“All beers were organic 100 years ago,” says Christopher Mark O’Brien, Silver Spring, Md.-based author of “Fermenting Revolution: How to Drink Beer and Save the World.”

Today, organic beers are a niche within a niche, constituting probably less than 1 percent of the craft beer segment (which itself produces less than 4 percent of the beer consumed in this country). But the sub-niche is growing rapidly: In 2006, sales totaled $25 million, up 32 percent over the previous year, according to the Organic Trade Association in Greenfield, Mass.

To be advertised as organic, beer has to pass muster, just as other foods do. Ingredients must have been grown without the use of chemical pesticides, herbicides or fertilizers. No irradiation, no GMOs (genetically modified organisms). Certifying organizations may make surprise inspections to make sure brewers aren’t commingling organic and non-organic supplies.

Drinking organic beer “is better for your health and better for the planet,” O’Brien says, because organic farming builds up the soil and eliminates toxic runoff of chemicals into the watershed.