Making blockchain solutions sustainable: the LETO approach

Blockchain technology has rapidly evolved from an initial wave of enthusiasm – often dominated by cryptocurrency speculation – into a tangible industrial reality, with governments and enterprises exploring diverse implementations that transcend financial tokens. Within Europe, for instance, the creation of regulatory sandboxes has enabled blockchain innovators to test solutions in controlled environments without facing immediate legal barriers, thereby accelerating adoption. The European Blockchain Services Infrastructure (EBSI) initiative further underscores this shift from hype to practical deployment: by establishing a cross-border platform for sharing trusted data, EBSI aims to harmonize blockchain projects within the European Union, demonstrating how public-sector leadership can foster responsible and standardized implementations. Despite this growing maturity, blockchain projects still frequently emphasize technological attributes, such as consensus mechanisms or transaction throughput, at the expense of sustainability considerations. Environmental impact, regulatory compliance, and equitable stakeholder governance are too often treated as afterthoughts, if addressed at all. Yet non-crypto applications, particularly in logistics, agriculture, and data management4, demonstrate that effectively tackling these broader challenges is essential for achieving long-term value and stakeholder acceptance. A key resource in bridging this gap has been the GUEST methodology, originally devised to provide a lean, iterative framework for designing and validating real-world non-crypto blockchain use cases. GUEST outlines a clear sequence of phases – GO, UNIFORM, EVALUATE, SOLVE, and TEST – that collectively ensure solutions address operational and strategic pain points before finalizing large scale implementations. Although this method has become a leading choice for organizations seeking to harness blockchain’s potential without focusing on cryptocurrencies, GUEST alone does not fully account for the multifaceted sustainability issues – including environmental footprints and social inclusion – that can arise when adopting blockchain at scale. In response, this paper presents the LETO Methodology, which builds on GUEST by incorporating four critical dimensions, Legal, Ethical (including environmental and social aspects), Technological, and Operational, into a single, integrated blueprint for sustainable blockchain deployments. By embedding sustainability principles throughout the development lifecycle, LETO ensures that solutions remain energy-efficient, compliant with evolving regulatory frame works (including the European regulatory sandbox initiatives), and aligned with best practices such as EBSI’s push for interoperable, cross-border blockchain services. This expanded perspective equips organizations to mitigate potential pitfalls, whether carbon-intensive consensus processes or data privacy vulnerabilities, while also capitalizing on blockchain’s capacity to foster transparency, trust, and efficiency. By combining GUEST’s lean foundation with an explicit emphasis on ethics, ecology, compliance, and real-world feasibility, the LETO Methodology offers a roadmap for advancing from proof of-concept projects to fully industrialized solutions. These solutions promise enduring value not only for direct participants – such as supply chain partners and end-users – but also for regulators, communities, and the broader market. By anchoring blockchain development in robust sustainability standards, LETO provides a forward-looking approach that addresses the critical challenges and opportunitiesshaping the next stage of blockchain’s evolution.