Environmentalists have been saying for years that we've all got to do our part to slow global warming. Now beer drinkers are being called to belly up.

A study by a Canadian economist indicates that "beer fridges" — those backup appliances that keep the Moosehead lager cold in the basement — are significant contributors to household greenhouse gases. (Insert your own joke about beer gases here.)

Denise Young, an associate professor at the University of Alberta, looked at the amount of energy that the old garage Frigidaire goes through in an average year. It turns out that lots of people in Canada have secondary refrigerators, and most of them are older and energy-inefficient.

Her study, which was sponsored by Natural Resources Canada, found that three in 10 Canadian homes have an extra fridge, and two-thirds of those are 10 years old or older, which knock back more electricity.

"Originally I was doing a study on the typical lifetimes of appliances in Canadian households," she said. Among the things that struck her: "For all appliances except refrigerators, people wait until the old one breaks down. For refrigerators, many people wait until the old one breaks, but a sizeable minority don't."

From there it was a short step to figure out how much energy the old fridges were gulping. According to the Canadian Appliance Manufacturers Association (which obviously has an interest in selling more refrigerators), today's energy-efficient models use around 380 kilowatt-hours of juice per year. A 20-year-old fridge might draw 1060 kWh, while a 30-year-old model could suck 1580 kWh.

Young found that middle- and upper-income families tend to keep two or more fridges, while lower-income folks are less likely to do so, perhaps because some of the older models cost their owners $150 per year to run.

She estimated that the older Canadian refrigerators consume more than a billion kWh of energy per year, enough for 100,000 suburban homes.

U.S. residents drink more
The effect on household greenhouse gas emissions depends on how the electricity is generated. "If it's coal-fired or natural gas-fired generation, there will be an impact," she said. If the electricity is generated via hydropower or wind, for example, the impact would be less. She calculated that a 1975 refrigerator located where electricity is generated from coal or natural gas is responsible for 1.4 tons of greenhouse gases each year.

As a result, Young suggests that homeowners jettison their energy-hogging second refrigerators if they want to lessen their carbon footprint. She also supports a Canadian government program that picks up and disposes of old refrigerators.

Not as many state-siders have extra refrigerators — fewer than two in 10 households here — but we drink a heck of a lot more beer than Canadians do. (Perhaps our beer is not around the house long enough to need additional refrigeration space.)

And what about the beer fridge researcher? Young said her family owns one refrigerator and no one in her house is a regular beer drinker, "but sometimes there's some beer in our fridge when we're having people over."