Biogas Offers Poor Country's a Cleaner, Safer Fuel.
New York Times, October 25, 2010.
“NEPALGANJ, NEPAL — In developing countries where domestic animals are
ubiquitous and sewage systems rare, biogas technology — in this case
methane derived from feces — can provide both valuable fuel and improved
sanitation. Unlike directly burning animal dung, the methane is
clean-burning and odorless. And the technology has benign byproducts:
reductions in deforestation and disease.
Dalla, a village of a hundred or so mud-walled, thatch-roof huts,
clusters along a narrow dirt road a few kilometers from the forests of
the Bardiya National Park in southwest Nepal. Buffaloes and cows lounge
under thatch lean-tos to escape the hot sun. But unlike typical
villages, Dalla’s approximately 550 residents use biogas for cooking in
place of wood.
Biogas can also work in urban areas and with human waste. A few hours
from Mumbai, a sprawling public toilet complex serving visitors to the
temple of the Indian guru Sai Baba generates enough biogas to provide
back-up power for the temple complex, which occupies almost a hectare,
or two acres.
There are clear environmental benefits to using biogas, for both forest
conservation and combating climate change. An average home biogas system
can reduce firewood use by about 4.5 tons each year, which translates
into 4 tons of greenhouse gas emissions, according to the World Wildlife
Jeet Bhadur Tharu, a 53-year-old farmer in Dalla, says almost all of his
family’s cooking fuel comes from methane piped into the kitchen from an
air-tight pit of dung and excrement dug beneath his backyard. In the hut
that is his kitchen, Mr. Tharu turns a valve on a narrow pipe and lights
a burner on the floor; a strong blue flame instantly appears. Before
using biogas, Mr. Tharu’s family of five needed five to seven kilograms,
or 11 to 15 pounds, of wood each day for cooking. The time-consuming
task of gathering wood fell to his wife and daughters who cook in the
small, unventilated kitchen.
More than 1.5 million people worldwide die each year from diseases like
lung cancer and childhood pneumonia caused by indoor air pollution from
unventilated cooking fires, according to the World Health Organization.
In the Terai, Nepal’s thickly forested south, 61 percent of the people
rely on wood for cooking, as fuel like liquid petroleum gas is too
expensive for them, according to the World Wildlife Fund. Meanwhile
there are 4.5 million cattle in the Terai that produce tons of dung each
year. Most rural areas lack sewage systems.
Given this equation, it is not surprising that the government of Nepal,
through its Alternative Energy Promotion Center, has helped build
200,000 biogas systems across the country and has set itself an
ambitious target to eventually reach two million. The World Wildlife
Fund supported the construction of 7,500 of the existing biogas systems
in Nepal, including the ones in Dalla village.
The technology for a home biogas plant is simple and low-tech. Dig a pit
ranging in size from 4 to 10 cubic meters, or 140 to 350 cubic feet (the
average size is 6 cubic meters), line it with concrete and fit it with
an air-tight concrete cover. Place animal dung and water into a round,
concrete mixing bowl. A metal crank blends the concoction and pushes it
into a pipe that feeds into the underground pit. Nearby, build a simple
latrine made of concrete and bricks; gravity and water push human
excrement into the same pit threough a pipe.
Deprived of oxygen, the waste mix decomposes, giving off methane, which
flows under its own pressure into a narrow PVC pipe leading into the
Another byproduct of this anaerobic process is pathogen-free manure,
which flows out of the pit when it fills up, and can be used by farmers
Ugan Manandhar, program manager with the World Wildlife Fund in Nepal,
says biogas systems require little maintenance and are safer than
combustible tanks of liquid petroleum gas. Villagers are taught to use
only dung and water in their biogas plants — no chemicals or plastic
should go into the pit. They are given a basic training to fix faulty
pipes, though Mr. Tharu says there have been no problems with his biogas
system since its installation two years ago.
Still, biogas systems are expensive for “middle poor” people like Mr.
Tharu. It costs about $550 to build a home biogas system, including
quality-control audits and a toilet. Most of that expense is paid by a
combination of government subsidies and financing programs for villagers.
For now, biogas systems do not work in the colder conditions of Nepal’s
Himalayan ranges, since the bacteria involved need warmth to thrive and
multiply. Mr. Manandhar of the World Wildlife Fund says research is
being done on insulation for biogas plants that could function at higher
On the other hand, biogas plants can work well in urban areas, where
their waste treatment role makes them doubly useful. Since 1970, Sulabh
International, a nongovernmental organization based in Delhi, has helped
build more than a million affordable latrines, which work without
running water. Barely a third of India’s 1.2 billion people have access
to hygienic latrines, and hundreds of millions have no choice but to
relieve themselves in the open, which easily leads to the spread of disease.
Across India, Sulabh has built 200 biogas plants attached to toilets
that are approved by the Indian government’s Ministry of
Non-conventional Energy Sources. Some are powered by large public toilet
facilities used by thousands of people each day. The biggest is in
Shirdi, about four hours’ drive from Mumbai, which serves up to 7,000
people a day. The city is home to a temple devoted to the guru Sai Baba
that attracts up to 100,000 visitors a day. With funds from a trust
established by Sai Baba, who died in April of this year, Sulabh built
what it describes as an “aesthetically exquisite and visually appealing,
colorful toilet-cum-bath complex,” with 120 toilets and 108 “bathing
cubicles.” Biogas from human waste runs lights at the complex during
Bindeshwar Pathak, founder of Sulabh, argues that biogas technology is
inherently safe, and so far there have been no accidents from leaks at
Sulabh’s biogas plants, he says. The organization has also helped build
sanitary facilities in a dozen African countries including South Africa
and Ethiopia, as well as in Laos, Bangladesh and Afghanistan.
In Kabul, where the city’s infrastructure is in shambles, five Sulabh
community sanitary complexes with biogas plants, financed by the Indian
government, were formally opened in 2007 in the presence of Mr. Pathak,
the mayor of Kabul, the Indian ambassador to Afghanistan and other
The underground pits remain warm enough even during Kabul’s cold winters
for bacterial decomposition to continue, and the design has attracted
interest from U.S. Army engineers, who are considering building 40
similar complexes elsewhere in Afghanistan, according to Mr. Pathak.
“Biogas technology from human waste has multiple benefits: sanitation,
bioenergy and manure,” Sulabh emphasizes. And in Afghanistan, the
unlikely benefits of dung could include an unconventional aid to
Dr. Ann C. Wilkie Tel: (352)392-8699
Soil and Water Science Department Fax: (352)392-7008
University of Florida-IFAS
P.O. Box 110960 E-mail: [log in to unmask]
Gainesville, FL 32611-0960
Campus location: Environmental Microbiology Laboratory (Bldg. 246).
BioEnergy and Sustainable Technology Society