Much academic research on low-carbon transitions focuses on the diffusion or use of innovations such as electric vehicles or solar panels, but overlooks or obscures downstream and upstream processes, such as mining or waste flows. Yet it is at these two extremes where emerging low-carbon transitions in mobility and electricity are effectively implicated in toxic pollution, biodiversity loss, exacerbation of gender inequality, exploitation of child labor, and the subjugation of ethnic minorities. We conceptualize these processes as part of an emerging "decarbonisation divide." To illustrate this divide with clear insights for political ecology, sustainability transitions, and energy justice research, this study draws from extensive fieldwork examining cobalt mining in the Democratic Republic of the Congo (DRC), and the processing and recycling of electronic waste in Ghana. It utilizes original data from 34 semi-structured research interviews with experts and 69 community interviews with artisanal cobalt miners, e-waste scrapyard workers, and other stakeholders, as well as 50 site visits. These visits included 30 industrial and artisanal cobalt mines in the DRC, as well as associated infrastructure such as trading depots and processing centers, and 20 visits to the Agbogbloshie scrapyard and neighborhood alongside local waste collection sites, electrical repair shops, recycling centers, and community e-waste dumps in Ghana. The study proposes a concerted set of policy recommendations for how to better address issues of exploitation and toxicity, suggestions that go beyond the often-touted solutions of formalisation or financing. Ultimately, the study holds that we must all, as researchers, planners, and citizens, broaden the criteria and analytical parameters we use to evaluate the sustainability of low-carbon transitions.