School of Chemical and Metallurgical Engineering (ETDs)

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    A Life Cycle Assessment of Plastic vs Cardboard Packaging in the Fast-Moving Consumer Goods Market
    (University of the Witwatersrand, Johannesburg, 2024) Rivett, Stephanie Anne; Harding, Kevin
    Globally there is a movement to mitigate the need for single-use plastics as well as the utilization of plastic materials when alternative options are available. This movement comes in response to the extensive research that has demonstrated the long-term negative environmental impact that plastics pose to our existence when disposed of into landfills. A significant contributing factor to the mass of single-use plastics is the packaging industry. This study focused more specifically on the single use plastic packaging in the fast-moving consumer goods (FMCG) market which are used to shrink-wrap bottles together to be supplied into the trade such as Pick ‘n Pay and Checkers. South Africa is facing two main challenges pertaining to the FMCG market: namely the constrained supply of energy and the socio-economic pressure to reduce the environmental impact caused by unrecycled packaging waste. This research aimed to investigate the energy requirements and environmental impact of packaging configurations that included shrink-wrap plastic and cardboard cartons versus packaging configurations that utilized only cardboard cartons to ascertain which option provides the lowest possible energy requirements, and environmental impact. This study aimed to execute a cradle-to-grave life-cycle assessment (LCA) of the two different packaging configurations by utilizing the SimaPro software. The LCA was executed with respect to one reference product that is supplied into the FMCG market year-round known as Prewash Promo. Prewash Promo is a laundry pretreatment that aids in the removal of stains. The first of the two packaging configurations under analysis was the traditional packaging configuration of Prewash Promo that has always been used. This packaging configuration consisted of six bottles that were grouped into two sets of three using rubber bands. The two sets of three were then shrink-wrapped into a group of six. Two shrink-wrapped sixes were then placed into a box that was sealed using plastic packaging tape or sellotape. The second packaging configuration under analysis mitigated the use of shrink wrap plastic and associated materials (elastic bands) thus the second packaging configuration consisted of twelve bottles placed into the box that was then sealed using packaging tape. The main objective of this LCA was to ascertain the packaging material configuration that was the most energy-efficient and environmentally responsible choice to utilize in the Stephanie Anne Rivett A Life Cycle Assessment of Plastic vs Cardboard Packaging in the Fast-Moving Consumer Goods Market iv FMCG market. This LCA was conducted utilizing the data pertaining to the year 2022 and the functional unit of this study was one year’s worth of packaging used in the production of Prewash Promo. Prewash Promo was chosen as the reference product as it does not demonstrate seasonal or geographically specific use, and it was a viable option for the change in packaging configuration. A significant factor that influenced the impact of LCA results was the waste scenarios associated with the use of different materials. In this study, the exact quantities of material that were recycled versus sent to landfills could not be definitively known. It was for this reason that the published industry standard recycling rates for the year 2022 and knowledge of socioeconomic habits were used to formulate assumptions. It was assumed that the minor materials included in the packaging configurations such as packaging tape and elastic bands conformed with social habits and did not exhibit any recycling and went directly to landfill. The recycling rate of corrugated board for the year 2022 was reported to be 61.4% and the recycling rate of plastic for the year 2022 was reported to be 42.8% (Mpact Recycling, 2019a). These recycle rates were utilized to model the packaging configurations to facilitate the comparison between the two. The validity and influence of these assumptions were assessed by means of a sensitivity analysis after the main LCA was executed. The ecoinvent 3 database library available via the SimaPro software (version 9.4.0.3, 2022) and the ReCiPe Midpoint method were used to execute the impact assessment calculations. This method consisted of eighteen impact categories that assessed the impact of each of the packaging materials with respect to the impact they posed to human health, biodiversity, and resource scarcity. The full eighteen category impact assessment was condensed into five focus categories based on the target audience, the research objectives and geographical location of the study. These five focus categories were: global warming, stratospheric ozone depletion, fine particulate matter formation, freshwater ecotoxicity and water consumption. These five categories were chosen because they provide the best overview of the impact in a summarized form pertaining to factors contributing to environmental decline, changing weather conditions, reduction in air quality and the impact of freshwater resources. The LCA was first executed for each packaging configuration