How about diluted PVA wood adhesive?

http://www.screwfix.com/p/no-nonsense-waterproof-pva-d3-5ltr/63895 (usual disclaimer).

Banu....

I was involved for sometime in the attempted briquetting of waste coal dust in the USA. The was part of a US synfuels program about ten years ago. We attempted to make sturdy briquettes that would survive transport.

For various complex reasons, it is very difficult to consistently briquette coal dust.

Effective and cheap are difficult standards to meet regarding coal dust.

We had some limited success with guar gum and various lignins.

In India ram extruder technology is in large scale use for economically converting the enormous agricultural biomass waste in to valuable clean fuel briquette .

http://www.ajol.info/index.php/ejesc/article/viewFile/56314/44754 is an excellent guide may provide the clues to your query.

Google search "ram extruder agro waste briquette machine".

Please refer to http://en.wikipedia.org/wiki/Briquette which says that there are no binders involved in the process of Briquette manufacture using saw dust along with carbon dust. The natural lignin in the wood binds the particles of wood together to form a solid.

Try gum Arabic

In Germany pellet makers (for pellet ovens/burners) use flour (probably not food grade anymore) with a tiny amount of water to bind the pellets, which are made from sawdust and similar....between 3 and 5% by weight of flour if I remember correctly.....

Now I know there are significant differences between coal dust and sawdust, but who knows? Cheap and easy to try out.....

I believe the USA uses petroleum products to bind pellets, but we here see that as a negaive method due to it coming mostly from fossil fuels.....

Our pellets only disintegrate if they come into contact with water......they travel well.....

Best of luck.

use molasses or lignosulfonates , find your best percentages to be added ..

Perhaps a tiny amount in percentage of biomass obtained as waste produce from a fruit juicing industry near to you could be added as an experiment?

Stu.

Im not sure if this would work for coal dust, here in New Mexico when making adobe bricks we add a little bit of cement to the mix to make the bricks more durable and then have a lot less breakage when working with them. Just a thought.

Euphorbia latex is one possibility:

http://www.scienceandsociety-dst.org/pyrolysis1.htm

tamarind kernel powder is another:

http://www.tnau.ac.in/aecricbe/aetc/proc5-3.htm