Environmental and health impacts of using food waste as animal feed: a comparative analysis of food waste management options

Urban food waste generation and sustainable management strategies: a case study of Nonthaburi Municipality, Thailand

Although increasing global attention has been devoted to food waste management, there is still a critical research gap in understanding waste patterns and developing contextualized solutions for rapidly urbanizing areas in developing nations, where waste management infrastructure lags behind urban expansion. Using stratified random sampling of 244 sources encompassing markets, restaurants, institutions, and residential areas in Nonthaburi Municipality, Thailand, this study identified and characterized three distinct food waste categories: edible surplus food (FW1), food preparation waste, including spoiled items and bones (FW2), and postconsumption remnants (FW3). Analysis of the waste proportion patterns revealed that FW2 predominated (65.53%), followed by FW3 (32.55%) and FW1 (1.92%). Fresh markets constituted the principal source of waste generation (294.1 ± 42.3 kg/day), yielding a significantly greater quantity than private markets (117.61 ± 35.7 kg/day) and supermarkets (20.4 ± 12.8 kg/day). Statistical analyses revealed significant variations (p < 0.05) in food waste proportions across source categories. Given these findings and local infrastructure limitations, this study proposes a systematic, three-phase implementation strategy: (1) Immediate application of FW3 conversion to aquaculture feed, with an estimated food waste diversion potential of 10.72 ± 7.15 tons/day; (2) medium-term establishment of FW1 redistribution programs, which target 1.92% of total waste identified as edible surplus food, with a projected daily redistribution capacity of 0.153 ± 0.11 tons; and (3) long-term development of FW2 biofertilizer facilities, with an estimated food waste diversion potential of 52.62 ± 18.95 tons/day. This integrated approach simultaneously advances multiple sustainable development goals and establishes a replicable framework for sustainable food waste management in rapidly urbanizing regions of developing nations. The findings provide essential guidance for policy-makers and urban planners in implementing resource-efficient waste management systems.

Navigating the nexus: unraveling the impact of sustainability and the circular economy on food safety

Sustainable food production systems can be achieved through a circular economy, yet the whole system remains susceptible to various known, emerging, or even unknown/novel food safety hazards and contaminants. These upcycled foods can introduce related risks for human or animal health and ecological balance. These potential risks can be effectively mitigated by adopting integrated smart "safe-by-design" approaches. These multi-effective strategies can cascade far beyond consequences by addressing all potential food safety risks at each stage of the food supply chain, even at the post-consumption stage. Sustainability through circularity without harming food production systems can be achieved by integrating and harmonizing evidence-based risk control strategies, fostered with extensive and objective-oriented research and development and preemptive ideological relationships with relevant stakeholders. The current review aimed at addressing the possible occurrence and risks associated with potential emerging or unknown hazards/contaminants linked to various production systems, along with relevant mitigation strategies. It also highlights the importance of implementing quality control measures and safety precautions throughout the food supply chain to prevent the occurrence and propagation of hazardous substances. Agricultural production systems can be transformed into sustainable entities by vigilant monitoring of end-products quality through the use of upcycled technologies.

Waste Cooking Oils into High-Value Products: Where Is the Industry Going?

Waste cooking oils (WCOs) are generated globally in significant amounts by various sectors including hospitality, households, and industrial operations. Many nations currently lack dedicated legislation for managing WCOs, creating a pressing environmental challenge. At present, WCOs are primarily utilized in industries as raw materials for biodiesel production and energy generation. However, their role in second-generation biodiesel production is contingent on availability, often necessitating imports of either biodiesel or WCOs from other countries. The European Union has emphasized the importance of prioritizing biowaste for high-value alternative products beyond biodiesel to achieve carbon neutrality by 2050. Many reviews have been published in the literature reporting potential WCO applications to produce biolubricants, biosolvents, animal feed, asphalt additives, among others, however, no detailed analysis of industrial trends has ever been presented. Within this panorama, unlike existing reviews that focus on specific polymer classes derived from WCOs, this work sought to present a comprehensive industrial overview of the use of WCOs in creating high-value polymeric materials beyond fuel and energy, providing a general overview of patents published (or alive) in the last 10 years, together with the analysis of which innovative products are being introduced and sold on the market today.

Strategies for the Transformation of Waste Cooking Oils into High-Value Products: A Critical Review

Waste cooking oils (WCOs) are generated globally from households, the hospitality industry, and other sectors. Presently, WCOs are mainly employed as feedstock for biodiesel and energy production, strongly depending on the availability of WCOs, which are often imported from other countries. The objective of this review is to give an overall comprehensive panorama of the impacts, regulations, and restrictions affecting WCOs, and their possible uses for producing high-value products, such as bio lubricants, bio surfactants, polymer additives, road and construction additives, and bio solvents. Interestingly, many reviews are reported in the literature that address the use of WCOs, but a comprehensive review of the topic is missing. Published studies, industry reports, and regulatory documents were examined to identify trends, challenges, production statistics, environmental impacts, current regulations, and uses for high-value polymer production. The data collected show that WCOs hold immense potential as renewable resources for sustainable industrial applications that are in line with global carbon neutrality goals and circular economy principles. However, achieving this shift requires addressing regulatory gaps, enhancing collection systems, and optimizing conversion technologies. This comprehensive review underlines the need for collaborative efforts among policymakers, industry stakeholders, and researchers to maximize the potential of WCOs and contribute to sustainable development.

Synergistic effects of heterogeneous mature compost and aeration rate on humification and nitrogen fixing during kitchen waste composting

Sludge mature compost (SMC) is notable for its high production, easy accessibility, and stable supply. This study investigated the impact of the SMC addition and different aeration rates on the humification and nitrogen fixing process during kitchen waste composting. The results demonstrated that addition of SMC prolonged the thermophilic phase, as a comparison, increased aeration shortened this phase. The addition of SMC and increased aeration enhanced humus formation and nitrogen retention. SMC introduced more amide and polysaccharide compounds into the compost, promoting the Maillard humification pathway. Additionally, both SMC and high aeration inhibited denitrification: the SMC reduced the abundance of the nirK gene, while high aeration decreased the abundance of nosZ gene. Network analysis revealed that higher aeration enhanced fungal interactions but diminished bacterial interactions. Conversely, SMC addition bolstered both bacterial and fungal interactions. The final compost product with SMC addition showed a 11.56%-44.19% reduction in antibiotic resistance gene content compared with the control group, and heavy metal contents remained within safe application limits. The combination of high SMC addition and high aeration achieved optimal humification and nitrogen retention, underscoring its potential as a promising solution for kitchen waste composting.

The high-value and sustainable utilization of grape pomace: A review

A large portion of global grape production has been utilized for wine production, accompanied by tremendous pressure to dispose grape pomace. To achieve circular economy, the high-value recycling of grape pomace must be considered. The social level barriers to circular economy promotion are also important constraints, like the acceptability of upcycled products. The main components of grape pomace and their utilization are summarized, and critical reviews of green extraction methods analyzed the key points of grape pomace recycling process to achieve the goal of sustainability in the production process, culminating in discussions of the factors affecting the acceptability of upcycled products. Grape pomace bioactive substances have higher added value. To realize its green extraction, various emerging technologies need to be made a comprehensive choice. Nevertheless, the acceptability of upcycled products is influenced by personal, context and product factors, optimizing them is essential to remove the constraints of circular economy development.

