What is a batch roaster?

A batch roaster is any roasting machine that roasts a fixed quantity of coffee at one time - with a defined start point (loading the green coffee) and end point (dropping the roasted beans). The vast majority of coffee roasters used in specialty coffee, from home machines like the Aillio Bullet to large commercial drum roasters, are batch roasters.

This distinguishes them from continuous roasters - large industrial machines used in commodity coffee production that feed green coffee in at one end and roast it continuously as it moves through the machine. Continuous roasters prioritise throughput over precision; batch roasters prioritise control over flavour development.

Within the batch roaster category, the drum roaster is the most common type in specialty use. The green beans are loaded into a rotating drum heated by gas or electric elements, tumbled for a defined time, and discharged at the roaster's judgement. Each batch is a self-contained roasting event with its own profile, milestones, and result - which is why batch roasting lends itself to data logging, profile comparison, and iterative improvement in a way that continuous roasting doesn't.