If you want to smelt or cook anything in Minecraft, you need a furnace and some fuel. The fuel that you can use range from simple wooden blocks, to coal, lava buckets or even blaze rods. The thing is, not all blocks are equally useful. In fact, some will burn longer than the other, while some are simply too difficult to get. In this guide, you will get the explanation which fuels are the most efficient in terms of time.
Lava bucket efficiency
Apparently, a bucket of lava needs a lava source block and a bucket, which is made out of 3 iron ingots. While it may not be the problem when you are deep underground with a big supply of iron, the fact that you lose the bucket and thus 3 iron ingots is already enough to lower the efficiency. In fact, it takes too long to find the lava and the iron to make the lava bucket an efficient fuel, but if you have one laying around, its 1000 seconds burning time is quite descend. However, please take a note that you are able to only put 1 stack of items in the furnace at a time, so you cannot even use the 1000 second burning time without having to come back at least once.
Coal vs charcoal
It might look weird that the coal is less efficient compared to charcoal, but it has to do with the time it takes to acquire the same amount of every item. In general, trees are way more widely available and renewable, while coal requires more effort and a bit fo luck to find in large quantities. The thing makes charcoal generally a much more efficient fuel compared to coal, as long as you keep replanting saplings.
Charcoal vs wooden planks
Based on burning time and farming time, charcoal is less efficient compared to wooden planks. Despite burning for 80 seconds, it is made by first burning a log for 10 seconds. The same log could be turned into 4 planks, which will burn for a total of 60 seconds, meaning 4 planks could smelt 6 items, as it takes 10 seconds to smelt 1 item. A lump of charcoal lasts 80 seconds, which smelts 8 items, but you need to add the 10 seconds it takes to burn a log to make the charcoal meaning that 1 item takes 11.25 seconds to be cooked if you use charcoal, while wooden planks will only take 10 seconds per item.
Wooden slabs, the best or the most efficient fuel
The most efficient or the best fuel for furnace is wooden slabs. With this one, you are able to make a lot of them out or just a few logs. For instance, 3 logs make 12 planks, which in turn create 24 wooden slabs, which all burn for 15 seconds. It means, just 3 logs give you 360 second of burning time, or little over 1/3 of the burning time of a lava bucket.