More than £5,700 worth of food was thrown away by Northampton General Hospital in the last financial year - equal to around 82 tonnes, according to official statistics.
However the Billing Road hospital pointed to the many schemes it was implemented to reduce food waste such as smaller portion sizes and 'finger food boxes'.
Energy and sustainability manager Clare Topping said: “We continuously work to improve our sustainability across the hospital and look at what we can do to reduce food waste in staff, visitor and patient areas.
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“Although we would like to still do more to reduce our food wastage we are pleased that any food waste we do have is collected in order to be made into biogas or biofertiliser.
"This means that our food waste is processed and turned into a valuable resource either as renewable energy or a nutrient-rich organic fertiliser.
“We also strive to make improvements to meet the needs of our patients which in turn reduces our food waste.
"This includes looking at how we can suit their individual dietary preferences and needs during their time in hospital”.
NHS Digital’s annual infrastructure data collection shows NHS trusts in England reported sending 6,228 tonnes of food waste for anaerobic digestion or composting in 2019-20.
But there are fears the amount could be far greater as hospitals only record the food waste they segregate and send to be composted or broken down in an environmentally-friendly way, not the stuff that is dumped in landfill or incinerated.
Rob Percival, head of food and health policy at environmental charity the Soil Association, said the waste of inpatient meals is a significant issue within the health service but that a lack of data makes it difficult to determine the true scale of it.
“Overall food waste from the NHS is likely to be much higher – and it is reported that the annual cost of hospital food waste is £230 million, which equates to 39 per cent of the total food budget,” he said.
Northampton hospital's schemes to reduce food waste include introducing smaller portion sizes for those with a reduced appetite and ensuring these are highlighted on patient menus.
Staff have also starting providing 'finger food boxes' for those who may have difficulties eating a conventional hot meal, particularly patients with dementia.
While in some departments a lighter option of soup and sandwich is available instead of a full meal and the same menu is offered for lunch and dinner mealtimes so patients can decide when to eat a larger or smaller meal depending on their usual eating habits at home.
A spokesperson said the majority of food is prepared freshly on site using locally-sourced ingredients and the majority of raw ingredients are ordered by the head chef to minimise waste.
Plus all new healthcare assistants are trained on patient feeding and how to reduce food waste and wards are regularly surveyed to identify issues.
"We have introduced a systematic measurement process for the food waste from wards and food waste is reported to the senior team during regular ward meetings," the spokesperson added.
"And we are assessing the option for an electronic meal ordering service which, using the results from the surveys, will reduce food waste."
Food redistribution charity FareShare said millions of people in the UK struggle to get enough to eat and that feeding people is the most environmentally friendly thing to do with surplus food.
"As we’ve demonstrated throughout the pandemic, FareShare is ready at any time, to receive large scale offers of food, and through our networks of 30 regional centres and 11,000 charities across the UK, get it to people who need it most,” a spokesperson said.
In 2017-18, NHS Digital asked trusts to report the weight of all unserved meals over a week-long period, to measure the amount of food that went straight in the bin.
But the process was fraught with errors and the data unreliable, with some trusts multiplying their weekly figures by 52 to reach an annual figure, reporting the total weight three times – once each for breakfast, lunch and dinner – or reporting their trust-wide figure multiple times for every hospital site.
The audit also did not take account of food left uneaten on patients’ plates.
Sustainable food charity FeedBack said that several trusts had moved from in-house kitchens to outsourced services involving pre-plated frozen meals.
The charity speculated this could be behind the drop in surplus food last year, but cautioned that it must be measured against the carbon cost of transporting meals around the country from centralised depots.
Other campaigners argue that using poor-quality, mass-produced and reheated meals over freshly prepared food contributes to waste on patients’ plates, which the Soil Association says is not currently measured.
An independent review of hospital food in 2020 stated the NHS must lead by example on public health and nutrition by improving hospital meals, and recognised the role of coronavirus in highlighting the importance of good food for recovery and rehabilitation.
But the report said it did not matter whether food was produced on-site, in a central production unit or in a factory, only that it must “start with good fresh ingredients, and be prepared by well-trained chefs using traditional processes and minimal additives”.
Mr Percival said: “The recent Hospital Food Review recommended the NHS establish a common method of recording and monitoring food waste, with food waste minimisation plans and a package of supporting materials alongside a campaign to raise awareness.
“These recommendations resonate with the Soil Association’s Green Kitchen Standard, a framework which recognises caterers that are making positive steps to sustainably manage their energy, water and waste.
“Wider uptake of the Green Kitchen Standard would help to deliver the recommendation of the Hospital Food Review, and could help to minimise food waste across the NHS.”
Waste from both inpatient meals and canteens open to staff and visitors is included.