Process designs were conducted for each unit of the conceptual ammonia fiber explosion (AFEX) process, and fixed capital investment and operating costs were estimated. APEX costs about $20-40/t of dry biomass treated. Several promising areas for reducing process costs exist. Return on investment (ROI) calculations were also done for AFEX-treated materials (as digestibility-enhanced animal feeds), in conjunction with sensitivity analyses on the overall processing costs. Estimated ROIs range from over 100%/y to negative, depending on the system variables. The most important variables are the cost of corn and corn fiber, ammonia loading, and whether or not drying is required.