Purpose – Production systems within the process industry are characterized by complex and interconnected flows where disturbances may affect the stability and capacity of the production system. Previous research within the sawmill industry has mainly focused on simulations and optimization models to identify capacity constraints and improve production flows, while research regarding how bottlenecks manifest in operational production environments remains limited. Therefore, the purpose of this study is to contribute to an increased understanding of what types of bottlenecks may occur and affect the production flow in the green sorting process of a sawmill. To fulfill the purpose of the study, the following research questions were formulated:[1] What types of bottlenecks may occur in the green sorting process of a sawmill?[2] To what extent do these bottlenecks affect the green sorting process?Method – The study was conducted as a qualitative case study with quantitative elements at a sawmill. Observations, time studies, and document studies were used to identify and analyze bottlenecks in the green sorting process. Time studies were conducted to document stop frequency and stop durations, while document studies were used to collect production and stoppage data from the production system. Statistical analyses in the form of t-tests were conducted to analyze differences between different machine groups.Results – The results show that the bottlenecks identified in the green sorting process were mainly related to waiting, material shortages, and capacity limitations between different subprocesses in the production flow. The extent of the bottlenecks varied between different subprocesses and types of disturbances, where some subprocesses were characterized by recurring high stop frequency while others had greater impact through longer stop durations and more extensive capacity losses. The results also show that subprocesses with high stop frequency did not necessarily have the longest stop durations, indicating that different types of bottlenecks affected the production flow in different ways.Implications – The study contributes with both theoretical and practical implications. Theoretically, the study contributes to an increased understanding of how bottlenecks and production disturbances manifest in operational production environments compared to previous simulation-based research. Practically, the results indicate that improvement efforts should not solely focus on long production stops but also on recurring minor disturbances that affect production flow stability over time.Limitations – The study is limited to the green sorting process within a specific sawmill and therefore does not include the entire production flow of the sawmill. Furthermore, the study was conducted during a limited observation period, meaning that other types of disturbances and variations may occur under different production conditions.Keywords – Bottlenecks, production disturbances, production flow, green sorting, sawmill industry, process industry