This article aims to add to the emerging empirical mitigation deterrence literature by drawing on ongoing research into a particular form of greenhouse gas removal technology – biochar – and associated biochar carbon markets. As such, the aim of this paper is to explore whether the UK carbon market for biochar, in practice is likely to contribute to delays in emissions reduction. In other words, we explore whether UK biochar carbon markets are (likely to be) as much of a problem for mitigation deterrence as imagined or envisaged within the mitigation deterrence literature. We draw from original data collected in 2022 from 33 semi-structured interviews with mostly UK based experts who have an interest or potential interest in biochar, supplemented with a document analysis. Conceptual approaches from the social studies of finance have guided the analysis, an approach that enables systematic investigation of experts’ understandings of the biochar carbon market landscape in the UK. Although biochar proponents forwarded narratives – or fictional expectations – about how the future trading of carbon credits in carbon markets could lower the cost of producing biochar on a large scale, other experts doubted the credibility of these narratives. Whilst the construction and sustainable functioning of a UK-based biochar carbon market remains a speculative, rather than credible proposition, it nevertheless constitutes a threat of mitigation deterrence because of the assumption that a UK biochar carbon market will become a reality. There is the promise of future removals even if this is only imagined.