Evaluation of the quality of products from multiple industrial-scale composting treatment facilities for kitchen waste and exploration of influencing factors

The aerobic composting process is extensively utilized to manage kitchen waste. Nonetheless, the variability in the quality of compost derived from engineering practices which significantly hinders its broader industrial application. This work investigated the final products of kitchen waste compost at multiple industrial-scale treatment facilities utilizing three distinct aerobic composting processes in a bid to explore key factors affecting compost quality. The quality evaluation was based on technical parameters like seed germination index (GI), and limiting factors such as heavy metal content. The results showed that most of the compost products failed to meet the established standards, with GI being the primary limiting indicator. Furthermore, maturity assessments suggested that compost with low GI exhibited reduced humification could not be recommended for agricultural use. The investigation delved into the primary determinants of GI, focusing on risk factors such as the oil and salt of kitchen waste, and the microbial community of the humification driving forces. The results indicated that products with low GI had higher oil and salt content and a relatively simple microbial community. A thorough analysis suggested that excessive levels oil and salt were potential influencing factors on GI, as they stimulated the activity of acid-producing bacteria like Lactobacillus, suppressed the activity of humification-promoting bacteria such as Actinomarinales, and influenced the decomposition and humification processes of organic matter and total nitrogen, thereby affecting product quality. The findings provide valuable insights for improving kitchen waste compost products for agricultural applications.

Circular Bioeconomy in Action: Transforming Food Wastes into Renewable Food Resources

The growing challenge of food waste management presents a critical opportunity for advancing the circular bioeconomy, aiming to transform waste into valuable resources. This paper explores innovative strategies for converting food wastes into renewable food resources, emphasizing the integration of sustainable technologies and zero-waste principles. The main objective is to demonstrate how these approaches can contribute to a more sustainable food system by reducing environmental impacts and enhancing resource efficiency. Novel contributions of this study include the development of bioproducts from various food waste streams, highlighting the potential of underutilized resources like bread and jackfruit waste. Through case studies and experimental findings, the paper illustrates the successful application of green techniques, such as microbial fermentation and bioprocessing, in valorizing food wastes. The implications of this research extend to policy frameworks, encouraging the adoption of circular bioeconomy models that not only address waste management challenges but also foster economic growth and sustainability. These findings underscore the potential for food waste to serve as a cornerstone in the transition to a circular, regenerative economy.

Characterization of municipal solid waste in Kuwait: Sector-specific composition analysis and implications

Municipal solid waste (MSW) characterization plays a pivotal role in devising effective waste management strategies conducive to fostering a circular economy. This study presents composition analysis across twenty-four subcategories sourced from residential, commercial, and industrial sectors in Kuwait. The study is conducted in accordance with the Standard Test Method for Determination of the Composition of Unprocessed Municipal Solid Waste (ASTM D5231). The results indicate that organic waste comprises 45.3%, followed by paper waste (19.9%) and plastics (19.8%). The remaining waste comprises glass waste (3.5%), diapers (2.7%), textiles (2.6%) and other waste. Paper waste (19.9%) consists mainly of mixed paper (12.1%), cardboard (3.7%), newspaper (3.3%), printer printouts (0.6%) and other office paper (0.2%). Plastic waste (19.8%) consists mainly of film (11.2%), PET (3.1%), HDPE (1.1%) and other mixed plastics (4.4%). Residential and mixed areas have the highest proportion of organic waste. Commercial areas produce the highest proportion of wastepaper (22.4%) and textiles (3.7%). Industrial areas produce the highest proportion of plastic waste (29.1%), most of which is film (17.3%). The study also provides an overview of the MSW management system in the country, an overview over the legislative framework, and forecasts of future waste generation rates with comparison to historical baselines.Implications: The precise and up-to-date characterization of municipal solid waste is imperative for scholarly journal submissions, as it establishes a foundational understanding of waste composition, aiding researchers and policymakers in the development of effective waste management strategies, resource recovery initiatives, and sustainable solutions to address the evolving challenges in waste management systems.This study provides detailed composition analysis for twenty-four municipal solid waste (MSW) subcategories collected across different sources: residential, commercial, industrial, and mixed areas. Time series forecasting is applied to predict MSW generation based on historical data obtained through the local municipality over the past decade. Factorial analysis is applied to investigate changes across source areas, and a hypothesis test is used to compare the current MSW composition against previous baselines. The results demonstrated significant variation across most waste categories. The plastic waste proportion has increased by 48.5% compared to 2013 data, despite awareness campaigns. Paper waste has also increased in proportion from 6.8% to 16.2%; this increase is associated with the mixed paper subcategory, which is mostly used for packaging. The composition data provided in this study are necessary for long-term monitoring, strategy assessment, and legislation associated with waste reduction and remediation.

Upcycling fruit waste into microalgae biotechnology: Perspective views and way forward

Fruit and vegetable wastes are linked to the depletion of natural resources and can pose serious health and environmental risks (e.g. eutrophication, water and soil pollution, and GHG emissions) if improperly managed. Current waste management practices often fail to recover high-value compounds from fruit wastes. Among emerging valorization methods, the utilization of fruit wastes as a feedstock for microalgal biorefineries is a promising approach for achieving net zero waste and sustainable development goals. This is due to the ability of microalgae to efficiently sequester carbon dioxide through photosynthesis, utilize nutrients in wastewater, grow in facilities located on non-arable land, and produce several commercially valuable compounds with applications in food, biofuels, bioplastics, cosmetics, nutraceuticals, pharmaceutics, and various other industries. However, the application of microalgal biotechnology towards upcycling fruit wastes has yet to be implemented on the industrial scale due to several economic, technical, operational, and regulatory challenges. Here, we identify sources of fruit waste along the food supply chain, evaluate current and emerging fruit waste management practices, describe value-added compounds in fruit wastes, and review current methods of microalgal cultivation using fruit wastes as a fermentation medium. We also propose some novel strategies for the practical implementation of industrial microalgal biorefineries for upcycling fruit waste in the future.

Impact of including two types of destoned olive cakes in pigs' diets on fecal bacterial composition and study of the relationship between fecal microbiota, feed efficiency, gut fermentation, and gaseous emissions

The microbial population in the pig's gastrointestinal tract can be influenced by incorporating fibrous by-products into the diets. This study investigated the impact of including two types of dried olive cake (OC) in pigs' diets on fecal bacterial composition. The correlation between fecal microbiota and growth performance, nutrient digestibility, gut fermentation pattern and slurry gas emissions was also evaluated. Thirty male Pietrain x (Landrace x Large white) pigs (47.9 ± 4.21 kg) were assigned to three groups: a control group (C), a group fed a diet with 20% partially defatted OC (20PDOC), and a group fed a diet with 20% cyclone OC (20COC) for 21 days. Fecal samples collected before and after providing the experimental diets were analyzed for the V3-V4 region of the 16S rRNA gene. Pigs were weighed, and feed intake was recorded throughout the study. Potential ammonia and methane emissions from slurry were measured. No significant differences in alpha diversity indexes were found. The taxonomic analysis revealed that Firmicutes and Bacteroidota phyla were dominant at the phylum level across all groups. Differential abundance analysis using ALDEx showed significant differences among groups for various bacteria at the phylum, genus, and species levels at the end of the experiment. Pigs from 20PDOC and 20COC groups exhibited increased abundances of health-promoting bacteria, such as Plactomycetota at the phylum level and Allisonella and an unidentified genus from the Eggerthellaceae family at the genus level. These changes influenced short-chain fatty acids' (SCFA) concentration in slurries, leading to greater acetic, butyric, caproic and heptanoic acids in OC-fed groups, especially 20COC pigs. A volatility analysis revealed significant positive correlations (p < 0.05) between Uncultured_Bacteroidales and Unculured_Selenomonadaceae and energy digestibility. Monoglobus and Desulfovibrio showed a positive significant (p < 0.05) correlation with total SCFA, indicating a high impact on gut fermentation. However, growth performance parameters and potential gas emission displayed no significant correlations with a specific bacterial genus. In conclusion, our results suggest that OC inclusion into pig diets could positively modulate and contribute to the gut microbiota's favorable composition and functionality. Also, nutrient digestibility and gut fermentation patterns can be associated with specific microbial populations.

