ALLIANCE, Neb. (AP) — Members of the Nebraska Master Gardener Program anxiously wait as Alliance's Russ Finch cuts an orange. While the excitement for a simple orange seems strange, this orange is different. It is a 3-year-old orange that Finch grew in his own backyard.

Finch was simply a mail carrier and farmer in Alliance, until 45 years ago when he started experimenting with heating houses with geothermal heat. Fifteen years later, he began using the geothermal heat to improve greenhouses.

Geothermal heat produces heat from the ground. A singular heat source dispenses heat into a tubing sys...