It turned out our fuel production system didn't work properly (Thanks Casper for the info about it) and we decided to fix it and rework a bit.
Now it produces 1 fuel per minute in real time for your convenience. You can speed up with 2 coals x2 for a minute or with 50 diamonds x5 for a week.
We hope the new system will greatly help you on your journey to islands!
P.S. Don't forget to update ZIC: Survival to check the new fuel production system
P.P.S. Don't afraid to communicate with us here. We're checking it every day!