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Wisconsin produced 8.57 million gallons of beer in 2003, more than 75 percent of which was from large-scale breweries. In the same year, the industry was estimated to have contributed more than $2.5 billion to the state's economy.¹

Brewing beer begins with the harvesting and cleaning of barley or other cereal grains. When steeped in water in a controlled environment, the grain begins to germinate. Once a certain ratio of starch, protein and enzymes is reached, germination is arrested through heating. The grain is now considered malt.

Malt is milled and combined with hot water to make mash, which is then left alone while the extracted enzymes convert malt's insoluble starches into fermentable sugars. When this process is complete, the malt extract is called sweet wort, and the solids, or spent grains, are filtered out. To flavor the beer, hops are added to the sweet wort, which is boiled to release the hops' oils. The wort is again filtered, leaving behind spent hops, or trub. Yeast is then added to cooled wort to ferment its sugars into alcohol. Carbon dioxide is produced during fermentation.

When fermentation is complete, the wort is now beer, and the yeast - which has multiplied in volume during fermentation - is removed by filtration, settling or centrifugation. Some yeast is set aside for the next batch of wort. The beer is then further conditioned depending on the desired character (lager, ale, etc.). A final filtration removes any remaining sediment, and the beer is either sealed in bottles or cans and then pasteurized, or pasteurized and placed in sterilized kegs and tanks.

The spent grains, spent hops and spent yeast all have secondary markets, primarily as brewers' grains and brewers' yeast.

• Spent grains (trub)
• Spent hops
• Spent (brewers) yeast
• Waste beer
• Wastewater (breweries)

• Anaerobic digestion
• Aqueous-phase reforming
• Biomass gasification
• Combustion
• Fast pyrolysis
• Fermentation of 6-carbon sugars and starches
• Fermentation of lignocellulosic biomass
• Thermochemical liquefaction

• 1,3-Propanediol (PDO)
• 3-Hydroxypropionic acid (3-HP)
• Acetic (ethanoic) acid
• Anaerobic digestion effluent
• Biobased fuel gas & syngas
• Bio-derived liquefaction oil
• Biogas
• Butanol
• Char
• Ethanol
• Hydrocarbon fuels
• Hydrogen
• Itaconic acid
• Lactic acid
• PHA (Polyhydroxyalkanoate) polymers
• Pyrolytic bio-oil
• Specialty chemicals
• Succinic acid
• Volatile gases (energy)

[1] Ivey, Mike. 2004. State says Cheers! Wisconsin brewers buck trend." The Capital Times, March 25. Madison, WI. (15 April 2004)

Energy Consumption Guide. 1992. "Guide 29: Small Breweries." Best Practice Programme, Energy Efficiency Office, Department of the Environment, Didcot, Oxfordshire, UK.

Pollution Prevention and Abatement Handbook: Breweries. 1998. World Bank Group. July 1998. (28 May 2004)