenarios (urban, urban–rural, and rural). For example, urban–rural (€76/tonne CO₂ equiv) and rural (€77/tonne CO₂ equiv) scenarios had lower cost than the urban scenario (€163/tonne CO₂ equiv), because of cofiring of carbonized material in an existing power plant instead of constructing a new power plant that was considered in the case of urban scenario, which exceeded the carbon prices in the region.¹⁹¹ However, hydrothermal pretreatment is currently considered redundant in the case of AD of hydrothermally treated biomass because of the higher pretreatment cost.¹⁵³

It is also noted that producing chemicals from agricultural and FW can be 10, 7.5, and 3.5 times more profitable than using tem for electricity generation, animal feed, and liquid fuel, respectively.^157,192 For example, a best-case scenario of the valorization of potato peel in an integrated biorefinery to produce multiple bioproducts (chemicals and biocarbon) generated $6300/tonne of dry potato peel.²⁵ The leach bed reactor operating cost of FW treatment and fermentation to volatile fatty acids was estimated to be $88.1–126.8/tonne of VS added in the process.¹¹¹ In addition, the biorefinery that processed multiple feedstocks such as agro-industrial and residential/commercial waste as well produced multiple products was noted to be the most promising biorefinery approach; however, the profitability is also dependent on the capacity of the plant and the value-added products.¹⁹³

Discussion

The valorization process of food waste (FW) faces challenges because of high moisture content, low calorific value, and variable compositions, which are the major constraints to a robust commercial process.¹⁴⁷ FW is also categorized as avoidable and unavoidable. Usually, the flow of unavoidable FW remains constant and is generated by the processing and manufacturing sectors. Therefore, investment in FW valorization needs to be planned mainly on the basis of the unavoidable FW to get an adequate feedstock supply, which is essential for the uninterrupted operation of the plant.

GHG emissions of various FW valorization processes, applications, and their ability to reduce the GHG emissions vary widely depending on the type of FW, refining and conversion process, and end-use of the products from the FW valorization processes. For example, the GWP of FW anaerobic digestion is lower than compositing or landfilling;¹⁹⁵ however, for the highest conversion efficiency, the AD process needs higher control and monitoring.¹⁹⁶ The authors also noted that the integrated biorefinery approach in the FW valorization process led to the circular bioeconomy.¹⁹⁶ The government of Taiwan is promoting AD and aerobic composting to valorize FW into biogas-electricity and biofertilizer because these are recognized as the best options.¹⁹⁷

Municipalities have introduced bins in an attempt to source the separation of waste streams, easing the waste management systems and reducing landfills. For example, with the green bin initiative, the City of Guelph in Ontario, Canada, could divert 10.4 thousand tonnes of organic waste to her composting facility; however, the city has sent 25.4 thousand tonnes of FW to landfills.¹⁹⁸ In an attempt to reduce FW, a food recovery hierarchy has also been developed by several authors where the source prevention^173,199 or reduction¹⁷⁴ is identified as the best action and landfills is the least preferable action based on their benefit to the environment, economy, and society. Consequently, source prevention or reduction would be the primary goal for FW reduction followed by diversion of the edible portion for human consumption wherever possible, if not then the low-quality food can be used for feed for animal, fishery, or insect industries. The nonedible portion can be used for material and nutrient recovery, energy recovery, and the last option would be the disposal/landfill.

Landfilling and incineration are identified as the least preferable options because these options are not only costly but also emit pollutants during burning or through leachate.²⁰⁰ Waste avoidance strategies such as source reduction/prevention, feeding people or feeding animals, and composting have supply chain carbon impacts that may be higher than the carbon reduction from avoiding FW. Biorefineries have both the carbon reduction from avoiding waste, plus the offset generated by replacing biobased products with what may largely be fossil-based products. Consequently, it might also be worth noting that biorefinery solutions may have the greatest climate impact for achieving net zero emissions and carbon-negative outcomes in terms of waste reduction.

Wu et al. noted that the multicriteria decision-making (MCDM) methods and decision-making trial and evaluation laboratory (DEMATEL) could be used for the catering industry to identify the root causes of FW as well as control and manage them.²⁰¹ In addition, Parizeau et al. also observed multiple relationships in the case of household FW generation, such as shopping, lifestyles, food-related attitudes, as well as food and FW awareness, which need to be accounted for in FW reduction and waste management system design; thus, multisectoral changes are required.¹⁹ For the transition from a linear economy to a circular bioeconomy, the valorization process of FW needs to be optimized,¹⁹⁶ as well as there are opportunities for transitioning FW management to a circular bioeconomy.²⁵ A valorization strategy has also been devised on the basis of the composition of FW, end-use applications, and the market of resulting products for a smooth transition to a circular economy. In addition, closed-loop systems for the valorization of edible and inedible waste streams from food chains have been devised for a circular bioeconomy.¹⁷³ Both edible and inedible FW is generated at various stages of food chains. Although the embodied carbon footprint and energy demand of food vary, any reuse of the edible portion plays a vital role in reducing the environmental impacts of FW. Consequently, the most preferable option for the edible portion is to reuse for human consumption followed by animal feed. For the inedible portion, depending on the type of products, it can either be reprocessed or sent for nutrient and resource recovery; however, the least preferable would be the energy recovery. Figure 4 represents the potential pathways for the edible and inedible FW generated from various stages of food chains.

Figure 4.

