Hesperian Health Guides
Biomass Energy
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| Common sources of biomass energy |
Biomass from plants is renewable, but when it is burned as fuel it contributes to global warming and health problems. When you make a fire with wood or cow dung, you are using biomass energy on a small scale.
On a larger scale, crop wastes (residues) can be used to generate electricity. In Cuba, for example, a large amount of electricity is generated by burning sugarcane stalks after they have been harvested and milled for sugar. Rice husks, wood waste, and other kinds of biomass can also be used in this way. While it may be renewable, pollution from burning crop wastes is bad for the health of the community and the environment.
Biogas
Biogas is produced when organic matter rots. When biogas is captured in a closed container, it can produce a small flame for cooking, or electricity for heating, lighting, pumping water, and operating motors and farm equipment. By converting the organic matter in human, animal, and plant waste into energy, biogas turns waste products into a resource that is good for the environment and for community health. Biogas can be made from many kinds of organic matter:
- animal manure and urine
- human feces and urine
- food waste such as meat, blood, bones, and vegetable scraps
- plant matter such as crop residues, straw, leaves, bark, branches, and grass cuttings
Biogas is invisible and does not smell. When it is burned, it produces a clean blue flame. Using biogas for cooking instead of solid fuels like wood reduces illnesses from indoor cooking smoke, and reduces the pressure to cut down trees for fuel. The material left behind after producing biogas can be used as a high quality fertilizer. Burning biogas does not lead to climate change and global warming.
Make a small biogas plant
The design of the biogas plant depends on the quantity and kind of wastes you have, the climate, and the construction materials available. You can collect biogas in a tank or a 5 to 10 meter long sausage-shaped plastic bag. Different kinds of animal and plant waste create different amounts of gas, so it is difficult to say how many animals are needed to produce biogas.
Manure from cows, pigs, chickens, and even human waste can be used to produce biogas. Cows produce the most, by far, and are the best source of biogas fuel. To have enough fuel to cook every day (5 hours per day on a 2-burner stove), 4 or 5 cows are needed.
Before building a biogas plant, you must be sure you have enough waste material available to generate the amount of energy for your needs.
A basic design for a biogas plant
(To learn more about biogas and to contact organizations that build biogas systems, see Other Environmental Health Resources.)
Biogas powers rural life
In Nepal, most people live in remote villages scattered across high mountains, foothills, and deep valleys. The combination of poverty and rugged terrain make it nearly impossible for the government to provide electricity throughout the country.
Because it is an agricultural nation, most households in Nepal have cattle. In the early 1990s the government of Nepal discovered that they could use cattle dung mixed with water to make biogas, providing energy for people in rural areas to have heat, light, and cooking fuel for very little money. With support from the governments of Germany and Holland, they established the Biogas Support Program (BSP).
The goal of this program is to provide a biogas system to as many homes in Nepal as possible. BSP designed a biogas system that was low-cost, efficient, and easy to use and maintain. BSP workers did outreach and education to teach rural people about the uses and benefits of biogas. They also started a microcredit program to help families pay the costs of the biogas systems.
In the first 2 years, 6000 biogas systems were installed. The program was so effective that over the next 10 years, 100,000 more systems were installed. By the year 2010, the government hopes to have installed 200,000 biogas systems.
Families all over rural Nepal now use biogas for cooking, heating, and light. By using biogas, each house saves 4 tons of firewood and 32 liters of kerosene per year. Each biogas plant also produces 5 tons of fertilizer per year, which farmers use to improve their crop yield. Thanks to biogas, many families in Nepal are now healthier, warmer, and less dependent on fuels that pollute and damage the environment.