Homemade Biogas in China


By Florita Botts

Biogas Plant Construction

The cadre described her village of forty-eight families.
“Biogas was introduced in our village four years ago. Up to now forty-four families have built their own individual units for cooking and lighting.”

1980. China

I was deep in the heart of rural Sichuan, sitting in the kitchen of a peasant farmhouse drinking green tea. A smiling young lady of the house was busy unwrapping cookies to offer us while the village cadre talked, and Ho, my interpreter, translated while I took notes.
The cadre, her style of presentation brisk and singsong as though memorized, continued: “By producing and using biogas in our homes we no longer have to burn coal nor kerosene for cooking. And trees need not be cut for firewood.”
I watched our hostess while she lit a burner attached to a rubber tube, inserted it in a gap in her cement stove– the gap for traditional fuels, but now it was for her own homemade biogas. The burner reminded me of my high-school chemistry classes; we’d called them “Bunsen burners.”
“We’ve improved our environment, and improved our health with biogas production.”

Dream words to me. After the countless countries I’ve been sent to, to photograph their trees — forests — being destroyed just for cooking fires: Ethiopia, Burkina Faso, northern Ghana, Mandalay in Burma, Nepal, India… everywhere in the third world, really. And when I was guided through peasants’ homes in Tsuong Ching County, Sichuan, and watched how each individual biogas unit functioned, it was a miracle sight.

The village people were eager to invite me into their ancient whitewashed stone houses and offer tea in their gemlike courtyards with pools of goldfish and flowers, and show off their own biogas cookers.
A handsome couple in classic Sichuan peasant garb posed together for a photo. Man in black velvet cap and matching jacket and trousers, woman in black velvet tunic and trousers, gray hair pulled tightly back in a bun. They stood proudly together at their cooking counter, made of slate, like the floors. The wife held a wok above the lit burner. Burner lit with biogas produced in their back yard.

Can you believe it? And why didn’t the rest of the world know about the millions of Chinese peasants in Sichuan who produced their own cooking and lighting gas?

I’ll tell you why. Because they made it from human shit, and shit is disgusting, a taboo subject. And it’s not journalistic.
The destruction of entire forests for cooking fires of the third world isn’t journalistic, either.

I was led outside, behind the house. The cadre and the housewife pointed out a concrete lid in the ground, with a plastic tube emerging from it and leading through the wall of their kitchen. Under that lid was an airtight pit called the digester, where organic wastes were fermenting and creating biogas. The gas was piped into the house through the plastic tube.

Next to the house were two sheds. One was the family pigsty, containing two very clean pink pigs snorting and snuffling. Their manure and urine were washed down a gutter that slanted directly into the underground digester. The other shed was the family privy. It was also piped directly into the biogas digester. The door of the latrine was opened so that I could have a look while the cadre was explaining. It was a two-seater. There was no stink.

Pig and human excreta washed into the underground tank, mixed with vegetable wastes such as straw or plant stalks, with enough liquid slurry to create a protective airtight cover, under which microbes worked to ferment this mixture and produce biogas. It’s defined as anaerobic fermentation.

The cadre explained that excreta from a family of four and two pigs would supply the daily household’s fuel requirements. Not only does this system produce a clean, odorless, smokeless fuel, it also provides an organic fertilizer with high nitrogen and phosphorus content. It’s all in the liquid slurry –also odorless. It is scooped regularly from an open outlet next to the digester and applied directly to crops.

One other extraordinary aspect of biogas is its contribution to environmental sanitation and pollution control. During the fermentation process intestinal parasites– like tapeworm, hookworm, amoeba– enteric bacteria, dysentery and paratyphoid bacilli are destroyed. This is an extremely important public-health feature in tropical and sub-tropical conditions. It means that the latrines are non-polluting, and clean fertilizer is going back to the soil and the crops.

This was rural China. There were no flush toilets in any of the villages I visited in 1980. (There still aren’t many.)

How much does the developed world know about how human excreta is dealt with in most of the villages of the Third World countries? For thirty years I’ve had to see and smell it, had to try not to step in it. And be only too well-aware that food and water are contaminated by it.
The Chinese are very relaxed and open about handling human excreta. They are the only people in the world who are. It’s been their main source of fertilizer for centuries. They have a variety of ways of handling it, collecting it, fermenting and sterilizing it, like no other country.

