Abstract This paper proposes that the approach of social acceptance of renewable energy technology needs to include the concept of naturalness to understand the social rejection of biogas technology. Because naturalness concerns are not only strongly associated with the physical emotions of disgust and fear but also with disgust as a moral emotion, which is experienced as an indignity to the community, they have the potential to prevent energy projects from succeeding. Results from a survey and a case study conducted in South Africa demonstrate that relative to other renewable energy technologies, biogas technology elicited stronger naturalness concerns and the emotions of disgust and fear (Study 1: N = 452) and that indignity experiences of community members of an informal settlement were sufficient to reject a small scale biogas technology project (Study 2: N = 155). The implications of our findings are discussed and solutions are provided to address the naturalness concerns about biogas technology.