Environmental Impact Modeling for a Small-Scale Field Test of Methane Removal by Iron Salt Aerosols

Abstract

Highlights: What are the main findings? No significant impacts of FeCl3 and HCl to the ship’s crew were identified in this assessment. For the marine environment, the natural iron levels and variability were found to be much greater than those produced by the hypothetical experiment. HCl deposition to the marine environment was found to have no significant impact. What is the implication of the main finding? The hypothetical small-scale field test can possibly be carried out. Various authors have highlighted the possible removal of methane from the atmosphere via oxidation by broad releases of iron salt aerosols in order to serve climate protection goals. This technique is known as enhanced atmospheric methane oxidation (EAMO). This study proposes and employs a modeling approach for the potential environmental impacts associated with a hypothetical small-scale field test of EAMO consisting of seeding cargo-ship exhaust plumes with iron salt aerosols. Using a sample region in the Southern Caribbean Sea as a hypothetical testing site, it provides assessments of potential impacts to air quality, human health, and the marine environment. The modeling focuses on the incremental difference between conducting the hypothetical field test and a no-action scenario. The model results are compared to ambient air standards and pertinent screening thresholds, including those associated with pertinent health risk metrics. The overall loading to the marine environment is contrasted against background rates of iron deposition to the marine surface. No significant impacts were identified in this assessment. The hypothetical atmospheric emissions of both FeCl3 and HCl that the ship’s crew may be exposed to remained below governmental guidance levels. The potential deposition of FeCl3 to the marine environment was found to be very minor in relation to the natural contributions experienced within the Southern Caribbean. Similarly, HCl deposition was assessed for potential impacts to the marine environment but was found to have no significant impact.