Wasted Food, Wasted Resources? A Critical Review of Environmental Impact Analysis of Food Loss and Waste Generation and Treatment

Food loss and waste (FLW) comes with significant environmental impacts and thus prevents a sustainable food system transition. Here we conducted a systematic review of 174 screened studies that assessed the environmental impacts of FLW generation and treatment. We found that the embodied impacts of FLW along the supply chain and impacts from FLW treatment received equal attention, but few studies have included both. The reviewed studies show narrow geographical (mostly conducted in industrialized countries) and food supply chain (mostly focused on the consumption stage) coverage. Life cycle analysis (LCA), material flow analysis (MFA), or their combination are the most commonly used to quantify FLW related environmental impacts. More method standardization, integration, and innovation and better FLW data with regional and stage resolution from a first-hand source are badly needed. Among the various proposed mitigation strategies covering technology, economy, behavior, and policy aspects, process optimization and waste management options are the most discussed. Our review calls for a more holistic environmental impact assessment of FLW generation and treatment and analysis of the trade-offs among different environmental impact categories and between supply chain stages, which would better inform relevant policy on effective environmental impact mitigation strategies toward sustainable food systems.

Effect of Maillard reaction based on catechol polymerization on the conversion of food waste to humus

The pollution and harm of food waste (FW) are increasingly concerned, which has the dual attributes of pollutants and resources. This study aimed to improve the synthesis efficiency of FW humic substances (HS), and investigating the effect of catechol on the formation mechanism and structure of humic acid (HA) and fulvic acid (FA). Results indicated that catechol incorporation could enable to exhibit higher HS yield and more complex structure, especially the maximum particle size of FA reached 4800 nm. This was due to the combination of catechol with multiple nitrogenous compounds, which accelerated molecular condensation. Spectroscopic scans analysis revealed that Maillard reaction occurs first. Subsequently, Maillard reaction products and amino acids were combined with different sites of catechol, which leads to the difference of molecular structure of HS. The structure of FA is characterized by an abundance of carboxyl and hydroxyl groups, whereas HA is rich in benzene and heterocyclic structures. The structural difference was responsible for the disparity in the functional properties of FA and HA. Specifically, the presence of amino, hydroxyl, pyridine, and carboxyl groups in FA contributes significantly to its chelating activity. This research provides an efficient and sustainable unique solution for the high-value of FW conversion, and provides evidence for understanding the structural evolution of HA and FA.

Interventions to increase circularity and reduce environmental impacts in food systems

Applying specific circularity interventions to the food system may have environmental benefits. Using an iterative linear food system optimisation model (FOODSOM), we assess how changes in human diets, imports and exports, and the utilisation of waste streams impact land use and greenhouse gas emissions (GHG). After including these circularity principles, land use and GHG emissions were on average 40% and 68% lower than in the current food system, primarily driven by a reduction in production volumes and a shift towards feeding the domestic population. Shifting from the current diet to a circular diet decreased land use with 43% and GHG emissions with 52%. Allowing up to half of each nutrient in the human diet to be imported, while balancing imports with equal exports in terms of nitrogen, phosphorus and potassium, also decreased land use (up to 34%) and GHG emissions (up to 26%) compared to no imported food. Our findings show that circularity interventions should not be implemented mutually exclusively; by combining a circular diet with imported food and fully utilising waste streams, the lowest land use and GHG emissions can be realised.

Transforming food waste into animal feeds: an in-depth overview of conversion technologies and environmental benefits

Food waste is a global concern, with significant quantities of edible food being discarded every day. However, innovative conversion technologies have emerged to effectively transform this waste into valuable animal feed. This review paper provides a comprehensive examination of the conversion technologies used to transform food waste into animal feed, along with an analysis of the environmental benefits associated with these processes. The paper delves into various conversion methods such as anaerobic digestion, insect-based conversion, and microbial fermentation along with exploring their mechanisms and suitability for converting food waste into valuable animal feed resources. Additionally, the environmental benefits, including waste reduction, greenhouse gas emission reduction, and resource conservation, are discussed in detail. The review highlights the potential of these technologies to address the pressing issue of food waste while contributing to a more sustainable and resource-efficient food system. The findings of this review emphasize the importance of adopting and further developing these conversion technologies as a means to mitigate environmental impacts, promote circular economy principles, and enhance the overall sustainability of the food and agriculture sector.

Insights into the management of food waste in developing countries: with special reference to India

Up to one third of the food that is purposely grown for human sustenance is wasted and never consumed, with adverse consequences for the environment and socio-economic aspects. In India, managing food waste is a significant environmental concern. Food waste output is increasing in Indian cities and towns as a result of the country's urban expansion, modernization, and population growth. Poor management of food waste can have negative consequences for the environment and pose a risk to the public's health issues. This review focuses on the current challenges, management strategies, and future perspectives of food waste management in India. The efficient management of food waste involves a comprehensive study regarding the characterization of food waste and improved waste management methods. In addition, the government policies and rules for managing food waste that is in effect in India are covered in this review.

Sustainable utilization of fruit and vegetable waste bioresources for bioplastics production

Nowadays, rapidly increasing production, use and disposable of plastic products has become one of the utmost environmental issues. Our current circumstances in which the food supply chain is demonstrated as containing plastic particles and other plastic-based impurities, represents a significant health risk to humans, animals, and environmental alike. According to this point of view, biodegradable plastic material aims to produce a more sustainable and greener world with a lower ecological impact. Bioplastics are being investigated as an environmentally friendly candidate to address this problem and hence global bioplastic production has seen significant growth and expansion in recent years. This article focuses on a few critical issues that must be addressed for bioplastic production to become commercially viable. Although the reduction of fruit and vegetable waste biomass has an apparent value in terms of environmental benefits and sustainability, commercial success at industrial scale has remained flat. This is due to various factors, including biomass feedstocks, pretreatment technologies, enzymatic hydrolysis, and scale-up issues in the industry, all of which contribute to high capital and operating costs. This review paper summarizes the global overview of bioplastics derived from fruit and vegetable waste biomass. Furthermore, economic and technical challenges associated with industrialization and diverse applications of bioplastics in biomedical, agricultural, and food-packaging fields due to their excellent biocompatibility properties are reviewed.HighlightsReview of the diverse types and characteristics of sustainability of biobased plasticsImproved pretreatment technologies can develop to enhance greater yieldEnzyme hydrolysis process used for bioplastic extraction & hasten industrial scale-upFocus on technical challenges facing commercialized the bioplasticsDetailed discussion on the application for sustainability of biodegradable plastics.

Strategies of managing solid waste and energy recovery for a developing country - A review

Solid waste is considered one of the major pollutants of both water and surface worldwide. The growing global population, urban expansion, and industrial growth are the main reasons for solid waste generation. This has become a major challenge with both regional and worldwide consequences. The yearly generation of municipal solid wastes around the world is 2.01 BT (billion tons) among which about 33 % are not ecologically handled. To address this, proper solid waste management, especially recycling waste products, is crucial to achieving sustainability. High-income countries are able to recycle 51 % of their waste, while low-income countries only recycle 16 % of their waste. Inadequate solid waste management practices can only compound environmental and social problems. To handle these issues thermochemical and biochemical methods are used to convert solid waste to energy. Thermochemical method is suitable for developing countries though it is energy extensive. This review provides a detailed analysis of developing countries' solid waste management and energy recovery. It explores energy recovery technologies, including thermochemical and biochemical waste conversion processes.

