One million trees worldwide are cut down each year to make toilet paper. Is it more sustainable to grow your own?

In Meru, a town in eastern Kenya, a lush, leafy plant sways over the landscape. Benjamin Mutembei, a Meru resident, is growing the Plectranthus barbatus plant – not for food, but to use as toilet paper. He started growing the plant in 1985. "I learned about it from my grandfather and have been using it ever since. It's soft and has a nice smell," he says.

Plectranthus barbatus is a leafy plant that can grow up to 2m (6.6ft) tall. Its leaves are roughly the size of an industrial toilet paper square and emit a minty, lemony fragrance. Covered in tiny hairs, the leaves have a soft texture. This plant thrives in warm tropical temperatures and partial sunlight and is widely grown across Africa, where it is sometimes used to demarcate property boundaries.

"This has been an African tissue for a long time, and everyone in my household uses the plant. I only buy modern toilet rolls when the leaves have all been plucked," Mutembei says.

The Plectranthus barbatus plant has provided Mutembei with a cost-effective alternative to purchasing toilet paper in Kenya. Like many commodities, the price of toilet paper has risen across Africa, largely due to the high cost of imported raw materials, such as wood pulp, which is essential for the production of toilet roll. Raw material costs now make up 75-80% of the final cost of tissue products in Kenya, according to the Kenya Association of Manufacturers.

Toilet paper made from virgin wood pulp currently dominates the global industry. "Typical toilet paper is made of 70-80% short fibre hardwood and 20-30% long fibre hardwood," says Ronalds Gonzalez, a professor in the Department of Forest Biomaterials at North Carolina State University.

According to research by the environmental impact consultancy Edge, roughly one million trees are cut down worldwide each year to make toilet paper.

The pulp and paper industry is the world's largest consumer of virgin wood, using roughly 35% of harvested trees for paper production. This is driving deforestation, biodiversity loss, soil erosion, species extinction and widespread ecosystem disruption according to the latest Ethical Consumer report on ethical toilet paper.

Martin Odhiambo, a herbalist at the National Museum of Kenya who specialises in traditional plants, thinks the solution to the environmental impact of cutting trees for toilet paper may already be here.

"Plectranthus barbatus is the African toilet paper. Many young people nowadays are unaware of this plant, but it has the potential to be an environmentally friendly alternative to toilet paper," he says.

There is no official data on exactly how many people use the plant as toilet paper in Kenya; however, it is widely grown in various parts of Africa and continues to be used in many rural areas where it is easily accessible, says Odhiambo.

Plectranthus barbatus grows to its full height in 1-2 months from a cutting and the cutting itself costs around 50 Kenyan shillings ($0.37).

"The leaves are similar in size to an industrial toilet paper square, making them suitable for use in modern flush toilets or for composting in latrines," says Odhiambo.

Visitors from across Kenya attend Odhiambo's lectures on the uses of Plectranthus barbatus and buy cuttings from his botanical garden at the National Museum of Kenya in Nairobi.

"My class has grown to over 600 participants. People are enthusiastic about learning how to use the plant and often ask for cuttings and seedlings to take back to their towns," he says.

The potential of the plant is also being explored in other countries.

Robin Greenfield, an environmental activist who runs a non-profit advocating for sustainable living in Florida in the US, has been using the leaves of Plectranthus barbatus for five years.

Greenfield runs a "grow your own toilet paper" initiative and cultivates over 100 Plectranthus barbatus plants at his Florida nursery. He shares cuttings for free or for voluntary donations, encouraging people to grow their own toilet paper. So far, he says he has distributed cuttings to hundreds of people.

"There are many people who associate using the toilet paper plant with poverty," says Greenfield, though he points out that industrial toilet paper is ultimately made from plants too.

Greenfield says he's had positive feedback from people who have used the plant. "For anybody who feels a little hesitant to try this plant, I would say to drop your worries about what people think about you. And simply by saying, 'I'm going to be me, and that might mean wiping my butt with some really soft leaves that I grow,'" he says.

But how realistic is it that this plant might become more widely used?

Large-scale production has not yet been explored. Instead companies such as WEPA, one of Europe's largest toilet paper manufacturers, are reducing the environmental impact of conventional toilet paper in other ways. WEPA has developed a new method using recycled cardboard to produce toilet paper, which does not involve bleaching the fibres, a spokesperson says.

Typically wood pulp is bleached before it is turned into paper, which releases chlorinated compounds into the environment. These compounds can react with carbon-based materials, creating dioxins which are highly toxic chemicals associated with cancer and other health risks, according to a report by the non-profit Natural Resources Defense Council.

The toilet paper plant, meanwhile, is expected to have a "minimal" impact on the industry, says a WEPA spokesperson.

One drawback is that wastewater and disposal systems, especially in Europe, aren't designed to handle this type of paper, as only soluble items can be flushed through the system, the spokesperson says.

Greenfield says that's where compost toilets come in. "I use a compost toilet. The leaves go back to the earth and produce soil, which can then support food growth. It's a closed-loop system, and I think using these leaves could lead us to a conversation about the environmental benefits of composting."

There are also limitations on the locations and countries where of Plectranthus barbatus can be grown, says to Wendy Applequist, an associate scientist at the Missouri Botanical Garden. In South Africa, for example, Plectranthus barbatus is regarded as an invasive species, and growing or selling it is banned. Invasive species cost the global economy more than $423bn (£333bn) every year and are a major driver of biodiversity loss. (Read about the proven ways to stop biodiversity loss.)

Applequist suggests that growing the plant in a controlled environment, within a designated area, and monitoring its growth to limit expansion into the existing ecosystem could help mitigate environmental risks.

Perhaps the biggest challenge to going mainstream, though, remains public acceptance. But from his plant nursery in Nairobi, Odhiambo remains hopeful.

"I know some people see using leaves as toilet paper as a step backward, but understanding the benefits of this plant, I believe it could become the next green alternative," says Odhiambo. "I've been growing it in my nursery and sharing it with communities across Kenya, and people have been amazed by its convenience. If we keep an open mind and continue promoting this plant, we could eventually mass produce it for widespread use."

This content was created with funding from the Bill & Melinda Gates Foundation.