A biorefinery is a combination of discrete operations (e.g. feedstock shipments, fermentation, maintenance) and continuous operations (e.g. distillation, drying). Discrete operations are often stochastic in nature as are equipment failures. An accurate representation of a biorefinery requires consideration discrete operations, the interface between discrete and continuous operations, and equipment failures. Discrete event modeling is a method of simulating a real-life process consisting of discrete operations and events such as equipment failures. Discrete event models are useful for determining storage requirements given supply chain interruptions and equipment failures, the need for spare equipment, evaluating operating personnel requirements, and other information needed to evaluate capital and operating costs.