Municipal solid waste composting is seen as a promising technology in Sub-Saharan Africa to offset greenhouse gas emissions under the Clean Development Mechanism (CDM) program. The main reasons given therefore are the large organic fraction in municipal solid waste in this world region and the low complexity of the technology. The investigation results of case studies from other world regions suggest that the knowledge of local stakeholders involved in CDM composting projects is another crucial factor for their success and sustainability. The existing knowledge and knowledge demand of these stakeholders, however, is rarely considered in CDM composting project design documents from Sub-Saharan Africa. The study presented in the article at hand aimed to investigate both the existing knowledge and knowledge gaps of local stakeholders in a CDM waste composting project implemented in 17 cities in the Sub-Saharan African country of Uganda. This was done by selecting one of these cities (Busia) as a case study. After identifying the most important local stakeholders, methods of data collection and analysis (i.e. interviews, focus group discussions, compost field tests, material flow analysis, and full cost accounting) were embedded in an action research framework and applied to the case study of Busia prior to implementation of the CDM project. Furthermore, ways of closing the knowledge gaps identified were elaborated. Results showed that city authorities implementing and operating the CDM composting project, as well as farmers as potential users of the compost, were the two most relevant stakeholder groups. For city authorities, a knowledge gap regarding the net costs and benefits associated with the CDM project was identified, due to the underestimation of operation costs for composting and the overestimation of revenues from compost sales in the CDM project design document. The overestimation of compost sales revenues was due to the non-existence of a compost market, explained by the lack of experience and knowledge of farmers with respect to compost use and its value. While this knowledge among farmers can be acquired, for instance by means of agricultural extension services, key factors for marketing the compost, such as appropriate compost prices and compost quality, must also be addressed as part of a comprehensive solution. Investigations like the one presented in the article at hand are important not only for future CDM composting projects in Sub-Saharan African countries, but also for designing greenhouse gas mitigation programs under the green climate fund in the post-CDM period, as stipulated in the Paris Convention of Parties 21 Agreement.