Efficient removal of Cd(II) and Pb(II) from aqueous solution using biochars derived from food waste

Massive amount of food waste has been generated annually, posing a threat to ecological sustainability and the social economy due to current disposal methods. Urgent action is needed worldwide to convert the traditional pathway for treating food waste into a sustainable bioeconomy, as this will significantly benefit food chain management. This study explores the use of pyrolysis to produce different types of food waste biochars and investigates their adsorption capabilities for removing Cd2+ and Pb2+ in aqueous solution. The results indicated that co-pyrolysis biochar from fresh food waste and rice husk (FWRB) exhibited superior adsorption performance for Cd2+ (61.84 mg·g-1) and Pb2+ (245.52 mg·g-1), respectively. Pseudo-second-order kinetics (0.74 ≤ R2 ≤ 0.98) and Langmuir isotherms (0.87 ≤ R2 ≤ 0.98) indicated that the immobilized Cd2+ and Pb2+ on biochars were mainly attributed to the chemisorption, including precipitation with minerals (e.g., carbonates, silicates, and phosphate), complexation with functional groups (-OH), cation exchange (-COO-), and coordination with π-electrons. Furthermore, FWRB demonstrated reduced EC and Na content in comparison to food waste digestate biochar (FWDB) and food waste digestate co-pyrolysis with sawdust biochar (FWSB), with levels of Cd and Pb falling below China's current guideline thresholds. These findings suggested that co-pyrolysis of fresh food waste with rice husk could be applicable to the recycling of food waste into biochar products for heavy metal stabilization in contaminated water and soils.

Preserving global land and water resources through the replacement of livestock feed crops with agricultural by-products

While animal-source foods contribute to 16% of the global food supply and are an important protein source in human diets, their production uses a disproportionately large fraction of agricultural land and water resources. Therefore, a global comprehensive understanding of the extent to which livestock production competes directly or indirectly with food crops is needed. Here we use an agro-hydrological model combined with crop-specific yield data to investigate to what extent the replacement of some substitutable feed crops with available agricultural by-products would spare agricultural land and water resources that could be reallocated to other uses, including food crop production. We show that replacing 11-16% of energy-rich feed crops (that is, cereals and cassava) with agricultural by-products would allow for the saving of approximately 15.4-27.8 Mha of land, and 3-19.6 km3 and 74.2-137.8 km3 of blue and green water, respectively, for the growth of other food crops, thus providing a suitable strategy to reduce unsustainable use of natural resources both locally or through virtual land and water trade.

Carbohydrate flow through agricultural ecosystems: Implications for synthesis and microbial conversion of carbohydrates

Carbohydrates are chemically and structurally diverse biomolecules, serving numerous and varied roles in agricultural ecosystems. Crops and horticulture products are inherent sources of carbohydrates that are consumed by humans and non-human animals alike; however carbohydrates are also present in other agricultural materials, such as soil and compost, human and animal tissues, milk and dairy products, and honey. The biosynthesis, modification, and flow of carbohydrates within and between agricultural ecosystems is intimately related with microbial communities that colonize and thrive within these environments. Recent advances in -omics techniques have ushered in a new era for microbial ecology by illuminating the functional potential for carbohydrate metabolism encoded within microbial genomes, while agricultural glycomics is providing fresh perspective on carbohydrate-microbe interactions and how they influence the flow of functionalized carbon. Indeed, carbohydrates and carbohydrate-active enzymes are interventions with unrealized potential for improving carbon sequestration, soil fertility and stability, developing alternatives to antimicrobials, and circular production systems. In this manner, glycomics represents a new frontier for carbohydrate-based biotechnological solutions for agricultural systems facing escalating challenges, such as the changing climate.

Upcycling of recycled minerals from sewage sludge through black soldier fly larvae (Hermetia illucens): Impact on growth and mineral accumulation

Phosphorous (P) resources are finite. Sewage sludge recyclates (SSR) are not only of interest as plant fertilizer but also as potential source of minerals in animal nutrition. However, besides P and calcium (Ca), SSR contain heavy metals. Under EU legislation, the use of SSR derivatives in animal feed is not permitted, but given the need to improve nutrient recycling, it could be an environmentally sound future mineral source. Black soldier fly larvae (BSFL) convert low-grade biomass into valuable proteins and lipids, and accumulate minerals in their body. It was hypothesized that BSFL modify and increase their mineral content in response to feeding on SSR containing substrates. The objective was to evaluate the upcycling of minerals from SSR into agri-food nutrient cycles through BSFL. Growth, nutrient and mineral composition were compared in BSFL reared either on a modified Gainesville fly diet (FD) or on FD supplemented with either 4% of biochar (FD + BCH) or 3.6% of single-superphosphate (FD + SSP) recyclate (n = 6 BSFL rearing units/group). Larval mass, mineral and nutrient concentrations and yields were determined, and the bioaccumulation factor (BAF) was calculated. The FD + SSP substrate decreased specific growth rate and crude fat of BSFL (P < 0.05) compared to FD. The FD + SSP larvae had higher Ca and P contents and yields but the BAF for Ca was lowest. The FD + BCH larvae increased Ca, iron, cadmium and lead contents compared to FD. Larvae produced on FD + SSP showed lower lead and higher arsenic concentration than on FD + BCH. Frass of FD + BCH had higher heavy metal concentration than FD + SSP and FD (P < 0.05). Except for cadmium and manganese, the larval heavy metal concentration was below the legally permitted upper concentrations for feed. In conclusion, the SSR used could enrich BSFL with Ca and P but at the expense of growth. Due to the accumulation of Cd and Mn, BSFL or products thereof can only be a component of farmed animal feed whereas in BSFL frass heavy metal concentrations remained below the upper limit authorized by EU.

Influence of biochar on succession of fungal communities during food waste composting

This study aims to examine the effects of biochar on fungal dynamics during food waste composting. The different dosage of wheat straw biochar from 0 to 15% (0%, 2.5%, 5%, 7.5%, 10%, and 15%) were used as an additive to composting and examined for 42 days. The results showed that Ascomycota (94.64%) and Basidiomycota (5.36%) were the most dominant phyla. The most common fungal genera were Kluyveromyces (3.76%), Candida (5.34%), Trichoderma (2.30%), Fusarium (0.46%), Mycothermus-thermophilus (5.67%), Trametes (0.46%), and Trichosporon (3.38%). The average number of operational taxonomic units were 469, with the greatest abundance seen in the 7.5% and 10% treatments. Redundancy analysis revealed that different concentrations of biochar applied treatments have significantly distinct fungal communities. Additionally, correlation analyses of fungal interactions with environmental elements, performed through a heatmap, also indicate a distinct difference among the treatments. The study clearly demonstrates that 15% of biochar has a positive impact on fungal diversity and improves the food waste composting.

Low-opportunity-cost feed can reduce land-use-related environmental impacts by about one-third in China

Feeding animals more low-opportunity-cost feed products (LCFs), such as food waste and by-products, may decrease food-feed competition for cropland. Using a feed allocation optimization model that considers the availability of feed sources and animal requirements for protein and energy, we explored the perspectives of feeding more LCFs to animals in China. We found that about one-third of the animal feed consisted of human-edible products, while only 23% of the available LCFs were used as feed during 2009-2013. An increased utilization of LCFs (45-90 Mt) could potentially save 25-32% of feed-producing cropland area without impairing livestock productivity. Parallelly, about one-third of feed-related irrigation water, synthetic fertilizer and greenhouse gas emissions would be saved. Re-allocating the saved cropland could sustain the food energy demand of 30-185 million people. Achieving the potentials of increased LCF use requires improved technology and coordination among stakeholders.

