Alternative Valorization Research Articles

Hydrothermal–enzymatic process for the bio‐valorization of keratin wastes by thermostable keratinase from Thermoactinomyces vulgarisTK1‐21

AbstractBACKGROUNDChicken feather (CF), pig bristle (PB), and pig hoof (PH) are substantial keratin wastes from slaughterhouses. They are generated in large quantity, are almost totally unexploited protein resources, and are potential substrates for value‐added products.RESULTSIn this study, Thermoactinomyces vulgaris TK1‐21 showed a good ability to produce keratinases for the degradation of all three keratin wastes within 5 days at pH 8.5 and 45 °C. Maximum keratinase activities of 5.72, 4.21, and 4.89 U mL−1 were obtained for CF, PB, and PH, respectively. T. vulgaris TK1‐21 secreted two types of extracellular enzymes (keratinase_TK1‐21), which were purified and characterized as thermitase (keratinase‐I) and carboxypeptidase T (keratinase‐II) with estimated molecular weights of 28 and 36 kDa, respectively. Dialyzed crude keratinase_TK1‐21 could efficiently hydrolyze the hydrothermally treated CF, PB, and PH into keratin hydrolysate (KH). Soluble protein concentrations of 6.94, 3.87, and 6.32 mg mL−1 were obtained at pH 9.0, 55 °C, and 72 h, which were three times higher than those of untreated substrates. In addition, this hydrothermal–enzymatic method showed high KH productivity (60–70%) with a production cost of 16.24 USD kg−1. The ferric‐reducing antioxidant power assay and radical scavenging activities of KH derived from CF, PB, and PH were 19–42, 2.5–4.9, and 608–1314 μmol TE gprotein−1. Bioplastic starch blended with these KHs showed improved tensile strength (2.55–4.40 MPa) and elongation at break (40–54%) when compared to bioplastics without KH blending.CONCLUSIONSBased on our results, we suggest an alternative valorization approach with techno‐economic feasibility for keratin waste bioconversion into a potential active ingredient for bioplastics via hydrothermal–enzymatic processing. © 2023 Society of Chemical Industry (SCI).

Thin Film Composite Polyamide Reverse Osmosis Membrane Technology towards a Circular Economy.

It is estimated that Reverse Osmosis (RO) desalination will produce, by 2025, more than 2,000,000 end-of-life membranes annually worldwide. This review examines the implementation of circular economy principles in RO technology through a comprehensive analysis of the RO membrane life cycle (manufacturing, usage, and end-of-life management). Future RO design should incorporate a biobased composition (biopolymers, recycled materials, and green solvents), improve the durability of the membranes (fouling and chlorine resistance), and facilitate the recyclability of the modules. Moreover, proper membrane maintenance at the usage phase, attained through the implementation of feed pre-treatment, early fouling detection, and membrane cleaning methods can help extend the service time of RO elements. Currently, end-of-life membranes are dumped in landfills, which is contrary to the waste hierarchy. This review analyses up to now developed alternative valorisation routes of end-of-life RO membranes, including reuse, direct and indirect recycling, and energy recovery, placing a special focus on emerging indirect recycling strategies. Lastly, Life Cycle Assessment is presented as a holistic methodology to evaluate the environmental and economic burdens of membrane recycling strategies. According to the European Commission’s objectives set through the Green Deal, future perspectives indicate that end-of-life membrane valorisation strategies will keep gaining increasing interest in the upcoming years.

