Photo by One Million Lights.

For kids in developing countries, it's crucial to have a reliable light source -- otherwise you can't see to read or do your homework. But many homes and villages don't have electric light, and the cheapest alternative -- kerosene -- is an environmental nightmare on both large and small scales. It pollutes the environment at large, but it also pollutes your home and potentially lights it on fire in the bargain.

The nonprofit One Million Lights is trying to change that one light at a time.

In the battle between food and fuel, cellulosic ethanol might not be a great idea or even a viable solution to our energy woes, but enzyme company Novozymes says it's coming, regardless. (Cellulosic ethanol is different than the regular kind -- it's produced from "leftover" crop waste that is first digested by enzymes.)

Solar probably won’t really take off until it makes more economic sense to slap some photovoltaics on your roof than to continue paying your utility company for their dirty, probably mostly coal-fired power. That day has arrived in parts of sunny California and Hawaii, and it's coming to (not-so-sunny) Germany by 2013, reports Michael Coren at Fast Company.

Germany just signed agreements with Kazakhstan and Mongolia to mine rare earths in those countries, in an effort to break China's monopoly over these 17 elements, which are essential to clean technology like solar panels and electric vehicles.

Sales of solar panels for Japanese homes are up 30.7 percent in 2011, despite -- or, let's be real, because of -- the economic hit the country took in the wake of the Fukushima disaster.

Swedish company Plantagon International is taking the urban greenhouse to the next level, and then the 17 levels beyond that. Their new vertical greenhouse in Linköping, Sweden will be 177 feet high.

If you're not already connected to an electricity grid, renewable energy is a no-brainer, argues Michigan professor of history and "scholar of the Muslim world" Juan Cole. For the one-third of the world's population that lives on less than a dollar a day, fossil fuels aren’t just environmentally unsustainable -- they’re financially unsustainable too.

Commercial satellites, private space flight, and just about everything else that travels outside the atmosphere uses hydrazine as a propellant. It's super toxic and dangerously unstable, so NASA is going to spend up to $50 million apiece to test alternatives.

Photo by Trey Campbell.

Everything single part of a building, from the windows the the air conditioning and heating system, has become significantly more energy efficient over the past 20 years. And yet buildings, as a whole, are using more or less the same amount of energy they always have. What gives?

An MIT scientist has developed a quick and dirty way to harness solar power using "anything green, even grass clippings." So basically, solar panels made out of yard waste.

This technology is way, way, way, way below the efficiency of commercial solar panels: It converts 0.1 percent of solar energy into power. Commercial solar panels clock in around 10 to 15 percent; the most advanced lab models are pushing even higher.

But the simplicity of the design makes up for that shortcoming.