If you are looking an extremely clean burning fuel that lasts a long time and produces very little ash residue, then smokeless coal would be ideal. Approved for use in smoke control areas it still generates a lot of heat but with far less smoke and C02 emitted. In fact, it outperforms traditional house coal in just about every way and with our significant bulk discount the cost difference is negligible. If you take into how efficient smokeless coal is, it actually works out cheaper as you can generate the same amount of heat with less volume of coal. That also means that you need less space to store it and there is much less soot to clean up.