Prospective environmental assessment of reprocessing and valorization alternatives for sulfidic copper tailings

Waste from primary mining operations, especially mine tailings, receive much attention as potential secondary resources that can transform liabilities into resources. The primary intention is to minimize mine tailings disposal problems through volume reduction while recovering secondary resources for industrial materials. However, the environmental benefits and tradeoffs behind these objectives remain unclear. This study conducts a process-based life cycle assessment (LCA) study to investigate multiple reprocessing pathways of copper tailings to co-produce secondary metals and building materials. Four design options representing different value-recovery routes are constructed to assess the environmental burdens of reprocessing chains and the associated benefits from displaced virgin products. This study assesses emerging technologies in a prospective LCA, with projections of bottom-up foreground process modeling and background data like energy supply scenarios. Our analysis reveals that the assessed technologies can only be beneficial when all co-products are utilized. Results indicate that reprocessing may save from 25 up to 930 kg CO2-eq per tonne of treated copper tailings. Potential environmental benefits depend on the reprocessing routes, technology upscaling parameters, and quality of secondary products. We propose recommendations to enhance the environmental performances of mine tailings reprocessing strategies, such as switching to low-impact chemical alternatives and optimizing energy use. Our findings can support the sustainable development of the metal industry in terms of waste management and secondary resource use.

Integrating the new age of bioeconomy and Industry 4.0 into biorefinery process design

Manufacturing processes and their economy are dramatically evolving due to machinery and digital control improvements. Artificial intelligence, big data analytics, and the Internet of Things are key tools for this new industrial revolution era based on Industry 4.0. Bioeconomy and circular economy concepts have appeared in the forest, agriculture, food, pharmaceutical, pulp and paper, chemical, biotechnological, and energy areas, etc., to achieve sustainable economic growth development via biomass valorization in a biorefinery platform. Biorefinery process development at an industrial scale requires the previous design and assessment of processes and technologies. Therefore, economic, environmental, and social factors should be evaluated to prevent the failure in one of these issues that could affect the performance of the others. With a growing interest in sustainable economic development, there is a need to incorporate new technologies early enough in the process design. This study aims to better understand how Industry 4.0 era tools can bring new solutions to the biorefinery process design, in terms of the technical, economic, environmental, and social factors. Thus, these tools could improve and revolutionize the process selection optimization, provide alternatives for biomass valorization, integration strategies, and the metrics selection for process evaluation, adding the approach toward sustainable economic development.

Valorization Strategies for a By-Product of Organic Tomato Processing as Potential Ingredient in Functional Food Formulations

Production of tomato-based products generates 5% of waste, composed mainly of peel. This has a significant amount of carotenoids, such as lycopene, and an appropriate amount of total dietary fiber (TDF). Both carotenes and dietary fiber are known to have functional effects on the human body. Therefore, the aim of this research was mainly divided into two parts. First, organic tomato peel obtained by a local processing industry was characterized in terms of percentage of macronutrients such as dietary fiber, protein, and ash, as well as total carotenoid content. Second, two valorization alternatives of these compounds as potential functional additives in food processing were proposed. The first one included carotenoid extraction using ultrasound-assisted extraction (UAE), the encapsulation of the enriched carotenoid extract using spray-drying technology, and its subsequent analysis of powder properties. The second one evaluated the potential use of TDF tomato peel as a replacement for fat and flour in four formulations of cookies. Each formulation was assessed using physicochemical, texture, sensory, and theoretical proximal analyses. The results revealed that UAE optimization was performed using a solvent ratio of 80:20 ethyl acetate:ethanol and 2.5% w/v of solvent:biomass ratio. The recovery percentage of total carotenoid content was 89.08%. The TDF content was 49.46 (3.91) g/100 g on a dry basis. For encapsulation, the drying yield and encapsulation efficiencies were 67.3% (0.5) and 58.1% (0.8), respectively. Sensory analysis showed no significant difference between the means for the control cookie and the 30% fat replacement cookie. Moreover, these 30% fat replacement cookies had the highest purchase intention by the consumers. This study presented a solution for unused tomato peel industrial byproducts, promoting the design of new functional food products with a high content of carotenes and dietary fiber, thereby increasing nutritional and health benefits for consumers.

A New Food Ingredient Rich in Bioaccessible (Poly)Phenols (and Glucosinolates) Obtained from Stabilized Broccoli Stalks.

