The geothermal option is now being implemented widely over here in The Netherlands. Almost any application for a building permit for new offices is accompanied by an application for a permit to pump up and pump back water out of and into the ground. Even the larger private houses start to use it. It's definetely paying off and I can remember my uncle in Austria using the technology for his floor heating almost twenty(!) years ago.

The menure option definetely needs a closed environment like a tank or a container. Or you'd have to grow A LOT of lavender around it to compensate for the rich.....perfume...:)