Runners generate a lot of unnecessary waste during large races.

Pontus Lundahl/Associated Press

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­You don't need much to be a runner, or so m­any of us believe. Just running shoes, right? For endurance runners, however, the gear list can quickly grow to include much more than shoes. A runner might assemble a collection of performance apparel, gadgets and nutritional drinks, gels and bars -- and then there's getting to and from marathons, which aren't always close to home.

All of this adds up to runners with giant footprints -- carbon footprints, that is. A carbon footprint measures the amount of carbon dioxide we put into the atmosphere as we live our daily lives. Running gear often includes synthetic materials, and the manufacturing and transportation of those materials and products emit toxins and fossil fuels.

In 2008, the magazine Runner's World calculated the annual CO2­ impact of a typical American runner, including everything from clothing and shoes to travel. It found that one runner generates 5,449 pounds (2,471 kilograms) of CO2 in one year. That's equal to driving an SUV (getting 15 mpg or 0.15 liters/kilometer) 300 miles (482 kilometers) per month every month for a year [source: Stevenson].

Green runners, on the other hand, make green choices about their gear and travel arrangements: They reduce, reuse and recycle. They trade synthetic fabrics for organics or alternative fibers such as bamboo or recycled materials. Running shoes are notoriously ungreen, but savvy runners reuse them for running errands instead of marathons or give them to organizations able to reuse or recycle them. They also choose to race close to home, carpool or purchase carbon offsets. Carbon offsets allow you to balance your greenhouse gas sins by buying into carbon reduction projects such as wind farms or other clean energy.

­Turning a race green is similar. Race directors can make eco-friendly choices when planning a marathon, from finish-line farmers' markets to recycling the waste generated at the event.