Feeding recycled food waste improved feed efficiency in laying hens from 24 to 43 weeks of age

There is renewed interest in utilizing food waste as animal feed due to its potential benefits in reducing feed cost and environmental impact while improving global food security. This study was conducted to examine the efficacy of recycled food waste-based feed for laying hen performance, egg quality, and nutrient digestibility. Hy-Line Brown hens (n = 150) were randomly distributed to three dietary treatments with 50 replicate cages of a single bird per treatment from 24 to 43 weeks of age. The treatments were: a standard/control feed based on wheat, sorghum, and soybean meal; a recycled food waste based-feed; and a 50:50 blend of control and food waste based-feed. Hens offered the food waste-based diets had similar egg weight, hen day egg production, and egg mass, but lower feed intake and higher feed efficiency, compared to those fed the control diets (P < 0.001). Hens fed the food waste diets exhibited lower shell breaking strength and shell thickness at week 34, and higher yolk color score and higher fat digestibility compared to the control treatment at week 43 (P < 0.001). Thus, feeding the recycled food waste based-feed maintained egg production while improving feed efficiency compared to the control feed.

Sustainable management of food waste; pre-treatment strategies, techno-economic assessment, bibliometric analysis, and potential utilizations: A systematic review

Food waste (FW) contains many nutritional components such as proteins, lipids, fats, polysaccharides, carbohydrates, and metal ions, which can be reused in some processes to produce value-added products. Furthermore, FW can be converted into biogas, biohydrogen, and biodiesel, and this type of green energy can be used as an alternative to nonrenewable fuel and reduce reliance on fossil fuel sources. It has been demonstrated in many reports that at the laboratory scale production of biochemicals using FW is as good as pure carbon sources. The goal of this paper is to review approaches used globally to promote turning FW into useable products and green energy. In this context, the present review article highlights deeply in a transdisciplinary manner the sources, types, impacts, characteristics, pre-treatment strategies, and potential management of FW into value-added products. We find that FW could be upcycled into different valuable products such as eco-friendly green fuels, organic acids, bioplastics, enzymes, fertilizers, char, and single-cell protein, after the suitable pre-treatment method. The results confirmed the technical feasibility of all the reviewed transformation processes of FW. Furthermore, life cycle and techno-economic assessment studies regarding the socio-economic, environmental, and engineering aspects of FW management are discussed. The reviewed articles showed that energy recovery from FW in various forms is economically feasible.

Valorization of Food Waste as Animal Feed: A Step towards Sustainable Food Waste Management and Circular Bioeconomy

The growing population and healthy food demands have led to a rise in food waste generation, causing severe environmental and economic impacts. However, food waste (FW) can be converted into sustainable animal feed, reducing waste disposal and providing an alternative protein source for animals. The utilization of FW as animal feed presents a solution that not only tackles challenges pertaining to FW management and food security but also lessens the demand for the development of traditional feed, which is an endeavour that is both resource and environmentally intensive in nature. Moreover, this approach can also contribute to the circular economy by creating a closed-loop system that reduces the use of natural resources and minimizes environmental pollution. Therefore, this review discusses the characteristics and types of FW, as well as advanced treatment methods that can be used to recycle FW into high-quality animal feed and its limitations, as well as the benefits and drawbacks of using FW as animal feed. Finally, the review concludes that utilization of FW as animal feed can provide a sustainable solution for FW management, food security, preserving resources, reducing environmental impacts, and contributing to the circular bioeconomy.

Converting food waste into soil amendments for improving soil sustainability and crop productivity: A review

One-third of the annual food produced globally is wasted and much of the food waste (FW) is unutilized; however, FW can be valorized into value-added industrial products such as biofuel, chemicals, and biomaterials. Converting FW into soil amendments such as compost, vermicompost, anaerobic digestate, biofertilizer, biochar, and engineered biochar is one of the best nutrient recovery and FW reuse approaches. The soil application of FW-based amendments can improve soil fertility, increase crop production, and reduce contaminants by altering soil's chemical, physical, microbial, and faunal properties. However, the efficiency of the amendment for improving ecosystem sustainability depends on the type of FW, conversion method, application rate, soil type, and crop type. Engineered biochar/biochar composite materials produced using FW have been identified as promising amendments for soil remediation, reducing commercial fertilizer usage, and increasing soil nutrient use efficiency. The development of quality standards and implementation of policies and regulations at all stages of the food supply chain are necessary to manage (reduce and re-use) FW.

Applications of agricultural residue biochars to removal of toxic gases emitted from chemical plants: A review

Crop residues are representative agricultural waste materials, massively generated in the world. However, a large fraction of them is currently being wasted, though they have a high potential to be used as a value-added carbon-rich material. Also, the applications of carbon-rich materials from agricultural waste to industries can have economic benefit because waste-derived carbon materials are considered inexpensive waste materials. In this review, valorization methods for crop residues as carbon-rich materials (i.e., biochars) and their applications to industrial toxic gas removals are discussed. Applications of crop residue biochars to toxic gas removal can have significant environmental benefits and economic feasibility. As such, this review discussed the technical advantages of the use of crop residue biochars as adsorbents for hazardous gaseous pollutants and greenhouse gases (GHGs) stemmed from combustion of fossil fuels and the different refinery processes. Also, the practical benefits from the activation methods in line with the biochar properties were comprehensively discussed. The relationships between the physico-chemical properties of biochars and the removal mechanisms of gaseous pollutants (H₂S, SO₂, Hg⁰, and CO₂) on biochars were also highlighted in this review study. Porosity controls using physical and chemical activations along with the addition of specific functional groups and metals on biochars have significantly contributed to the enhancement of flue gas adsorption. The adsorption capacity of biochar for each toxic chemical was in the range of 46-76 mg g^-1 for H₂S, 40-182 mg g^-1 for SO₂, 80-952 μg g^-1 for Hg⁰, and 82-308 mg g^-1 CO₂, respectively. This helps to find suitable activation methods for adsorption of the target pollutants. In the last part, the benefits from the use of biochars and the research directions were prospectively provided to make crop residue biochars more practical materials in adsorption of pollutant gases.

The use of animal by-products in a circular bioeconomy: Time for a TSE road map 3?

In 2005 and 2010, the European Commission (EC) published two subsequent 'Road Maps' to provide options for relaxation of the bans on the application of animal proteins in feed. Since then, the food production system has changed considerably and demands for more sustainability and circularity are growing louder. Many relaxations envisioned in the second Road Map have by now been implemented, such as the use of processed animal proteins (PAPs) from poultry in pig feed and vice versa. However, some legislative changes, in particular concerning insects, had not been foreseen. In this article, we present a new vision on legislation for increased and improved use of animal by-products. Six current legislative principles are discussed for the bans on animal by-products as feed ingredients: feed bans; categorization of farmed animals; prohibition unless explicitly approved; approved processing techniques, the categorization of animal by-products, and monitoring methods. We provide a proposal for new guiding principles and future directions, and several concrete options for further relaxations. We argue that biological nature of farmed animals in terms of dietary preferences should be better recognised, that legal zero-tolerance limits should be expanded if safe, and that legislation should be revised and simplified.

