Hot air ballooning used to have an image of strawberries and champagne in the wicker basket, whilst watching the (switch on Noel Coward accent) terribly, terribly English countryside drift by. In just the same way that snowboarding attracts a somewhat different crowd to the "skiing in Klosters" types, so too does one-man hot air ballooning, or "cloudhopping" (click for website).
Once upon a time I got a Private Pilots Licence(group D) for Microlights. I was somewhat surprised to see that it also licenced me to fly hot air balloons, although I didn't ever fly one because no-one ever got me a "round tuit".
I think it will be harder to get people to vote for a sustainable society if there’s no fun in it! Although these things use fossil fuel (propane gas cylinders) to fly and the canopy is made from oil derived polyurethane coated rip stop fabric (near enough the same as paragliders are made of today, and hang gliders used to be made of 35 years ago, when I started flying) I still think there will be a future for "toys" like these "leap a building in a single bound" cloudhoppers.
Don't quote me but I imagine that cylinders of methane gas could substitute for the propane - methane can be generated in one's backyard by anaerobic decomposition of organic waste.
Jersey has been generating methane industrially from sewage waste for many years (and using the gas to generate electricity which partially runs the waste treatment plant). There are smaller domestic size systems which can generate your own gas from food waste, like this one from India.
Here’s a link to a good website on anaerobic digestion.
The balloon seat, harness and supporting structure are mostly made of stainless steel so few problems there, but what about the balloon fabric, I hear you cry. Well, how about this company that recycles, or repurposes, this type of fabric and turns it into neat, lightweight backpacks, gym bags, laptop covers and wallets, among other things. Click for Baumm's website.
Treehugger.com did an article about them (click link here)