Browsing by Author "Chikande, Adriano Quondie Persuade"

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    Development of a tier 3 method for calculating greenhouse gas emissions from pulp and paper mills in South Africa
    (Stellenbosch : Stellenbosch University, 2023-03) Chikande, Adriano Quondie Persuade; Chimphango, Annie Fabian Abel; Van Rensburg, Eugene; Stellenbosch University. Faculty of Engineering. Dept. of Chemical Engineering.
    ENGLISH ABSTRACT: The increasing threat of climate change caused by greenhouse gas (GHG) emissions has resulted in strict government emission regulations as a control measure toward emissions mitigation. These regulations and associated emission taxes have increased the cost of operations for large GHG-emitting industries, including the pulp and paper industry. The South African government requires pulp and paper mills (PPMs) to report emissions at the highest level (Tier 3) of the three-tiered IPCC GHG reporting method, which requires facility-level emission data. However, obtaining this type of data is challenging for PPMs due to the lack of continuous measuring systems at key points such as steam boilers and recovery furnaces. Therefore, there is a need to develop a method for Tier 3 reporting without a need for continuous measurements. This study investigated the feasibility of using a mass balance approach based on the principle of conservation of mass to develop a Tier 3 reporting method for the PPMs. The study involved analysing carbon flow from the entry gates to the exit gates of thirteen South African PPMs. This carbon was quantified using composition-based mathematical models developed for each carbon-containing input and output stream. These models were combined into a single mass balance model that calculates the emitted carbon as the difference between the input and output carbon using an Excel-based tool. In addition, this tool was used for sensitivity analyses to determine how emissions vary with changes in independent variables like the carbon content of input and output streams. The approach accounts for variations in the fuel quality and combustion efficiencies in PPMs using different technologies; hence, it is reliable. Sankey diagrams were used to report the carbon flow through the specified mill boundaries, and the total GHG emissions were calculated as the sum of CO2, CH4, and N2O emissions in tCO2-eq. Results showed that in 2020, 51% of the carbon leaving the PPMs was emitted as GHGs. 39% and 10% left the mills as pulp and paper products and as byproducts and wastes, respectively. The sector emitted 5 602 671 tCO2-eq (53% biogenic and 47% fossil) from activities under IPCC Codes 1A1a, 1A2d, 1A2f, 2A2, and 2A4d. Results also showed that virgin fibre-based mills produce 2.8 times more GHG emissions than recycled fibre-based mills, which suggested that recycled fibre usage should be promoted. Moreover, the models indicated that replacing coal with natural gas can halve emissions. Therefore, using natural gas could be the next step to environmental sustainability for South African PPMs. Sensitivity analyses revealed that the higher a process stream’s carbon flow rate, the larger the extent by which emissions will change with stream properties like carbon and moisture content variations. This study is the first to provide a Tier 3 reporting method for South African PPMs. A Tier 3 methodology results in improved GHG accounting accuracy which is crucial in developing climate change mitigation strategies in line with South African environmental legislations.