Anheuser-Busch Brews Up Biogas with High-Rate Anaerobic Treatment
Environmental stewardship has been a core philosophy for Anheuser-Busch Inc. since the company’s inception in the late 1800s. Back then, the company recycled surplus grain from its brewing process as cattle feed, among other sustainable measures. That practice continues today along with the implementation of new technological processes, including advanced wastewater pretreatment and treatment systems, which keep the 12 U.S. A-B breweries running at optimum efficiency while successfully establishing the company as a responsible citizen within the communities where they are based.
A-B produces more than 100 different beers, and alcoholic and nonalcoholic beverages. Not only must each in-house treatment system meet all state and federal regulatory standards, it must also meet A-B’s own high aesthetic standards, including a zero-odor tolerance policy. Several of the A-B breweries serve as tourist destinations, so the brewer places particular emphasis on plant cleanliness and an odor-free environment. For wastewater treatment, the company uses anaerobic digestion systems, Bio-Energy Recovery Systems, or BERS in company nomenclature, at 10 of its breweries.
In fact, A-B is the largest operator of anaerobic digesters in the world. Anaerobic digestion is a natural fit for breweries and has become a proven and energy-efficient way to clean brewery wastewater. Low energy use, a small reactor surface area, lower chemical usage and minimal sludge handling costs are advantages of this technology over aerobic alternatives. The technology does not require blowers and mixers like an aerobic system, and the anaerobic reactor produces biogas (methane) that can be used within breweries to fuel boilers or combined-heat-and-power units. In addition, anaerobic reactors are sealed, so no odor escapes. This is a special advantage for A-B facilities that provide daily tours, such as the company’s brewery in Merrimack, N.H.
The Merrimack Brewery
The A-B Merrimack Brewery, built in 1969-1970, is set on 294 acres in the scenic Merrimack Valley and is contained within a 1-million-square-foot plant. The brewery is the New England home to the Budweiser brand. It hosts tours daily as well as a number of special events each year and is home to the world-famous A-B icons, the Budweiser Clydesdale horses.
When A-B elected to upgrade its existing pretreatment system at its Merrimack brewery in 2004, it contracted Biothane, a Veolia Water Solutions & Technologies Co., to design and install the upgrades. Biothane had worked with A-B on seven previous brewery projects, and the Merrimack project merged the best technologies from prior BERS plants with design improvements based on experience to provide an extremely efficient BERS plant for the brewery.
Typical brewery wastewater chemical oxygen demand (COD) consists mainly of easily biodegradable organic compounds such as sugars, ethanol and soluble starch. As each brewery has different production practices, a study was conducted to determine the characteristics of A-B Merrimack’s effluent as well as the stringent site requirements in order to select the most appropriate system. Based on this study, the final design for the upgrades included the installation of the Biobed Expanded Granular Sludge Blanket (EGSB) technology, a high-rate anaerobic digestion process.
Groundbreaking for the project commenced in May 2005 with the laying of foundation piles and construction of the BERS began the following September. Although Biothane faced a number of challenges during construction, such as a brutal New England winter during which building construction wrapped up, and a 100-year storm that caused the adjacent Merrimack River to flood the job site, the plant was commissioned in August 2006—three weeks ahead of schedule.
The site for the upgrade was tight, which was one of the reasons for the EGSB reactor selection. The system features significantly smaller reactor volume, compared to other anaerobic technologies, due to its ability to handle high COD volumetric loading rates. The system’s smaller footprint and fewer material requirements provide for compact installation and lower investment cost.
Each day, the system treats 500,000-750,000 gallons of wastewater from the Merrimack Brewery. The treatment system modifications take up the waste stream and direct it to an influent well prior to entering a 320,000-gallon equalization tank, where pH is adjusted.
