To qualify the sustainability of organizations, the business model approach questions whether it is possible to identify "sustainable value creation" (Lüdecke-Freund, 2020). While the polysemous notion of value was already unclear, its sustainable nature adds a further definitional difficulty. What's more, business model approaches do not enable to precisely address the impact of activities on the values in question. Our aim is to help clarify the sustainable business model approach to company sustainability through the prism of CARE ecological accounting framework (Rambaud & Richard, 2015). Our conceptual approach consists in applying CARE concepts and methodology to an illustrative case study inspired by a real farm business. We highlight how CARE repositions the understanding of sustainability in terms of the ability of a business to preserve human and natural capital while creating value (i.e. selling goods or services to obtain money resources). This reading leads to identify value propositions that consist in providing services that preserve the client's natural or human capitals. While other value propositions ultimately refer to the company's own human or natural capitals preservation. Thus, "sustainability" in business models should be clarified at least between making its own production process sustainable vs. contributing to its client's sustainability. Relying on an ecological accounting framework help designing strategies and activities to reach capital's preservation objectives according to anticipated costs. In the end, such framework can be used to lend credibility to sustainability claims possibly opening the door to the capture of financing solutions or market opportunities.