The Shipping Industry’s Polluted Secret
This article sheds light onto the dark side of how the shipping industry meets the IMO 2020 global sulfur cap by taking advantage of a loophole, and the effects it has on the world.
Table of Contents
The Sulphur Emission Problem and Solution
Scrubbers
The Grim Consequences
Current Gaps in the Solution Landscape
The Sulphur Emission Problem and Solution
The fact that the shipping industry transports more than 90% of all world trade by sea using around 90,000 ships means that very high quantities of marine fuel oil are being consumed for energy at a time. And since almost all of these ships use combustion engines, some sort of emissions are ever-present as an outcome of the combustion process — it’s just a given. The contents of these emissions, harmful or not, depending on the type of fuel being used. This leads us to explore the industry favorite: Heavy Fuel Oil (HFO).
HFO is extremely energy-dense, containing very long hydrocarbon chains that allow for lots of energy to be produced while the bonds break apart during combustion. This oil is also extremely inexpensive since it’s a type of leftover oil from the crude oil mining process. It’s 30%-50% cheaper than other energy-dense alternatives, making this fuel generally stand out as the “best deal” economically. Unfortunately, this means that alternatives are not easily adopted since the industry is comfortable using this oil, they get a lot of what they want (energy) for low costs.
This is an issue because of the amount of pollution the usage of HFO creates. Being a “leftover” oil, HFO often contains high concentrations of sulfur, heavy metals, and other pollutants. 99% of the carbon in fuel oil is converted to CO2 during the combustion process, leading the industry to produce 1 billion metric tons of CO2 annually — 3% of all greenhouse gas emissions. But what’s worse is that this isn’t all, the industry also emits nitrogen oxides, alarming amounts of black carbon, sulfur dioxides, and other pollutants. That’s only considering the air pollutants. Read more about this specific issue in depth in this article. This article will focus on the issues around sulfur emissions only.
According to my previous article, HFO often contains heavy metal impurities and is usually high in sulfur, with an average content of around 2.5% by weight, equivalent to 25,000 parts per million (ppm). When it is consumed through combustion, the sulfur and oxygen create Sulfur Dioxide, a gaseous air pollutant. This pollutant is so dangerous because in the atmosphere it can turn into sulfates, a major part of fine particle pollution in the U.S. It can even mix with water and air to create the main component of acid rain, sulfuric acid. Aside from these already detrimental issues, sulfur dioxide can also cause a variety of respiratory diseases and problems to those who are exposed to it. All of these detrimental issues led the International Maritime Organization to create a sulfur cap in 2020 — a global regulation that limits the amount of sulfur in fuel used in ships to 0.50% m/m.
This left the shipping industry with two general options:
- Change to a new, more environmentally friendly fuel oil. These specific alternatives are generally more expensive and less energy dense than HFO, as mentioned in my previous article.
- Buy and fit a “scrubber”, a technology that strips the fuel exhaust of sulfur to prevent sulfur air pollution from the combustion process. It allows the ships to continue using cheap fuel while abiding by the IMO sulfur cap.
The second option was unsurprisingly very popular. Although scrubbers are initially expensive to buy and fit, their cost is recovered within a year. As some of the biggest industry players start rapidly start fitting their fleets with scrubbers to keep using cheap but energy-dense fuel, others follow suit. The scrubber industry is being expected to grow to be valued at USD 14 Billion by 2030.
From this graph, we see a sharp increase in the number of ships with scrubbers. And although the 4,000 may seem like a measly quantity when compared to the 90,000 ships currently out there, the changes brought on in the past two years by the sulfur cap have shown incredible results. A study on the human health impacts of sulfur emissions from ships in 2016 by Finland estimates that lowered emissions contribute to preventing more than 570,000 additional premature deaths that would have been caused by emitted sulfur-related causes worldwide between 2020–2025. The regulation was forecast to lead to a 77%, around 8.5 million metric tons, drop in overall sulfur oxide emissions from ships.
Scrubbers sound like a great solution to preventing pollution, and they are, but only for air pollution.
Scrubbers
As the scrubber market advances so do scrubbers. In general, scrubbers “scrub” the exhaust (polluted air produced from combustion) by hosing it with seawater/freshwater (depending on the water available), this water collects the pollutants. This creates a sludge that contains high concentrations of sulfur compounds and heavy metals as a byproduct of the process. What happens to this wastewater sludge then depends on the type of scrubber being used.
