The bioeconomy, grounded in the shift from fossils to bio-based resources, plays an important role in the Net Zero 2050 scenario. However, even if rooted in circular thinking, bioeconomy business models are not free from environmental, social, and economic concerns. This paper deals with the causes of the unsustainability of business models in the biofuels sector, embracing an unconventional approach that focuses on the uncaptured value. The value uncaptured is the negative aspect of value, and it consists of creating too much or not enough value during the product lifecycle. Value uncaptured can threaten the sustainability of circular business models, which is why it constitutes the ‘dark side’ of circular strategies. Starting from a gap in the existing literature and supported by theoretical background, this study aims to suggest a theoretical framework to identify the causes of the negative value in the biofuel sector. The paper uses a qualitative tool, namely a case study analysis. The findings reveal that circular business models can suffer from value uncaptured, which can take the form of value absence, value destroyed, value surplus, and value missed. Identifying these forms of value can transform them into opportunities for value creation. These results enrich the research on the circular economy with a new and unconventional approach. The elaborated theoretical framework can become a qualitative tool to identify what causes companies’ circular business models to underperform.