Hugelkultur is a type of gardening with raised beds where wood is buried under the soil in the bed. As the wood decomposes it supplies heat and nutrients to the crops in the bed and retains water for the use by those crops. The initial set up of the be looks to be fairly labor intensive but those pushing this method claim that is sustainable in that it is labor and resource saving in the long run. The "long run" being the potential 20+ year life of the garden bed. It is supposed to require less or no additional watering or fertilization.
There are also some other interesting sustainable gardening and living videos at the site. The rocket stove/heated mass bench (video) looks like there could be some risk of carbon dioxide poisoning if all the mechanical connections are not completely and correctly sealed. So please use common sense and if you do not know if something is safe to do or use ask a licensed professional who knows the answer.