Carbon emission trading is supposed to use market mechanisms to make carbon-intense processes less attractive. Unfortunately, the EU market is flooded with emission certificates, such that the mechanism does not work.
Obviously, it would be most ecologic to leave the coal where it is. But since this does not happen, instead of buying emission certificates, it may be more effective to buy and store/sink coal to cut emissions and drive up the price.
My question is, what good ways are there store/sink coal? Just sinking large quantities of coal in the oceans is probably be a bad idea, and can have disastrous side effects. So what is known in this direction?