Current literature involving meta heuristic approaches towards the scheduling of multipurpose batch plants has been limited to objectives which maximise profit. An important part of scheduling, however, involves the ability to find the makespan minimisation of potential product demands - a problem known to be substantially more difficult than profit maximisation. This work adapts a recently introduced general metaheuristic framework by Woolway and Majozi (2019) [1] to solve the makespan minimisation problem for multipurpose batch plants. The modified framework and corresponding genetic algorithm are applied to two well-known literature examples, with results showing that not only is this metaheuristic approach able to solve the makespan problem often: but it is able to do so at substantially reduced computational times.