After equalization, the wastewater is pumped into a 250,000-gallon Biobed EGSB reactor through an influent system that evenly distributes the wastewater into the reactor base and biomass bed. The biomass/wastewater mixture subsequently flows upwards through the tank. As wastewater contacts the biomass (anaerobic organisms, which ball together to form granular particles), contaminants contained in the wastewater are converted into biogas in an oxygen-free medium. The biomass, or self-creating black granules, are 2-4 millimeters in diameter, with a high-settling velocity of greater than 50 meters per hour and a density of 40-80 kilograms of dry solids per cubic meter.
No mechanical agitation of the reactor contents is required because the biomass mixing effect inside the reactor is essentially brought about by the feed distribution system, which maximizes the contact of the biomass with the influent. Production of biogas occurs during the natural upward current that begins in the lower reactor section. A three-phase settler at the top of the reactor separates treated water, biomass and the produced biogas. A portion of the treated effluent water flows back to the equalization tank where it is mixed with raw influent wastewater for another pass through the reactor.
The biogas produced in the reactors flows through a gas holder, which buffers flow gradients, and is then compressed for use as a supplementary fuel source for the brewery’s boilers. Recirculation of the treated water and removal of degassing carbon dioxide within the equalization tank helps control alkalinity in the system.
Biomass build-up in the Biobed EGSB is sold as seed for new anaerobic plants, thereby avoiding the biomass storage and disposal issues encountered with aerobic systems. Following anaerobic treatment, the effluent may be flash aerated to remove odor through sulfide oxidation before it is discharged into its own sewer system at the brewery’s previous treatment plant’s discharge point.
The EGSB reactor complies with A-B’s zero tolerance policy regarding odors. The reactors form a closed, gas-tight unit, which positively prevents biogas from escaping into the atmosphere. All other odor-producing components of the BERS, including the equalization tanks, are connected to the BERS off-gas scrubber system that pulls out and oxidizes the odorous compounds before releasing the air into the atmosphere.
The plant upgrades have led to immediate cost savings. A-B has achieved energy savings by idling energy-intensive brewery residuals processing units and by generating biogas to help offset costs for fueling its boilers. A-B Merrimack’s BERS provides approximately 10 percent of the fuel used in its steam boilers.
An average 70 percent of total COD and 88 percent of soluble COD is removed in the BERS anaerobic step. The town of Merrimack has benefited from these upgrades by avoiding costly upgrades to its own treatment plant due to reduced loadings. By working together with the town to resolve environmental and financial issues related to wastewater treatment, rather than relying on the town’s facility to treat all of its wastewater, A-B has developed a process that works to the benefit of everyone.
A-B holds itself to stringent standards, and is an industry leader in finding and implementing efficient and environmentally friendly technologies to optimize brewery processes. In addition to adopting anaerobic treatment at its breweries, other pollution prevention approaches have led to A-B facilities recycling 99 percent of their solid waste. In addition, at A-B’s Fairfield, Calif., brewery, a 1.18-megawatt photovoltaic system constructed in 2008 generates about 3 percent of the brewery’s electricity needs. The company’s Newark, N.J., brewery has also recently added a 1.1-megawatt photovoltaic system. A-B’s Houston, Texas, brewery has started using biogas recovered from a local landfill. When combined with the biogas recovered from the brewery’s BERS installation, biogas provides approximately 70 percent of the Houston brewery’s energy needs.
An Award-Winning Approach
In 2008, the A-B Merrimack Brewery received the New Hampshire Governor’s Award for Pollution Prevention, in recognition of the energy-efficient measures installed at the brewery. The award-winning environmental improvement project carried out at the brewery has reduced emissions by 178 metric tons, energy consumption by 1.02 million kilowatt-hours and has resulted in a net savings of 91,000 MMBtu. These comprehensive measures, which have resulted in significant reductions in energy and water usage, also qualified the A-B Merrimack brewery for an Association of Energy Engineers Energy Award in 2009.
Authors: Bradley Smith
Engineering Manager, Biothane LLC
Vice President Marketing and Sales, Biothane LLC