What is 'Anaerobic Digestion'?
Anaerobic digestion is the process by which naturally occurring bacteria, which can only live in places where there is no air, break down organic, biodegradable material over time and converts it to biogas and an inorganic fertilizer. In fact anaerobic means "no oxygen."
What kinds of material can be digested in a Biogas Plant?
Theoretically, any organic material can be broken down through Anaerobic Digestion. Wasted or spoiled food, plant clippings, animal manure, meat trimmings, and sewage after it's been treated are especially well suited to this type of digestion. Inorganic material such as rocks and dirt, and man-made materials such as plastic, metal cans, and glass, will not be broken down through anaerobic digestion. In addition, woody wastes do not digest well because their strong fibers are naturally resistant to degradation and also the anaerobic bacteria.
Does something specific have to be grown to feed into Biogas Plant?
Certain crops like corn and grasses can be used to feed biogas plants, but most organic waste materials like manure, and food scraps work even better than specially grown crops.
What makes a Biogas plant work?
The key is to keep the microscopic bacteria, which break down the material fed into the biogas plant, living and constantly multiplying inside the biogas plant. The bacteria require a sufficient amount of organic feedstock, vitamins, supplements, and some water to live. The bacteria also thrive in a warm environment without large fluctuations in the acidity levels. Like all living things, the bacteria work better without toxins.
How long does it take to break down the organic material in the biogas plant?
It varies based on the type of organic material you feed into the biogas plant and the design of the biogas plant. Simpler organic compounds, such as simple sugars, fats and proteins, will digest fairly quickly. More complex organic compounds may take 30 plus days to completely digest, especially fibrous materials like cellulose, the major constituent of paper, paperboard, and card stock and of textiles made from cotton, linen, and other plant fibers). The operating temperature of the biogas plant also has a significant impact on the time it will take to break down the material.
Isn't methane a greenhouse gas?
Methane is a greenhouse gas that is more than 20 times as damaging to the environment as carbon dioxide, but it has to be released into the air and atmosphere to take part in the "greenhouse effect." That is why people who run biogas plants are very careful to contain the biogas and not let it be released into the air-it should be used for energy! One of the benefits of anaerobic digestion is its ability to capture the methane that would normally be emitted into the air if the organic material was left to decompose in an uncontrolled landfill.
What is organic material?
Organic material is something that was living and can decay. Wasted or spoiled food, plant clippings, animal manure, meat trimmings, and sewage are common types of organic material used with Anaerobic digestion. In contrast, inorganic material includes things like rocks, dirt, plastic, metal and glass.
What materials yield the most biogas?
When put into a biogas plant, fats, oils and greases and food waste create the most biogas. For this reason, many dairy farms that have biogas plants add local food scraps to the manure in their biogas plants to increase the amount of biogas produced. Digesting different materials is called co-digestion.
How big is a Biogas Plant?
From the size of a large refrigerator to the size of small building. The size of the biogas plant depends on how much organic material will be fed into the biogas plant, and how quickly that specific biogas plant can break down the organic material.
Are biogas plant cold or hot?
To keep the right bacteria alive and multiplying, many of the larger biogas plants are kept at or above 30 to 38 degrees Celsius or 86 to 100 degrees Fahrenheit. Biogas plants can also work at temperatures that are both lower and higher than this. Because the bacteria working in the biogas plant are very sensitive to temperature, cooler biogas plants take more time to break down the biodegradable feedstock, while hotter ones may break down the biodegradable feedstock more quickly.
How is Biogas used?
Biogas is lighter than liquid and rises to the top of the biogas plant From the top of the biogas plant, tubes and pipes allow the biogas to slowly release from the tank into a container so it isn't released into the air. Biogas can be used as fuel for a boiler to generate hot water or steam, or for an engine to power an electric generator to generate electricity. Biogas can be also be "scrubbed", meaning the carbon dioxide and other non-methane "contaminants" are removed, leaving purer methane gas. Methane is the prime component of natural gas so this scrubbed biogas can then be pressurized and injected in an existing natural gas pipeline, liquefied for other storage or even used as a vehicle fuel.
Is Biogas a kind of renewable energy?
Yes. biogas technology is employed world-wide to create renewable energy. Biogas produced from an biogas plant is comprised primarily of methane gas, which can be used instead of fossil fuels to produce energy. This "renewable natural gas" can substitute for fossil fuel natural gas for any need including heating, cooking and driving. Biogas can also be used as fuel to make clean electricity. All of these options provide us with the opportunity to turn organic "waste" and into a valuable renewable energy resource in a sustainable manner.