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Former construction worker Houn Nhean builds a biodigester for a family in Thorm Ney village. It takes two weeks to build a biodigester, and the unit should last for 20 years.
Former construction worker Houn Nhean builds a biodigester for a family in Thorm Ney village. It takes two weeks to build a biodigester, and the unit should last for 20 years. Hong Menea

Burning manure for a cleaner, greener future

The WHO says cooking indoors using wood or coal is a serious health risk for billions of people. Biodigesters – structures that use animal manure to generate methane gas for cooking and lighting – significantly reduce pollutants, and are being installed here by the thousands

There is a quiet killer in households across Cambodia, and women and children are its primary victims. It is not an airborne illness or a sexually transmitted disease, and it can’t be solved by reducing risky behaviour or seeing the doctor. People are losing years of their lives by doing something as simple as cooking their daily meals, and the only way to stop it is to alter the way food is prepared.

The World Health Organization (WHO) estimates that the health of 40 percent of the world’s population is negatively affected by indoor air pollution from cooking fires made by burning solid biomass like wood. (See sidebar.)

In Cambodia, where pots bubble over open flames in every kitchen and on every street corner, the percentage is even higher: up to 98 percent in rural areas. These fires cause respiratory problems and other illnesses that, the WHO estimates, cause nearly 15,000 premature deaths in Cambodia each year.

Most of those affected are women who are cooped up inside their homes as they toil over flames to make meals.

Although many women have been aware of the health risks for years, they believed there was no alternative, and in large part that was true. But in recent years, some have encountered a better way to cook, and they are working to spread the word.

Yin Saran, who says her neighbours’ fears over biodigesters are misplaced, prepares dinner using methane generated from manure.
Yin Saran, who says her neighbours’ fears over biodigesters are misplaced, prepares dinner using methane generated from manure. Hong Menea

The solution: a biodigester, a renewable energy technology that produces clean natural gas for cooking. Biodigesters are starting to experience some success locally, and it is women like Yin Saran who have adopted the technology that are its main advocates.

With her long black hair tied in a low ponytail around the nape of her neck, Saran appears younger than her 43 years. Her high cheekbones pull her skin taut. A constant look of unease and the glassy film covering her left eye reveal the poverty and hardship she has endured.

Saran’s kitchen, which is where she cooks for her husband and four children, has walls of tin and cardboard, and is built under the base of her home.

For most of her adult life, Saran used foraged wood for cooking, a time consuming and difficult task. Often she would have to roam for 6 or 7 kilometres to collect her weekly firewood. Sometimes she would come home covered in thorns.

And then one day in late August this year, the village chief hosted a meeting to tell the community about biodigesters – a way for owners of livestock to turn animal manure into natural gas. Saran and her family decided they would give it a shot.

These days, she says, fuel for cooking comes by flicking a switch and using a lighter to spark the gas. “I heard that it was easy to use, and that was true,” says Saran. “But the easiest thing now is washing the dishes. Before, my pots would be covered in black stains from coal and wood, but now washing the dishes is easy.”

Saran’s biodigester is an underground chamber into which she loads manure from the family’s three cows. Natural heat causes the manure to release gas, which is then collected and used for cooking and lighting.

Seam Thorn, who had a biodigester in the 1990s, is an advocate for the energy solution.
Seam Thorn, who had a biodigester in the 1990s, is an advocate for the energy solution. Hong Menea

Saran ticks off the benefits: aside from making it easier to wash cooking utensils, she saves money she would otherwise spend on coal or electricity, and she saves the hours she used to spend looking for wood. And, perhaps most importantly, she’s happy her house is no longer filled with smoke.

“When we used wood, it was much smokier. We were worried about the possible health risks but there was no other choice,” she says. “Also, I have a problem with my eye, which gets worse when I’m exposed to smoke.”

Health risks

Saran is far from alone in having such health-related issues. Vision problems, eye diseases and, occasionally, blindness are common among people who inhale the carbon dioxide generated by cooking fires, according to research published in 2013 in the peer-reviewed International Journal of Environmental Research and Public Health.

