see a briquette as a piece of coal... the briquettes i made where only compacted by pressure , no additives to hold them together.
Applying a given amount of heat to a given amount of surface to a given kind of combustible results in a transformation from a solid state into a gaseous state.
I could try to go into it deeper, but it is obvious that as long you choose the right circumstances any combustible can be used as fuel.
The size of the briquette, the degree of compaction and the sort of combustible used will define how much energy you can set free in a given time.
look at a wood-pellet... the density is higher then wood, but the ratio surface-density-combustible makes it a perfect fuel.
Try anthracite as fuel for a gasifier... same principal ... works fine if you use the correct sizing
Or the charcoal in our gasifiers... size, moister density...
anyhow, a briquette or pellet from the right sizing with the correct proporties (even charcoal dust or small particles) will be a good fuel for a gasifier.