Please note that the fuel values for non-nuclear fuels in v0.17 have been reduced.

Old: https://stable.wiki.factorio.com/Fuel
New: https://wiki.factorio.com/Fuel

It is just really funny to me that 4 MJ of raw wood (2 wood) can be turned into a wood fence that burns for 12 MJ, or 6 pulp that burns for 12 MJ. It wasn't as bad when the 2 wood was worth 8 MJ, but it was still silly, at least in the case of the fence. I enjoy a bit of cheesing in my games, but this is too much cheese.

When coal was still worth 8 MJ, turning charcoal into coal would result in a little bit of energy loss (-8 MJ) with Coal Processing 2, and a little bit of energy gain (+8 MJ) with Coal Processing 3. Now it results in a loss of 40 MJ and then 32 MJ. I doubt that was your intention, right?

Oh and the normal boiler is now 100% efficient, while the Bio boiler is 75% efficient, which isn't a big deal since the Bio Boiler has half the pollution output and there are plenty of power options available anyway (looking at you solar farms :) and charcoal), but you might want to take another look at that, too.

Thanks Dr.INZANE,
I changed some of the fuel values. Please review. Always open to improvements :)

When I heat my ovens, I start by taking out the ashes from the previous day, then I put in a starter log and cover that with wood and, finally, coal. That always made for a warm, cozy room. Now I wonder, however, if I should just reuse the ashes. Coal (in RL) takes quite a bite ouf of my budget each year. Priming the circle with some wood and coal, then burning the resulting ashes over and over again, would actually save me quite some money. :-)

Seriously, is it necessary that ash has a fuel value > 0? It doesn't seem very realistic to burn the remains of a burning process again, so it would be great if you'd consider removing it.

Removed fuel value of ash for the next version.