Fortunately for Saran, those days are behind her. She bought her biodigester from the National Biodigester Program (NBP), which the Ministry of Agriculture launched in 2006 with help from donors such as the Dutch development organisation SNV, the German international development group GIZ, and the Czech non-profit People in Need, among others.

The NBP, which has many moving parts, is in charge of establishing, training and supporting 62 small companies, known as Biodigester Construction Agents, that build, sell, and maintain biodigesters in 14 provinces: Battambang, Siem Riep, Pursat, Kampong Thom, Kampong Chhnang, Kampong Cham, Kampong Speu, Sihanoukville, Kampot, Kep, Takeo, Kandal, Prey Veng and Svay Rieng.

There was plenty of scepticism when the program launched in 2006 – not least because the UN’s Food and Agriculture Organization (FAO) had tried a similar endeavour in the 1990s using biodigesters that were made of plastic.

They quickly fell apart. Not surprisingly, biodigesters had a reputation – among the few people who had heard about them – for being expensive and easy to break.

Yin Saran empties manure into the pipe of the biodigester.
Yin Saran empties manure into the pipe of the biodigester. Hong Menea

But outreach initiatives like the one Saran attended, and user networks where biodigester owners meet to tell their neighbours about their experience, seem to have helped. As of the end of August, the program had seen a total of 25,265 biodigesters built in Cambodia.

“There are 4,752 biodigesters in Takeo province that are supported by the Cambodian government,” says Meng Sothy, a program officer for Takeo province’s biodigester program, who has been working on the project since it launched in the province a decade ago.

The units come in seven different sizes, he says, depending on the amount of people in the family using it and the number of animals they own. He is quick to extol the virtues.

“There are so many advantages and almost no disadvantages,” Sothy says, rattling off a list ranging from saving money on wood and coal to improving health and waste management.

“We estimate that each family is saving about 1 million riel [$250] every year just from not spending money on coal,” he says. Additionally, biodigesters are good for the environment and for combating climate change, he says, because each uses 16 tonnes of waste per year, reducing the amount of animal manure left outside to release planet-warming methane into the atmosphere.

(Methane, a potent greenhouse gas, heats the earth’s atmosphere about 25 times faster than carbon dioxide; capturing methane and converting it into energy reduces its impact. Indeed, natural gas is the least carbon-intensive fossil fuel.)

And each biodigester can power up to four light bulbs, providing a sustainable form of electricity for communities that aren’t connected to the electrical grid.

A brief guide to biodigesters

Nop Vanna, a former construction worker, is an agent for the National Biodigester Program (NBP) in Takeo, where he manages the workers who build the devices.

Vanna says it takes two people about a week to build a biodigester. The design is simple enough: a brick-and-cement cylinder buried in the ground; a pipe; and a chimney.

Once the structure is built, manure is shovelled down the pipe where it slides into the brick cylinder. Natural heat generates methane from the manure; the methane rises into the chimney, where a tube runs the gas into the home to power the kitchen burners.

It takes between three and five days for the methane to be generated, and the manure – by now an odourless sludge – to flow out of the other end of the cylinder. The slurry can be used as organic fertiliser or sold to a paper mill to be recycled by converting it into pulp for making paper.

The NBP says biodigesters should last 20 years. The smallest model, which is 4 cubic metres, requires as little as 20 kilograms of manure per day, generates two hours of methane for a biogas stove (or eight hours of light for a biogas lamp), and saves 4 kilograms of fuel such as wood or coal each day – nearly 1.5 tonnes a year.

Under the NBP’s deal with three microfinance companies, households are charged 1.2 percent interest per month should they need a loan for a biodigester.

The biodigester pays for itself within three years; after that, the NBP says, each family saves an average of $250 annually on wood, charcoal, batteries and chemical fertilisers – to say nothing of the savings from the health benefits.

Indoor pollution and health

The World Health Organization (WHO) says household air pollution due to the inefficient use of solid fuels for cooking causes 4.3 million premature deaths annually around the world. Strokes account for a third of that number, with the remainder due to heart disease, lung diseases and pneumonia.

