More American homes could be powered by the Earth's natural underground heat with a new, nontoxic, and potentially recyclable liquid that is expected to use half as much water as other fluids used to tap into otherwise unreachable geothermal hot spots. The fluid might be a boon to a new approach to geothermal power called enhanced geothermal systems. These systems pump fluids underground, a step that's called "reservoir stimulation," to enable power production where conventional geothermal doesn't work.

The new fluid expands when exposed to carbon dioxide underground, which creates tiny, deep cracks in otherwise impermeable rock.

The new fluid, developed at the Department of Energy’s Pacific Northwest National Laboratory, features an environmentally friendly polymer that greatly expands the fluid's volume, which creates tiny cracks in deep underground rocks to improve power production. This fluid could also substantially reduce the water footprint and cost of enhanced geothermal systems. The fluid is a solution of water and 1 percent polyallylamine, a chemical similar to polymers used in medicine.