http://www.dim.esdm.go.id/makalah/sunic ... i_NEDO.pdf
This link is broken, either the page no longer exists or there is some other issue like a typo.
Some clean coal research going on in Japan. The Ashless Coal (Hyper-Coal, HPC) caught my interest. Up to 70% yield from Bituminous coal with less than 200ppm ash content. That's 0.02%!!! Burn a ton and make less than 1/2lb ash.
They actually built a "benchscale unit" that does 0.1Tons/day and tested various Bituminous coal types. There's production ramp/scaling that show 5000Tons/day production. This is targeted for industrial use but I see no reason why it couldn't be made for consumer/home use. Imagine a coal stove, boiler or furnace without an ashpan? How long before the treehuggers kill this one?