Some level of food waste has to be accepted by any catering operation, so when you’ve done all you can to minimise it the question remains: what to do with it?
Sending it to landfill is not only an increasingly expensive option, but one that carries the biggest carbon footprint.
Other options include macerators that can cut or grind food waste so that it can travel easily through the regular waste water system, or dewaterers that first pulverise the waste and then filter out the water content reducing the volume of waste by as much as 80%.
There is also the process of anaerobic digestion, where waste is sent to a plant where bacteria break down the waste without oxygen, giving off gas which can be used as fuel and creating material that can be used as fertiliser.
And a relative newcomer to the scene is a related process called aerobic digestion, also known as bio digestion. Traditionally used in sewage systems, the technology is now being applied to food waste.
Aerobic digestion involves oxygen and is very fast, with bacteria breaking down food in about 24 hours.
The process does not produce biogas but breaks food, including items like bones, down into nothing but grey water that can be disposed of in drainage systems or used as a fertiliser for plants.
The appeal of it becomes more obvious when you consider that the Environment Act 2021 comes fully into force this year in England and under it macerators are banned, removing one previous option.
The process of chopping up food waste and using large volumes of water to tip it into the drainage system is considered both unsustainable and environmentally unfriendly and has already been outlawed in Scotland, Wales and Northern Ireland.
The new legislation is going to affect hospitals, hotels, restaurants, prisons, military barracks, universities, schools and many other catering establishments in England.
Food waste will now need to go into separate wheelie bins for collection as a distinct waste stream and local authorities will start billing for food waste disposal. Not only that, but catering operators will need to fill out an annual food waste return detailing how much they have disposed of.
Aerobic Technologies, which makes a range of the digesters, has had units installed in some NHS Trusts for several years, and believes the results achieved since make a good case for bio-digestion.
Nicholas Bloom, the company’s chief operating officer, says: “The system reduces carbon emissions, reduces the carbon footprint, reduces food waste and complies with the NHS Plastics Pledge to reduce and eliminate single use plastic.
“The technology can also include an application to convert food waste into clean water for recycling onsite whilst extracting and preserving the calorific value from food waste for use as feedstock in ‘waste to energy’ facilities. This can enable an organisation to meet its climate change initiatives for 2023 and beyond.
“A single bio digester installed on site can digest up to 500kg of food waste in just 24 hours. They require little maintenance, do not need to be cleaned out and leave no smells.
“Best of all, the food waste is converted into grey water, like the waste water generated by homes and offices, which can be safely discharged into the main drainage system.”
Among the hospitals that have already used Aerobic Technologies to install its digesters are North Lincolnshire and Goole NHS Foundation Trust, University of North Midlands NHS Trust and, just last September, Doncaster and Bassetlaw Teaching Hospitals.
At the last of these, the Trust decided to invest in a bio digester for its Stafford County Hospital as part of its commitment to dispose of all food waste in an environmentally friendly way.
Louise Jenkins, the Trust’s transformation project manager, said: Our catering staff are delighted with the new machine and how easy it is to use. The feedback we’ve had has been very positive, making a real difference to their daily duties.
“Our new bio digester meets our Trust objectives to dispose of our food waste in an environmentally safe way, providing us with data and monitoring.”
Mike Brown, the Trust’s head of soft facilities, added: “This is a really positive step forward. Using this equipment has allowed the Trust to reduce the impact of food waste on the environment and improve our reporting capabilities, which will now allow us to further reduce waste at source.”
The North Lincolnshire and Goole NHS Foundation Trust put a 300kg digester into The Diana Princess of Wales Hospital in Grimsby in 2018, the first NHS site to employ the technology. It was pleased enough with its performance to have a second machine installed in Scunthorpe General Hospital in 2022.
Sally Yates, the Trust’s logistics and waste manager, said the technology reduced the cost of the Trust’s food waste and the size of its carbon footprint, as well as saving time for staff.
She said: “Our objective is to adopt an environmental solution in conjunction with our long term sustainability targets whist achieving material cost savings straight away. The Trust was able immediately to cut waste costs and has been able to reduce food waste by having access to the electronic data that the machines provide in real time.”