The biomethanation process is a promising eco-friendly solution for the treatment of organic biomass that can further lead to efficient bioenergy production. Thus, the analysis of operational reliability and maintainability is important when considering the availability assessment of operative plant conditions, and accordingly, an analysis of plant operational effectiveness impact (P-OEI) is necessary to identify the opportunities for improvement in asset management. A fundamental aspect of an industrial plant is to determine what the effect of each element is on the system. To clarify the importance of the primary equipment and improve the decision making related to asset management, a novel methodology proposal has been developed and applied to real data of a biomethanation plant located in Spain. This new methodology develops an analysis based on a reliability block diagram configuration that structures the process analysis by levels, i.e., ascending for availability analysis from the element to the system and descending for the P-OEI analysis from the system to the smallest element. The expected operational impact of EOI (i.e., the expected effect of an element constraint on the overall system) is also calculated. The P-OEI analysis conducted in this study reveals important results that can be used to evaluate the design and performance of an industrial plant. (C) 2016 Elsevier Ltd. All rights reserved.