Today, sanitary landfilling is a widely known solution for disposing Municipal Solid Waste (MSW) and keeping urban environment clean. If MSW is stored under conditions of oxygen absence, rising temperature and moisture, anaerobic biological decomposition of organic waste takes place. One of the products of this process is landfill gas which is composed of methane (50–65%), carbon dioxide (35–50%) and a small amount of impurities such as nitrogen, hydrogen sulfide and volatile organic compounds. Landfill gas is a toxic gas which continues to generate even after 10 to 30 years after the landfill’s closure.
Landfill gas poses ecological and health dangers, if not collected and treated properly. Open fires can break out at the surface of the landfill and smoldering combustion can occur inside the landfill’s waste body. The prediction and prevention of landfill fires can hardly be made, because tracing the source of landfill fires visually is almost impossible, until the fire or smoke has surfaced. Furthermore, large cavities may develop inside the landfill body as a result of fires and smoldering. This leads to dangerous settlements and instabilities of the waste layers, which cause dangerous landslides and slope failures.
The odors of landfill gas caused by mercaptan impurities (organosulfur compounds) can have a heavy impact on the health of residents living in the surrounding area. The generation of those toxic gases creates a longtime problem and their mitigation and elimination are complex and costly.
In order to avoid ecological and health risks which occur due to landfill gas, proper collection and treatment systems have to be worked out. ECOCOM is specialized in the design of landfill gas collection, treatment and ”landfill gas to energy“ systems which meet all current environmental requirements.
A standard collection system consists of a network of vertical wells connected to horizontal pipes. The average radius of a landfill gas collection area around such a well is about 50 m. The gas collection system should cover not only the already filled, but also the waste compartments in operation.
A landfill gas collection and treatment system is primarily an environmental protection measure, especially if the collected landfill gas is treated in flare stacks. From an economic point of view it is reasonable to utilize landfill gas as a renewable energy source.
In order to achieve the highest efficiency of the system, a preliminary theoretical calculation and computer simulation of gas formation within the landfill has to be made. This way it can be determined how many wells are required and where they should be located.
Elements of gas collection, treatment and ”landfill gas to energy“ systems:
The main objectives of a landfill gas collection, treatment and ”landfill gas to energy“ systems are to: