In the Changes for 6.00 thread (which used to be Changes for 5.70), Steve posted:
"Civilian Fuel Harvesters
Civilian Shipping Lines will build fuel harvesters in v5.70. These harvesters will (slowly) make their way to gas giants with Sorium and start harvesting. Unlike other civilian shipping, these fuel harvesters will appear as potential destinations when you select Task Groups on the F12 orders window, so you can order your fleets to refuel from them. Refuelling from civilian harvesters costs 1 wealth for each 10,000 litres of fuel.
Once a civilian fuel harvester is full, any excess fuel is sold to the private sector. This also generates tax revenue equal to 20% of the fuel price."
Personally, I confiscate fuel harvesters using my tugs to keep them from pillaging my strategic fuel reserves, but I've been considering allowing them to do their work and just setting a small tanker to cycle orders to refuel from them and dump the fuel on a nearby moon.