Broccoli (Brassica oleracea var. italica) stalks account for up to 35% of the broccoli harvest remains with the concomitant generation of unused waste that needs recovery to contribute to the sustainability of the system. However, due to its phytochemical composition, rich in bioactive (poly)phenols and glucosinolates, as well as other nutrients, the development of valorization alternatives as a source of functional ingredients must be considered. In this situation, the present work aims to develop/obtain a new ingredient rich in bioactive compounds from broccoli, stabilizing them and reducing their degradation to further guarantee a high bioaccessibility, which has also been studied. The phytochemical profile of lyophilized and thermally treated (low-temperature and descending gradient temperature treatments), together with the digested materials (simulated static in vitro digestion) were analysed by HPLC-PDA-ESI-MSn and UHPLC-3Q-MS/MS. Broccoli stalks and co-products were featured by containing phenolic compounds (mainly hydroxycinnamic acid derivatives and glycosylated flavonols) and glucosinolates. The highest content of organosulfur compounds corresponding to the cores of the broccoli stalks treated by applying a drying descendant temperature gradient (aliphatic 18.05 g/kg dw and indolic 1.61 g/kg dw, on average, while the breakdown products were more abundant in the bark ongoing low temperature drying 11.29 g/kg dw, on average). On the other hand, for phenolics, feruloylquinic, and sinapoylquinic acid derivatives of complete broccoli stalk and bark, were more abundant when applying low-temperature drying (14.48 and 28.22 g/kg dw, on average, respectively), while higher concentrations were found in the core treated with decreasing temperature gradients (9.99 and 26.26 g/kg dw, on average, respectively). When analysing the bioaccessibility of these compounds, it was found that low-temperature stabilization of the core samples provided the material with the highest content of bioactives including antioxidant phenolics (13.6 and 33.9 g/kg dw of feruloylquinic and sinapoylquinic acids, on average, respectively) and sulforaphane (4.1 g/kg dw, on average). These processing options enabled us to obtain a new product or ingredient rich in bioactive and bioaccessible compounds based on broccoli stalks with the potential for antioxidant and anti-inflammatory capacities of interest.

Almond hull biomass: Preliminary characterization and development of two alternative valorization routes by applying innovative and sustainable technologies

Almonds are considered one of the most valuable fruits worldwide due to its high nutritional value. Moreover, a growing attention has been paid over the last years to other parts of the fruit, such as skins, shells or hulls, which are commonly found as almond by-products and scarcely exploited for valorization. In this study, two approaches were evaluated. Firstly, a green innovative processing technology, pulsed electric fields (PEF), was applied for the first time to assist the extraction of antioxidant compounds from almond hull biomass (AH). In particular, this technology was used with the aim of developing a feasible valorization strategy, being a sustainable alternative for polyphenols extraction compared to traditional methods. Then, the total phenolic content (TPC) and the antioxidant activity (TEAC and ORAC values) were measured, obtaining a higher extraction of TPC and TEAC values when PEF was used compared to conventional soaking. Secondly, the characterization of AH by means of fiber, ultimate and proximate analysis was carried out. Ultimate and proximate analysis provided information about the exploitation towards bioenergy and biofuels, demonstrating the so-called derived AH-EFB being useful for that purpose. Moreover, the high percentage in terms of carbohydrates suggests that AH could be a useful source for high-added-value chemicals, such as levulinic acid, furfural and 5-hidroximethylfurfural, displaying an interesting energetic valorization route for this biomass.

Simultaneous determination of H2SiF6, HF and total fluoride in fluorosilicic acid recovered from wet phosphoric acid production by potentiometric titration

