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Assessment of Integrated Multi-Product Biorefineries
- Author / Creator
- Giwa, Temitayo
Concerns about the climate and the need for energy security motivate the shift towards sustainable means of energy production. Biorefineries are facilities that convert biomass into material and energy products. Biorefineries are a key component of ensuring increased sustainability of the global energy mix and for decarbonization of demand sectors such as transportation and power generation. However, economic viability have hampered commercial adoption of biorefineries. There have been efforts to improve the economics of biorefineries, but more efforts are needed.
The traditional approach in biorefining focuses on the production of one product or material path at a time. This approach limits the opportunity to fully use the original feedstock and thus derive maximum value. A multi-product approach, wherein multiple material paths are valorized to produce multiple products from a biorefinery, has been the subject of interest recently. This approach encourages the full use of the original feedstock and increases the revenue stream of the biorefinery. Hence, it has the potential to improve the economics of a biorefinery. The multi-product approach has been applied to various biomass valorization technologies like fast-pyrolysis. However, the application of this approach to the fast-pyrolysis process has been limited to the bio-oil material flow path, with the biochar and non-condensable gases material flow paths being ignored and used for less valuable applications like combustion.
The aim of this research is to investigate the economic and environmental implications of additional products produced through the valorization of biochar and hydrogen-rich non-condensable gases in a fast-pyrolysis biorefinery. Simulation models were developed for six different scenarios of modified biorefineries for value-adding to biochar and non-condensable gases and were compared to a conventional fast pyrolysis biorefinery. The scenarios differ by three proposed uses of the non-condensable gases and two types of external fuel, namely, natural gas and woodchips. It is assumed that ethanol is produced from both biochar and non-condensable gases and hydrogen from the non-condensable gases, depending on the scenario. The economic performance of the biorefineries was assessed using the internal rate of return, while the environmental performance was measured using the life cycle net energy ratio and greenhouse gas emissions of the biorefineries and their products.
The research findings show that multi-product approach improves the economic performance of biorefineries compared to the conventional fast pyrolysis process. The conventional fast pyrolysis process, the base case, has a rate of return of 7%, while the assessed scenarios have rate of return values in the range of 7.5 – 13%. However, the conversion of the original feedstock, in the assessed scenarios, did not show marked improvement relative to the conventional fast pyrolysis process. Generally, the products of the biorefineries showed lower greenhouse gas emissions intensity than their fossil counterparts. The results of this research will be of value to decision-makers in the public and private sectors.
- Graduation date
- Fall 2022
- Type of Item
- Master of Science
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