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The Audubon Center of the North Woods, on Grindstone Lake near Sandstone, Minnesota, is a non-profit residential environmental learning center, wildlife rehabilitation facility, and conference/retreat facility.
Located about 5 miles (8.0 km) west of Sandstone, the Audubon Center provides environmental education about the various renewable energy systems that it uses, including geothermal heating and cooling (ground source heat pumps), wind generators, biodiesel-powered vehicles which run on used vegetable oil, and grid-connected solar arrays. The 535-acre (2.17 km2) sanctuary includes over 7 miles (11 km) of hiking and cross-country ski trails through a variety of habitats, such as old-growth red and white pines, hardwood forests, restored wetlands and prairies.