Robusta is a sturdy species of coffee bean with low acidity and high bitterness; it is used primarily in instant coffee, espresso, and as a filler in ground coffee blends. The bean comes from the Coffea robusta variety of the Coffea canephora plant (widely known itself by the synonym Coffea robusta) which has its origins in central and western sub-Saharan Africa. Robusta is one of the two main beans used for coffee – the other is Coffea arabica; robusta is easier to care for and has a greater crop yield than arabica, so is cheaper to produce. Roasted robusta beans produce a strong, full-bodied coffee with a distinctive earthy flavour, but usually with more bitterness than arabica due to its pyrazine content.