Event detailsDate: Thursday, 28 April 2022
Presenters: Kushveena Gokul and Professor Anne Stark
Host: Dr Takunda Chitaka
BackgroundThe introduction of the waste hierarchy promotes the diversion of waste away from landfills towards value-adding opportunities. However, there is no clear methodology for the comparison of waste beneficiation pathways as decentralised waste treatment options in South Africa. As a result, most waste is landfilled in the country even though it contains large amounts of recyclable and recoverable materials. This study investigates the use of techno-economic assessments to determine the viability of decentralised waste treatment options and comparison to larger-scale processes in three selected locations in South Africa (Calvinia, Garden Route District, and eThekwini). These preliminary results may be used to estimate economics before intense, expensive, and time-consuming design and scoping is performed.
Six different scenarios were investigated: the separation and recycling of waste streams (scenario 1), composting (scenario 2a), anaerobic digestion (scenario 2b), pyrolysis of plastics (scenario 2c), and combination scenarios (composting and pyrolysis (scenario 4a), as well as anaerobic digestion and pyrolysis (scenario 4b)). The separation and recycling of waste from each location found a credit of R2.4 to R17.8 / t waste based on specific assumptions. The increase in municipality size positively influences the feasibility in this scenario. The economic parameter of the Net Present Value was used to analyse the feasibility of the remaining scenarios. None of the scenarios are economically feasible in Calvinia, with Net Present Values less than zero. Composting is feasible in the Garden Route District and eThekwini with a Net Present Value of R44 Mio and 89 Mio, respectively. Based on electricity sales, anaerobic digestion is feasible in Garden Route District (R14.5 Mio) and eThekwini (R208.6 Mio). Plastic waste pyrolysis is feasible in the Garden Route District and eThekwini. The combined pyrolysis scenario with either composting or anaerobic digestion also produces feasibility in the Garden Route District and eThekwini, with higher Net Present Values for the latter scenario. The \ inclusion of EPR targets decreases the NPV of pyrolysis by reducing the amount of product and thus the revenue from fuel. Suppose EPR targets were fulfilled, and the recyclate stream was diverted to the BBCs for sales. In that case, the overall income could not overcome the capital and operational costs in any location.
The different parameters were investigated through sensitivity analysis to determine the different leverage points for each process and inform the influence of market fluctuations due to legislative instruments such as the EPR regulations. The landfill credit can be considered a key parameter since the true cost of landfilling is not widely recognised and may be underestimated.