Renewable energy from coffee-bean wastewater

Matagalpa, Nicaragua

THAT cup of coffee gives many of us a needed boost, but Central American coffee farmers have found a new source of energy in their beans: turning agricultural wastewater into biogas.

An often-overlooked byproduct of the world's favourite stimulant, the water used to process raw coffee beans is usually dumped back into the environment untreated.

In Central America, locals call it "honey water" because of its sweet taste and yellowish colour.

Extremely polluting, it is high in methane gas - a leading contributor to global warming produced, in this case, …