In the middle of a cavernous factory floor in Pudsey, Leeds, sits a gleaming steel cylinder. One day, its maker believes, most of us will end up in something similar.

The machine is a Resomator – a pressurised canister in which corpses are submerged in a mixture of 150C water and potassium hydroxide solution for three to four hours until the flesh is dissolved, leaving behind only soft, greyish bones. After drying in an adjacent oven, these are ground down into paper-white powder, while the fluid is sent to a water treatment plant for disposal. The entire process is operated by a touchscreen and a single “start” button, away from the view of mourners. Ashes to ashes no more.

The Resomator, its supporters say, is badly needed by a burial and cremation industry that is increasingly damaging to the environment. More than three-quarters of Britons now choose cremation over burial, a process that, on average, releases 400kg of CO 2 into the atmosphere per body. Cremation fumes also include vaporised mercury from tooth-fillings, accounting for 16% of the UK’s mercury emissions in 2005, along with other toxic emissions from burnt prosthetics and melted bone cement used during common surgeries such as hip replacements.

Burial, too, has its consequences, with embalming fluid seeping into the soil as the body and coffin decompose, as well as other toxins such as radiotherapy or chemotherapy drugs. Burial space is also becoming increasingly scarce and expensive in built-up areas. The Money Advice Service found that the average cost of a basic burial in the UK is £4,267, with prices increasing by 6% each year – twice the inflation rate – for the past 14 years. A UK league table, compiled by the Cremation Society, shows that the cost of a cremation on its own can top £1,000 in 2019, compared with £650 in 2010. This continued hiking of prices has prompted the Competition and Market Authority to undertake an investigation into the funerals sector.

Two Resomators at Resomation’s Leeds HQ

In the US, resomation, also known as alkaline hydrolysis, has been used since the mid-1990s and is legal in 19 states. The technology was initially developed in the US to dispose of cows during a decade-long foot-and-mouth epidemic. In 2008, Dean Fisher, a doctor at the University of California, Los Angeles, realised that it could be used for donated medical cadavers once they were no longer needed. “Everything about this process is a win-win; everything is recyclable,” he says, adding that 1,200 bodies have gone through UCLA’s Resomator since it went into service in 2012.

Fisher bought the machine from the Leeds-based company Resomation Ltd, which is hoping the process will become part of public funeral rites. “There’s an ‘ick factor’ involved with this technology,” Fisher says. “People worry their bodies are being dissolved or that it’s a waste of water – but that 250 gallons we use per body can then be used as fertiliser because of the nutrients that are in it. People’s perceptions need to change.”

Resomation’s founder, Sandy Sullivan, has been dealing with this “ick factor” ever since he began in 2007. The company got initial funding from Co-Op Funeralcare and then a partnership with the Leeds and Bradford Boiler Company. Funeral directors in the US and Canada bought its technology, including a California-based company that even uses resomation on pets. In 2017, Rowley Regis crematorium, in the West Midlands, was set to become the first in the UK to use a Resomator, but the local water company, Severn Trent, banned it from doing so, citing “serious concerns about the public acceptability of liquefied remains of the dead going into the water system”. Sullivan insists: “There’s no reason why resomation can’t go into operation, though – it’s a water-like, sterile liquid with no DNA in it and it’s cleaner than most of the things that go into the water treatment plant, like blood and chemicals from hospitals. Crucially, this isn’t water that we will be drinking.” Water UK, the regulatory authority, has refused to comment on the issue.

In the two years since the Rowley Regis debacle, however, Sullivan says progress has been made with Water UK. He is convinced the technology will get the go-ahead within the next year. “It leaves six times less carbon footprint and uses seven times less energy than burial,” he says, noting that a Danish government-funded study also found that the environmental impact of burial/cremation and resomation, can be costed at €63 per body for the former, while the latter is only €3. “We’re reaching a climate catastrophe and yet we’re still burning bodies,” Sullivan says. “Our feedback from the US has been that people are interested because they feel a water-based process is gentler than flame.”

Sandy Sullivan: ‘Resomation leaves six times less carbon footprint and uses seven times less energy that burial’

Resomation’s PR problem has been eased in recent years by the rise of other alternatives to cremation and burial, including promession – the freeze-drying of bodies, which are then broken into smaller remains through vibration – and a “mushroom suit” that uses funghi to speed up decomposition. In May, the state of Washington legalised human composting.

Pioneered by Katrina Spade and her company Recompose, this involves placing a corpse in an above-ground receptacle filled with soil and organic materials. After about four weeks, Spade says, “Your body is transformed into a usable soil, to grow new life. Your family can then grow a tree and maybe your great-grandchildren will swing from its branches some day.” Despite opposition from the Catholic church, Spade hopes to open the first Recompose facility in Seattle next yearin 2020.

According to Prof Douglas Davies, the leader of the Durham University Centre for Life and Death Studies, our attitudes towards death have changed significantly in recent decades. Cremation was popularised in the UK in the late 19th century, pushed on by growing secularism and the Industrial Revolution, but environmental concerns have led to a rise in natural burials and new technologies. “We now have roughly the same number of woodland burial sites across the UK as we have crematoria,” Davies says. “Language is really important when it comes to these new methods and I think the term ‘resomation’ will catch on in the UK because it’s sufficiently opaque. People go for cremation because they dislike ideas that burial is somehow gruesome or ‘lonely’, but then they are also uneasy about the use of fire in cremation, and that’s where resomation will come in.”

Devon-based Claire and Rupert Callender opened their Green Funeral Company in 2000 and are now among the country’s best-known eco-friendly funeral directors. They are raising funds to buy a Resomator. “Funeral directors are conservative, worried about peoples’ perceptions and about how to sell resomation to the public,” Claire says, “but, with cremation, your grandma is basically going up a chimney and then coming out as particles of soot and carbon and everybody is inhaling them.”

Where larger funeral directors will often take on three to four cremations a day, the Callenders perform only about 70 a year, with some ceremonies taking up to 12 hours at the Sharpham Trust’s natural burial ground at Sharpham Meadow. “People are hungry to talk about death and to get involved in it, yet high-street funeral directors totally miss this,” Claire says. “They have this barrier between themselves and the people, they wear those ridiculous suits and they’re all about upselling. It’s a faux-Victoriana of ‘dignity’ and ‘respect’ – schooling you in the etiquette of bereavement.”

Flowers and other markers at the Sharpham Trust’s natural burial ground at Sharpham Meadow. Photograph: Beccy Strong/The Guardian

When her grandmother died in 2018, Oona Mills decided to avoid this conventional approach, opting for a woodland service instead. “She was a natural gardener for most of her life and lived very minimally,” Mills says, “so it seemed very fitting for her to have a natural service, especially since she’d told me that the greatest achievement in her life was the compost that she’d made.” Mills’s service aimed to keep the burial as low-tech as possible, using a wicker coffin and no embalming fluids. She feels that resomation or human composting is unnecessary: “Natural burials are very effective. You can bury someone at three feet rather than six feet under, which is much quicker for the body to decompose.”

For Sullivan, the priority is not to replace natural burial but to provide more green options. “We’ve been told that our technology comes out at about the same price as cremation,” he says, “so the choice is there. People need to overcome their assumptions and do what is best for the planet.” The National Association of Funeral Directors also “welcomes any proper method of disposal that offers the public choice”. Fisher, meanwhile, is so enthusiastic about resomation that he would like to undergo the process once he dies. “They’ll put me in here when I’m dead, too – and if that isn’t enough of an endorsement for you, I don’t know what is,” he says.

Back in Leeds, one of Sullivan’s two Resomators is humming quietly during a test cycle, liquid sloshing around as in a dishwasher. It is about to be shipped to a Minnesota funeral home. “This is the future,” Sullivan says, stroking the curved steel exterior. “Change is always difficult in such a conservative market, but we need to look after the planet even once we die, since we keep on destroying it while we live.”

• This article was amended on 10 July 2019. The original said that the natural burial site at Sharpham Meadow was run by the Green Funeral Company. This has been corrected.