The underground digester was built by the family whose home I was visiting. Neighbors helped with the digging and construction of the pit, supervised by biogas technicians. The technicians were peasants from their village sent and paid by the State for training in other villages where the system had already been perfected. They learned the science and technology, and returned to their village, paid to spread the system. In Sichuan province, in 1980, there were 150,000 trained technicians.

In Chengdu, capital city of Sichuan, a U.N.-sponsored training course for biogas technicians from other Asian countries was in session. My assignment was to produce two video and slide programs which trainees could use when they returned to their respective countries. Program 1 would be a documentary on Chinese biogas technology, from the family-size unit to large community-size units producing enough biogas to run farm machinery, generate electricity, run large power plants. Program 2: a detailed step-by-step process of constructing a family-size digester, technical enough to give a clear notion of how it was built from scratch.
I went with the trainees to a farm village just outside Chengdu, called Production Team No. l of Kwangrong Brigade. (It was still the Commune system in 1980: the Commune, divided into production brigades, subdivided into production teams. In 1981 the Commune system was broken up by Deng Xiao Ping, and China quickly became the free-for-all that it now is. “Letting the capitalist fox into the socialist henhouse,” it’s been called.)

The trainees were in a large shed at work on a diesel-powered generator. They were learning how to modify the air filter for the engine to run on biogas. “Diesel engines run very well on biogas, with just a minor modification,” my interpreter said as I watched the instructor in Mao jacket handing a wrench to the petite and pretty Thai trainee, the only woman in the group. “Engines can run with eighty percent biogas and only twenty percent diesel fuel.”

The trainees had already finished hands-on work on the construction of a farm-size digester to collect the manure of thirty pigs. The amount of biogas it was already producing was sufficient to generate electricity to run the village rice- and feed-processing mill and to light the homes of forty families.

The trainee from India — a young engineer — showed me two huge polythene balloons in a loft above the generator. “They store the surplus gas. That plastic tube comes directly out of the digester into the storage bags. The other tube feeds into the generator.”

“Those must be the cheapest storage tanks in existence,” I said. “What about safety problems though?”

“There’s the pressure gauge,” he said, pointing to a panel on the wall with numbers in gradation marked along the side of a vertically attached glass tube. It contained water and floated a tiny red ball.

“We learned how to make it last week.” He explained how it functioned as a warning system when too much gas accumulated in the digester, or when there was too little.
“What do you think about this Chinese biogas system for India?” I asked. I knew that the Indians were experimenting with it, on a very small scale.
“It’s very practical, and so inexpensive. Our digesters are different. They’re made of metal. It’s another system. The containers are above ground. Only cattle dung is used, it’s added by hand.”
“How can that be?” I asked. “Dung! That’s the most precious commodity in India. It’s your cooking fuel! Fertilizer! The core principal here is human waste. Latrines.”
“We in India would never be able to do that. Human waste is a delicate subject. A taboo subject. It can’t be discussed.”
I stared, incredulous. I was about to blurt out: but Indians are defecating everywhere, in the streams, rivers, fields, behind every bush, on the sidewalks. Polluting, spreading infection. But I only said: “You mean that there can never be such a thing as the underground digester attached to latrines?”
“No, never. The people would never accept that idea. We’ll start to experiment with this system attached to dairy farms, stables, feeding in cattle manure and urine. But that’s all.”


I settled in one village for the filming of construction of the family-size unit. The technician of the biogas development brigade invited me into his home to have a look at his modest kitchen now equipped with biogas.
The pigsty was in the kitchen, separated from the cooking area by a low partition.

Pigs and sty were kept so clean, no smell, the pig wastes washed down a hole in the wall into the digester just outside. A one-seater outhouse was in the back yard, also attached to the digester. A clay burner was lit, tea was made.

There was a notable change in the atmosphere since my first work in China in 1978. No one tried to rush me out of the house when I photographed the pigsty in the kitchen. In 1978, when I first had an assignment in China, foreigners were just being allowed into the country, we were kept on a strictly watched path, any attempt to photograph something which could be considered a criticism of China’s backwardness would be immediately stopped.

