Cities can be hot-spots of pollution, with thousands or millions of people, cars, pets, industries, and more contributing to global warming. But they can also be centers of innovation, as bright ideas, available funding, and green sensibilities combine.
These seven cities are doing their part to cut down on greenhouse gases -- from running town centers on geothermal heat to running a solar-powered farmers market -- and they just might be the inspiration for your city's next big green change.
1. Eco-City in Hamburg, Germany
The three-phase Eco-City in Hamburg, Germany, is scheduled for completion next year -- and when it's finished, the state-of-the-art mixed use area will incorporate everything from business offices and hotels to wind turbines and pedestrian walkways.
The complex is on track to receive the highest possible rating from three sustainability rating organizations -- LEED, BREEAM, and the Germany-based GSBC -- and nearly half of the area will be building-free, open-air plazas.
High-rise towers outfitted with wind turbines could potentially bring in as much as 10 percent of the city's power needs, and the builders have also used solar water heating systems, reused materials, roofs that minimize storm water runoff, and passive design techniques that cut energy use by as much as 30 percent.
2. Geothermal Energy in Newcastle, England
The quaintly-named Newcastle-Upon-Tyne took highest honors in a 2009 sustainability audit, which named it the greenest city in Britain -- and the town just announced plans to cement its spot at the top by implementing a geothermal heating project that will provide heat to its main shopping center.
The plan is to drill 2000 meters underground, where the city can tap into a collection of groundwater kept at 176 degrees Fahrenheit by the Earth's heat -- and by circulating this hot water, they can keep the new 24-acre Science Centre and the 140-shop strong Eldon Square mall at a comfortable temperature without using fossil fuels. Estimated cost: 900,000 pounds.
3. Stormwater Capture in New York, New York
In 2010, the New York City Department of Environmental Protection awarded more than $2.6 million to organizations with plans for capturing stormwater runoff as part of the Flushing and Gowanus Green Infrastructure Grant Initiative.
The idea behind the grant is to fund plans that would "reduce combined sewer overflows, which occur when stormwater and wastewater is diverted into New York City's surrounding waterways during heavy storms" -- and to improve the overall quality of the city's harbor.
A few of the winning ideas: a Greenstreets capture system in Rego Park that would catch water from a "three acre-watershed"; bioretention basins that would store more than 200,000 gallons of water under the Long Island Expressway; and 5,000-square-foot treatment wetlands that could address 72,000 gallons of runoff in Flushing Meadows Corona Park after every storm.
4. Solar-Powered Farmers Market in Albuquerque, New Mexico
Becoming a regular fixture at your local farmers market can do a lot for your green eating habits -- by teaching you to rely on and enjoy seasonal produce, encouraging you to pack your diet with more vegetables and fruit instead of processed food, and putting you in touch with the farmers in your area -- but for residents of Albuquerque, New Mexico, the market goes beyond fresh produce.
Cash machines, the sound equipment, and other electricity-based devices were powered by a four-panel solar array that brought in about 1,000 watts; the city hopes to make the solar-powered market a regular occurrence and spread the how-to to cities all over the country.
5. World's Largest Wind Farm in Shepherds Flat, Oregon
Eastern Oregon will soon be home to a wind farm said to be the world's largest -- the result of a $1.3 billion loan that the U.S. Department of Energy approved in December.
The farm will comprise 338 GE wind turbines -- scheduled to be installed in 2011 and 2012 -- and will provide 845 megawatts of power on a piece of land 30 miles square.
The planned output would be enough "clean energy to power approximately 235,000 average California households...and will avoid more than 1.5 million tons a year in greenhouse gas emissions," according to the EPA.
6. Public Housing in Sydney, Australia
Government housing developments around the world can provide an affordable home for citizens -- but sustainability is rarely a priority. Not so in Sydney, where the Lilyfield Housing Redevelopment project received a 5 -- the highest rating -- from Australian LEED-like company Green Star.
A few of the eco-friendly design touches: Passive solar and natural ventilation mean the building doesn't need air conditioning; the development offers no parking for cars but does have space for residents' bicycles; water tanks capture more than 100,000 liters of rain to water gardens and fill toilets; and the building -- which now comprises 88 apartments instead of 40 -- has been outfitted with solar photovoltaic and solar thermal panels. Keep watching to see if these innovations inspire other cities to do the same.
7. Solar-Collecting Bicycle Paths in the Netherlands
In the Netherlands, where bicycling is common, several companies are joining forces for a pilot installation of bike paths that could collect solar energy to go back into the grid.
The idea is simple: A "modular cycle path system," set to be up and running in 2012, would consist of concrete panels topped with glass; between the glass and the concrete, silicon solar cells would capture energy -- as much as 50 kWh every year per square meter. (That may not sound like much, but the paths could eventually cover 137,000 kilometers of pathway.)
And while the cells are powering public utilities, like street lamps and traffic lights, the paths will also encourage commuters to trade four wheels for two.