Gallons of freshwater consumed in the production of a gallon of milk and beer, respectively: 1000, 300.The source was a little obscure, but I tracked it to a Dutch professor of water engineering (a discipline that sounds obscure until you consider how much time the Dutch spend trying to engineer water) who hosts a site called Water Footprint. What's a water footprint? The professor, Arjen Hoekstra, explains:
The water footprint is an indicator of water use that looks at both direct and indirect water use of a consumer or producer. The water footprint... is defined as the total volume of freshwater that is used to produce the goods and services.... Water use is measured in terms of water volumes consumed (evaporated) and/or polluted per unit of time.He doesn't explain exactly how he calculated the water use for beer, save for mentioning the ingredients, but the result is counterintuitive. Beer is generally described as a water-intensive product. Yet he lists a number of products (apples, bread, cheese, chicken, pork, tea, etc.), and beer is quite low compared to most others, not just milk. For example, it takes about the same amount of water to produce a single apple as a glass of beer (70 liters vs. 75 liters). Other products have their footprints listed in other measures, so it's not so easy to compare (40 liters per slice of bread, 2400 liters per hamburger, 3,900 liters per kilo of chicken meat)--but these are obvious water hogs by comparison.
This is a lesson in measuring total consumption versus final-stage consumption. Breweries consume a lot of water, but when you compare the water consumed by the ingredients used to make beer along with the brewery's use, beer's water footprint is quite low. So drink up--beer is a low-water-use product.