Biogas is produced by industrial, municipal and agricultural waste treatment processes. Composed primarily of methane and carbon dioxide, it is often flared off as part of the effort to reduce greenhouse gas emissions. However, with rising gas costs, and potential funding opportunities available, biogas recovery has become economically viable.

Captured from wastewater treatment plants, biogas contains 50-80% methane. This chemical energy can be converted into electrical and thermal energy. Biogas has a heating value of approximately 600–800 Btu/ft3. Utilization may be on-site, nearby or at a remote facility.

For relatively large energy users, economics is the driving force behind biogas recovery. This system can satisfy both thermal and electrical needs of a facility. Biogas recovery can reduce or even eliminate the facility’s dependence on imported natural gas and electricity. In some cases, sufficient biogas has been collected to offset natural gas costs by 30-35%.

The optimal biogas recovery system for a given facility depends on the evaluation of a range of factors, including the facility’s location, type of waste treatment process, characteristics of the wastestream and demand for natural gas or electricity.

BDS can provide design and build services to capture biogas from anaerobic lagoons at your facility. Typically, the project consists of installing a floating, impermeable cover over the lagoon to capture methane produced in the lagoon. The cover is constructed of HDPE material and is placed over the entire lagoon.

Once the cover is installed, the methane produced under the covered area of the lagoon is trapped. The biogas is harvested using a collection manifold that is placed under the cover along the sealed edge of the lagoon. Methane is removed by the pull of a slight vacuum on the collection manifold (by connecting a suction blower to the end of the pipe) that draws the collected biogas out from under the cover and on to the end-use application.

The cover is held in position with cables and weights, and is anchored by a concrete footing along the edge of the lagoon. Where the cover attaches to the edge of the lagoon, an air-tight seal is constructed by placing a sheet of the cover material over the lagoon bank and down several feet into the lagoon, and clamping the cover (with the footing) onto the sealed bank. Seals are formed on the remaining edges with a weighted curtain of material that hangs vertically from the edge of the floating cover into the lagoon.

The covered lagoon system has several merits. The covered lagoon system operation and maintenance is simple and straightforward. More importantly, the typical return on investment is within 16-24 months.

BDS offers design and build services which include: