2025 Spring Meeting and 21st Global Congress on Process Safety

(85c) Cradle-to-Gate Greenhouse Gas Emissions from Ethylene Produced Via Corn Ethanol

Authors

Pahola Thathiana Benavides, Argonne National Laboratory
Ulises Gracida Alvarez, Michigan Technological University
Troy Hawkins, Eastern Research Group, Inc. (ERG)
The purpose of this study was to evaluate the potential cradle-to-gate greenhouse gas emissions or carbon footprint estimate of producing ethylene from U.S. corn ethanol.

The analysis covered bio-based ethylene production pathways via corn ethanol dehydration from the following routes:

  • Stand-alone ethanol-to-ethylene processes
  • A co-processing route via fluid catalytic cracking (FCC) process wherein corn ethanol was co-processed with vacuum gas oil (VGO)

Fossil-based ethylene production was included as a reference case for carbon footprint estimate comparison with corn-ethanol derived ethylene.

For this study, carbon-14 (C-14) content was used to determine how much of the product was derived from bioethanol in the co-processing case. Additionally, modeled yields based on co-processing yields of ethanol and VGO and base FCC unit yields (based on 100% VGO) were used to generate bio-ethylene yields for comparison purposes.

This study demonstrated that corn ethanol-based ethylene showed lower carbon footprint estimate when compared to fossil-based ethylene production (103% - 127% reduction in the base case scenarios). The study also evaluated the impact of low carbon intensity (CI) ethanol on the carbon footprint of bio-ethylene. For example, substituting natural gas used in ethanol production with renewable natural gas (RNG) from animal manure and utilizing heat and power from corn stover collected during farming reduced the carbon footprint estimate of bio-ethylene compared to the baseline corn ethanol production. This reduction was due to the addition of biogenic CO2 sequestration credits and avoided emissions of current waste management practices by use of RNG.

Additionally, the correlation between the CI of ethanol and carbon footprint of bio-ethylene for ethanol sources beyond corn was studied as a sensitivity. Since lignocellulosic feedstocks resulted in lower CI estimate of ethanol compared to non-lignocellulosic feedstocks, the carbon footprint estimate of bio-ethylene produced was lower in the former cases.