Though this resource isn't coffee, Kopi Luwak could be considered the most expensive form of this resource.
Conflict over this economic resource was the defining characteristic of the Chincha Islands War, during which a Spanish fleet seized the islands, ostensibly in place of reparations for the Talambo Incident. This resource is also responsible for the past wealth and current poverty of the island of Nauru, and in 1856 the US Congress passed an act that recognized any American claims to islands containing this resource. Though this resource isn't coffee, Kopi Luwak could be considered the most expensive form of this resource. For 10 points, name this economic resource used more commonly as fertilizer and explosives, the solid waste product of animal digestive systems.
Conflict over this economic resource was the defining characteristic of the Chincha Islands War, during which a Spanish fleet seized the islands, ostensibly in place of reparations for the Talambo Incident.
{feces} (accept equivalents, {especially guano})