in isolation to ascertain the impact contributions of each of the individual factors involved in the construction of the Stephanie Anne Rivett A Life Cycle Assessment of Plastic vs Cardboard Packaging in the Fast-Moving Consumer Goods Market v packaging set-up. The analysis of each packaging configuration in isolation facilitated highlighting major contributing factors to consider replacing with alternatives or mitigating the use thereof. This assessment highlighted the drastic impact contribution that the use of electricity had on the impact score of the heat shrink-wrap plastic configuration. The full LCA comparison was then executed to compare the two packaging configurations. In each of the five focus impact categories the corrugated board only packaging configuration achieved an environmental impact score 83% lower than the heat shrink-wrap plastic packaging configuration. This drastic difference was only reduced to 79.6% when excluding long-term emissions. Upon the conclusion of the LCA comparative assessment the validity of the recycle rate assumptions for corrugated board and shrink-wrap plastic were assessed by executing sensitivity analyses. These analyses determined that the conclusion achieved at the end of the LCA comparison stage remained valid irrespective of the recycling rate of corrugated board or shrink-wrap plastic. The final objective investigated in this study was the uncertainty analysis to assess the accuracy and reliability of the data utilized in the LCA. The uncertainty analysis was executed in the SimaPro software by utilizing a Monté Carlo analysis with the ReCiPe 2016 midpoint (H) method which consisted of 1 000 fixed runs with a confidence interval of 95%. An uncertainty bar chart was generated that displays the error associated with each of the eighteen impact categories. The uncertainty analyses for both packaging configurations determined that the data for global warming, stratospheric ozone depletion, fine particulate matter formation and freshwater ecotoxicity demonstrated low error. The cardboard only configuration exhibited very low error values of between 8% and 61% as opposed to the plastic packaging configuration which exhibited errors between 16% and 214%. The water consumption data in contrast exhibited significant uncertainty for both configurations due to the difficulty in definitively determining accurate water consumption data for such extensive life cycles. Water was utilized extensively in the developmental stages of each of the materials (forestry, paper/pulp manufacturing and plastic polymer and plastic shrink manufacturing) and exhibited significant variation in volume of consumption due to high degrees of variation in plant technology and process equipment age. Stephanie Anne Rivett A Life Cycle Assessment of Plastic vs Cardboard Packaging in the Fast-Moving Consumer Goods Market vi The culmination of the results of each of the assessments executed concluded that the corrugated board only configuration is the packaging configuration that is the most environmentally friendly, and energy-efficient packaging option of the two that were considered.
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    Design of an Industrial Process for Enzymatic Cannabidiol Conversion
    (University of the Witwatersrand, Johannesburg, 2024) Flavell, Erin Reece; Harding, Kevin; Rumbold, Karl
    This work aims to model a theoretical enzymatic bioreactor and all the necessary surrounding processes required to facilitate the bioremediation of THC into CBD, to produce a CBD product with THC levels below the legal concentration limits (0.001%). The primary purpose is to explore whether further research into the potential biochemical remediation of THC into CBD would be worth pursuing in terms of both functionality and profitability within the CBD industry. Two primary process designs were modelled using SuperPro Designer, one producing a CBD isolate, and another producing a full spectrum CBD blend containing other cannabinoids beyond CBD, as well as other compounds like flavonoids and terpenes. The CBD isolate model is composed of four parts: the extraction of the crude oil (including the pre-extraction process); the upstream processing of the oil; the reaction of THC into CBD; and the downstream processing of the oil. The full spectrum CBD model is similarly structured but with a different fourth process stage (downstream processing). Cultivating one’s own cannabis was calculated to be more economical than purchasing it from a third-party supplier, and thus a drip-based irrigation system of 1.2108 hectares was used, requiring capital costs of $ 24 641.90 and a yearly cultivation cost of $ 7629.76. Both processes begin with milling to increase the surface area of the cannabis, followed by passing through two consecutive cold ethanol mixer-settler extraction units. Next, the oil-plant matter mixture passes through a plate-and-frame filtering system and then a decarboxylation oven, which will convert the cannabinoids into their neutral forms, producing CBD from CBDA and THC from THCA, and releasing CO2 as a co-product. The oil then passes into a PFR, where CLEAs catalyse the reaction of THC into CBD. Due to the theoretical nature of the as-yet-unknown enzyme, conversion was assumed to be 85 %, where 37.46 kg of the enzyme was calculated to be required per year, assuming replacement is required