Energy from food waste

Abstract

Food Science and TechnologyVolume 35, Issue 2 p. 41-43 FeaturesFree Access Energy from food waste First published: 15 June 2021 https://doi.org/10.1002/fsat.3502_12.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 Philip Simpson of ReFood explains why anaerobic digestion (AD) should be considered central to the long-term success of the UK's food waste strategy. The volume of food waste generated every year across the retail supply chain, the hospitality sector and in UK homes stands at around 9.5m tonnes1. While innovative thinking, behavioural change and positive action from across the supply chain has seen this volume slowly decrease (down from 10m tonnes in 2015 and 11.2m tonnes in 2007), there is still a long way to go. While there is much emphasis on waste reduction initiatives and redistribution programmes, not widely appreciated is the crucial role anaerobic digestion (AD) is playing in the management of unavoidable food waste. However, there are several challenges that need to be overcome. Indeed, while the nation's AD capacity is increasing – up to 6m tonnes per year according to recent Defra figures2 – the most pressing challenge facing the industry today is on the supply side. Introduction to AD Anaerobic digestion is accepted by multiple sources, including the British Government, Defra, the Welsh Assembly, the Scottish Parliament and Friends of the Earth, as one of the most effective methods of managing unavoidable food waste. It is a natural process that biologically breaks down organic material to generate large amounts of biogas – a mixture of methane and carbon dioxide – and is able to turn food waste into green energy and sustainable biofertiliser. The process, from initial delivery to export, can be broken down into the following six steps: 1 Pre-treatment When unavoidable organic waste arrives at an AD site, it is placed into hoppers, which effectively mix and grind waste together. In some state-of-the-art ReFood facilities, de-packaging equipment allows all plastic packaging to be removed, cleaned, sorted and collected for use as refuse-derived fuels (RDF). Liquid is added to the waste so that it can be pumped to the next stage. 2 Heating, pasteurisation and cooling The waste is then passed through a heat exchanger and warmed to 70°C for an hour. This effectively pasteurises the material, destroying any dangerous bacteria and ensuring the process complies with animal by-product regulations. The pasteurised waste is cooled naturally, by channelling it to run alongside the cold, incoming material, which lowers its temperature to approximately 40°C. 3 Mixing Next, the organic waste is moved to a mixing tank and agitated for three days. This ensures that a smooth and well-blended product can be transferred to the digestors and is important to maximise continuity. 4 Digestion Once mixed, the waste is pumped to a digestor tank. Each tank is filled with blended organic material which, over the next 30 to 35 days, is broken down by bacteria in the absence of oxygen to release biogas. 5 Gas collection The biogas, which rises to the top of the digestors, is pumped through a biological scrubber to remove any hydrogen sulphide molecules and minimise odour before moving onto the final stages of production. 6 Screening, storage and dispatch The biogas is kept in storage tanks until required. It is then pre-conditioned, cooled and pressurised before being sent for processing. At ReFood's Doncaster plant, the gas is used to fuel large industrial-scale combined heat and power engines – the electricity generated is delivered directly to the National Grid and provides enough energy to power 10,000 homes per year. The heat generated by the engines is used to produce hot water and steam for the process and the pasteurisation of the raw food waste. A ReFood employee opens the hopper cover, ready for a bulk delivery of food waste. Facility and equipment for removal of packaging from food items. At ReFood's London and Widnes plants, the biogas undergoes a further refining process to remove carbon dioxide and volatile organic compounds. Once the refining process is complete, an odorant is added to the biomethane before it is pumped directly into the National Gas Grid. Refood's Dagenham facility is capable of processing more than 160,000 tonnes of food waste every year and generates 14m m3 of biogas (enough to power 12,600 homes) per annum. Biofertiliser Once the AD process has been completed, the digestate (which has been pasteurised and therefore meets PAS110 accreditation) is transformed into a ReGrow bio-fertiliser for local farming and agricultural use. This means that every ounce of organic waste entering the process is repurposed to maintain its place in the value chain. This effectively closes the food supply loop, with food waste being used to grow tomorrow's crops. Zero waste economy Although AD has been used for the treatment of organic waste since the 1800s, it has only recently become widely appreciated as a commercial-scale solution for food waste. It is an ideal way for businesses in the food, agricultural and industrial sectors to recycle their waste, cut their carbon footprint and reduce reliance on fossil fuels. As part of the Waste Strategy for England3, businesses were encouraged to consider AD as a way to meet UK energy targets – and this commitment continues. As concerns about the environment grow, so has the demand for ways to generate renewable energy and as a result, more businesses have been investing in AD as its commercial benefits become apparent. In terms of environmental benefit, it has been calculated that every tonne of food waste recycled by AD as an alternative to landfill prevents between 0.5 and 1.0 tonne of CO2 entering the atmosphere, alongside contributing to offsetting the need for chemical fertilisers. As the biogas is repurposed to produce energy, the process prevents the environmental impact that would otherwise occur when methane (a damaging greenhouse gas) escapes from landfill. The Government is working towards a zero-waste economy, with resources being fully valued and recycled as far as possible. To encourage more recycling, it has introduced tough financial penalties to divert