Transformation of bread waste into 2,5-furandimethanol via an efficient chemoenzymatic approach in a benign reaction system

Via combination catalysis with deep eutectic solvent lactic acid:betaine (chemocatalyst) and HMFOMUT cell (biocatalyst: E. coli HMFOMUT whole-cell), one-pot manufacture of 2,5-furandimethanol from waste bioresource was constructed in a chemoenzymatic approach. With bread waste (50 g/L) as substrate, the 5-hydroxymethylfuran yield reached 44.2 Cmol% (based on bread waste) by lactic acid:betaine (15 wt%) at 180 °C for 15 min. With glucose as co-substrate, HMFOMUT could transform 5-hydroxymethylfurfural (150 mM) to 2,5-furandimethanol (84.5 % yield) after 1 day at 37 °C and pH 7.0. In lactic acid:betaine-H₂O, HMFOMUT effectively converted bread-derived 5-hydroxymethylfurfural into 2,5-furandimethanol in a productivity of 700 kg 2,5-furandimethanol per kg 5-hydroxymethylfurfural (230 kg 2,5-furandimethanol per kg bread). In an eco-friendly lactic acid:betaine system, an effective one-pot chemoenzymatic strategy was firstly developed to convert bread waste into 2,5-furandimethanol, which would reduce the operation cost and has potential application value for valorizing waste food bioresource into value-added furan.

Optimizing the environmental sustainability of alternative post-harvest scenarios for fresh vegetables: A case study in Spain

The aim of this research is to define different scenarios that optimize the environmental sustainability of the post-harvest stage of vegetable products (cauliflower and brassicas mix). These scenarios considered different packaging materials; energy generation technologies for the processing plant (standard electricity mix vs. renewable options); organic waste management (composting, anaerobic digestion, and animal feeding); and refrigerated transportation (local, national, and international, using diesel, natural gas, and hybrid trucks and railway). The analysis has been carried out based on a foreground inventory provided by a company that operating internationally, in accordance with the International Organization for Standardization (ISO) 14,040 methodological framework and following the latest Product Environmental Footprint (PEF) protocols. The analysis describes four midpoint categories, single score (SS) using EF3.0 life cycle impact assessment (LCIA) methodology and the Cumulative Energy Demand. The carbon footprint (CF) of the post-harvest stage for a base case scenario ranged between 0.24 and 0.29 kg CO₂ eq/kg of vegetable, with a strong contribution associated to the production of packaging materials (57.8-65.2 %) and the transport stage (national range in conventional diesel vehicles) (31.5-38.0 %). Comparatively, lower emissions were associated with the energy consumed at the processing factory (up to 4.1 %) while the composting of organic waste management produced some impact savings (up to -3.5 %). Although certain differences were observed, the dominance of the transport stage and the packaging materials is sustained in all the other environmental impact and energy categories evaluated. The most effective measures to reduce the environmental footprint of the post-harvest stage involve: i) using reusable packaging materials; ii) reducing the transport range and using vehicles running on natural gas or hybrid technologies; iii) the incorporation of renewable energy to supply the factory; and iv) the utilization of the organic residues in higher value applications such as animal feeding. Implementing the measures proposed in this study would reduce the post-harvest CF of fresh vegetables by 90 %.

Innovative Research Offers New Hope for Managing African Swine Fever Better in Resource-Limited Smallholder Farming Settings: A Timely Update

African swine fever (ASF) in domestic pigs has, since its discovery in Africa more than a century ago, been associated with subsistence pig keeping with low levels of biosecurity. Likewise, smallholder and backyard pig farming in resource-limited settings have been notably affected during the ongoing epidemic in Eastern Europe, Asia, the Pacific, and Caribbean regions. Many challenges to managing ASF in such settings have been identified in the ongoing as well as previous epidemics. Consistent implementation of biosecurity at all nodes in the value chain remains most important for controlling and preventing ASF. Recent research from Asia, Africa, and Europe has provided science-based information that can be of value in overcoming some of the hurdles faced for implementing biosecurity in resource-limited contexts. In this narrative review we examine a selection of these studies elucidating innovative solutions such as shorter boiling times for inactivating ASF virus in swill, participatory planning of interventions for risk mitigation for ASF, better understanding of smallholder pig-keeper perceptions and constraints, modified culling, and safe alternatives for disposal of carcasses of pigs that have died of ASF. The aim of the review is to increase acceptance and implementation of science-based approaches that increase the feasibility of managing, and the possibility to prevent, ASF in resource-limited settings. This could contribute to protecting hundreds of thousands of livelihoods that depend upon pigs and enable small-scale pig production to reach its full potential for poverty alleviation and food security.

Life cycle environmental impacts of using food waste liquid fodder as an alternative for pig feeding in a conventional Cuban farm

This work aimed to compare cleaner production alternatives for pig production in the Cuban context through the Life Cycle Assessment (LCA) approach emphasizing the utilization of food waste (FW) as a substitute for traditional grain-based pig feeding. A conventional waste management method (lagooning) was assessed, including more environmentally friendly approaches (use of anaerobic digestion (AD) process); including the substitution of a fraction of solid fodder with food waste liquid fodder (LF), obtained from food waste. The analysis was based on one porcine equivalent livestock unit. The environmental impact categories assessed were global warming, terrestrial ecotoxicity, human carcinogenic toxicity, freshwater ecotoxicity, terrestrial acidification, and freshwater eutrophication. The major environmental benefits for pig production were observed when the maximum capacity of pigs was considered. In addition, favorable environmental performance was achieved by considering the substitution of solid fodder by LF, the AD as a waste management process, and the valorization of the solid and liquid effluents. The avoided products-related activities were the main contributor to freshwater ecotoxicity, human carcinogenic toxicity, and terrestrial ecotoxicity impact categories (up to 71 %). The sensitivity analysis showed that the variation in LF composition (protein concentration) could have a remarkable impact in all impact categories. Climate change performed as the more sensible impact category, suggesting that greenhouse gas (GHG) emissions, such as CO₂ and N₂O, are important drivers to change the environmental impact and need more attention. This research demonstrates that the environmental profile of the process can be improved by applying a cleaner production approach (AD as a waste management alternative and LF substituting solid fodder).

Bioconversion of food waste to crayfish feed using solid-state fermentation with yeast

In order to realize the value-added utilization of food waste (FW), the preparation of crayfish (Procambarus clarkii) feed by yeast fermentation was investigated. Firstly, the suitable fermentation condition was obtained through a single factor experiment as follows: the initial moisture of the FW was adjusted to 60% with bran and inoculated with a 2% yeast mixture (Saccharomyces cerevisiae, Candida utilis, and Yarrowia lipolytica, 3:2:1) followed by aerobic solid-state fermentation for 7 days. The crude protein and acid-soluble protein contents in the fermented feed were 25.14% and 5.16%, which were increased by 8% and 140.67%, respectively. The crude fat content was 0.74%, decreased by 68.29%. The content of antioxidant glutathione (571.78 μg/g) increased 63.33%, and the activities of protease and amylase increased nearly 9 and 3 times, respectively. The maximum degradation rates of aflatoxin B1, zearalenone, and deoxynivalenol were 63.83%, 77.52%, and 80.16%, respectively. The fermented feeds were evaluated by substituting (0%, 10%, 30%, 50%, and 100%) commercial diet for crayfish (30-day culture period). When the replacement proportion was 30%, the weight gain of crayfish reached 44.87% (initial body weight 13.98 ± 0.41 g), which was significantly increased by 10.25% compared with the control (p = 0.0005). In addition, the lysozyme and SOD enzyme activities in crayfish hepatopancreas were also increased significantly. Our findings suggest that yeast-fermented feed from FW can replace 30% of crayfish's conventional diet, which may improve crayfish's antioxidant capacity and enhance non-specific immunity by providing molecules such as glutathione.

