Coffee pulp, what is left after processing of harvested coffee, tremendously speeds up the recovery of tropical forests on what was deforested land. A study, in Costa Rica, by the British Ecological Society, found that a 1.6 foot layer of coffee pulp prevented growth of pasture grasses but allowed native tree species to re-seed themselves and grow dramatically.
After two years the pulp-treated land had an 80% canopy cover vs 20% in a control area that had no coffee pulp. The treated area also had higher levels of nutrients such as carbon, nitrogen and phosphorous.
For more details read the study in Ecological Solutions and Evidence.