The Denver Zoo has to deal with a lot of waste. A good deal of that waste comes from visitors, but the zoo also produces hundreds of thousands of pounds of animal poo each year. Now, zoo engineers have found a positive use for it: They rigged up a poo-powered tuk-tuk. (A tuk-tuk is a motorized rickshaw.)

"We want to show people that we're not crazy for wanting to take elephant poop and turn it into energy," one engineer told the Denver Post.

Germany is involved in a wildly ambitious overhaul of its power system. Its official targets are to hit 35 percent renewable power by 2020 and 80 percent by 2050. The Green Party advocates for 100 percent by 2030.

The most controversial aspect of this power overhaul is Germany's post-Fukushima decision to completely phase out nuclear power by 2020, which caused the heads of Very Serious People to explode on multiple continents. To many, passing ambitious low-carbon energy goals and then axing a good chunk of your low-carbon energy seems irrational and self-defeating.

There are good-faith debates to be had about the speed of the phaseout and its proximate effects. It will probably lead to a temporary increase in carbon pollution. The hope is that it will accelerate the transition to renewables.

Putting those questions aside, though, I want to focus on one of the deeper debates about Germany's nuclear gambit. Nuclear power's proponents frequently point out that it is one of the only low-carbon sources that can serve as "baseload" (always on) power. Baseload power is needed, they say, because renewable sources like solar are intermittent (the sun isn't always shining) and non-dispatchable (the sun can't be turned on and off at will). You need large, steady, predictable power plants if you're going to have all those flighty renewables involved.

Believe it or not, Germans have heard this argument before. They just think it's wrong. They don't think renewables and baseload are complimentary; they think they're incompatible. In 2010, Federal Minister of the Environment Norbert Röttgen said:

It is economically nonsensical to pursue two strategies at the same time, for both a centralized and a decentralized energy supply system, since both strategies would involve enormous investment requirements. I am convinced that the investment in renewable energies is the economically more promising project. But we will have to make up our minds. We can’t go down both paths at the same time.

I find that non-energy nerds have a little trouble wrapping their heads around this, so let's walk through it with the help of this report by the German Renewable Energies Agency.

In the spectrum of alternative fuel sources, biofuel made from algae is perhaps the most easily mocked. How could the slimy green muck that grows in your aquarium and washes up on the beach be a future cornerstone of American energy independence? So when President Obama stood before the University of Miami recently and said algae could provide up to 17 percent of our transportation fuel, we wanted to know: Is he right? Here's what we found out:

Cross-posted from Climate Progress.

After months of speculation and debate about unfair Chinese subsidies to domestic solar manufacturers, the U.S. solar industry finally has an answer to one piece of the ongoing trade case: Solar panels imported from China will be hit with a small tariff.

The Department of Commerce issued a preliminary decision today based upon the agency’s impartial review of Chinese subsidies to domestic solar companies.

The tariffs range from 2.9 percent to 4.73 percent -- dramatically lower than the 20 percent expected by many industry analysts. But this decision from Commerce is just the first of two key tariff rulings. While today's ruling addressed the issue of subsidies, a separate decision on whether Chinese companies are dumping panels into the U.S. market below cost is expected in May.

Now you can dump energy waste just by, well, taking a massive dump. Green tech company OriginOil is working on a project that uses toilet wastewater as a way to heat apartment buildings.

OriginOil, a start-up based in Los Angeles, CA., has begun a pilot of its urban algae farm concept at the La Défense complex near Paris. Wastewater from buildings nourishes algae growth; algae is processed to make heat. The company is attempting to prove that integrating algae production into large building complexes will help bring them closer to net zero.

Photo by Nick Knupffer.

The Obama administration has learned from history, it seems. They're not going to sit passively by as their opponents demagogue gas prices. This week they've gone on the offensive, with the president giving a series of interviews and speeches, including a major address today at Prince George's Community College in Largo, Md.

Most of the details from today's speech were familiar from previous speeches. Obama argued that his administration has substantially increased oil and gas drilling, but that drilling will never be enough to reduce gas prices or make America independent of imported energy. Thus, America needs to invent and build new technologies to produce clean energy and use less energy.

That's all been said before (though obviously nothing's wrong with repeating it). There was, however, a new theme in the speech, tying all these points together. I don't know if it's entirely new, but I've never heard it emphasized as much. And since it's a theme I've been pushing for years (clearly Obama is reading my blog), I was quite gratified to see it.

It's simply this: the past vs. the future. In his prepared remarks, he said a state of constant vulnerability to events overseas is ...

Now you can feel good after knocking back a few brewskis -- and not just because you’re tipsy. Beermaker Anheuser-Busch has found a way to turn its waste grain into an array of products, from clothes to cosmetics to biogas.

The beer behemoth has partnered with a company called Blue Marble Bio, which plans to set up large-scale biorefineries at Anheuser-Busch breweries that will use naturally occurring bacteria to break down spent grains using proprietary “polyculture fermentation technology.” That process will create both biogas, which can be used to generate electricity, and chemical compounds called carboxylic acids that are used to make everything from nylon to soap to food additives to floor polish.

Melbourne’s Greenhouse restaurant wants your patronage. But more importantly, it wants your pee.

That’s right -- this pop-up restaurant, which is open from March 2 through the 21st in honor of the Melbourne Food and Wine Festival, wants you to get all up in its custom-made toilets. The green eatery is collecting human urine and using it to fertilize soybean and canola crops. The restaurant, which is designed by Joost Bakker who is clearly a maniac, then uses unrefined canola oil to generate electricity for all of its operations.

Urine may seem an unorthodox energy source, but it is actually a great source of fertilizer when diluted. According to Bakker, “Urine is incredible for nitrogen, it’s so valuable -- you only need the urine of 25 people to provide fertilizer for a hectare of crop.”

Get a load of this:

Nearly 100 million Americans could install over 60,000 megawatts of solar at less than grid prices – without subsidies – by 2021.

That's from a new report by John Farrell at the Institute for Local Self-Reliance called "Rooftop Revolution: Changing Everything with Cost-Effective Local Solar."

It's about the spread of "solar grid parity" over the next 10 years, where grid parity is defined as "when the cost of solar electricity -- without subsidies -- is equal to or lower than the residential retail electricity rate." People often talk about grid parity as if it's some magic moment, but in fact it will happen in different places at different times, depending on local conditions and electricity prices. And it's a moving target: It depends on how fast the cost of solar falls and how fast electricity rates rise.

Photo by Dan Correia.

Cross-posted from ThinkProgress Green.

Rush Limbaugh continued his bizarre attacks on clean energy innovation Monday, claiming that the solar and wind energy sectors don't exist. Limbaugh was responding to a ThinkProgress Green post that noted his role in scaring American customers against the Chevy Volt. He has even claimed that GM is "trying to kill its customers." Attempting to justify his denigration of the extended-range electric vehicle, Limbaugh said that "all of Obama’s green energy" is a mirage (listen here):