Each week our friends at Inhabitat recap the week's most interesting green developments and clean tech news for us -- it's the Week in Green.

With Thanksgiving in the rearview mirror, it's time to start thinking about holiday decorations. London's Southbank Centre recently gave new meaning to the phrase "green energy" by unveiling a Christmas tree powered entirely by Brussels sprouts. And in Austria, a family claimed their second Guinness World Record by stringing over half a million LED Christmas lights across their property. In other tech news, Recchi Engineering and Carlo Ratti Associati won a competition to design Holland's 17,000-square-foot pavilion for the 2015 World Expo in Milan. The pavilion's green roof will be tended by a pair of self-driving tractors. Manuel Dominguez dreamed up a design for a futuristic mobile metropolis that can actually move to different locations in search of resources. And in Bogotá, a crowdfunding campaign has been launched for what could be Colombia's tallest skyscraper.

Solar power makes a lot of sense as an alternative to kerosene in sub-Saharan Africa, but photovoltaic panels are too expensive for many families to buy outright. To deal with that problem, Azuri Technologies has come up with pay-as-you-go solar kits that provide safer and cheaper solar energy to those who need it most. And in Haiti, Enèji Pwòp recently launched a program that enables Haitian immigrants to send solar lights to loved ones. In other green energy news, the French company Alstom recently completed the world's largest offshore wind turbine off the coast of Belgium, and CellEra has developed a new platinum-free fuel cell that doesn't require rare-earth metals -- it might just be the cleanest engine ever created.

In green transportation news, an incredible all-electric sports bike is set to be unveiled this December at the Clean and Cool Missions in Colorado. The wood-frame Sandwichbike, which can be assembled like a piece of IKEA furniture, is set to begin shipping in December. The bike's beech plywood frame "sandwiches" the wheels, and it's locked in place using hand-milled aluminum cylinders. And Ford just announced that its Interceptor police sedan is the most fuel-efficient law enforcement car sold in the US.

When the world's first 3D-printed gun was produced and tested, it showed how far digital fabrication had come -- but it also raised some serious questions about gun control. Now, Philadelphia has become the first city to ban the production of firearms made by 3D printers. In other green tech and innovation news, the London Science Museum just unveiled the U-CAT, an adorable turtle-shaped robot designed to explore underwater wrecks. Dutch designer Lieske Schreuder recently discovered that snail poo could be formed into a variety of useful materials. Goldee officially launched a $100,000 crowdfunding campaign for the world's smartest light switch. And the modular building company NRB created the Pedia-Pod, a prefab unit that is designed to make kids forget they're in the hospital.