I wanted my Chinese colleagues to understand that we needed to pick a photogenic family, an attractive couple as “actors” to take us through all the phases of construction of the digester. It wasn’t an easy concept for them. The individual doesn’t count, physical beauty should not be commented on. The Chinese were just as sensitive to male and female beauty as I was, but no one could admit it, it would be labeled bourgeois.

Ho, my interpreter, didn’t understand the word “photogenic.” I wanted to say to him, “You’re photogenic. You’re handsome, you’ve a beautiful full mouth, a sweet smile, perfect white teeth, fine clear skin, a Greek nose. Your thick shiny raven hair; big almond eyes– an exquisite shape. Your eyebrows curve so nicely. I wish I could photograph you.”

It would have been supreme embarrassment. Ho Xiao Chi, still a university student, was taken out of English Class One of the Foreign Language Department at Chengdu, to be my interpreter for three weeks. I was lucky; he was a gem, not only to look at.

The photogenic family was located after a few visits to a few houses: a young couple, bright, attractive, friendly, with two healthy rosy-cheeked children. And two pigs. A neat home, Sichuan peasant home, thatched roof with bamboo beams, whitewashed brick walls, bamboo chairs, a radio protected with embroidered cover, plastic flowers under a portrait of Chairman Mao (already three years dead).
The kitchen was primitive, adobe walls and floor. One clay pot hung on a nail. A wooden water bucket on the floor. The stove was one big block of cement. On top, a wide hole to accommodate a wok. On the side, a hole as fireplace for fueling with bundles of rice straw and wood. No chimney.

I photographed Lee Yu Lan, the wife, seated on a footstool stuffing the straw into the fireplace under the wok.

It would be the same stove I’d photograph again when she would be using biogas. She wore a dark-blue apron over her Mao jacket. Psychedelic crimson underwear peeked out below the cuffs of her trousers.

Work started on the construction of the pit behind the house. I photographed the first step of measuring and marking the circumference. The family-size digester was ten cubic meters.

When the digging started neighbors came to assist. The men hoed and shoveled and the women carried the clay soil away in baskets on poles to another group of women who were already making adobe bricks with it, wetting and pressing it in wooden frames. Precious soil is never wasted.

The radio was playing loudly from inside the house. “Jingle Bells.” Ho sang along with it, to show me that he was up on the latest. “It’s very popular now in China,” he said.
“What else is popular?” I asked, gagging on “Jingle Bells” in June in Sichuan.
“American songs are the rage. ‘My Old Kentucky Home,’ ‘Old Black Joe.’ Songs by a writer named Stephen Foster.” And he started to hum then sang: “…..’Way down upon the
Swan-eeee River…..'”
China was opening up to the West in 1980, beginning with Stephen Foster.

On the bus returning to Chengdu in the evening, Ho sat beside me and we talked. I asked him about the university. His parents paid for food and books. He got a free room in a dorm, shared it with nine others and it was very crowded. He had a tiny desk but had to share it with another roommate, and it was too small for them to use at the same time. The toilets in the dorm were a big problem — one for every hundred students.
“What books do you read in your English courses?”
“Modern writers: Dreiser, Jack London, O’Henry. Hemingway, Farewell to Arms. We had an English literature course: Thackeray, the Bronte sisters, David Copperfield. We started with Beowulf.”
Beowulf! Whatever for? It’s impossible for us who know English!”
“It was terribly difficult, in fact.”
They weren’t allowed contemporary authors. Forbidden.
“What are the current translations hot off the press in the bookstores?”
Death On the Nile, Chaucer, Hamlet, Wilkie Collins.”
“That’s an odd mixture. I wonder who makes such a selection.”
“I want to read what’s being written now,” he whispered. “The books our so-called leaders don’t want us to. The more they insist on forbidding modern writers, the more we want to obtain them.” He wanted to read Updike’s Couples.
“I’ll send it to you,” I said.
He jerked in his seat. “No! You can’t! I’d be in trouble if I received a subversive book like that!”


In a few days the digester was completed, every step filmed, technical data recorded.

The pit was entirely lined with bricks, given a coating of cement, and topped with a brick dome. In the center of the dome, a manhole which would be closed with a concrete lid and a pipe for the gas hose coming out of it.

Lee stuffed rice straw and a pile of leaves through the manhole before the heavy lid was put in place and sealed with clay. They would be the organic material that stays in the bottom and decomposes during fermentation.

Once a year the digester should be cleaned out and fresh vegetable matter added. The ideal mixture half organic and half liquid.
Lee carried buckets of slurry scooped from another digester and poured it into her new digester outlet, to speed up the fermentation process with developed bacteria.

Her pigsty and new latrine were already in full use. I could film her lighting a biogas burner in her stove in a couple of days.


Some images of Lee Yu Lan using biogas slurry to fertilize her vegetables



1982 Ethiopia.

I was there working for an FAO reforestation project.
I’d been asked by the U.N. representative to show my film on the construction of the Chinese back-yard biogas system to the Ethiopian National Planning Commission.

Six men and one woman arrived at the appointed hour. I’d set up the projector, the meeting room was darkened. I introduced myself as the producer of this program.

The title was projected on the screen: Home-made Biogas. There was Lee Yu Lan stuffing rice straw into her cooking stove and the narration saying how scarce wood for fuel was in her part of China.
We saw her visiting her neighbor Mrs. Wong who had built her own biogas unit, and who demonstrated how easy it was to cook with this new fuel.


The film lasted 45 minutes.

When it was over, the group started a lively discussion. They were excited, amazed. “This is what we need here!” … “This is the answer to our fuel problem!”… “It’s fantastic!”… “So simple!”… “Cheap,” etc.
As I was the only “expert” in the room (my Forestry Project director didn’t attend the showing, nor did anyone from the U.N. rep’s office), these high members of the National Planning Commission had only me to talk to.
They started pumping me with questions. “How do you think we can get biogas production going in Ethiopia?”

Who was I to tell the National Planning Commission? But it was up to me.
“It seems to me that you could request technical assistance from China. Bring over a team of their biogas technicians,” I said. “It’s a government-backed system there. Your government is friendly to China; it should be easy. Or you could send your apprentices over there for training.”

They discussed this among themselves; all were positive to the idea.

I got going, feeling the audience. “The Chinese technicians could conduct training courses at various levels. You could develop large-scale biogas plants for entire communities, collecting manure from dairy farms or cattle yards, and sewage in the towns. Electricity plants in Sichuan and Guangdong provinces run on biogas. Diesel engines, trucks, city busses. First start here as soon as possible on the necessity for backyard pit latrines… There are so few latrines in the villages,” I added in a small voice, wanting to say Rural sanitation in this country is a disaster. “You could launch a national campaign to educate the people to build latrines properly.”
“We couldn’t do that,” one answered.
“Why not?” I asked. “You’re a socialist government. Once you’ve made the choice to launch rural sanitation, you’ll blanket the entire country. You proved it with illiteracy. Your national campaigns to combat it were successful in an incredibly short time, a masterpiece of organization at every level.”
“We can’t deal openly with the subject.”… “Toilets are a taboo subject.”… “We’d only use cattle manure in the digesters.”… “We couldn’t use human wastes. The people wouldn’t accept that.”
I was bowled over. It was exactly what the engineer from India said to me in Sichuan.
Rage! The urge I had was to shout: The filth, the stench, the pollution in this country! The parasites, diseases, dysentery… But shit’s a taboo!…

It would have been a diplomatic disaster. I managed to say quietly, evenly: “You’d be blindfolding the people. This is a rational system, based on turning human excreta into clean fuel, clean fertilizer, a high-grade plant nutrient, a clean environment, while now they’re a source of disease and pollution. You’ll have solved three of your most basic and dramatic problems by intelligently – and openly — dealing with urine and feces. You’ve an opportunity to make a brilliant political choice: launch a public-health campaign, a tree-saving campaign, an agricultural improvement campaign, all at once.”
Their collective answer was: “It’s too soon.”… “Too offensive.”… “Human waste is a taboo subject.”
“Start with a pilot project in one province,” I mumbled, in desperation.
The session was over, the seven members of the National Planning Commission left the room. I unplugged the projector, put it back in its case.

Resource: BACK-YARD BIOGAS IN CHINA by Florita Botts

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