TLDR; If it’s an open loop scrubber, the wastewater is dumped into the sea with little to no treatment. If it’s a closed loop scrubber, the water is stored to be discarded of on land in treatment facilities. If it’s a hybrid scrubber, it can do both.
Closed Loop Scrubber: This type of system has an alkaline-dosed freshwater tank on board, this just means that this water has been treated with certain chemicals to make it more alkaline so that it can collect the pollutants more efficiently and with less water. As the tank of water is being circulated through the scrubbing process, it returns to the primary system to be filtered of solid particles and reused. The collected sludge sits in storage tanks to be then taken to treatment facilities on land. This type of system is the most expensive. Closed-loop scrubbers account for less than 2% of the scrubbers installed in ships (Comer, 2020).
Open Loop Scrubber: This type of system utilizes the water around the ship to spray the exhaust. As the seawater circulates through the scrubbing process, collecting all the sulfate and hard metals, it gets discharged into the sea with low or no wastewater treatment. This system is initially somewhat expensive to buy and fit, but the cost is usually recovered within a year according to an industry expert. Open-loop scrubbers account for around 80% of the scrubbers installed in ships (Comer, 2020).
Hybrid Scrubber: This system has the capabilities of both types of scrubbers; it can treat water and hold onto the sludge and release it into the sea at a later time or not at all (if taken to a treatment facility). This is useful for ships when they sail around areas where open-loop scrubbers are prohibited or in similarly protected zones because they can switch to the closed-loop system and just swap to the open-loop system where allowed, allowing for ships to easily bypass local restrictions. Another loophole is being exploited here. Hybrid scrubbers account for around 17% of the scrubbers installed on ships (Comer, 2020).
On the left is a diagram of a closed-loop scrubber, and on the right, an open-looped scrubber. The closed-loop scrubber has to have tanks to hold specific chemicals to dose the stored water with, a process tank to be able to reuse that water efficiently, and all sorts of other bits that an open-loop scrubber simply doesn’t need. Using a closed-loop scrubber is more of a hassle and more expensive than using an open-loop scrubber. What happens with the sludge is a big driving factor for the industry too. According to independent shipping analyst Ned Molloy, “This [the sludge] is sulfurous waste going into the sea. It would be illegal to just dump this anywhere on land anywhere in the EU, except in specialist facilities” (Laville, 2018). It’s difficult and costly to contain and transport the sludge to a treatment facility, especially as ships move internationally.
To prevent the detrimental effects of discharging acidic wastewater into the seas, some countries have prohibited the usage of open-loop scrubbers. Here’s a link to more about that, and a picture from the article.
Although there are regional limitations, this doesn’t limit the discharge in more distant waters. It seems as if whenever there’s a new regulation, a new loophole is just being exploited. Something needs to be done from the root causes, not to prevent with policy 100% but to deal with the sulfur before it hits the oceans because of how many problems it creates.
The Grim Consequences
So why is acidic wastewater so bad for the ocean?
The main problem that this situation contributes to is ocean acidification. This is when we have excess acidic atoms leading to a lowered pH (lower means more acidic). The ocean generally has alkaline buffers, materials that bond with the acidic atoms to neutralize them. However, as the ocean gets polluted with more and more acidic materials (Carbon dioxide, sulfur, etc.) the buffers are not enough to curb ocean acidification. Ocean acidification is an occurrence that causes multiple detrimental effects including but not limited to:
- Coral reef death. Coral reefs bleach and die out, disturbing the 25% of all marine life that depends on coral ecosystems for sustenance and protection. 33% of all reef-building corals are threatened and/or dying. 50% of all corals have already died. Read the first half of this article to find out more about coral reef death and its consequences.
- Rising temperatures. Seawater temperatures rise because DMS emissions lower under acidic circumstances. DMS is a particle released from various oceanic organisms that helps form clouds that shade parts of the sea, a natural defense process that has been proven to cool down the climate regionally.
- Declining organism populations. Coral, oysters, clams, and other organisms that use carbonate to grow their shells and exoskeletons start dissolving and are unable to rebuild their bodily structures.
- Food insecurity. As smaller organisms start to get affected, biodiversity and food chains are jeopardized, creating food insecurity for shoreline communities.