Food waste valorization approaches for a circular bioeconomy. [For a circular bioeconomy, edible and inedible FW need to be separated at sources and at different stages of the food supply chains. On the basis of the type of FW, the first priority of edible portions is to divert for human consumption, and the low-quality edible food can be sent to the animal/fishery/insect industry. However, some of the inedible parts can be remanufactured for various applications. Spoiled or expired food and the rest of the inedible portion of FW can be sent to a biorefinery for nutrients and energy recovery.]

The valorization of FW or even employing the industrial symbiosis in the circular economy initiative can be attempted on the basis of the unavoidable FW to avoid any interruption in feedstock supply because of the FW reduction drive throughout the jurisdiction. The circular economy initiative/industrial symbiosis coupled with technological advances can play an important role in improving the sustainability of FW valorization processes. Another potential benefit of FW valorization would be the allocation of carbon credit to renewable energy or biomaterials. However, there are still many gaps in understanding the industrial symbiosis/circular economy and permanence of carbon credit to different value-added products; thus, GWP needs to be interpreted and conveyed carefully. Furthermore, many studies have reported benefits to GWP based on the modeling or small-scale production; therefore, the benefits may not be compatible with commercial plants.

The interaction between the income and share of available FW was incorporated in a global partial equilibrium model to project the trajectories of future household FW and noted that the emerging economies might play a decisive role in shaping the global FW of the midcentury.²⁰² Several authors also outlined the FW management framework in an attempt to reduce FW. For example, a framework has been outlined for the hospitality sector incorporating major stages where managers/operators can initiate/implement adequate measures to minimize FW.¹⁷⁵ It is worth mentioning that every stakeholder needs to be accountable/responsible to reduce FW, that is, policymakers for legislation/regulation, producers, suppliers, marketers, distributors, wholesalers, retailers, and consumers (Figure 5). In addition, onsite waste management also needs to be emphasized to minimize the environmental impacts of FW instead of sending it to landfills.

Figure 5.

Food waste minimization framework. [It seems that transdisciplinary approaches are required where all of the stakeholders in the food sectors need to be involved in reducing FW. Consequently, a multisectoral approach would be required to minimize FW generation in different jurisdictions. For example, intensive awareness of the implications of FW in the environment, economy, and society might be the key for emerging economies. In addition, supply/packaging/marketing and purchasing strategies may also play a crucial role in controlling FW, such as bulk buying or push selling often become one of the causes of FW as the expiration date (shelf life) of some expired before those could be consumed. Proactive stock management is another issue that often becomes responsible for pushing sales or sales at a reduced price, resulting in bulk buying. In addition, intelligent/innovative packaging (to help improve self-life and carry adequate information to facilitate all stakeholders) may also be useful in reducing FW, especially from retail and residential sectors.]

Food supply chains are often interrupted because of geopolitical uncertainty as well as weather conditions. Consequently, improving food self-sufficiency reduces the FW and food carbon footprint and contributes to the circular food economy. The local, regional, and national authorities, producers, processors, and the supply chain management authorities have to merge ideas in formulating the FW reduction plan and regulating the food systems as well as educate the consumers that reduced the generation of FW. In addition, all of the stakeholders need to be involved in formulating FW prevention strategies as well as considering not only the amount of FW but also their environmental impacts.¹⁰ The United Kingdom has launched a program called love food and hate waste to edify consumers of the repercussions of FW across the stakeholders.²⁰³ The European Commission also argued that the circular economy would protect against the volatile prices and the scarcity of resources and boost more efficient and innovative production and consumption,²⁰⁴ thus reducing FW. Restaurants and grocery stores in the United States of America are mandated to donate excess food to organizations working on hunger relief to reduce FW.⁷¹ In addition, countries are required to halve FW throughout the food chain by 2030 to meet the sustainable goals of the United Nations.⁷² In addition, promoting small-scale producers and creating a marketing environment for their products not only improves food security but may also play a crucial role in reducing FW from the supply chains and distribution cost, especially in the case where fresh fruits and vegetables create rural employment. Consequently, for sustainable FW valorization and transition to a circular bioeconomy, emphasis needs to be placed on the following measures: the deployment of an adequate sorting method and source reduction of FW; conversion technology needs to be selected on the basis of the composition of FW; a simulation model can be used to optimize the FW management system including the conversion process parameters as well as investment; and the stakeholders’ joint efforts to enhance the investment, markets for value-added products, and marketing strategy as well as public awareness on the potential impacts of FW valorization.

Conclusion

Numerous efforts are underway to mitigate food waste (FW) across countries in an attempt to improve food security and the sustainability of the food industry. The economic and environmental impacts of FW varied depending on valorization and the end-use products from the process. It seems that the sustainability of food industries can be enhanced by effective and efficient conversion and valorization of products or coproducts generated from FW. To date, FW waste is usually used for energy recovery, biofertilizer, and biomaterials. However, rich and innovative conversion of FW might open more opportunities to produce high-value products, which would lead to more collaboration among the industries promoting the industrial symbiosis approach as well as contribute to the circular economy initiative. The following steps would be the key to the sustainability of FW management as a resource management opportunity and transition to a circular economy:

FW conversion and valorization need to be standardized and regulated to avoid any economic, environmental, and social risks associated with FW.

Integrated/industrial symbiosis should be used to improve the economic and environmental sustainability of the food waste management process as a resource recovery opportunity, which may reduce food insecurity.

A systematic and transdisciplinary approach is needed, which can play a crucial role in combining multiple technologies as well as improving the sustainability of FW.

A broader sustainability check has to be associated with FW valorization to avoid any risk on investment and rebound effects.

The authors declare no competing financial interest.