Wind turbines on vast ranches and fields of corn, soy and wheat have transformed US farmers into energy producers. Eight large turbines in one Iowa community produce 12.8 megawatts, enough to power 6,000 Iowa homes, and “generate healthy annual returns of up to 16 percent on the $12,000 to $50,000 individual investments from 180 local farmers,” reports Edward Humes for Sierra. “At four cents a...