In creative I can build a railcraft boiler and stuff methane cells into it and it will heat up. It uses the cells *very* fast on startup though. A 3x3x3 high pressure ran through four stacks before hitting 100degC. I'll have to try the transposer to save the empty cells though.
You can make methane with 4 hydrogen and 1 carbon cell equaling 4 methane cells. This loses one cell. Carbon cells are side effects of rubber tree wood centrifuging, or electrolyzing coal, ash, sugar, or charcoal, but hydrogen is only from water or bauxite in an electrolyzer
Is NEI not showing these recipes for you?
Yup yup, though some notes:
Electric crafting tables detect when a cell is used in a recipe but not in the output, and places the deficiency in an internal buffer, accessed from the sides when auto-magically accessing it, or from the bottom of the interface manually. (In other words, it lets you keep cells from recipes)
Also, although rubber wood does provide methane directly, it DOES NOT PROVIDE MORE!! then normal wood.
normal wood gives you 1 carbon cell per block, good for 4 cells, while rubber wood requires 16 blocks to give you... Less. I don't remember how much, exactly, but it's pretty simple to determine that 16 carbon cells from normal wood will give you more then what 16 rubber wood gives you.
Also, rubber woods drop less saplings, which can be macerated into dirt, the clay balls crafted into blocks and macerated, and then the dust centrifuge to give, among other things, aluminium. Costs a LOT of dirt, though, and if you get some decent mycelium production going it can provide a lot more clay. (You can't make mycelium out of saplings automatically, though, unless you can find a way to silk touch blocks)