Abstract

Food Science and TechnologyVolume 36, Issue 1 p. 24-27 FeaturesFree Access Managing food waste is key to tackling climate change First published: 13 March 2022 https://doi.org/10.1002/fsat.3601_7.xAboutSectionsPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Jenny Grant and Emily Nichols of the Association for Renewable Energy and Clean Technology (REA) discuss how managing food wastes sustainably can have multiple benefits and lead to reductions in greenhouse gas emissions. Introduction The carbon footprint of food consumed in the UK is 150Mt of carbon dioxide equivalents – this equates to around 30% of the UK's territorial greenhouse gas (GHG) emissions. Production of food requires significant resources, yet around 30% of food is lost or wasted globally. Food waste as a resource for a circular economy In 2018, WRAP estimated that UK food manufacturing produces 1.5Mt of food waste per year1. Food waste is a major contributor to climate change and food system stakeholders have a critical role to play in a Net Zero future. Wherever possible, food waste should be avoided, e.g. through minimisation at source and redistribution of unsold but still fit-to-eat food. However, there will always be some unavoidable food waste and it is a valuable part of the circular economy. Instead of being landfilled, the carbon and nutrient contents of food waste can be converted to renewable energy, organic fertilisers, soil improvers or growing media; some food wastes can be extracted, modified or transformed into a range of bio-based products. All these bioresources can replace fossil-based products, such as mineral fertilisers, peat and fossil fuels. Treating food wastes There are multiple benefits in composting or anaerobically digesting food waste, instead of letting it decompose in landfills. These include the avoided emissions, the generation of renewable energy, which replaces fossil fuels, and the production of organic fertilisers and soil improvers. These can replace energy intensive mineral fertilisers, in the case of digestate, and bring multiple soil health benefits in the case of composts. Anaerobic digestion (AD) has been successful in replacing the fossil fuel heat required in some commercial and farming operations that already have access to significant levels of biogenic materials. The use of biogas or biomethane – either produced on-site or delivered by road to farms or factories that do not have gas grid access – is effective for decarbonising farm buildings, on-site drying and other manufacturing processes, such as the manufacture of food and drink. It can also meet local demand for renewable heat and deliver numerous additional environmental and agronomic benefits, such as the application of biofertilisers to agricultural land to replace chemical fertilisers. The food and beverage sector has significant volumes of on-site residues and effluents that need treating, as well as considerable requirements for process heat (and in some cases power). Haulage fleets are also in need of decarbonisation too. An onsite AD system deployed at factory or farm processing sites could make use of residues and effluents, whilst providing part of the heat and power requirements for the beverage or food manufacturing process. This is especially true for processes that have a significant heat requirement, for example distilleries and breweries. The AD system's biomethane can fuel the distribution fleet, both for delivering materials and hauling output products. Anaerobic digestion plant BECCS is the process of extracting bioenergy from biomass then extracting the carbon dioxide (CO2) from the biogas and capturing and storing the carbon by geologic sequestration or land application. WRAP2 estimates that 6,700 SMEs account for 97% of businesses in the food manufacturing sector. Members of the REA estimate that 100 of these (1.5%) with on-site AD producing 100m3 of biogas – each generating circa 4GW of heat per year or 1.8GW of electricity and 2.2GW heat in a CHP (combined heat and power) – could supply 400GW per annum of clean heat or over 30,000 tonnes of low emission, decarbonised HGV fuel. Bioenergy with carbon capture and storage (BECCS) represents a further opportunity to reduce GHG emissions. BECCS is the process of extracting bioenergy from biomass then extracting the carbon dioxide (CO2) from the biogas and capturing and storing the carbon by geologic sequestration or land application. Net GHG emissions footprint of AD Defra's food and drink waste hierarchy statutory guidance, says: ‘where possible, taking into account the feasibility and impact to do so, you should choose AD rather than composting for separately collected food waste. Composting is normally best for garden waste or mixed food and garden waste.’ As AD is the preferred option for separately collected food waste, it is important to quantify its GHG footprint. A study by the University of Bath3 assessed where emissions and savings occur at a commercial food waste AD plant. The plant has annual emissions of almost 2,000 tonnes of carbon dioxide equivalents (t CO2e), but enables the avoidance of approximately 4,100t CO2e so its overall effect is a net benefit of around 2,100t CO2e. The study also assessed the impact of switching from using the biogas for electricity generation to biomethane production and found there was the potential to more than double the overall net GHG benefit, increasing it to 4,830t CO2e. The researchers also considered the impact of capturing CO2 for storage, which would take the plant's overall GHG net benefit to 6,886t CO2e. Supply of CO2 from AD Most CO2 supplied in the UK is currently produced as a by-product of fertiliser manufacturing processes with the CO2 industry relying heavily on these sources for domestic CO2 supply. However, due to issues, such as increasing energy costs and aging production assets, the ammonia industry in the UK has become extremely volatile, with numerous long-term shutdowns for economic and mechanical reasons. There are currently around 11 AD plants in the UK that capture around 80,000 to 90,000 tonnes of CO2 per annum (most of which feed in crop-based inputs, with a few others also feeding in animal manures/slurries). The CO2 from these biomethane plants is largely supplied to the food and beverage sector for which the CO2 must be ‘food-grade’. The two key specifications for food-grade CO2 are the standards issued by EIGA (European Industrial Gases Association) and ISBT (International Society of Beverage Technologists). These are broadly aligned, requiring analysis of over 20 different contaminants; both specifications allow CO2 from AD plants to be used. The technology to capture CO2 from AD plants already exists in the UK. It is proven and commercially available and can be practically retrofitted to most AD plants. In addition to the 11 already capturing CO2, there are another 70 operational AD plants that could easily retrofit carbon capture. This could yield around 500,000-600,000 tonnes per annum of biogenic CO2, boosting our domestic supplies and protecting the sector from future shortages. Benefits of applying composts and digestates to cultivated soils Soil plays an important role in fighting climate change. The organics industry produces valuable products that can improve soil quality, increase organic matter and carbon in the soil and enable the production of food for years to come. Using digestate can help to reduce a farm's carbon footprint by replacing the need to apply inorganic fertilisers, thus avoiding emissions from the latter's production. Digestate is a renewable fertiliser and a good source of readily available nutrients, especially nitrogen – around 80% of total N content in food waste-derived digestate is readily available in the first year of application. Around 50% of the phosphate and 80% of the potash is available to crops in the year of application. Digestate can also supply useful quantities of sulphur and magnesium. Using digestate can help to reduce a farm's carbon footprint by replacing the need to apply inorganic fertilisers, thus avoiding emissions from the latter's production. Replacing manufactured fertiliser with food based digestate can reduce a farm's carbon footprint by around 20kg CO2e per tonne of digestate applied. There is a great deal of innovation going into digestate processing. Food waste at AD Plant Various technologies can transform the nutrient density of digestate, extract or recover nutrients and transform it into specialised products, such as pelletised fertilisers that can help to lock up the carbon. Compost is an excellent soil conditioner and a source of organic matter. Increasing the organic matter in soils has multiple benefits, such as improving the soil structure, reducing erosion and increasing water holding capacity and soil biological activity. Studies have shown that application of compost helps grow more nutritious, nutrient-dense crops. In terms of carbon benefits, research shows that over a period of four to 12 years, in the region of 11-45% of the organic carbon applied to soil as compost remained in the soil organic carbon4. So one tonne of green waste-derived compost applied to soil over one hectare results in a net CO2e saving of 143kg/ha/year due to the increase of soil organic matter alone. Compostable items for food products A Plastic Planet's working paper ‘The Compostable Conundrum’ aims to pivot plastic pollution discussions away from ‘compostable materials are better because they are not plastic’ towards a better understanding of their ‘key role in capturing biowaste which can be converted into high-quality compost and digestate to regenerate our rapidly depleting agricultural soils’. This working paper includes a ‘green ‘list’ recommending product types that should be industrially compostable, identified through applying the principles that they: carry food and beverage residues, plant waste or soil to composting or AD facilities; are too small, flimsy, flexible, multi-laminated and hard to recycle in any other waste stream; currently contaminate biowaste streams when made of non-compostable plastic. Examples are tea bags, food condiment sachets, hot ready meal trays, food tray films, cling film used in food packaging, wrappers and food condiment sachets. The working paper ‘red lists’ product types that should not be designed for industrial composting, applying the principles that they: do not carry food waste to composting or AD facilities; are not easy to compost or anaerobically digest; can be made of material(s) other than industrially compostable ones. Examples are pallet shrink wrap, newspaper and magazine sleeves, mailing bags, bottles, non-food packaging bags and non-food wipes. These lists and others produced by different