I suggest a fluid/solid canner in fluid enrich mode, using soul sand, water, and maybe redstone to produce some fraction of a bucket of liquid oil, as well as a block of sand. Oil can then be processed in the fluid/solid canner with redstone to make fuel.
Alternatively, the above process could use biogas instead of water for initial enrichment, making the process essentially an upgrade to biogas at the cost of a mostly non-renewable resource.
Coal fuel could also be added back as a conversion of coal dust to oil in the same way as above.