“Around 3 billion people still cook and heat their homes using solid fuels [i.e. wood, crop wastes, charcoal, coal and dung] in open fires and leaky stoves,” the WHO states. “Most are poor, and live in low- and middle-income countries.”

The global health body says using such fuels leads to high levels of household air pollution comprised of numerous damaging pollutants, including tiny particles of soot “that penetrate deep into the lungs”.

“In poorly ventilated dwellings, indoor smoke can be 100 times higher than acceptable levels for fine particles,” the WHO states. “Exposure is particularly high among women and young children, who spend the most time near the domestic hearth.”

More than half of all premature deaths attributable to pneumonia in children under 5, it says, are caused by inhaling sooty particles.

Misplaced fears

Despite the many benefits, some livestock owners are still too afraid to buy biodigesters for their homes.

“The neighbours are worried that there will be a gas explosion. They gossip and make rumours [about] that, but I’m not that worried,” Saran says with a grin. “It’s just manure.”

Apart from the misplaced fears, however, one of the biggest obstacles is the cost. Saran’s biodigester, for example, cost $470, a significant expense for a poor family that supports itself with a rice farm of 1 hectare.

As far as biodigesters go, Saran’s is at the lower end: the price ranges from $290 to $1,250 depending on size; the NBP’s subsidy is just $150. The program does work with a handful of microfinance companies that offer low-interest loans to families who want to invest in a biodigester, but it can still prove difficult to convince the poor to make such a large investment.

But not everyone. Take Mok Sokhun, a construction worker and farmer in the tiny village of Thorm Ney in Takeo province. He didn’t worry about the cost when he bought one five years ago.

“Because I wanted the best facilities for my wife – and now I don’t have to worry if she’ll have enough firewood if I go away for work,” he says.

Meng Sothy, the NBP program officer for Takeo province.
Meng Sothy, the NBP program officer for Takeo province. Hong Menea

In Thorm Ney, the smell of animal manure wafts through the air. Families lounge under their houses along the dry and dusty streets, hiding from the midday sun. In a backyard, a biodigester is being built inside a jug-shaped pit where the soft brown earth was recently dug up.

That’s just across the road from the house where Sokhun lives with his wife, Seam Thorn, and their four children and six grandchildren. Their home bustles with activity. The family owns 20 buffalo, which makes them moderately better off than Saran and her family; a television blares in the kitchen, a dog dozes in the dirt under the kitchen table; and a few chicks run around the floor trying to peck the dog, which twitches in annoyance.

Sokhun and Thorn were one of the first families to build a biodigester when the FAO started its program in the 1990s. After the FAO ended the program, Thorn went back to using wood and coal, but when she heard about the opportunity to get a new biodigester she jumped at the chance.

“The manure from the buffalo is more than enough to make gas to cook for the whole family,” she says. “And now we don’t need to carry wood or travel far to get wood. There is more time to do other things – such as my husband working in construction and bringing money home.”

Significantly, she says, her family’s health has improved: “Before, we easily caught colds and were coughing a lot of the time, but not anymore.”

Thorn and Sokhun are fans of the biodigester program, but even their enthusiasm can’t convert their neighbours: Thorn says, despite her efforts, they still think it’s too expensive.

Still, almost all of the biodigester owners who were last year asked for their opinions say their lives have improved dramatically since adopting the device. Cambodia’s 2015 Biodigester User Survey reported a 96 percent satisfaction rate among users.

And while studies have not yet been conducted that draw a direct line between improved health and biodigester use here, Sothy says he sees a difference between people in his province using a biodigester and those cooking over flame: the former report fewer coughs, colds and vision problems.

The NBP’s program is scheduled to continue until 2024, after which donor funding will end. The hope is that by then, it will be self-sustaining – providing its workers with a steady income. That means making sure there is consistent demand, but Sothy is optimistic about that.

“There will always be a need for them,” he says. “People like to cook with gas.”



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