Peer-Reviewed Study Highlights Scrubbers’ Role in Science-Based Decarbonization

A peer-reviewed study conducted by the Massachusetts Institute of Technology and the Georgia Institute of Technology in cooperation with Oldendorff Carriers (Oldendorff) provides new insights into the environmental impact of exhaust gas cleaning systems (scrubbers) and their role in broader decarbonization efforts. 

The study finds that for large, ocean-going bulk carriers operating in open seas, heavy fuel oil (HFO) used with a scrubber can, in various instances, outperform low-sulfur fuels when assessed from a life cycle perspective. The study also provides scientific evidence that open-loop scrubber washwater discharges are well within International Maritime Organization (IMO) environmental thresholds, while being significantly lower than stringent U.S. and EU limits for municipal and industrial effluents. Even under a conservative 1,000-fold dilution assumption, the expected final concentrations in receiving water bodies remain significantly below EU environmental quality standards and U.S. EPA water quality criteria for marine ecosystems. 

This first-of-its-kind study, based on a full, well-to-wake life cycle assessment using real-world, in-situ data, offers new clarity in the ongoing global debate around the environmental impact of scrubbers. 

Implications for future maritime regulations  

The study arrives at a critical moment for maritime regulation, as policymakers work to balance emissions reductions with operational feasibility. Past regulatory decisions on scrubbers were often shaped by concerns that real-world data and peer-reviewed research has now refuted. By providing robust scientific evidence, this research highlights the need for policy decisions grounded in verified information.  

“Studies like this are urgently needed to resolve complex environmental questions, uncover unknowns, and support science-based policy and decision-making in the shipping sector and beyond. While many reports have been released on this topic, peer-reviewed studies are limited. The peer-review process is essential to ensure scientific rigor and build trust in the results.” Patricia Stathatou, Assistant Professor in the School of Chemical and Biomolecular Engineering at Georgia Tech and Lead Author of the study, states. 

Addressing the Research Gap 

The study was commissioned by Oldendorff in 2021 to generate independent data on scrubber performance under real operating conditions. Testing was carried out during a voyage of the Hedwig Oldendorff (209,131 tdw) from Taicang to Hong Kong. 

Most earlier studies evaluating scrubber impact lacked a complete Well-to-Wake life cycle assessment, and many were based on outdated data from first-generation systems. These limitations contributed to continued regulatory uncertainty. This new study, published in the American Chemical Society journal, Environmental Science and Technology, addresses those shortcomings, using up-to-date data on air and washwater emissions from a modern scrubber system operating at sea. 

"This study demonstrates the scientific complexity of the waste stream of scrubbers. Having finally conducted a multi-year, comprehensive and peer-reviewed study, commonly held fears and assumptions are now put to rest. For far too long, regulators and the shipping industry have relied on outdated or incomplete scientific analysis when developing regulations with profound financial impact on shipping." Scott Bergeron, Managing Director Fleet at Oldendorff Carriers, concludes.

*Clarksons, 2024 (Green Technology Tracker: 41% of tonnage ordered in 1H 2024 alternative fuelled – Clarksons Research)