Impact analysis of novel routes in alternative fuel production

The escalating challenges of climate change and plastic pollution call for solutions that simultaneously reduce CO₂ emissions and upcycle waste. This thesis investigates the PHOENIX system, a solar-driven tandem electrochemical platform that integrates CO₂ utilization with polyethylene terephthalate (PET) plastic recycling. PHOENIX couples a photovoltaic–electrolyzer (PV-EC), which reduces CO₂ to carbon monoxide while oxidizing PET-derived ethylene glycol into glycolic acid, with a photoelectrochemical reactor (PEC) that converts carbon monoxide into n-propanol and produces additional glycolic acid. The process yields two products: n-propanol, a potential alternative fuel, and glycolic acid, a precursor for biodegradable plastics. Comprehensive mass and energy balances were developed, followed by a cradle-to-gate life cycle assessment (ISO 14040/44, EF v3.1) benchmarking PHOENIX against fossil-based production. Results show that, when powered by renewable electricity, the system achieves major reductions in CO₂ emissions and fossil resource use. However, photovoltaic infrastructure introduces trade-offs, notably higher critical metal consumption and resource depletion. Scalability analysis indicates that large-scale n-propanol fuel substitution is impractical due to high energy needs, land footprint, and excessive glycolic acid co-production. Instead, PHOENIX shows strong promise for high-value chemical manufacturing, particularly glycolic acid, where both environmental and industrial performance are more favorable. In conclusion, PHOENIX demonstrates a meaningful advance in linking CO₂ conversion with plastic waste upcycling. While unsuitable as a bulk fuel route, it offers a sustainable pathway for producing specialty chemicals. Future efforts should focus on improving reactor efficiency, lowering energy intensity, and targeting applications where smaller-scale, high-value production maximizes sustainability and industrial relevance.