organisations will evolve over time. We have yet to see how well ‘green list’ items will match with Defra's waste collection consistency guidance for England, which may describe item types that should be included in food and garden waste streams. Collecting and treating compostable packaging Taking account of how collection of England's household and business food and garden wastes is likely to be mandated and appropriate applications for industrially compostable packaging and non-packaging items, the principle way of collecting these materials should be with food waste. A second option should be their collection with co-collected food and garden wastes in circumstances where local authorities justify that it is not technically, economically or environmentally practicable for household food wastes to be collected separately from garden wastes. Applying digestate to farm land Courtesy 4R Group Considering treatment facilities, a UK network of approximately 42 in-vessel composting processes treat source-separated biodegradable wastes that include food wastes. While these facilities are capable of biodegrading compostable packaging and non-packaging items, few of the approximately 96 UK AD facilities, whose feedstocks include food wastes, are currently suitably designed and/or equipped to biodegrade such items. Several drivers may lead to changes in how digestates are produced, upgraded and used in future. The REA believes that these, together with packaging considerations, should cause government to mandate that: new-build food-waste AD facilities are capable of biodegrading industrially compostable items; where feasible existing food-waste AD processes should be adapted so they can do the same; where suitable adaptation of existing food-waste AD facilities is not feasible, industrially compostable items should be frontend removed and sent to in-vessel composting facilities (provided that contamination by non-compostable items is acceptably low). The REA's policy on liners and re-purposed bags for the collection of household and business food wastes provides further detail on this issue. High percentages of the UK's AD and composting facilities that accept food wastes are operated as per End of Waste rules. These rules enable waste-derived composts and digestates to exit waste regulatory controls and thus be traded and used as products in specified markets. Packaging and non-packaging items fed into facilities managed as per those rules must be independently certified as industrially compostable. Conclusions Much development and diversification of compostables has taken place over the last 21 years, with a growing diversity of items designed to biodegrade in other environments jostling for market share. We hope the array of R&D, industry and policy-focused discussions will result in aligned policies that: see the differences between material origins, product degradation behaviours and suitable management options for End of Life phase; drive appropriate uses of biodegradable items; in the case of compostables for organic recycling, support more efficient biowaste management and better protect soils from plastic pollutants. Policy changes are needed to drive new food-waste AD plants and evolve suitable, existing food-waste AD plants so they are capable of biodegrading compostable items, producing CO2 products (especially food grade) and upgrading their digestates. Organically recycling food waste represents a significant opportunity for net GHG emissions reduction and is a proven technology. There are multiple benefits including the production of renewable energy – for both heat and power, potential to produce bio-methane for transport and carbon dioxide along with the production of renewable fertilisers that can be used to maintain soil health, grow more food, offset emissions and tackle climate change. GLOSSARY OF TERMS AD Anaerobic digestion GHG Greenhouse gases CO2e Carbon dioxide equivalents CHP Combined heat and power BECCS Bioenergy with carbon capture and storage Jenny Grant, Head of Organics and Natural Capital at the Association for Renewable Energy and Clean Technology (REA) and Emily Nichols, Technical Manager, REA Organics and Natural Capital The REA is the UK's largest trade association for renewable energy and clean technologies with members operating across heat, power, transport, and the circular bioeconomy. For more information on REA membership, visit: r-e-a.net email info@r-e-a.net web r-e-a.net References REFERENCES 1Wrap. 2020. Food surplus and waste in the UK – key facts. Available from: https://wrap.org.uk/sites/default/files/2020-11/Food-surplus-and-waste-in-the-UK-key-facts-Jan-2020.pdfGoogle Scholar 2Wrap. 2016. Quantification of food surplus, waste and related materials in the supply chain. Available from: https://wrap.org.uk/resources/report/quantification-food-surplus-waste-and-related-materials-supply-chainGoogle Scholar 3 University of Bath. 2021. GHG assessment of Bore Hill Farm biodigester. Available from: https://researchportal.bath.ac.uk/en/publications/ghg-assessment-of-bore-hill-farm-biodigesterGoogle Scholar 4 International Solid Waste Association. Biological treatment of waste. Available from: https://www.iswa.org/biological-treatment-of-waste/?v=79cba1185463Google Scholar Volume36, Issue1March 2022Pages 24-27 ReferencesRelatedInformation

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