Volunteering is an important cornerstone of our society, from social welfare to disaster relief, supported by a variety of volunteer management systems (VMS). These VMS focus primarily on centralized task management within non-profit organizations (NPOs) but generally do not provide mechanisms that allow volunteers to privately digitize and exploit their engagement assets in terms of digital badges for activities accomplished or competences acquired, in a trustful manner. This lack of sovereignty hampers volunteers in the exploitation of their engagement assets wrt. self-exploration, but also with regard to possible transfers of assets to other NPOs and beyond, e.g., to the education or labor market. We put volunteers in the middle of concern by investigating “how engagement can be digitized and exploited in a lifelong way”, thus adhering to the idea of human-centric personal data management. First we propose a conceptual architecture for a web-based volunteer platform based on a systematic identification of the requirements for trustworthy digitization and exploitation of engagement assets. Second, to address the massive heterogeneity that prevails in different areas of volunteering, a generic and extensible engagement asset model is proposed. Third a reification-based configuration mechanism is proposed so that each NPO can adapt the proposed model to its specific needs. Finally, a prototypical web application is presented which allows to »blockchainify« lifelong volunteer engagement in order to establish trust between all stakeholders.