We have compiled recent data from nine full-scale prefermenters in Australia and Canada. Using this data, we compare their design, operation and performance. The design parameters of importance are the prefermenter configuration, the fraction of total flow that is fed to the prefermenter, the prefermenter volume and the hydraulic and solids residence time (HRT and SRT). With respect to prefermenter performance, we use the rate of volatile fatty acid (VFA) production to compare prefermenter efficiency. A number of other performance indicators are also used to compare the output of the prefermenters (for example total mass of VFA produced). All side-stream prefermenters compared in this study have relatively similar rates of VFA production (typically 14 to 28 mg/L/h), which indicates that they all perform with similar efficiencies, regardless of their respective type.