Wood briquettes.
These need to be stored dry. If you get them damp they turn into porrridge.
Brilliant for burning and often very cheap depending on the season. I found some of these which were waste from a window frame production company and they only wanted 50p for 20kg. In the middle of the summer. Better than landfilling the sawdust.
A lot of wood product companies have bought the briquetting machines. I imagine there was some fairly well thought out marketing but I'm unsure as to whether it proved economically sensible. When I bought some of these they were offering to cart a van load to the Boat for a good price. Trouble is they turn into porridge (inedible but exactly the same consistency) at any hint of moisture. They really do. Would be great dehumidifiers or bilge soaker uppers.
Just a random example. There will be others.