Life cycle analysis of biomass derived fuels for fuel cells

Archer, Sophie Alice (2019). Life cycle analysis of biomass derived fuels for fuel cells. University of Birmingham. Ph.D.

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Abstract

The core purpose of this thesis was to identify and assess alternative sources of fuel gases for use in fuel cells and demonstrate their environmental impact in comparison to fossil fuel reference cases. By utilising biomass, fuel gases were found to be sourced from several feedstocks, including biowastes. The chosen methodology for achieving this purpose, was Life Cycle Analysis (LCA). Through the exploration of LCA methodologies and gaining new understanding of the varieties of techniques available, the guidance provided by the ISO standards (ISO 14040 and 14044) established a core four-stage method that all LCA practitioners must abide by to be consistent. ISO 14025 provides in-depth guidance for comparative LCAs.

Concerning advancements in biomass conversion techniques, three core biomass generations can provide a multitude of gaseous and liquid fuel products from a variety of feedstocks. In order to produce an LCA for gaseous fuels from biomass, a novel synthesis of primary data, using the baseline chemical composition of inputs and outputs, alongside process efficiencies and gas clean-up technologies was required. All gaseous biomass pathways identified were established alongside fossil derived reference cases. In addition, an overview of different types of fuel cells, a technology that converts a fuel gas (e.g. hydrogen) to electricity electrochemically is presented.

Finally, the conduction of a comparative LCA of viable biomass pathways produced a multitude of results, across a number of assessments. The key findings of this thesis include the insight that even pathways with low efficiency and high fuel gas demands have the potential for low ecological impacts, as metabolic processing has some of the lowest process efficiencies due to biological limitations, whilst also producing high yields of gas per kg of biomass feedstock (in this case, algae). Fuels derived from biomass were found to be highly ecologically competitive against fossil fuel reference cases, with third generation algal pathways and second generation biowastes utilised in SCWG, being the most favourable, followed by anaerobic digestion. SOFCs also proved to be a more favourable technology than PEFCs, due to their wide range of fuel choices and higher efficiency.

Supplementary data for this thesis can be found on the University of Birmingham eData repository at: https://doi.org/10.25500/edata.bham.00000378

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):