Katrina Spade is the founder of Recompose, and lobbied for the law

Washington on Tuesday became the first US state to legalize human composting after its eco-friendly governor signed a bill to that effect in a bid to cut carbon emissions from burials and cremations.

Under the new law that will go into effect in May of next year, people who die in the state will have the option to have their bodies transformed into soil suitable for use in gardening in a process called recomposition.

"Recomposition offers an alternative to embalming and burial or cremation that is natural, safe, sustainable, and will result in significant savings in carbon emissions and land usage," said Katrina Spade, who lobbied for the law and is the founder of Recompose, a Seattle-based company set to be the first to offer the service.

"The idea of returning to nature so directly and being folded back into the cycle of life and death is actually pretty beautiful," Ms Spade added in a statement sent to news agency AFP.

She said she became interested in the process about 10 years ago after turning 30 and thinking more about her own mortality.

Spade then began examining the technical aspects of creating an environmentally friendly "third option" that could compete with the $20-billion US funeral industry, which offers conventional burial and cremation.

Her approach - developed with Washington State University, which did clinical trials with donor bodies - calls for a dead person to be placed in an hexagonal steel container filled with wood chips, alfalfa and straw.

The container is then shut and the body is decomposed by microbes within 30 days. The end product is a dry, fluffy nutrient-rich soil resembling what one would buy at a local nursery and suitable for vegetable gardens.

"Everything - including bones and teeth - is recomposed," Spade said. "That's because our system creates the perfect environment for thermophilic (i.e. heat-loving) microbes and beneficial bacteria to break everything down quite quickly."

The process used by Recompose is the same as that used for decades with farm animals and the clinical trials carried out by the university in Washington found that it was also safe for use with humans.

'Socially acceptable materials'

"We have found that the essential methods that we use for livestock mortality composting are also effective for human disposition," said Dr Lynne Carpenter-Boggs, a professor of soil science at Washington State University. "We have substantially changed the materials used, to be socially acceptable, but the basic principles that we have learned from livestock mortality composting are very effective for the human research subjects that we used."

According to statistics, more than one in two Americans opt for cremation. In Washington state, nearly 75 percent of people choose that option.

Spade expects her company to charge some $5,500 for a "natural organic reduction," an amount a little bit over the price of cremation but less than the price of burial in a casket.

Her innovation comes as so-called "green" or earth-friendly burials are gaining traction in the United States, where companies are now offering organic caskets or a burial in which the body is wrapped in a simple shroud in towns that allow it.

The actor Luke Perry, star of the hit-series "Beverly Hills 90210" who died in March, was buried in a biodegradable suit made partly out of mushrooms, as he requested.

The so-called "mushroom suit" was developed by Coeio, a California startup, that said the attire helps the body decompose, neutralizes toxins found in the body and transfers nutrients to plant life.

But not everyone is enthusiastic about turning bodies into garden-variety soil, notably the Catholic church, which has denounced recomposition as undignified.

"The Catholic Church believes that disposing human remains in such a manner fails to show enough respect for the body of the deceased," Joseph Sprague, executive director of the Washington State Catholic Conference, said in a letter to the legislative committee that examined the bill signed on Tuesday.