Should pig swill from waste food be back on the menu?
Chef Thomasina Miers wants to talk about food - not the food served up in her Mexican restaurant chain Wahaca, but the food fed to Britain's pigs.
"Pigs are the most efficient converter of food waste to calories - we need calories in this world to feed growing populations, but in the meantime all pigs throughout Europe are being fed soya which is being grown in the Amazon basin.
"Rainforests are crucial, but we are chopping them down to feed our pigs and it is just crazy."
Together with food waste expert Tristram Stuart she has launched the Pig Idea, a campaign lobbying for a return to the age-old practice of feeding leftover food to pigs.
"The Pig Idea is a crucially brilliant idea because man and pig have been living in perfect harmony and synergy for thousands of years," she says.
"Man creates waste; pig eats waste and turns it into food that we eat again. It is a perfect circle which means food has a use."
As recently as the 1990s "pig bins", into which uneaten food was placed, were a familiar sight in schools and canteens across the UK, but all of that changed when the foot-and-mouth crisis hit in 2001.
Concerns that the outbreak had started on a farm where pigs had been illegally fed unprocessed restaurant waste led to a nationwide ban on using waste from homes and catering outlets as animal feed.
Farmers are allowed to give their animals non-meat based products from food manufacturers and suppliers as long they have not reached any form of kitchen.
In 2003 the UK ban was rolled out to the whole of the European Union.
Pig farmers now rely heavily on crops such a soya beans, wheat and maize to feed their herds, food which humans could otherwise eat and which require arable land for cultivation.
"Since the ban on feeding food waste to pigs in 2001, a practice which has been going for millennia all over the world has come to an end.
"As a result we import millions more tonnes of soya from South America and that increases demand for deforestation, which contributes to biodiversity loss, interruption of hydrological cycles and contributes to global warming," Mr Stuart says.
"And of course on top of the environmental impact it puts additional strain on global food supplies... essentially our pigs in Europe are competing with people for food."
Ms Miers says that allowing pigs to eat more left-over food such as unsold bread, fruit and vegetables that are unfit for humans, would not only be good for the planet, but good for pigs and consumers too.
"If a pig is fed an incredible diversity it makes logical sense that it is going to have a better diet and going to taste better having got a much wider range of food," she says.
However, not all pig farmers agree. John Rigby, whose family was involved in the pig swill business before the ban as well as raising animals, says that feeding swill leads to a reduction in meat quality.
"The quality of the meat is far poorer. Swill contains an awful lot of animal fat, and these animal fats produce a very greasy, oily fat on the meat, it's not very presentable, it looks poor quality. No supermarket today would stock it."
Provenance is paramount
Mr Rigby also says that the idea of not being able to fully account for everything that pork-producing pigs have been fed runs counter to the public's current desire to know the exact provenance of what they eat:.
"The horsemeat scandal highlights the need for traceability, the knowing where everything has come from," he says.
"I think the eye was off the ball for a certain period of time and price became very, very important rather than looking at the traceability of the food. I think currently traceability is everything and not necessarily the price tag."
A third of each of the pellets that Mr Rigby's pigs are fed is made of food such as biscuits, cakes and cereals which either have gone past their human sell-by dates, or which were surplus to requirement. The food comes directly from the manufacturers to the feed mill and is mixed in with other ingredients to provide the pigs with a balanced diet.
"Each batch of food delivered to the farm has a batch number; each batch number is traceable back to the feed mill," Mr Rigby says.
"At the feed mill the ingredients can been traced back to the supplier, the supplier holds records tracing them back to point of production, so everything is traceable almost back to the field at which it was produced."
He believes that a return to swill feeding "breaks all of the promises on traceability that the supermarkets want to put in front of the consumer".
He remembers incidents in the 1980s when swill was contaminated with bleach, pan scourers, and even light bulbs.
"If your pigs are getting fed floor cleaner and bleach because the screening process hasn't been adequate then none of it would be fit for human consumption, even if it was boiled - you can't boil bleach, you just get hot bleach."
Zoe Davies from the National Pig Association agrees that following the horsemeat contamination scandal both retailers and customers are very sensitive to where food comes from. She also cites problems with policing swill content as a matter of concern for pig farmers.
"The further you go down the food chain the more risk there is of cross-contamination. People could be well meaning but not fully understanding of why they need to keep food separated.
"Even if it was mainly vegetable, a bit of meat in there could be enough to spark the next foot-and-mouth outbreak."
However, the Pig Idea campaigners insist that they are not proposing a return to how swill was gathered and processed in the past, but a much more tightly controlled, centralised system on an industrial scale as happens in parts of South Korea, Japan and the United States.
This, they says, would instil confidence in producers and customers alike.
"We are not talking about a nostalgic return to the old way of doing things, we're talking about a really well-regulated system where waste is properly collected, properly screened on a conveyer belt, treated and made properly sterile," Mr Stuart says.
"It goes to pig farmers who turn it into pork, then it is sold on the very shop shelves from where the food waste came and nothing moves more than 20 or 30km, and it can be sold as premium eco-pork because we can say we produce pork without negative impact on the environment."
Ms Davies says the Pig Idea campaign is well intentioned, but that assuming the pig industry would take on the extra risk is "naive".
"We only produce 40% of our pork in the UK; 60% is imported," she says.
UK pig farmers are competing with European pig producers on a "really high level" and margins are very important, she said. They would not want to do anything that would risk the public's view of British pig production "or that would risk the long-term viability of their businesses".