An ultra sonic sensor positioned at the center of the sphere monitors the volume of gas present. This gives the operators full control of optimizing the utilization of gas to feed generators and/or heating systems.
"Storing digester gas and eliminating or reducing 'flaming' from the digester(s) can help your facility reduce or completely eliminate the need for electric grid power when generators and/or hot water boilers are incorporated into the system/facility design," the company says on its website.
Wastewater Treatment
New Belgium is the third largest craft brewery in the United States, producing about 800,000 barrels of beer annually. Its water and wastewater treatment operations are designed to be as earth-friendly as possible, in keeping with the company's environmental emphasis.
All process wastes and wastewaters associated with brewing drain into three sumps and are pumped to the wastewater treatment system. There, the water passes through screens and then is transferred to a holding tank for pH buffering and flow equalization. The wastes are then digested anaerobically, before moving on to an aerobic basin equipped with fine bubble diffusers for further BOD reduction. A clarifier provides settling of remaining solids, and the overflow passes to an outfall pit and then to the local municipal sewer system.
"The quality is good enough for direct discharge," Skinner said, "but we've opted to send it to the municipal treatment plant."
Screenings and any other solids collected from the digestion process are hauled away to a composting facility.
Not content to simply produce clean water and compostable solids from the wastewater treatment operation, New Belgium Brewing is a pioneer in the use of digester biogas for co-generation of electrical power and hot water.
The brewery operates the pair of double membranes in series, pulling biogas from the single anaerobic digester and feeding both "spheres" with a single pipe, teed to the balloons. The older membrane, in place since 2005, fills first. When it reaches 100 percent of its 780 cubic meters capacity, the gas fills the newer membrane (also 780 cubic meters capacity), installed in July 2011. The consumption cycle is reversed; the newer balloon is emptied first, and then the older membrane is burned down to 20 percent volume remaining.
"We've had anaerobic digestion for some time," Skinner said. "It was a different style anaerobic basin with methane captured and stored directly above the basin.
"When the new anaerobic basin was installed we had the idea of using the gas sphere concept for the gas holder."
With one in place, the second was added a little over a year ago under a Department of Energy Renewable Systems Integration program.
"With two cogen engines running and only one sphere, we weren't getting enough run time," Skinner said, adding that a minimum of two hours running time is desirable.
"We're pretty fortunate that-with a well controlled waste stream-we get a relatively clean biogas," Skinner added. "We have the potential capability of scrubbing the gas, but we have not had to put scrubbers in place."
The energy content of the biogas is about 80 percent that of natural gas, or about 800 BTUs per cubic foot.
The brewery uses the biogas to fuel two cogeneration engines, manufactured by GUASCOR. One is rated at 262 KW and the other at 500 KW. The electricity generated by the engines offsets about 15 percent of the brewery's total energy needs, although Skinner said he's seen times when -- with the larger of the two engines running on biogas -- the brewery is consuming zero outside electricity.
"When we're meeting all the plant's demands, excess energy is returned to the city's electrical grid" as a credit, Skinner said.
The hot water is produced by recovering the spent water used to cool the engine jackets.
"The engine exhaust is very hot," he said. "We use city water to cool the jackets. Normally that heat value would be lost, but we capture that hot cooling water (85 degree C) and re-use it in the brewery."
Skinner says the water is used primarily for cleaning.
With over seven years of experience recovering and using biogas, Skinner and New Belgium are advocates for cogeneration.
"We're a little surprised at the lack of cogeneration here in the United States," he said. "It's more the norm in Europe, where they try to eke out every last drop of energy. But we're doing it here -- capturing our waste heat and doing something positive with it. We're a big proponent of educating people about cogeneration.
"It's part of our fabric, our core beliefs," Skinner said.
