Life cycle assessment (LCA) and Techno-economic Analysis (TEA) of extracting valuable chemicals from tail gas reactive pyrolysis oil

Inadequate disposal of horse manure is a threat to the environment and water quality. These threats are caused by deposit of surplus nutrients into the environment via surface runoff or leaching from landfill. As a result of... [ view full abstract ]

Inadequate disposal of horse manure is a threat to the environment and water quality. These threats are caused by deposit of surplus nutrients into the environment via surface runoff or leaching from landfill. As a result of the significant impact to the environment, proper disposal can be costly. A cost-effective alternative to disposal is to convert horse manure to a fast pyrolysis bio-oil that can be further upgraded to an advanced biofuel or valuable chemicals like phenols. We use life cycle assessment (LCA) and techno-economic analysis (TEA) to evaluate the environmental tradeoffs and cost of reacting horse manure in a modified fast pyrolysis process termed, tail gas reactive pyrolysis (TGRP), that produces a bio-oil that can be upgraded to transportation fuel, and phenol in New York State. We explore the environmental and resource depletion metrics global warming potential (GWP) and cumulative exergy demand (CExD) and test different allocation rules for the coproducts. The LCA results show that the allocation method and system expansion used plays a significant role in the results.

Using mass, energy and economic allocation, the GWP and CExD of the TGRP renewable fuel production process is 30gCO₂ eq. and 0.36 MJ per 1 MJ of fuel produced, which indicates a GHG emission savings of 67-68% in comparison with aviation fuel. With economic allocation, most of the burden placed on the GWP comes from the phenol due its higher economic value compared to aviation fuel. With system expansion, because co-products such as phenols and coke are credited, the GWP (2.5g CO₂eq.) is much lower than the functionally equivalent petroleum product it replaces. On the other hand, CExD of the TGRP renewable fuel (0.33MJ) is higher than aviation fuel. In comparison to other alternative upgrading processes like hydroprocessing [1-4] , the GHG emission savings in the TGRP process falls within the range of these processes with savings of 50-87%.

We also estimate the economic feasibility of the process in comparison to the production of aviation fuel, by calculating the minimum fuel product selling price (MFSP) based on capital and operating costs. The results show that, using a best-case scenario of low cost of raw materials (catalyst, hydrogen and feedstock), high cost of co-product (phenol), high process yield while including social cost of carbon, we achieve a MFSP of $2.62 per gallon which is twice the average price of aviation fuel.

References

1. Hsu, D.D., Life cycle assessment of gasoline and diesel produced via fast pyrolysis and hydroprocessing. Biomass and Bioenergy, 2012. 45: p. 41-47.

2. Iribarren, D., J.F. Peters, and J. Dufour, Life cycle assessment of transportation fuels from biomass pyrolysis. Fuel, 2012. 97: p. 812-821.

3. Peters, J.F., D. Iribarren, and J. Dufour, Simulation and life cycle assessment of biofuel production via fast pyrolysis and hydroupgrading. Fuel, 2015. 139: p. 441-456.

4. Shemfe, M.B., et al., Comparative evaluation of GHG emissions from the use of Miscanthus for bio-hydrocarbon production via fast pyrolysis and bio-oil upgrading. Applied Energy, 2016. 176: p. 22-33.