The government of the southern Brazilian state of Paraná has been conducting an interesting experiment in environmental design utilizing waste materials. Since August 2006 state agencies have sponsored projects to construct solar water heaters constructed from used PET bottles and “long life” (aseptic) milk packaging. So far some 3,000 such heaters have been constructed and put into operation in 254 Paraná municipalities, in the process diverting about 1.2 million PET bottles and aseptic milk cartons that otherwise might have gone into landfills. It takes 200 PET bottles and 200 aseptic milk cartons to construct the solar water heater array. putting the PET bottles together (click to enlarge) (photo: AEN)It’s estimated that if the heater is used to heat the water for two bathrooms, it can save as much as 120 kilowatts per month.