after seven days of operation. The possibility of either producing or purchasing the enzyme was considered, but producing the enzyme worked out more economically viable, at a yearly cost of $ 2.84. This is where the full spectrum process halts. In the isolate process, the oil is then mixed with an acetonitrile-TBME stream before entering the CPC, alongside a heptane stream. Most of the CBD passes into the heptane, which moves iv to a distillation column after exiting the CPC process, with CBD isolate emerging from the bottom stream. The acetonitrile-TBME stream exiting the CPC will contain other cannabinoids and remaining cannabis compounds and will flow into a separate distillation. The bottom stream of the distillation column provides other valuable cannabinoid isolates, forming ancillary products (CBG, CBN, and THC isolates). In the full spectrum CBD model, the oil flows directly into a series of three consecutive distillation columns upon exiting the PFR, designed to reduce the THC concentrations in the oil to acceptable levels. The CBD oil emerging from both processes must then be incorporated into an MCT carrier oil. CBD isolates were assumed to be sold for $ 39.00 per 30 ml, with each unit containing 600 mg of CBD. Full spectrum CBD oil was assumed to be sold for $ 40.00 per 30 ml, where every 30 ml contains 1500 mg of cannabis oil. Once the costs of the MCT oil were deducted from the theoretical revenue values, the net revenue values came to $ 64 089.93 per kilogram for CBD isolate and $ 26 302.64 per kilogram for the full spectrum CBD oil. Collectively, the ancillary cannabinoid products (CBG, CBN, and THC) yielded a net revenue value (less the cost of the required MCT oil) of $ 17749.48 /kg. CBD isolate was produced at a rate of 637 kg/year, at 99.47 % purity, with ancillary cannabinoid products being produced at 494 kg/year by the isolate process. The full spectrum CBD blend was produced at a rate of 656 kg/year and did not contain any solvent residues. The isolate process was found to have a gross margin of 83.86%, an ROI of 101.58%, a payback time of 0.98 years, and an NPV of $ 190 458 000. The full spectrum blend has a gross margin of 50.89%, an ROI of 21.75%, a payback time of 4.60 years, and an NPV of $ 14 199 000. Thus, the isolate process was deemed the more economically viable of the two processes. An additional CBD isolate design involving supercritical CO2 extraction was also modelled for comparison. In this variation, the cannabis buds undergo milling before passing through the supercritical CO2 extraction unit. The CO2-ethanol solvent feed enters a CO2 storage unit wherein is pressurised to achieve supercritical conditions before entering the extraction unit alongside the cannabis stream. The bottom stream from the extraction unit then passes into a plate-and-frame filtration system, which removes the plant matter from the stream; the recovered cannabis oil is then reunited with the top stream from the extraction unit. The combined oil stream then undergoes winterisation, in 24-hour cycles, before moving into a distillation column which removes any remaining solvent. The bottom stream from the column then enters the decarboxylation oven; the remainder of the process continues in the same manner as the original, cold ethanol extraction isolate process. The CO2 extraction process produced CBD isolate at a rate of 600.54 kg/year. CBD purity of 99.29 % was achieved. An economic analysis produced project indices of a gross margin of 84.07%, an ROI of 95.28%, a payback time of 1.05 years, and an NPV of $ 173 404 000. Thus, with gross margin being the sole exception, all project indices indicate the cold ethanol process being the process with greater potential profitability to produce CBD isolates. Because the isolate process proved the most profitable of the alternatives, its potential profitability when scaled up to industrial size was also assessed. The process feed rate was increased to 79 200 kg of cannabis buds per year, solvent input streams were proportionally scaled up, and several equipment units were multiplied as required. Additionally, the quantity of the enzyme required for catalysing the reaction was recalculated based on the increased plant material in the process, coming to a yearly mass of 576.25 kg, for $ 345 750. The scaled-up process produced a CBD isolate product with a purity of 99.47% and a production rate equivalent to 9800 kg per year and the ancillary cannabinoid product at a rate of 7587 kg per year. The NPV of the scaled-up process came to $ 3.99 billion and a gross margin of 99 % was achieved, with an ROI of 1340 % and a payback time of 0.07 years. Therefore, from the simulated model and the economic analyses, the production of CBD oils using THC-to-CBD bioremediation was found to be a potentially profitable, as-yet-untapped production method that would benefit from further research. It is worth noting, however, that the research is limited by its reliance on theoretical models and assumptions, which may not fully reflect real-world conditions, potentially affecting the generalisability of the findings. The lack of empirical validation and practical factors not captured by simulations, such as enzyme stability, further constrain the applicability. Future work should focus on empirical testing and exploring a wider range of parameters to improve the results' relevance and generalisability.