Fluorosilicic acid is generally obtained unintentionally in phosphate fertilizer manufacturers, particularly during wet phosphoric acid and triple superphosphate (TSP) production from fluorapatite. Since sustainability is a major environmental concern, phosphoric acid production factories have a fluorine recovery process as fluorinated products, mainly consisting of fluorosilicic acid (H2SiF6). In other words, to optimize the control of the fluorine recovery during the phosphate chemical process and to investigate the valorization alternatives of the concomitantly produced fluorosilicic acid, the main fluorine-based by-products have to be analyzed.The present work describes the development of a potentiometric analytical method for the major constituents of fluorosilicic acid produced during the chemical phosphate process, i.e., H2SiF6, HF and total fluoride. Therefore, a preliminary speciation study was investigated on industrial and synthetic fluorosilicic acid samples using fluorine-19 (19F) and silicon-29 (29Si) nuclear magnetic resonance (NMR) spectroscopies. Interestingly, we observed the presence of two forms of fluoride in a highly acidic medium (pH = 1.80) ascribed to HF and H2SiF6, as well asasingleformofsiliconwhichis assigned toH2SiF6. Moreover, a potentiometric titration of fluorosilicic acid with known H3PO4 content, using a 0.5 mol.L−1 NaOH solution as a titrant, allowed us to determine the H2SiF6 concentration as well as the amount of total acid content. Then, the amount of hydrofluoric acid is calculated from the difference between total acid, phosphoric acid and fluorosilicic acid contents. The total fluoride content is deduced from H2SiF6 and HF contents. The results obtained with this method are compared to other standard methods, e.g., silicon determination by flame atomic absorption spectroscopy and total fluoride determination by fluoride ion selective electrode (F-ISE). It is worth noting that, based on this comparison study, the developed method provides consistent results. Furthermore, the analysis is fast and accurate, and is therefore applicable to the control of recovery process as well as to the characterization of industrial fluorosilicic acid.

Life cycle assessment of the supply chain processes for the valorisation of corn cob

The circular economy can find a wide range of application in the agricultural sector given the countless possibilities of transforming crop residues and recycling precious resources, playing a strategic role in increasing the sustainability of the agriculture. Under this perspective, crop production provides several residues and waste along the production chain. In the maize cultivation process, a significant amount of residual organic materials is produced and commonly left on the field as soil conditioner and source of nutrients. However, some parts of these residues, such as corn cob, could be considered for valorization processes.Focusing on corn cob as a valuable raw material, the sustainable solutions for its valorization depend on economic and environmental factors. The main aims and novelty of the work is the evaluation of the environmental performance of alternative supply chain in a life-cycle perspective in order to compare the overall sustainability of this valorization alternative, maximizing its environmental added value. The paper reports the results of a Life Cycle Analysis, from cradle-to-gate, of corn cob valorized as a raw material for corn cob pellet. A comparison with wood pellet available on the market and with analogous function has been performed. The results show that cob-based product has environmental impact lower than wood-based products currently used. Finally, the work provides indication for evaluating the benefits of turning an agricultural waste in natural-based material and paves the way of promoting circular economy processes in agriculture production.

Prospective Environmental Assessment of Reprocessing and Valorization Alternatives for Sulfidic Copper Tailings

Prospective Environmental Assessment of Reprocessing and Valorization Alternatives for Sulfidic Copper Tailings

Characterization of Wet Olive Pomace Waste as Bio Based Resource for Leather Tanning.

Olive mill wastes represent an important environmental problem. Their high phenol, lipid, and organic acid concentrations turn them into phytotoxic materials. Specifically, wet olive pomace (WOP) is the waste generated in the two-phase continuous extraction process. WOP is a paste with around 60% water. The total volume of WOP generated is around 0.25 L/kg of olives processed. Its current waste management practices result in environmental problems as soil contamination, underground seepage, water-bodies pollution, and foul odor emissions. Some valorization alternatives include composting, biological treatments, direct combustion for energy production, or direct land application. The leather industry is making great efforts to apply cleaner processes while substituting chemical products for natural products. In this way, different alternatives are being studied, such as the use of zeolites, triazine derivatives, grape seed extract, olive leaf extract, etc. In this work, the use of wet olive pomace is presented as a possible alternative to conventional vegetable tannins (mimosa, quebracho, chestnut, etc.). Although different projects and studies have been developed for the valorization of olive mill wastes, there is completely a new approach to the WOP application for tanning purposes. This study shows that WOP has a significant number of polyphenolic substances, so it has a great potential to be used as a tanning agent. Specifically, this study has been able to determine that, of the polyphenols present in WOP, 39.6% correspond to tannins that are capable of tanning the skin. Additionally, it contains 14.3% non-tannins, that is, molecules that by themselves do not have the capacity to tan the leather but promote the tanning mechanism and improve the properties of the tanned leather.

