Abstracts

102 of AD may be the most promising solution to address most of the problems related to organic waste. AD is a process through which organic waste, such as domestic food wastes, farm wastes, wastewater, and other biomass, are naturally broken down in the absence of oxygen. There are two main outputs of the AD process that can be captured and stored (Freese & Han, 2019). The first is biogas, which is composed of methane and other energy- rich gaseous molecules. Another is digestate, which is a nutrient-rich sludge suitable for use as a fertilizer in agricultural applications. AD allows control of an otherwise harmful and environmentally dangerous breakdown of organic matter. AD technology allows for the valorization of organic waste and thereby the ability to realize the economic potential of organic waste. A diversion of waste from landfills can alleviate current burdens on the landfills specifically and the environment more broadly. The biogas output of AD can help individuals and families meet their energy demands in the form of electricity or direct heating potential from the gas. An example of such an approach exists in the Vhembe district of the Limpopo province. Here, the main feedstock for the digesters is not organic food waste but rather agricultural wastes including manure. The gas is used primarily for cooking and heating purposes (Rasimphi & Tinarwo, 2020). This type of adaptation of the technology can valorize waste material, creating economic pressures and drivers to expand waste management infrastructure. Greater challenges ensue when attempting to implement this technology in urban settings. In urban areas, a major organized effort must be actively and reliably functioning in order to support any AD project. A potentially useful model for South Africa to consider exists in a project planned for the city of Dar es Salaam in Tanzania. Dar es Salaam has a population, poverty level, and organic waste generation rate similar to Johannesburg. As a result, Dar es Salaam faces many of the same problems as Johannesburg related to waste and the environmental issues it causes. Dar es Salaam’s provincial government ordered a feasibility study for the Taka gas project to ease the burden of waste being illegally dumped or landfilled, while also generating electrical power for the city’s grid. The project was never commissioned due to bureaucratic reasons; however, the underlying analysis in the feasibility study still holds (Kumar). The project estimated using 60 tons of organic waste per day to produce 4.91 MWh of electricity daily. The project identified the procurement of source-separated organic biomass as a primary constraint, potentially limiting the project’s success. Project managers were aware that poorer areas within the city have only a 20% waste collection rate, which is not separated by type (Mbuligwe, 2002). Thus, rather than initially focusing on domestic sources for their feedstock, the Taka gas project managers planned to go after commercial waste generators, which include restaurants, hotels, and butcher shops. These establishments are known to produce high volumes of organic waste and are forced (via regulation) to maintain good waste disposal practices. By working with these types of businesses to develop better collection sites and methods, the Taka gas project surveyors were able to predict the critical mass needed for daily operations. The team also partnered with local groups to devise a strategy to collect waste from noncommercial domestic areas with low collection rates. They realized that many poor residents of Dar es Salaam did not have proper waste bins and other personal waste storage mechanisms. As a result, the Taka gas project group suggested partnerships with NGOs to distribute a two-bag system to individuals, one bag for organic wastes and another for inorganic material. According to the study, this method was proven to work in urban areas based on past success in other localities (Mbuligwe et al., 2004). This case study and its subsequent results can be extrapolated as a potential model solution for implementation in Johannesburg. Some conditions, including waste transportation and real estate considerations, disallow an exact adaptation of the Taka project in Johannesburg. However, this project proposal study suggests that it is possible to monitor and regulate the nature of waste in an urban environment that faces similar challenges.