## 1 Introduction  
Mission-oriented approaches are emerging as popular solutions to contemporary sustainability challenges, as seen in the United Nations Sustainable Development Goals (SDGs) [1] and the Horizon Europe R&D program of the European Commission [2, 3]. As a contemporary framing of science, technology, and innovation policy, mission-oriented innovation policies (MIPs) such as these call for transformational change to sociotechnical systems [4]. Missions are challenge-based, urgent, and strategic goals [5]; rather than having a static focus on technological innovation, missions are emergent and evolutionary in nature [6], supporting experimentation and promoting stakeholder alignment and cooperation toward common goals. The challenges they tackle are complex, consisting of multiple stakeholders and requiring insights from many perspectives [7]. Governmental bodies are increasingly engaged in the use of missions to take societal challenges, like promoting a more sustainable society [8]. The Council of the European Union emphasizes \"the crucial role that public procurement can play in the proper implementation\" of the SDGs, and the \"incorporation of these goals to serve the public interest\" [9]. One instrument that public contracting authorities can use to achieve such environmental missions is green public procurement (GPP), as purchasing that reduces environmental impacts across product or service life cycles [10]. As an innovation procurement mechanism, GPP is a tool that supports the uptake of eco-innovations by markets [11] and can be conceptualized as mission-oriented innovation policy (MIP) [12] and thereby offers a mission-oriented approach to furthering sustainable development progress. GPP stimulates the development, commercialization, and market penetration of products and services with the best environmental performance [10]. A core mechanism by which it does so is via the incorporation of voluntary standards and eco-labels into public calls for tenders, creating competition between potential suppliers that rewards those with the most sustainable products, services, or works. Voluntary standards (often referred to simply as \"standards\") are documents that specify what (if any) is required by regulation [13] created through a process of standardization: the voluntary development of \"technical specifications based on consensus amongst the interested parties\", Ref. [14] including industry, interest groups, and public authorities. Standardization can occur for de jure standards via different methods such as (1) via consensus processes at standards development organizations (SDOs) like ISO and its national member bodies (e.g., Stichting Koninklijk Nederlands Normalisatie Instituut [NEN] in the Netherlands and Deutsches Institut fur Normung [DIN] in Germany), or (2) more closed or proprietary processes by various industry associations [15]. In comparison, de facto standards can be created by public procurers via specification in tender documentation [10]--this will be explored later in more depth, as it is the use of either de facto or de jure voluntary standards in GPP tender projects that can contribute toward achieving missions, as compared to non-tender projects where the relevant public authority does not have the authority to set requirements beyond those specified by regulation. The European Commission encourages GPP, including through the availability of guidance for considering sustainability standards in public tenders. A variety of types of voluntary standards and eco-labels may be used in public procurement provided that they are \"clear and ambitious\" [16], based on \"scientific information using a procedure in which stakeholders, such as government bodies, consumers, manufacturers, distributors and environmental organizations can participate\" [17]. This paper considers GPP as being relevant to all types of innovation activities within an MIS, and therefore considers all types of voluntary standards used for their relation to furthering missions by their application in GPP tenders.