Optimization of Liquid Fuel Production from Microwave Pyrolysis of Used Tyres

Used tyres pose a threat to the environment, especially in developing countries, since the current disposal methods lead to environmental pollution. Pyrolysis liquid from used tyres can be used as a source of fuel to replace petroleum diesel. Microwave pyrolysis is an alternative valorization process that is supposed to save energy and, therefore, is environment friendly. In the current study, microwave pyrolysis was used to produce liquid fuel. Processing variable levels for microwave were power levels of 20, 30, 40, 50, 60, 80, and 100%; the reaction times were 8, 13, 18, 23, and 28 minutes; and the particle sizes were 25, 50, 100, and 200 mm2. Design-Expert 13 was used for data analysis and optimization, and GC-MS was used for chemical composition analysis, while physiochemical properties were tested using standard methods. Response surface methodology (RSM) was used to study the effects of operating variables and identify the points of optimal yields. For microwave pyrolysis, the highest liquid yield of 39.1 wt. % was at 50% power, 18 min reaction time, and particle size of 25 mm2. The yield decreased as the particle size increased. RSM gave conditions for optima in agreement with the experimental results. The calorific value for liquid fuel was 48.99 MJ/kg. GC-MS analysis showed that the oil comprised complex mixtures of organic compounds with limonene, toluene, and xylene as major components. The liquid fuel properties meet the required international standards and can be used as an alternative to diesel fuel.

Turning Agricultural Wastes into Biomaterials: Assessing the Sustainability of Scenarios of Circular Valorization of Corn Cob in a Life-Cycle Perspective

Circular economy plays a key role in increasing the sustainability of the agricultural sector, given the countless possibilities of transforming crop residues and recycling precious resources. The maize cultivation process produces a significant amount of residual organic materials, commonly left on the field, as a soil conditioner and source of nutrients even if some parts, such as the cob, play a minor role in these actions. The solutions for the valorization of this remnant depend on economic and environmental factors and the evaluation of the environmental performances of the processes in a life-cycle perspective is important to compare the overall sustainability of the valorization alternatives, maximizing their environmental added value. This work reports the results of Life Cycle Analysis, from cradle-to-gate of corn cob valorized as a raw material in two scenarios: corn cob pellet and corn cob abrasive grits to use as blasting or finishing media. A comparative study has been performed with two products available on the market and with the same functions. The results show that cob-based products have lower impact than those currently used. The work provides indication for evaluating the benefits of turning agricultural wastes in natural-based materials and intends to promote circular economy processes in agriculture production.

Utilization of waste engine oil for expanded clay aggregate production and assessment of its influence on lightweight concrete properties

The generation of waste engine oil (WEO) is characterized by high volumes since 24 × 106 tons of WEO are discarded annually. The chemical composition of WEO presents heavy metals dangerous to both humans and the environment and, thus, valorization alternatives of WEO are a major challenge. Consequently, this study evaluates the feasibility of WEO as an expansive additive to be used in the production of expanded clay aggregates (ECAs) for lightweight concrete (LWC) applications and assesses the effects of these ECAs on physical and mechanical concrete properties. Initially, WEO was chemically characterized and then, an optimization of the ECA production was assessed modifying WEO dosages, thermal cycles, and initial sizes of clay granules. Subsequently, morphological, physical, chemical, and mechanical properties of optimized ECAs were obtained through scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, abrasion and impact resistance and compressive strength tests to validate the feasibility of these ECAs as coarse aggregates in LWC. Then, the incorporation of ECAs in LWC was assessed using four concrete mixes with increasing volume dosages of ECAs replacing natural coarse aggregates (i.e.; 0%, 25%, 50%, 100%) and its impact on physical and mechanical concrete properties was evaluated. Positively, ECAs significantly reduced concrete bulk density, but with a collateral negative impact on the mechanical performance of concrete mixes as ECA dosages increased. For a 50% ECA replacement, density and compressive strength values were 1980 kg/m3 and 19 MPa, respectively, representing reductions of 13% and 2% with respect to the plain concrete, respectively, and successfully satisfying LWC requirements for structural applications.

