My solution. Repuposed bulk bin - 9 ft dia - least surface area, can be moved, can be buried, no maintenance for ever pretty much if coated correctly (rubberized asphaltic basement water proofing) and a very long time of not coated. Field formed SIP made with pourable dock insulation - super high performance. Maybe not green per se but certainly not resources frittered away in a Hummer cruising the mall. Fast, strong, high performance and recyclable. I made my own insulation pump for under $100. When everything is factored in this is a very viable environmentally sound option.