They’ll leave behind a little more than footprints, however. Marathons don’t produce much in the way of a carbon impact, since most of the action takes place on foot, and most of the runners live within easy driving distance.

There’s a bit of trash generated, however. While recycling can be difficult at an event with thousands of people, endurance events are beginning to do their part.

The Frederick Running Festival will collect shoes and used clothing to give to the Frederick Rescue Mission, a partnership that began several years ago. Rescue Mission residents get shoes that are barely worn out, and runners don’t have to trash shoes they’ve only worn for three or four months.

It’s likely that one day cups, water bottles and more will be recycled. That trend has already started in Boulder, Colo., home of 5430 Sports, which puts on three triathlons in Boulder, plus a series of short road races.

The Tri Sustainability Initiative is an effort by 5430 Sports to see how much a long-distance sports event can recycle, and it turns out that it’s a lot. 5430 Sports was able to recycle 93 percent of trash at seven events last year, including all three triathlons.

That’s an accomplishment, considering all the food that’s consumed during triathlons. The Boulder Triathlon Series consists of a sprint, Olympic-distance and half-iron distance triathlon. A total of 4,000 athletes, and a lot more volunteers, participate in the three events.

“We would have a 20-cubic yard Dumpster for each event, and it would be overflowing and end up in a landfill,” said Barry Siff, president of 5430 Sports, in a telephone interview from his office in Boulder. “Now we don’t have any Dumpsters, and we have very little trash.”

Electricity for this summer’s events will be solar-powered, Siff said. His goal is to get all the 5430 Sports events down to what is called zero waste, where all trash generated is recyclable or reusable.

Last year’s 93 percent recycle rate was the highest for any event in the Boulder area, Siff said. “We want people to try sustainability,” he said. “That’s why we call it Tri Sustainability. All the cups are recycled. We collect all the water bottles that people throw away, wash them and give them to children’s groups.” At a triathlon, athletes will often toss re-usable water bottles with event logos on them. In the past, Siff said those bottles would end up in a landfill, but kids love to have water bottles with event logos.

Here are some statistics of recycled materials from the three triathlons:

4,036 gallons of cardboard, which requires 38 trees to make

3,350 gallons of commingled containers, which include plastic bottles, cups and cans

19,649 pounds of compostable material

All the disposable plates and utensils at the events were made with corn-based compostable material. Paper cups were recycled with other paper materials. Vendors are also asked to use compostable materials.

5430 sports also joined with Clif Bar and Native Energy to buy $2 renewable energy credits used to fund a local electric company’s wind farm.

Racers had the chance to purchase renewable energy credits for the wind farm from Clif Bar for up to 300 miles of travel to get to the event.

Goody bags given to race participants were actually cloth tote bags from Whole Foods, rather than the typical plastic bags given out at many sports events.

The Frederick Turkey Trot gave out similar goody bags at last year’s Thanksgiving Day race. Racers got small backpacks from the Common Market with all their race goodies.

Siff said he’d like to replace the fliers and coupons that come in many race goody bags with a computer chip that will allow participants to view the promotions, rather than get them printed on paper. “We’re a business, and our sponsors want advertising,” he said.

Prizes for age group winners were made out of recycled bike parts. Age group winners at this summer’s Boulder Triathlon Series will get plaques made from a local natural stone.

Some interesting stats about the Frederick Running Festival: 71,500 — Number of cups used for water and Gatorade throughout the course 4,800 — Number of single-serve water bottles at the finish line 3,500 — Number of Utz snack bags available race day 2,800 — Number of PowerGels on the course 2,800 — Number of PowerBars on the course 2,100 — Gallons of water along the course and at the finish line 1,440 — Gallons of Gatorade along the course and at the finish line 400 — Number of trash bag liners used on race day.

Saturday is the 5th annual Mission of Mercy, or MOM, 5K Race. This race has become a Mother’s Day weekend tradition. This year’s race will be at 8:30 a.m., at Whittier Elementary School. Registration begins at 7 a.m.

The Frederick Steeplechasers will provide race support, and the race is a club Grand Prix event. Race fee is $20, and runners will get a T-shirt and refreshments. The money goes to support the Mission of Mercy area health clinics. For more information, check the website, www.amissionofmercy.org.