Earlier this month I visited Greensburg, Kan., and toured a few of its many green buildings. It was a great trip, and you can see more photos from my visit in this Greensburg photo gallery.

Background. Greensburg is the rural Midwestern town that was struck by an EF5 tornado on May 4, 2007. The storm was 1.7 miles wide — it killed 11 people and destroyed most of the town.

After the storm, the people of Greensburg made a commitment to rebuilding the town as a model green community. That effort is already well underway, and you can even watch its progress on TV. A Greensburg TV series on the Planet Green network is following the progress of rebuilding. The third season begins filming soon.

My visit.  Mother Earth News is based in Topeka, Kan., so Greensburg is relatively close to where we’re located — about a 4 hour drive — but this was my first visit to the town. I took a walking tour guided by volunteers from Greensburg Greentown, a community-based nonprofit devoted to helping Greensburg build green.

So what does Greensburg look like these days? Well, there’s still a lot of evidence of the storm, even more than two years out. As our tour guides explained, Greensburg used to be locally known for its trees, but now most of the trees are gone. You can see from one end of town to the other — the view is wide open. Most of the storm debris is gone, too, but there are still remnants of many buildings — a wall here, some steps there. But already many homes and buildings have been rebuilt, and many more are under construction.

There are nine different buildings on the walking tour of Greensburg (some you can go into, and others are just visible from the street). While there are many green features to see, I was struck by one recurring theme: concrete. Many of the buildings are being built with insulated concrete form walls (ICFs). In fact, ICF construction makes a lot of sense for Greensburg. Not only does it provide excellent insulation, the buildings are also structurally strong, and therefore very resistant to storm damage. From a green standpoint, one of the disadvantages of concrete is that it takes a lot of energy to produce. But in Greensburg, there are always more opportunities to go green — in this case by recycling concrete debris from the storm. The Silo Eco-Home in Greensburg is made of precast concrete, and 35 percent of that concrete is recycled from local storm debris.

Another noticeable fact about Greensburg: There are renewable energy systems everywhere, especially on the new city buildings. The arts center has wind turbines, city hall has building-integrated solar panels, and many buildings have renewable energy systems that are not readily visible from the street, including rooftop solar panels and underground geothermal heating and cooling systems.

If you want to visit.  For anyone who’s interested in renewable energy or green building, Greensburg is a great place to visit. You can simply walk up and down Main Street and see numerous examples of eco-friendly building in action, and even more green buildings are planned for the future. One exciting project is the Chain of EcoHomes being planned by Greensburg Greentown. This project is designed to help visitors understand the green options available to homeowners.

If you’re in the area, don’t miss the chance to stop by and check out what’s happening, and be sure to check in with Greensburg Greentown for more information about tours. You can also download their self-guided tour booklet for much more information about the green features of individual buildings.

If you’re interested in the big picture of what’s happening in renewable energy, you’ll find a lot of interesting stuff at RenewableEnergyWorld.com. Check out their about us page for a quick list of links to more info on green jobs, breaking news and product descriptions.

Some of the information is very technical, but you can find basics too. Take a look at the Renewable Energy Technology Overview for background on solar, wind, geothermal and other renewable technologies. I also enjoy listening to the weekly podcast, Inside Renewable Energy.

Finally, there’s some interesting material from the Renewable Energy World Conference and Expo that took place in Las Vegas earlier this week. You can find video from the event here, or click here to go to the event’s blog.

This week, there’s a nice article from Worldwatch with statistics on exactly how fast renewable energy is growing in the United States. The good news is, it’s growing rapidly — especially electricity from wind and geothermal.

But it made me wonder, exactly how much of our electricity already comes from renewable sources? Well, according to this fact sheet from the Energy Information Administration (EIA), it’s about 8.5 percent, and almost all of that is from hydropower — 6 percent.

Where are we going? One EIA projection says that we could be at 12.6 percent renewable electricity by 2030. Not very inspiring, is it? However, the U.S. Department of Energy also projects that we could produce 20 percent of our electricity from wind by 2030 if we address several challenges, including the need for additional transmission lines.

On the other hand, Al Gore recently challenged the country to set the audacious goal of getting 100 percent of our electricity from renewables within 10 years, so by 2018. It’s easy to see why he compared it to the challenge of putting a man on the moon: That would be a huge leap forward from where we are now. But it might be just the push we need to make the transition to renewable energy.

What about the presidential candidates? On his campaign Web site, Barack Obama specifically calls for 10 percent of our electricity to come from renewable sources by 2012, and 25 percent by 2025. (On his Web site, John McCain doesn’t suggest a specific goal for renewable electricity, but does say he favors support for renewables, including through tax credits.)

What kind of goals for renewable energy do you think the United States should aim for? Share your comments below.