The effect of two dairy manure treatments, solid–liquid separation (SLS) and anaerobic digestion (AD), on methane potential and the speed of production was evaluated. Assays were performed in the lab to measure methane (CH₄) production over 202 d from dairy manure samples taken before and after each treatment. Compared to raw manure, CH₄ emissions on a per-L basis were reduced 81% by SLS and 59% by AD, on average. The mean (SD) ultimate CH₄ emission potential (B₀) per kg of volatile solids (VS) was 247 (8) L CH₄ kg⁻¹ VS for raw manure, 221 (9) L CH₄ kg⁻¹ VS for separated liquid, and 160 (4) L CH₄ kg⁻¹ VS for anaerobic digestate. Thus, SLS reduced the B₀ of the liquid fraction by 11% and AD reduced B₀ by up to 35% compared to raw manure. Manure treatment affected the speed of CH₄ production: SLS increased the CH₄ production rate and thus separated liquid manure was the fastest to produce 90% of the ultimate CH₄ production. Therefore, both the speed of degradation and B₀ should be considered when assessing these techniques for farm-scale manure storages, because actual emission reductions will depend on storage conditions.