Russ Finch is the ultimate grandaddy of Farm Hack . He designed a greenhouse in his backyard that is heated using geothermal energy. Despite the fact that winter temperatures in Nebraska can drop to -20°F, the retired mailman grows oranges, lemons, grapes, pomegranates and more without paying for heat. The setup he uses draws on the earth's stable temperature which is around 52 degrees in Nebraska to grow exotic fruit in the snow.
Finch first discovered the joys of geothermal heating while building his first house with his wife in 1979. Years later they decided to add a huge greenhouse in the backyard. The greenhouse is designed so that all components work together - the the foundation is 4ft deep and the roof is angled to catch the southern sun. The only energy input in the greenhouse is the fan used to pump the naturally warmed air around evenly.
Finch reckons that anybody can build a geothermal market producing greenhouse for about $25,000. Once the system is set up, it starts to pay for itself immediately due to the huge decrease in energy inputs. He sells a "Citrus in the Snow" report detailing his work with his "geo-air" greenhouses.