Hugh Pickens writes writes: "Brian Palmer writes that although none of the major manufacturers has released data on their energy consumption and how much greenhouse gas making a bicycle requires, Shreya Dave, a graduate student at MIT, recently estimated that manufacturing an average bicycle results in the emission of approximately 530 pounds of greenhouse gases. Therefor given a "typical U.S. diet," you would have to ride your bike instead of driving for around 400 miles to cover the bike's initial carbon footprint. However calculating the total environmental impact of a mode of transit involves more than just the easy-to-measure metrics like mileage per gallon. Using a life-cycle assessment Dave concluded that an ordinary sedan's carbon footprint is more than 10 times greater than a conventional bicycle (PDF) on a mile-for-mile basis, assuming each survives 15 years and you ride the bike 2,000 miles per year. What about other ways to get to work? According to Dave's life-cycle analysis, the only vehicle that comes close to a bicycle is the peak-hour bus—and it's not really that close. A fully loaded bus is responsible for 2.6-times the carbon emissions total of a bicycle per passenger mile while off-peak buses account for more than 20 times as many greenhouse gases as a bicycle. What about the carbon footprint of walking? “Walking is not zero emission because we need food energy to move ourselves from place to place,” says environmentalist Chris Goodall. “Food production creates carbon emissions.”"