California city celebrates 25 years of converting waste to energy

California city celebrates 25 years of converting waste to energy

City of Tulare has used an anaerobic digester with four-acre gastight cover from GTI.

July 8, 2014
REW Staff

The city of Tulare, California, home to several cheese and dairy producers, is celebrating its 25 years using anaerobic digestion technology as well as its 25-year partnership with equipment provider Geomembrane Technologies Inc. (GTI), headquartered in the Canadian province of New Brunswick, with U.S. offices in Denver.

Tulare is home to six large-scale cheese and dairy producers, including Nestlé-Dreyer’s, Saputo Cheese and Kraft USA, which together produce large volumes of high-strength industrial wastewater which is sent to the city for treatment. In 1989 the city installed an ADI-BVF anaerobic digester (AD) with a four-acre gastight cover manufactured by GTI. The same AD unit continues to operate today, and GTI has maintained, replaced and updated the cover as needed over the years.

The AD unit was designed to treat the city's industrial wastewater, comply with discharge limits and also allow for the conversion of wastes to energy. GTI's cover was installed to expand over the entire four-acre surface of the city’s digester to contain and collect the biogas generated by the reactor so it could be used to power plant operations. With the GTI cover, the city has been able to collect biogas for energy while also controlling odors and reducing greenhouse gas emissions.

Darrin Evans, vice president of product management for GTI, says reaching the 25-year AD milestone with one system is quite an achievement for a city that is likely among the top producers of dairy wastewater in the world.

"That AD unit has been the heart of their industrial wastewater treatment for a continuous period of 25 years," he says. "In a lot of other cases you wouldn't have that continuity and the one tank doing all that work for so many years." Further, Evans adds, "the cover is a vital step in the conversion of the waste to energy." 

According to GTI, Tulare’s gas collection cover collects up to 600,000 cubic feet of biogas per day, which is enough to generate a significant portion of the plant’s power. Evans says the covers can last for around two decades depending on environmental conditions, and the city's AD cover was most recently replaced and updated in 2013.

GTI says its cover is chemical- and UV-resistant to withstand environmental conditions. The cover is also designed to be strong and stable, allowing personnel to walk across the BVF reactor for operations and maintenance. Rainwater that pools on the cover surface is collected and drained, the company says.

In addition to AD unit covers, GTI also offers AD liner systems, containment systems, internal piping, installation and biogas removal systems.

The city has been honored by Green Technology magazine as a 2011 winner of the Green California Leadership Award for its energy strategies, including the waste-to-energy initiative designed to reduce greenhouse gases generated in the community.