Overlooking the coastal sandstone cliffs south of Sydney’s CBD, gravestones in Waverley Cemetery stand like sentinels, aligned like a military parade. A Yulan magnolia grows out of the grave of a post World War II Italian migrant, at rest since 7 May 1977. It’s as if it is drawing its sustenance from the deceased.
Life depends on death – a circle that has been going on forever. Saplings grow out of rotting trees, and marine carcasses provide a bounty of nutrients for deep water organisms.
When creatures die, they decompose and become the nutrients that other life forms need to flourish. But most humans end up embalmed and buried, or cremated. Are the rituals we have created messing with this cycle of life?
Some think so. “Green death” trends have emerged in the funeral industry to respond to people’s growing concerns around the ecological burden of traditional burial practices.
The science of human decomposition
First, what happens when a body decomposes out in the open? A little warning here is due: this is not a story for the squeamish. When you die, your heart no longer pumps blood through your veins. Gravity draws the blood towards the ground, where it settles. Your lungs stop functioning, which means you’re not breathing in oxygen or expelling carbon dioxide. As carbon dioxide builds up and dissolves in the pooling blood, it begins to form carbonic acid, which dissociates into bicarbonate and hydrogen ions, making the blood acidic.
Simultaneously, enzymes involved in your cells’ metabolism throughout life begin to digest the cells’ membrane, which, combined with a decreased blood pH, causes cells to rupture and spill out their guts. “Everything starts to break apart,” says Dr Maiken Ueland, a researcher at the Centre for Forensic Science and the deputy director of the Australian Facility for Taphonomic Experimental Research (AFTER) at the University of Technology Sydney.
When your cells begin to crumble, they release nutrients that the human microbiome – all the bacteria, fungi and viruses and other microbiota living in you – love to gobble up, literally eating your body from inside out.
Your microbiome helps digest food and keeps your immune system in good shape throughout life. But when you’re dead, your immune system shuts down, and all of a sudden, trillions of microorganisms have free rein.
The microbiota break down carbohydrates, proteins and lipids, producing liquids and volatile organic compounds as byproducts. These build up inside your abdomen and make you look bloated. After three days of decomposition, these compounds release, causing a distinctive “death” smell. Carbon dioxide, methane, and ammonia gasses are among the contributors. Hydrogen sulphide, also present in farts when you’re alive, plays a critical role. But putrescine and cadaverine, which are formed from the breakdown of amino acids, are the biggest culprits.
Ueland, who studies forensic taphonomy – the process of corpse decomposition – says the gasses emitted from the body as it breaks down attract more fungi, bacteria, worms, insects and scavengers to the banquet. A decomposing body creates a remarkably complex ecosystem, which taphonomers call the necrobiome.
Blowflies are generally early comers. They start to lay eggs from which maggots hatch within 24 hours. One blowfly can lay about 250 eggs, so if a few hundred blowflies lay eggs, there are soon tens of thousands of hungry maggots crawling on your body, ready to contribute to the decomposition process. Larvae consume the soft tissue first, says Ueland. Then the skin falls apart, and all that is left is your skeleton, which will continue to break down for decades.
As the feast goes on, more nutrients are released into the surrounding environment. For every kilogram of dry body mass, a human body naturally decomposing will eventually release 32g of nitrogen, 10g of phosphorus, 4g of potassium, and 1g of magnesium. So an average 70kg live human body, which consists of 50–75% of dry body mass, would release roughly 1,400g of nitrogen, 434g of phosphorus, 174g of potassium and 43g of magnesium after death.
Taphonomers call this puddle of nutrients around a body “the cadaver decomposition island”. Initially, some of the vegetation in this island dies off, possibly because of nitrogen toxicity. But as the nutrients are further digested by bacteria within the island they act as fertilisers, transforming the island into a vegetation oasis.
Death 1.0: the industrial age
In a typical burial, the body is embalmed and put in a coffin made of oak or elm. The wooden capsule is buried about two metres underground, possibly under a slab of concrete. Formaldehyde is often used as an embalming fluid. It bonds proteins and DNA in the cells together so tightly that the microbiome can’t break it down, preventing tissue from decomposing for decades.
Even if a body isn’t embalmed, the coffin in which it lies hinders the natural decomposition process, and the nutrients released are not easily accessible to the microorganisms and scavengers in the soil.
If you’re not keen on burial, you can always choose to be cremated. Since the 1950s, cremation has become more popular than burial, with about 70% of Australians opting for it. But cremation, too, cuts the circle of life and death short. It transforms a body into mainly three things: ash, water vapour and a lot of carbon dioxide. Not only will cremated bodies not fertilise any vegetation oases, burning them up is far from sustainable.
According to the Department of the Environment and Energy, a modern cremator uses the equivalent of 40 litres of petrol for an average body. An older crematorium furnace can consume up to twice that amount of fuel.
Cremating a dead body releases about 50kg of carbon dioxide and a bunch of toxins into the atmosphere. And the carbon footprint doesn’t end at the crematorium door.
