Performance of domestic biodigesters in Kenya Towards the development of a comparative method for measuring the performance of different biodigester types in Sub‐Saharan Africa
Summary
To eradicate (extreme) poverty, the Sustainable Development Goals (SGDs) framework has been set by the United Nations (UN). Providing access to clean energy resources to populations of the least developed countries (LDCs) is considered crucial. For a number of decades, domestic biogas has been introduced as a promising technology, providing multiple benefits in the context of sustainable development. Through daily feeding of cow dung, a biodigester provides clean cooking and a nutrient rich digestate that is usable as a high‐quality fertilizer. Africa Biogas Programme Partnership (ABPP) was set up by Dutch development organisations to help develop a biogas market in five ountries in Sub‐ Saharan Africa. Growth of the biogas leads to a diversification of the available biodigesters. However, the
biodigester selection process is still based on applying single‐standards for large regions, due to a lack of practical knowledge on biodigester performance. This research was conducted to develop a performance measuring method suitable for obtaining comparative and scientifically robust results for multiple digester types.
By considering a techno‐operational and financial performance definition, a profile containing was set, including eight performance indicators: gas production per unit of dung input, gas pressure, stability of gas production under feeding and temperature instability, gas storage volume, investment costs, ease of use, robustness, and surface requirements. The usability of five measuring tools (biodigester database,
user survey, logbook, data logger, visual observation) was assessed during four performance measuring pilot studies in Kenya and Uganda. Scores were given both for the use process of the tool and the quality of the data that is generates. In addition, the availability of potentially improved measuring tools was researched. Pilot results show that the database is easy to use but does not deliver high‐quality data. The
survey and visual observation have reasonable process scores. The survey is slightly recommended for measuring investment costs and ease of use, while visual observation measures surface requirements and can be used occasionally for other indicators. The logbook scored intermediate for the process, but is nevertheless the best tool for measuring dung input, although standardization of dung input for every
biodigester is an alternative. The data logger is a complex, expensive and complex tool to use, putting the process of successful data collection at risk. However, the tool seems to be essential for monitoring most technical parameters. Developing a second‐generation data logger with updated technology would have many benefits in comparison to the initial data logger for the process of using the tool and the
quality of the generated data. The required investment for the development of this tool is expected to be profitable after a couple of field studies, taking into account the savings on logistics.
A first fundamental step towards a performance measuring method is described. A method based on surveys, visual observations and a second generation data logger is suitable for explaining seven of the described performance indicators. A measuring tool that can monitor the robustness of multiple digester types is yet to be found. For a number of indicators, concrete measures of expressing the performance
are required ‐ a recommendation for further research. Furthermore, a review of the quality of various flow meter types should be done before developing a new data logger. Future experiences with performance measuring, in accord with this framework, could lead to revision of the selection of measuring tools or widening of the performance profile, including economic, environmental and business‐quality related indicators.