Review: Connecting circularity to animal welfare calls for a 'novel' conceptual framework based on integrity

The current food system is not sustainable. Circular agriculture aims to save the environment and produce food sustainably by closing nutrient cycles, possibly without improving animal welfare. This paper proposes a new conceptual framework, called a circular welfare economy (CWE), to facilitate a transition towards a sustainable agriculture based on integrity. The CWE framework explains how welfare relates to circular agriculture, how potential conflicts can be solved and what future livestock farming could look like. CWE applies the notion of circularity to welfare defined as the quality of life as perceived by the individual itself. CWE also identifies human integrity, defined as being open and honest, as a sine qua non for sustainability. Animal-welfare problems arise when animals are merely used as a means, e.g., for profits. Instead, profits and circular agriculture are means to the end of welfare. In a CWE, welfare is promoted sustainably, without causing undue need frustration in other individuals. This requires informed moral decision-making involving human integrity and the closure of welfare-related feedback loops. Conflicts between circular agriculture and animal welfare are solved by weighing all welfare needs impartially. Three future scenarios are presented: Animal-welfare-exclusive circular agriculture, which resembles modern intensive livestock farming, animal rights agriculture without livestock farming, and a CWE-based agriculture which integrates circular agriculture and animal welfare. In the latter case, we will not use animals merely as a means to close nutrient cycles, but take every effort, openly and honestly, to understand and benefit their points of view as we do our own.

Anaerobic digestion of fruit and vegetable waste: a critical review of associated challenges

The depletion of fossil fuels coupled with stringent environmental laws has encouraged us to develop sustainable renewable energy. Due to its numerous benefits, anaerobic digestion (AD) has emerged as an environment-friendly technology. Biogas generated during AD is primarily a mixture of CH₄ (65-70%) and CO₂ (20-25%) and a potent energy source that can combat the energy crisis in today's world. Here, an attempt has been made to provide a broad understanding of AD and delineate the effect of various operational parameters influencing AD. The characteristics of fruit and vegetable waste (FVW) and its feasibility as a potent substrate for AD have been studied. This review also covers traditional challenges in managing FVW via AD, the implementation of various bioreactor systems to manage large amounts of organic waste and their operational boundaries, microbial consortia involved in each phase of digestion, and various strategies to increase biogas production.

Environmental assessment of casual dining restaurants in urban and suburban areas of peninsular Malaysia during the COVID-19 pandemic

Food waste has been considered a global problem due to its adverse impacts on food security, the environment, and the economy; hence needs urgent attention and action. Its generation is expected to increase as the world population grows rapidly, leading to more global waste. This study sought the impacts of the COVID-19 outbreak on the 1-week operation of selected casual dining restaurants in urban (Ampang, Kuala Lumpur) and suburban areas (Kota Bharu, Kelantan and Jasin, Melaka) of Peninsular Malaysia, as the local community adjusted to life with COVID-19. The food waste in this study was classified into three categories: preparation loss, serving loss, and customer's plate waste. Our material flow analysis revealed that the highest food loss at these locations came from preparation loss (51.37%), followed by serving loss (30.95%), and preparation loss (17.8%). Meanwhile, the total average electricity consumption and its carbon footprint for Ampang were 127 kWh and 13.87 kgCO₂e, Kota Bharu 269.8 kWh and 29.47 kgCO₂e, and Jasin 142.2 kWh and 15.54 kgCO₂e, respectively. As for water, Ampang exhibited 22.93 m³ total average consumption and 7.91 kgCO₂e greenhouse emissions from this source, Jasin consuming 17.11 m³ of water and releasing 5.88 kgCO₂e of carbon footprint, while Kota Bharu emitted 20.21 kgCO₂e of greenhouse gases from its 58.71 m³ water consumption. Our findings indicate a major 'food leak' at the preparation stage, from which the waste could be utilised as livestock feed, and that electricity consumption is a greater carbon emitter than water consumption, suggesting a need for improvement to the kitchen practices and equipment.

Pearls before Swine: Plant-Derived Wastes to Produce Low-Cholesterol Meat from Farmed Pigs-A Bibliometric Analysis Combined to Meta-Analytic Studies

Due to environmental and human factors, there is a growing amount of agri-food waste worldwide. The European Commission is incentivizing a zero-waste policy by 2025, pushing to find a "second life" for at least the avoidable ones. In this review, after summarizing the nutritional values of pork and the importance of its inclusion in human diet, a phylogenetic analysis was conducted to investigate potential differences in the structure and activity of HMGCR, which is a key enzyme in cholesterol metabolism. In addition, a bibliometric analysis combined with visual and meta-analytical studies on 1047 scientific articles was conducted to understand whether the inclusion of agro-food waste could affect the growth performance of pigs and reduce cholesterol levels in pork. Although some critical issues were highlighted, the overall data suggest a modern and positive interest in the reuse of agri-food waste as swine feed. However, although interesting and promising results have been reported in several experimental trials, further investigation is needed, since animal health and meat quality are often given marginal consideration.

Investment priorities for research and innovation in urban agri-food systems: Toward more resilient cities in the Global South

Urban and peri-urban agriculture (UPA) is widely distributed throughout the Global South. Despite urban population growth and diversifying food habits, UPA delivers an important part of urban food supply, as well as other types of services to cities, such as employment and waste reuse. Nevertheless, the extent and importance of UPA varies between different urban areas, while challenges like limited recognition, land conversion, and water pollution and competition threaten the potential of UPA to contribute to urban resilience. Key investment priorities for research and innovation for overcoming current challenges include incentivized peri-urban zoning, urban allocation of productive lands, and increasing capacities for controlled environment agriculture (CEA). Innovative repositioning of food marketing can help to strengthen supply of healthy food from UPA production, increase decent employment, and turn food markets into nutrition hubs. Priority innovations for contributing to the circular bioeconomy of cities include scaling the safe use of wastewater for irrigation through investments in the adoption of multiple risk-barrier approaches and scaling UPA-based ecosystem services for valorising solid waste and environmental management. Innovations in urban governance are required to support these processes by bringing food systems into urban planning through food mapping and the multisectoral platforms for dialogue and policy formulation across city regions and with vertical levels of government.

Dehydrated Food Waste for Composting: An Overview

Food waste disposal has recently received much attention worldwide due to its major impact on environmental pollution and economic costs. Using high moisture content of food waste has the highest negative environmental impact due to increased greenhouse gas emissions, odor, and leachate. Drying technologies play an important role in reducing the moisture content of food waste, which is necessary for environmental sustainability and safety. The first part of this review highlights that sun-drying is the most cost-effective drying method. However, it has not been widely recommended for food waste management due to several limitations, including the inability to control sunray temperature and the inability to control end-product quality. Thermal drying eliminates moisture from food waste quickly, preventing hydrolysis and biodegradation. Thermal dryers, such as the GAIA GC-300 dryer, and cabinet dryer fitted with a standard tray, are the best alternative to sun drying. The second part of this review highlights that dehydrated food waste products are slightly acidic (4.7–5.1), have a high electrical conductivity (EC) value (4.83–7.64 mS cm-1), with high nutrient content, due to low pH levels, dehydrated food waste is not suitable for direct use as a fertilizer for the plants. So, the dried food waste should be composted before application to the plants because the composting process will dominate the limitation of phytotoxins, anoxia, salinity, and water repellence. Trench compost can be a good choice for decomposing dried organic waste because trench compost relies solely on soil decomposing microorganisms and insects.

