Potential for greenhouse gas (GHG) emission reduction by institutional biogas plants - case study Dar es Salaam
The increase of greenhouse gases (GHG) in the atmosphere, resulting from both natural sources as well as from human activities, has become a heated global issue. Reducing their concentration is a subject being tackled my many scientists and companies. Although water vapour and carbon dioxide are very abundant GHGs, methane has a 21 times stronger global warming potential (EPA, 2006) and needs to be reduced likewise.
Due to the increase in population and rapid industrialization, another challenge facing the world today is solid waste management, and in particular its disposal. In developing countries, the increasing amount of waste is typically crudely dumped. As the municipal solid waste consists to a big extent of organic material, methane is produced under anaerobic conditions on dumpsites. As a means of dealing with kitchen waste, some biogas plants have been installed in several households and institutions in East Africa, especially in Dar es Salaam.
This study identifies the potential for institutional biogas plants to reduce greenhouse gas emissions and shows their possibilities and limitations to become a carbon project. The study was divided into two major sections, which included data collection through semi-structured interviews conducted in Dar es Salaam, and calculations made using the 2006 IPCC guidelines methodologies. The baseline GHG emissions for the current waste management system were calculated both for the emissions resulting from anaerobic digestion on the dumpsite, as well as from transportation of waste. The project emissions from the biogas plant were considered to be the physical leakages as well as emissions through the effluent.
The study showed that the GHG emissions resulting from transportation and decomposition of all organic waste dumped in Dar es Salaam is 300,153 tCO2e/year, of which kitchen waste is responsible for 52%. Due to the fast degradation rate of kitchen waste, there is need to deal with this fraction almost immediately.
The case of the Azania secondary school, which is equipped with ARTI biogas plants to treat their food leftovers, showed that 56% of the GHG emissions could be reduced by treating all kitchen waste in biogas plants. This figure would even increase to 76% if the ARTI design was improved and gas loss from the biogas plants was minimized.
In order to comply with the requirements for a small-scale CDM project, a maximum of 7500 institutions similar to Azania secondary school could install biogas plants so that 60,000 CER per year are not exceeded. To cover the transaction costs of a voluntary carbon offsetting project and make it economically attractive, a minimum of 1585 institutions would be needed.
Such a project would also comply with CDM regulations since it would contribute to sustainable development of the country by improving the waste management and providing renewable cooking energy for the people.