September 15, 2020
Are scrubbers the answer to compliance for the shipping industry?
The shipping industry is facing challenging new requirements set forth by the International Maritime Organization (IMO) 2020 Sulfur Cap that limit the sulfur content in fuel oil and restrict air emissions of sulfur oxide (SOx). The temporary setback in shipping activities due to the COVID-19 pandemic will not derail requirements for regulatory compliance or the industry's plan to reduce air pollution. As an alternative to the use of expensive, low-sulfur fuel, ocean-going ships are increasingly using exhaust gas cleaning systems (EGCS), also called scrubbers. Scrubber systems redirect greenhouse gases and other constituents (e.g., metals, petroleum hydrocarbons) in engine exhaust gas into effluent that is either discharged to the ocean (open-loop scrubbers) or treated and held for later discharge (closed-loop scrubbers).
The leading, more economically sound alternative is an open-loop scrubber. More than 3,500 vessels have already been retrofitted with this system. As their use increases, it is imperative to determine whether these scrubber systems are environmentally sound, especially in coastal areas with less potential for dilution and dispersion compared to the open sea. A task force recently convened by the United Nation's Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection to give an opinion on the potential environmental and public health risk of EGCS effluent concluded that additional information and analyses are needed.
How Exponent Can Help
Exponent can help identify knowledge gaps and develop strategies for addressing key issues highlighted by the task force:
- Reliable monitoring data for effluent are scarce. Exponent can design sampling plans with a focus on quantifying concentrations of bioavailable contaminants in the effluent, which are expected to be better predictors of risk than concentrations of "total" contaminants.
- The current regulatory limit for hydrocarbons in EGCS effluent is not well defined, and its level of protection is questionable. Exponent staff are experts in the development and implementation of the most recent, reliable, and globally utilized effect thresholds for hydrocarbons.
- Laboratory toxicity tests indicate that adverse effects to test organisms were predominantly caused by the low pH and low dissolved oxygen of the effluent, which may not reflect conditions in the field. Exponent has extensive experience in the use of whole-effluent toxicity (WET) tests and toxicity identification evaluations (TIEs) for effluents.
- Fate and transport models will be needed to account for dilution and mixing of the effluent at different spatial scales (e.g., open seas, harbors). Exponent has considerable experience with developing and employing fate and transport models that can specifically be applied in EGCS effluent impact assessments.