Cultivation of Pleurotus ostreatus Mushroom on Substrates Made of Cellulose Fibre Rejects: Product Quality and Spent Substrate Fuel Properties

This paper explores an alternative valorisation method for high-moisture content waste streams from the pulp and paper industry. Cellulose fibre rejects from industrial-scale recycling/pulping of waste paper was used as an ingredient in substrates for cultivation of Pleurotus ostreatus, commonly known as oyster mushroom. Three substrates with 40, 60, and 80 wt% fibre rejects were tested, and a conventional substrate formula based on birch (Betula ssp.) sawdust was used for comparison. The spent mushroom substrate (SMS) fuel characteristics were assessed through ashing procedures. Mycelium growth was faster on substrates based on fibre rejects. The average biological efficiencies of the first flush of fruit bodies were between 29 and 36% compared to 42% for birch sawdust substrates. The fruit bodies had good nutritional values, i.e., crude protein (22–25 wt% d.b.), crude fat (3–3.5 wt% d.b.), crude fibre (8–10 wt% d.b.), and carbohydrates (57–62 wt% d.b.). The concentrations of heavy metals, 5–10 µg/kg Pb, 19–28 µg/kg Cd, 5–6 µg/kg Hg, and 26–53 µg/kg As were well below the limit values for food products set in EU regulations. The SMS could be used as fuel for direct combustion or co-combusted with other biomasses.Graphic

Pre-treatment of used cooking oils for the production of green chemicals: A review

Exploitation of waste lipids in the production of higher value-added and green chemicals will become a common practice in the future to enhance the sustainability of the oleochemical industry. However, waste lipids are highly heterogeneous and contain a large variety of impurities that can affect potential valorization routes. Thus, there is need for carry out refining processes to obtain suitable oleochemical feedstocks. This work reviews the available and potential technologies for the pre-treatment, purification and refining of waste lipids, emphasizing the transformation of used cooking oils (UCOs) into oleochemical raw materials. Initially, a description of the world generation and supply of UCOs is presented, and some potential valorization alternatives are reported. Then, the chemical nature and composition of typical UCOs is considered, and the main physicochemical properties are recognized in order to identify suitable separation processes for impurities removal. In particular, acidity and moisture reduction are priorities considering that they affect further thermal, chemical and biochemical transformations. Also, toxic compounds need to be reduced to enable the use as fermentation substrates, or as raw material for value-added application. Nitrogen-, phosphorus-, and sulfur-containing compounds as well as polar compounds must to be removed to enhance sensorial properties, and to avoid negative effects during subsequent transformations. Among the most popular up-grading methods, esterification, adsorption, solvent extraction, and distillation have been adopted industrially. Also, some intensification alternatives have been effectively implemented in UCO refining (e.g. reactive separations). • Used cooking oils (UCOs) pre-treatment processes are presented. • Typical chemical composition and impurities are described in depth. • Potential effects in further valorization processes are explained in detail. • Comprehensive review of processes for removal of impurities of different nature. • Current process intensifications alternatives for UCOs pre-treatment are reported.

Carbon Emissions and Energy Balance in the Design of a Sustainable Food Waste Network

In this paper, the food waste valorization alternatives are evaluated from a sustainability point of view. Using food waste characteristics as input data, we estimate the sustainable benefits such as energy utilization and GHG emission reduction for each potential food waste processing technique. Additionally, the sustainable benefits of reverse logistics of food waste are quantified based upon geographic distance and valorization characteristics. We formulate the food waste network framework as a strategic linear programming (LP) model that aims to minimize total food waste management costs while satisfying emissions and energy use constraints. Given the recent regulations of the commercial food material disposal ban, we test the efficiency of the proposed framework by designing a sustainable food waste treatment network for the state of Massachusetts. Results show that with a marginal increase in the treatment cost of food waste, the model has achieved zero net emissions, zero net energy use, and a competitive overall sustainability impact. Thus, by utilizing the food waste network model, policymakers can achieve the best sustainable strategies for food waste management. The paper contributes theoretically to the assessment of the food waste recovery alternatives by expanding the system boundary and presenting additional key performance measures of sustainability. Practically, this study provides case studies based on real-life data and generates multiple scenarios to better analyze the results and select the best recovery options from a sustainability perspective.

