Kipchoge Spencer. What work do you do? I'm president of Xtracycle Inc. and cofounder of Worldbike. I'm also lead singer of the Ginger Ninjas. What does your organization do? Xtracycle invented and makes car-trip-replacing, life-enhancing, sport-utility bicycles, long bikes, and the FreeRadical Hitchless Trailer -- for toting your kids to school, loading up with groceries, or making an off-road camping trip to the hills. Acts like a bike but works like a truck. Testing the Bigga Boda bicycle in Kenya. Photo: Ed Lucero. We started the Worldbike nonprofit to reach the people who most need but can least afford a …

For the sake of argument, how does one recycle condoms? Unused they are plastic of some sort? I know it's a bit silly, but don't you just hate to have to flush them and all the water that goes with? Flavia S.Milan, Italy Dearest Flavia, In brief: condoms are generally made of latex and are not recyclable. (Though the actual recyclability of Milan condoms may be a question for the Milan Recycling Bureau, not yours truly.) Used condoms would be revolting if gathered in bundles and shipped to a reclamation plant, so don't feel sad. But do stop flushing them: …

Stop drooling over concept cars we'll never own That is, as soon as we're done gawking at this stackable, shareable, electric two-seater dreamt up by MIT's Smart Cities team. It's inspired by corralled shopping-carts, powered by four "wheel robots" with 360-degree movement, and fully customizable. Drool. Photo: Franco Vairani. Be as eco-conscious as Britney Spears K-Fed up with news about Britney Spears' kid? Us neither! The latest? Motherhood has sparked an eco-streak in the popster -- she now buys "organic" and "get[s] rid of rubbish in a green way." Says Spears, "Since becoming a mum, I have become so green." …

Last year was a banner one for nature movies, kicking off with The Wild Parrots of Telegraph Hill and ending up with the wild cowboys of Brokeback Mountain (c'mon, Jake wasn't the only gorgeous scenery). In the middle, there were record-grossing Penguins, a trip to Syriana, and the horrors of The Island. So what does 2006 hold? We took a gander at the major studios' planned releases -- which include such irritatingly surefire hits as Mission: Impossible III and The Da Vinci Code -- to see whose screens will be tinted green. We hereby present a semi-informed, handily categorized list …

Demand up for eco-friendly home-building supplies Consumers have turned on to the benefits of eco-timber, sustainably harvested cork flooring, and low-VOC paint, moving green home-building supplies out of the fringe and into the mainstream. "There's no question where this is going; it's hot," says Timothy Taylor. His company, Environmental Home Center, started up in an 800-square-foot Seattle storefront in 1992; today it's a multimillion-dollar business Taylor hopes to take nationwide. Established national chains are also noticing the green tint in buyer preferences: Home Depot is testing an "EcoOptions" marketing theme in all of its Canadian stores. For now, the added …

Dear Umbra, I've done the research, and I'm ready to buy my first front-loading washing machine. And then a pesky friend starts asking the tough questions. "Does your existing machine work?" Yes. "Are you going to sell it to someone else who will keep using it?" Yes. "So, two machines where there used to be one ... how is that better for the environment?" Can you help me answer this one? I'm facing the same issue on the transportation front, as I just convinced my spouse that he should sell his 2002 Subaru and buy a Toyota Prius. Kathleen WhitsonSeattle, …

On the first day ... ... the Grist staff gave to me: the notion that Kwanzaa, Christmas, and Hanukkah are eco-holidays. Kwanzaa ("first fruits" in Swahili) has its roots in African harvest festivals. Christmas involves serious tree-hugging (thank the pagans for that). And Hanukkah celebrates squeezing every last drop from a tiny bit of oil. Photos: iStockphoto. On the second day ... ... the Grist staff gave to me: a fair to remember. The mall-weary across America are turning to alternative gift fairs, where nonprofits ask you to shop till you drop -- the dough, that is. Dang, we'll miss …

David Nova. While camping alone in the Mojave Desert three years ago, David Nova was suddenly struck by the lack of human influence -- no buildings, no streetlights, no cars, all the way to the horizon. It wasn't the first time the avid hiker had thought about the effects of population on the environment, but it was the moment he decided he could do something about it. A longtime social activist who is president and CEO of a western Virginia Planned Parenthood network, Nova began making plans to hike the 2,650-mile Pacific Crest Trail. The journey would not only fulfill …

This old earth has spun 'round the sun 40 times since my founding egg and sperm got cozy with each other, and yet I'm still a solo act: no wife, no family, no tribe. While a life partner and tribe can be left to happen whenever they happen -- if they happen -- I'm at the point where I think I need to either become a daddy, soon, or give up the idea once and for all. Hope floats. Photo: iStockphoto. If I ever did co-create a baby, I would want to revel in being a father, rolling and tumbling …

Dear Umbra, I have a couple of questions that relate to how I live and ask others to live. First, my guess is that many of your readers are above average in terms of income and education; who is the average American that we need ultimately to create a sustainable life for? Second, as we try to make our personal lives more sustainable, what is the ecological footprint we need to seek (i.e., square acres or miles or whatever) and what resources does that block contain for us to use in a sustainable way? Kit RobisonColumbus, Ohio Dearest Kit, A …