Triple Bottom-Line Evaluation of the Production of Animal Feed from Food Waste: A Life Cycle Assessment

This study applies a triple bottom line (TBL) framework that incorporates the environmental, economic, and social impacts of producing animal feed from food waste (FW) collected at the post-consumption stage of the food supply chain. The environmental bottom line (BL) is conducted using life cycle assessment (LCA), the economic BL is calculated using the net present value (NPV), while the social BL is assessed using the strengths, weaknesses, opportunities, and threats (SWOT) analysis. The results within the environmental BL indicate that at a 13.8% recovery rate, animal feed produced from a ton of FW saves 0.33 m² equivalent of crop land but requires 3.5 tons of water compared to 0.9 tons and 0.78 tons for landfilling and incineration for FW treatment respectively. In addition, the production of animal feed from one ton of FW emits 1064.6 kg CO₂-eq, compared to 823.6 kg CO₂-eq using landfilling and 781.9 kg CO₂-eq when incinerated. The economic BL indicates a profit of $3.65/ton from incinerating FW, compared to cost of $93.8 and $137.6 per ton for animal feed production and landfilling of FW respectively. The analytic hierarchy process (AHP) is applied to integrate the TBL scores and rank the scenarios accordingly. AHP recommends animal feed and incineration over landfilling by a fourfold higher score. A simulation using an augmented simplex lattice mixture (ASLM) design recommends incineration with energy recovery over animal feed production from FW collected at the consumer stage. Sensitivity analysis indicates that the production of animal feed from FW is environmentally feasible if the safe recovery rate exceeds 48%, is which possible for FW collected at early stages of the food supply chain.

Proof of concept for developing novel feeds for cattle from wasted food and crop biomass to enhance agri-food system efficiency

Modern agri-food systems generate large amounts of crop-based biomass that are unfit for direct human consumption but potentially suitable for livestock feeding in production of meats, milk, and eggs. This study aims to develop novel feeds for cattle from some of those biomass materials through the natural microbial-driven processes of ensiling. Fruit and vegetables resembling supermarket discards were ensiled alone or co-ensiled with corn crop residues, mushroom wastes, etc. via laboratory experiments. Longitudinal sample analyses showed that (co-)ensiling was successful, with pH and fermentation acids changing rapidly into desirable ranges (pH < 4.5, the acids 5-13% DM with lactic acid dominating). The (co-)ensiled products had key nutritional parameters comparable to those of good quality forages commonly used on dairy farms. Additionally, in vitro incubation experiments indicated that the ensiled products could substitute certain conventional feeds while maintaining diet digestibility. Findings from this pilot study provide a proof of principle that quality novel feeds for cattle can be generated by co-ensiling food discards and low-value crop residues. Future research and animal feeding trials to demonstrate the utility of this approach can help societies more effectively utilize untapped biomass resources, strengthening the regenerative capacity of agri-food systems towards a more sustainable food future.

Production efficiency of animal feed obtained from food waste in Japan

Converting food waste into animal feed is highly useful for tackling the problem of food waste, which is particularly severe in developed countries. This study quantified the inefficiencies in converting food waste into animal feed and identified the sources of inefficiencies through a data envelopment analysis (DEA) of the monthly input-output data of two food waste-based animal feed producers in Japan. Our empirical analysis revealed that the producers of animal feed obtained from food waste (especially those treating food waste from retail and service industries) demonstrated inefficiencies in production technology and scale; moreover, expanding the production scale and improving the quality of food waste could enhance production efficiency. Based on the empirical results, specific policy implications were provided for the widespread use of animal feed obtained from food waste in Japan and elsewhere, globally. Furthermore, it was suggested that the COVID-19 pandemic contributed to a severe reduction in the production efficiency of animal feed producers treating food waste obtained from retail and service industries.

Application of Geopolymer in Stabilization/Solidification of Hazardous Pollutants: A Review

Geopolymers, as a kind of inorganic polymer, possess excellent properties and have been broadly studied for the stabilization/solidification (S/S) of hazardous pollutants. Even though many reviews about geopolymers have been published, the summary of geopolymer-based S/S for various contaminants has not been well conducted. Therefore, the S/S of hazardous pollutants using geopolymers are comprehensively summarized in this review. Geopolymer-based S/S of typical cations, including Pb, Zn, Cd, Cs, Cu, Sr, Ni, etc., were involved and elucidated. The S/S mechanisms for cationic heavy metals were concluded, mainly including physical encapsulation, sorption, precipitation, and bonding with a silicate structure. In addition, compared to cationic ions, geopolymers have a poor immobilization ability on anions due to the repulsive effect between them, presenting a high leaching percentage. However, some anions, such as Se or As oxyanions, have been proved to exist in geopolymers through electrostatic interaction, which provides a direction to enhance the geopolymer-based S/S for anions. Besides, few reports about geopolymer-based S/S of organic pollutants have been published. Furthermore, the adsorbents of geopolymer-based composites designed and studied for the removal of hazardous pollutants from aqueous conditions are also briefly discussed. On the whole, this review will offer insights into geopolymer-based S/S technology. Furthermore, the challenges to geopolymer-based S/S technology outlined in this work are expected to be of direct relevance to the focus of future research.

Producing insect protein from food waste digestate via black soldier fly larvae cultivation: A promising choice for digestate disposal

The treatment of food waste digestate with high salinity is a big challenge. This paper evaluated the possibility of using black soldier fly larvae for food waste digestate disposal and insect protein production. Results showed that both digestates from hydrogen and methane fermentations were rich in protein and lipid contents, which benefited the BSFL cultivation. The BSFL reared on digestates from hydrogen and methane fermentations of food waste performed better in pre-pupal weight (19.12% and 41.13% higher, respectively), body length (3.62% and 18.21% higher, respectively) and crude protein contents (7.85% and 39.05% higher, respectively) than that reared on raw food waste. In addition, the maximum body weight growth rate (R_m) of BSFL cultivated on both digestates were 28.28% and 47.10% higher than that of BSFL cultivated on raw food waste, respectively. During BSFL cultivation, organic matter reduction between 40.97% and 46.07% were achieved. Digestates from hydrogen and methane fermentations represent favorable feeding substrates for BSFL cultivation. Using BSFL to treat AD digestate not only provides a digestate disposal approach, but also produces insect biomass and organic fertilizer as value-added byproducts, which shows tremendous potential in digestate disposal.

Co-Combustion of Food Solid Wastes and Pulverized Coal for Blast Furnace Injection: Characteristics, Kinetics, and Superiority

The combustion characteristics and kinetics of food solid wastes (FSW), pulverized coal (PC), and their mixtures were studied by a non-isothermal thermogravimetric method. In the co-combustion of FSW and PC, with the increase in FSW content in the mixture, the initial decomposition temperature, burnout temperature, and ignition temperature of the mixture decreased, and the flammability index and comprehensive combustion characteristic index gradually increased. The co-combustion of FSW and PC showed an inhibitory effect in the devolatilization stage but exhibited a combustion-promoting effect in the fixed carbon combustion stage. The interaction between FSW and PC while co-combusting them appeared to be dominated by thermal effects. On one hand, FSW combusted first and released heat that was partially absorbed by the PC, which hence suppressed the devolatilization stage of the co-combustion process. On the other hand, the PC absorbed the heat released by the combustion of the FSW, which increased the combustion rate of the PC in the fixed carbon combustion stage of the co-combustion process. The activation energy of the devolatilization stage and the fixed carbon combustion stage of the co-combustion process was calculated to be 34.16–74.52 kJ/mol and 15.04–36.15 kJ/mol, respectively. In general, the combustion performance of FSW is better than that of PC. The mixed injection of FSW and PC can improve the overall combustion efficiency and reduce CO2 emissions in the iron-making process.