Valorization of Orange Peel Waste Using Precomposting and Vermicomposting Processes

The industrialization process of oranges generates waste, which is inadequately disposed of; this produces adverse effects on the environment. Among the alternatives for valorization is the vermicomposting process, which consists of the degradation of organic waste through the action of earthworms and microorganisms. Therefore, this research aimed to study this process using orange peel (OP) waste at the laboratory level. For this purpose, it was necessary to determine the degradation conditions through the monitoring of physicochemical parameters (temperature, pH, humidity, organic matter (OM), total organic carbon (TOC), total nitrogen (TN) and the carbon/nitrogen (C/N) ratio). To balance the substrate’s nutrients, load material (LM) that included vegetable waste and eggshells was added to three different mixtures: M1 (50% OP + 50% LM), M2 (40% OP + 60% LM) and M3 (60% OP + 40% LM). To condition the substrate for earthworm (Eisenia fetida) activity, a previous precomposting process was performed. The results showed that all the mixtures fulfilled the requirements for a quality and mature vermicompost; however, the highest concentrations for TN were in the mixtures M1 and M2. The total time required for degradation of the OP waste was 13 weeks.

Environmental impacts of waste management and valorisation pathways for surplus bread in Sweden

Bread waste represents a significant part of food waste in Sweden. At the same time, the return system established between bakeries and retailers enables a flow of bread waste that is not contaminated with other food waste products. This provides an opportunity for alternative valorisation and waste management options, in addition to the most common municipal waste treatment, namely anaerobic digestion and incineration. An attributional life cycle assessment of the management of 1 kg of surplus bread was conducted to assess the relative environmental impacts of alternative and existing waste management options. Eighteen impact categories were assessed using the ReCiPe methodology. The different management options that were investigated for the surplus bread are donation, use as animal feed, beer production, ethanol production, anaerobic digestion, and incineration. These results are also compared to reducing the production of bread by the amount of surplus bread (reduction at the source). The results support a waste hierarchy where reduction at the source has the highest environmental savings, followed by use of surplus bread as animal feed, donation, for beer production and for ethanol production. Anaerobic digestion and incineration offer the lowest environmental savings, particularly in a low-impact energy system. The results suggests that Sweden can make use of the established return system to implement environmentally preferred options for the management of surplus bread.

Decision-Making Process in the Circular Economy: A Case Study on University Food Waste-to-Energy Actions in Latin America

Economies have begun to shift from linear to circular, adopting, among others, waste-to-energy approaches. Waste management is known to be a paramount challenge, and food waste (FW) in particular, has gained the interest of several actors due to its potential impacts and energy recovery opportunities. However, the selection of alternative valorization scenarios can pose several queries in certain contexts. This paper evaluates four FW valorization scenarios based on anaerobic digestion and composting, in comparison to landfilling, by applying a consistent decision-making framework through a combination of linear programming, Life Cycle Thinking (LCT), and Analytic Hierarchy Process (AHP). The evaluation was built upon a case study of five universities in Costa Rica and portrayed the trade-offs between environmental impacts and cost categories from the scenarios and their side flows. Results indicate that the landfill scenario entails higher Global Warming Potential and Fresh Water Eutrophication impacts than the valorization scenarios; however, other impact categories and costs are affected. Centralized recovery facilities can increase the Global Warming Potential and the Land Use compared to semi-centralized ones. Experts provided insights, regarding the ease of adoption of composting, in contrast to the potential of energy sources substitution and economic savings from anaerobic digestion.