An exploration of carbon emissions linked to research study delivery (MARIE project)

Abstract Background Large-scale scientific research studies are critical for advancing knowledge and innovation, but they require substantial human and financial resources. Given their scale, such studies also generate a notable environmental footprint. Aligning research practices with Sustainable Development Goals (SDGs) 3 (health and wellbeing), 12 (responsible consumption and production), and 13 (climate action) necessitates assessing and mitigating these impacts. This study investigates the carbon emissions associated with different participant recruitment strategies such as digital, hybrid, and in-person across a selected group of countries from the MARIE project. Methods Recruitment-related data were collected from Brazil, the United Kingdom, Nigeria, Ghana, Singapore, Sri Lanka, Malaysia, and India, covering a total of 3,875 participants. Emissions were estimated from paper use, printer electricity, participant and staff transportation, and IT device usage. Calculations applied internationally recognised emission factors alongside country-specific carbon intensity metrics. Statistical comparisons between recruitment modalities were conducted using analysis of variance (ANOVA) and the non-parametric Kruskal–Wallis test to account for small group sizes and non-normal data distributions. Results Digital recruitment demonstrated the lowest carbon emissions, ranging from 0.23 to 437 kg CO 2 e, largely attributable to the limited electricity consumption of IT devices. Hybrid recruitment generated moderate emissions (mean ≈ 126 kg CO 2 e) due to combined digital engagement with some travel and material use. In-person recruitment produced markedly higher emissions, ranging between 4,260 and 27,070 kg CO 2 e, with transportation accounting for more than 90% of the total footprint. While statistical analyses did not reveal significant differences across modalities ( p > 0.05), likely due to small sample sizes, effect sizes suggested meaningful environmental variation. Findings Digital and hybrid recruitment strategies substantially reduce the carbon footprint compared to traditional in-person approaches, offering sustainable alternatives for large-scale research. These approaches can help research institutions meet global sustainability targets while maintaining efficiency. Nevertheless, considerations of equity, accessibility, and cultural appropriateness remain critical, particularly in low-resource settings, to ensure inclusivity and generalisability of study findings.