To combat rising oil and fuel prices, a new energy project in Oslo, Norway, taps the heat from raw sewage to warm homes and offices, according to a Reuters report. Large machines at the end of 300-meter long tunnels use fridge technology to pull heat from the sewers and transfer it to a network of hot water pipes feeding thousands of radiators and taps around the city. The heat pump costs $13.95 million and has an effect of 18 megawatts, enough to heat 9,000 apartments or save burning 5,900 tons of oil a year.

A larger heat pump in Sweden has a 160-megawatt capacity, and a 90-megawatt plant recently ran on wastewater in Finland.