waste away from landfill (backed by a European Union Directive). Another tangible benefit of adopting AD is the avoidance of landfill tax, which is currently capped at £80 per tonne. In addition, more businesses are adopting AD as part of their corporate social responsibility (CSR) policy. By adopting a technology that uses waste to create clean energy, businesses in the food sector, such as restaurants and cafes, as well as the hospitality sector, are enhancing their reputations and values. AD in action Waitrose Three months ahead of its original schedule, Waitrose achieved its aim of sending zero food waste to landfill in the UK. Through its ‘Treading Lightly’ environmental strategy, the company conducted a thorough review of operations and its wider supply chain, which enabled it to identify all the factors contributing to food waste so that these could be addressed individually. As a result, it implemented a series of solutions, including donating surplus food for redistribution through food banks, animal charities and zoos, with any remaining food waste sent to AD. Indeed, Waitrose was one of the first organisations to identify AD as the preferred solution for its unavoidable food waste. Mustard Foods Mustard Foods is a speciality food producer supplying sauces, soups, dressings, fillings and marinades to more than 400 restaurants across the UK. It handles hundreds of ingredients and products every day, generating food waste as a by-product typically from technical samples and internal staff meals, with a smaller volume also coming from take-back systems and inconsistency. As a part of its ‘Good Business Journey’, Mustard Foods partnered with ReFood to implement an integrated food waste recycling solution. The aim was to lower unavoidable food waste volumes, cut carbon emissions and cut waste management costs. To increase efficiencies and allow staff to separate waste at source, ReFood provides a ‘bin swap’ service with full-size, sanitised bins supplied for use in kitchen areas. Once bins are full, food waste is collected and transported to ReFood's AD facility in Dagenham to be converted into green energy. All bins are sanitised, allowing them to be hygienically used in kitchen areas. In addition, as Mustard Foods supplies packaged products, having to unpack unwanted food was considered a potential barrier to recycling. Although the company already had a 100% non-landfill solution in place, the partnership with ReFood has enabled the business to take this a step further, collecting and recycling all excess produce, both packaged and non-packaged plus library samples. Anaerobic digestion plant. QHotels Following an initial three month trial at a number of sites across the country, QHotels achieved considerable cost savings as a result of the diversion of waste from general waste collections and subsequent disposal to landfill. The waste collection service for AD was expanded to cover all the north of England sites, which helped QHotels to achieve further cost savings as well as delivering on their recycling targets. Barriers to progress The UK has made significant progress in reducing food waste, thanks to a multitude of supportive initiatives and visionary thinking by organisations across the food supply chain. However, recent data4 shows that while corporate entities – such as the hospitality sector and food service industry – have begun to address food waste, homeowners are still lagging behind. Indeed, household food waste is by far the biggest contributor to the UK's food waste mountain. While it may be possible to minimise waste by changing purchasing habits, improving redistribution and penalising unnecessary waste, the ‘unavoidable’ fraction (shells, bones, gristle, etc.) – an estimated 30% of the total – will continue to be landfilled unless legislative change is made. We are throwing away millions of tonnes of food waste into landfill that could be generating much needed decentralised electricity. A robust, national strategy to ban food waste to landfill is the only solution to completely solving the issue. Key to this would be access to food waste collection services for all homeowners and businesses nationwide. Two developments are critical to the success of reform: 1. Business waste – all organisations that create food waste, including restaurants, schools and hospitals, would need to switch to commercial food waste recycling collections. 2. Household waste – every home in the UK should have access to kerbside food waste recycling collections. Adopting commercial food waste recycling systems is a simple task. Indeed, more businesses are switching away from landfill disposal voluntarily as it ticks sustainability boxes and can help to save up to 50% of waste management costs. When it comes to kerbside collections, however, the challenge is more onerous. Historically, decision making on refuse collection design was devolved to individual councils to keep decision making local. However, in practice, this has created a confusing pattern of varying collection schemes across the UK with no economies of scale. While green bins collect garden waste in one area, they are used for household waste in another. While some councils collect glass bottles and food waste at the kerbside, others do not. The Government has considered plans to roll out kerbside collection of food waste for all UK households, but the implementation of this legislation has slipped back, with the proposed start date now being 2023. A clear, national strategy on kerbside collection is needed to create a world-class food waste supply chain in the UK. Leadership and vision from the Government could turn this into a reality Philip Simpson, Commercial Director, ReFood Email info@refood.co.uk Web refood.co.uk References 1https://refood.co.uk/wp-content/uploads/2019/07/SARIA_NFWH_report.pdfGoogle Scholar 2https://www.letsrecycle.com/news/latest-news/food-waste-capacity-hits-6m-tonnes-in-2020/Google Scholar 3https://www.gov.uk/government/publications/resources-and-waste-strategy-for-englandGoogle Scholar 4https://wrap.org.uk/sites/default/files/2020-11/Food-surplus-and-waste-in-the-UK-key-facts-Jan-2020.pdf) Google Scholar Volume35, Issue2June 2021Pages 41-43 ReferencesRelatedInformation