Depending on how complicated you want to make it you can build a pyrolysis plant this produces various forms of fuel and can be run of a solar panel. The feedstock to this plant is plastics waste be careful of the plastics though as certain plastics produce chlorine gas.

I.t.o farming I highly suggest into looking at aeroponics and aquaponics. Both have disadvantages and advantages. You can construct systems using off the shelf materials. Stay away from turn key solutions. Aeroponics is really interesting and we’ve been playing around with it for a number of years.