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Green Guru
Advice for the eco-minded


Is a full or empty refrigerator more energy efficient?
—Abbey Myszka, Emeryville, CA

It’s cool that you want to keep your fridge humming efficiently, but the amount of food you store in it doesn’t matter. “A full refrigerator doesn’t decrease energy use,” says researcher Jacob Talbot of the nonprofit American Council for an Energy-Efficient Economy (ACEEE). Your fridge’s foodstuffs most likely don’t displace enough space to reduce the amount of energy needed to keep it chilled, he explains.

There are a number of other ways, however, to reduce your refrigerator’s demand for power. These appliances use more energy than almost any other in your home (aside from air conditioners and heating equipment), so you want one that has earned the government’s Energy Star certification. And plan before you open. Keeping the door ajar while deciding what’s for dinner, or going in repeatedly, are the main reasons fridges lose their cool.

Keep your unit between 36 and 38 degrees Fahrenheit, suggests the ACEEE. Check the seals on the door to prevent leaks, and position the box away from heat sources, like ovens, dishwashers, or sunny spots—they force it to work harder. And be sure to give those leftovers time to cool before you pop them into the fridge.
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Is there a way to estimate how much carbon mature trees remove from the environment?
—Jim Richburg, Indiana, PA

Whether it’s a stand of oaks or an oak standing alone, trees play an important role in soaking up carbon dioxide from the atmosphere. The contiguous United States has 625 million acres of forest that sequester an estimated 790 million metric tons of CO2 equivalent each year, or about 12 to 18 percent of our annual greenhouse-gas emissions.

Sequestration rates for tree species that grow here are pretty well known, but the amount varies by soil type, climate, topography, and management practices, according to the EPA. Scientists can take these factors in a specific area and extrapolate to estimate the amount of carbon a stand of trees there holds. The U.S. Forest Service has calculated the average amount of carbon that each of 51 forest types locks away each year. If you’re curious about how much carbon a particular urban tree sequesters, check out the Forest Service’s online Tree Carbon Calculator.

Trees cut emissions in other ways. “If a tree provides shade, then you get additional carbon benefits,” says Linda Heath, a Forest Service research forester. “It keeps your house cooler so you don’t have to run your air conditioner as much.” So plant a tree for some shade, and become a shade greener.
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Does eating tofu contribute to the destruction of the rainforest?
—Eliza Pascal, Brooklyn, NY

Tofu is a protein-rich alternative to beef and chicken. While a meat eater’s annual carbon footprint is 1.6 tons bigger than a vegetarian’s, demand for tofu’s source—soybeans—has been growing globally, at the rainforest’s expense.

The Amazon rainforest holds carbon and provides habitat for hundreds of thousands of species and water for agriculture. Soybean farmers, who grow one of the world’s most popular crops, are exploiting cleared land in Brazil, thus encouraging ranchers to cut down more and more of the rainforest to create rangeland for their cattle. Globally, countries harvest 250 million tons of soybeans each year, more than a quarter of which comes from Brazil—and that amount is growing by about six million tons annually.

But your Tofurkey didn’t originate in the Amazon: Most soy-based foods sold in the United States are made with beans grown at home. “The United States is the world’s largest soybean-producing country and exporter,” says Mark Ash, an agricultural economist with the USDA. “There is no need to import soybeans from Brazil for producing tofu or any other soybean product here.”

Twenty percent of our soybeans are turned into oil, and 10 percent go toward food products including Tofutti Cuties and soy sauce. The rest winds up in livestock feed because soybeans significantly increase an animal’s ability to gain weight, bolstering meat and poultry production.

But demand from other nations could spur more deforestation. China imports nearly half of all soybeans, primarily for feeding cattle. Europe imports most of its soy from South America.

Though there are downsides to the global hunger for soybeans, dining on tofu is still better for the environment than consuming meat.
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