Green hydrogen has gathered increasing interest as a medium in the transition to a carbonneutral economy, with several large, export-focused projects currently under development in Southern Africa. However, the environmental implications of hydrogen production and utilisation are not well understood. To address this challenge, a comprehensive literature review for hydrogen production and utilisation lifecycle assessment studies was conducted, and two prospective comparative lifecycle assessments are presented for green and grey hydrogen production and utilisation in the South African context. The first LCA aims to quantify the environmental impacts of producing green hydrogen, relative to grey hydrogen, and determine the production route with the least environmental impacts. The scenarios investigated for hydrogen production are water electrolysis powered by wind, solar PV or concentrated solar power, steam methane reforming, and water electrolysis powered by a 2040 grid electricity mix. Furthermore, the impacts of three available electrolysis technologies; viz. polymer electrolytic membrane (PEM), alkaline, and solid oxide electrolysis were compared. The second LCA aims to compare two systems of utilisation for the green hydrogen that would be produced in South Africa to determine the option where the highest level of decarbonisation could be achieved. The application considered for the assessment is the fuelling of heavy-duty truck transportation. The systems considered are local utilisation for fuelling heavy-duty trucks and hydrogen exportation to Germany also to fuel heavy-duty trucks. These two systems were expanded to include conventional fuel utilisation, making the functional units of the systems equal and thus the systems comparable. SimaPro was used to conduct the two LCAs, and the ReCiPe 2016 midpoint method was used for the lifecycle impact assessments. Grid-powered water electrolysis is found to have the highest potential impacts across most impact categories, even for the case of the significantly decarbonised 2040 grid mix, with SMR second. Solar PV-powered electrolysis leads to the highest potential human non-carcinogenic toxicity impact caused, by the supply chains of PV panels. Wind-powered water electrolysis is the least impactful option across most categories. However, it has the highest potential human carcinogenic toxicity impact among the renewable production options, though it is less than half compared to the value for non-renewable hydrogen production. This toxicity is caused by the supply chains of wind turbines. Considering optimal electrolyser utilisation, combined wind and solar PV-powered electrolysis is the best option. When comparing the water electrolysis technologies, PEM electrolysis leads to the highest environmental impacts. The energy input for production dominates all the impacts. In terms of utilisation, the environmental impact reductions achievable by the export case outweigh the environmental impact reductions achievable by using the green hydrogen locally, across all impact categories. The highest level of decarbonisation is achieved by replacing the most environmentally harmful fuel; South African coal-based diesel used to fuel heavy-duty trucks. The results of the first LCA confirm that green hydrogen is indeed significantly less environmentally impactful compared to grey hydrogen, but with one hotspot for each of the PV and wind-powered electrolysis, which require attention by project developers. The environmental impacts of all the production scenarios are dominated by the energy required for the production processes. The main finding for the second LCA is that local hydrogen utilisation for heavy-duty truck transportation leads to a larger environmental benefit compared to hydrogen exportation in the case of usage for heavy-duty truck transportation in another country. The highest level of decarbonisation is achieved by displacing South African coal-based diesel first.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/37514 |
| Date | 24 March 2023 |
| Creators | Mbaba, Ongezwa |
| Contributors | von Blottnitz, Harro, Fadiel, Ahjum |
| Publisher | Faculty of Engineering and the Built Environment, Department of Chemical Engineering |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MSc |
| Format | application/pdf |
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