“What about the 100 people driving to the crematorium, then driving back to Uncle Bob’s house to have a barbecue?” says Kevin Hartley, founder and director of Earth Funeral. “And what about all the catering and all the energy and bits that go into it?”
Hartley estimates that at a typical, small-size cremation and funeral, the event can release up to one tonne of carbon dioxide – the equivalent of driving a petrol car for six months. Fifty trees have to grow for one year to capture just one tonne of carbon dioxide emissions.
Death 2.0: the eco-age
An interest in pared-down, eco-friendly, end-of-life options has grown, ranging from biodegradable pods that turn a body into a tree, to mushroom burial suits that devour dead tissues.
“There’s a whole suite of alternative technologies in this space,” says Dr Hannah Gould, a cultural anthropologist with the DeathTech Research Team at the University of Melbourne. “But alkaline hydrolysis and natural organic reduction are the major alternatives that have legs.”
Alkaline hydrolysis, also known by the catchier name of “aquamation”, is the fire-free alternative to cremation. It produces less than 10% of the carbon emissions of traditional cremation, doesn’t release toxins, and generates nutrient-rich water.
The body is placed in a pressure vessel filled with an alkaline water solution of potassium hydroxide or sodium hydroxide or a combination of both, with a pH of 14. The solution is stirred and heated to about 160°C at high pressure to prevent boiling.
In a few hours, the body breaks down into its chemical components. All that’s left is a tea-like solution that is very good for plants, so family can take home the sediment of minerals for scattering.
“The environmental footprint of alkaline hydrolysis is much less than cremation and much, much, less than conventional burial in a graveyard,” says Professor Michael Arnold, a historian and philosopher with the DeathTech Research Team.
According to a report by the Netherlands Organisation for Applied Scientific Research (TNO), the estimated environmental cost for disposal of the dead is about $102 for a burial, $77 for cremation, and $4.15 for alkaline hydrolysis. “It’s a huge factor,” says Arnold.
Aquamation is legal in Australia but not widely available. There are only a handful of companies that offer the service, and, Arnold says, the practice remains little known by most. It was recently in the spotlight after the death of South African archbishop Desmond Tutu, who requested his remains be aquamated. Arnold hopes Tutu’s choice will increase the practice’s popularity.
The other alternative is natural organic reduction, or human composting. The body is placed into a vessel with a mix of soil, wood chips, straw and alfalfa. Microbial activity stimulates decomposition. Within about four weeks, the result is around 760 litres of humus. Family members are welcome to keep some of it; the rest is used as a fertiliser. The world’s first human composting company opened its doors in Seattle, US, at the end of 2020 and has since expanded to four states, but human composting isn’t yet legal in Australia.
The regulatory approval path of a new way to dispose of corpses is tedious. But appealing to the mass market remains the biggest challenge – eco-friendly body disposal is still a niche market.
“People who might want to pick these options tend to be those who are pretty concerned about the environment, who are into sustainability, alternative lifestyle, are a bit hippie,” says Gould. “But there is also a growing cultural desire to return nutrients to the earth.”
Arnold agrees. “A lot of people think that the body is something to be disposed of without much fuss, and cremation is appealing for that reason,” he says. “A smaller group of people think of the body as a resource rather than a waste – a resource that can and should be utilised by other living beings.”
In recent years, natural burial grounds have gained some popularity. Here, the body is buried without embalming in the topsoil, in a softwood or cardboard coffin or a shroud. Usually, there is no gravestone or headstone. Only about 2% of people opt for a natural burial.
Restoration burial grounds
Hartley had worked in funeral services for 15 years when someone asked what his plans were for his body after death. “Being reasonably young, I hadn’t really thought about it,” he says.
It was then that he began to ponder the environmental impact of the furnace he
had operated for so many years, and began to question whether that was indeed what he wanted his final act to be.
Hartley began to contemplate taking natural burial to the next level. “Restoration burial grounds is the term that we favour,” he says.
His not-for-profit organisation plans to convert pieces of distressed land, such as overused farmland on the edges of cities, to burial grounds that offset the cost of burial by “multiple times”.
The bodies will nourish and fertilise the barren land, restoring the native Australian bush. That, in turn, will attract native wildlife and, eventually, the land will be managed like a national park.
Regular natural burial grounds might offset the carbon cost of a burial, but being carbon neutral is no longer enough, Hartley says.
“We put the Earth bank account into deficit,” he says. “We are way overdrawn. We want to put back into the planet.
“Death is part of life. Everything is cyclic. We’re interested in the restoration of the nexus between death and life for people and have a genuine return to the earth.”
It’s a plan that might revolutionise the look of Australian cemeteries – rows of gravestones giving way to Australian native forests buzzing with wildlife.
MANUELA CALLARI is based in Sydney. Her last feature, on the potential of mRNA treatments, appeared in Issue 92.
This excerpt is republished online from Cosmos Magazine Issue 94, on sale now.
To see more of this story, subscribe today and get access to our quarterly magazine in print or digital, plus access to all back issues of Cosmos magazine.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.