- Money loss. Around 2.7$ trillion annually comes from and depends on the ecosystem service value provided by coral reef ecosystems. The death of corals means the depletion of this money.
The wastewater produced by the scrubber's discharge can be up to 100,000 times more acidic than regular seawater. And since a whopping 10 gigatons (10,000,000,000 tonnes) of this highly acidic sludge is being discharged annually, ocean acidification has greatly worsened. In fact, according to new studies, if 15% to 35% of the fleet operating in the English Channel and the southern North Sea used open-loop or hybrid scrubbers, the pH would drop by each year the pH would drop by 0.004 and 0.010 pH units annually. This is about as much as the ocean acidifies in two to four years due to climate change. Even more startling the pH decrease near Rotterdam was estimated at up to 0.088 pH units per year, which would have taken between 30 and 50 years from climate change.
While comparing maps I noticed that most of the sludge is discharged around where major coral reefs are located. This is very concerning since the death of corals is one of the biggest and most dangerous effects of ocean acidification.
Current Gaps in the Solution Landscape
With this issue gaining more recognition as some countries start to ban scrubbers, the solution landscape comes into color. Alternative fuels, location restriction, and using more closed-loop scrubbers are all viable solutions, except that the industry finds a way to bypass these as the “solutions” pose some sort of drawback for them. To be more specific about the holes in the solution landscape, we need to look at why the industry has historically avoided such solutions, and more specifically, understand what prevents solutions from existing in this situation.
Reluctant Industry→ Limits Expansion
Scrubbers help the industry meet the sulfur cap and keep profiting from using cheap oil for fuel. Without an economic incentive, they don’t have a monetary reason to be interested in adopting new technology that could filter their wastewater sludge.
We have to work to make sure that a potential solution integrates into the existing processes since we can’t depend on the shipping industry to change to a more environmentally friendly fuel or a new type of scrubber. The solution needs to be easy to implement and use, relatively cheap, and offer some sort of incentive for usage, or at least not increase costs.
Public Policy
Creating a sulfur cap mandate to reduce air pollution has been a strong step in the right direction, but it highlights the public policy gap because it took around 4 years to be put into action, yet is still flawed in its approach to environmental health because instead of reducing overall sulfur emissions, it allows the sulfur to be transferred from the air to the water at hardly an increased cost to ship owners.
Technical Operational Gaps
There are existing solutions that separate sulfur from seawater using liquid injections or other chemical-based separation methods. However, storage and a lack of incentive prevent these solutions from being commonly used. Having to store tanks of other liquids and fit extra technology to clean the wastewater sludge to alkalize the seawater before it flows back into the sea is not an ideal solution because it just poses a new hassle, often costly as well. Some existing methods of filtering sulfur from water and why they won’t work are:
- Reverse Osmosis: This is when water is pushed through a semi-permeable membrane to filter out the pollution from the seawater. Think of the polluted water getting pushed through a material with tiny holes. The sulfur gets filtered out. This is not ideal because only small amounts of sulfur and other contaminants get filtered; it is not efficient.
- Distillation: This is when water is boiled to physically separate the water vapor from the sulfur and other pollutants. Components with low boiling points (including sulfur) are separated from the mixture this way. To isolate sulfur and vaporize water, a large amount of energy is required which proves to be a disadvantage of distillation, especially when you multiply it by how many ships would need to expend said energy. Additionally, boiling water with sulfur in it may cause unwanted chemical reactions.
To summarize, because the International Maritime Organization set a sulfur (present in conventional fuel) cap in 2020, the shipping industry has been rapidly adopting scrubbers on board.
While open-loop scrubbers separate the pollutants from the exhaust with water, this wastewater, which is extremely acidic and toxic, is dumped into the sea, defeating the purpose of the IMO sulfur cap. It’s vital to add an extra step to further filter the sulfur and pollution from the seawater before it gets sent back into the sea. This is hard to solve for because of industry reluctance, operational gaps such as storage issues, and a lack of economic incentives.
As I continue to research the specifics of this issue, I’m also looking into biological and chemical processes that not only separate the dissolved sulfur from the water but also “get rid of” the sulfur in some way. I’m currently looking into a few different solutions threads, namely sulfur-eating bacteria, lily-pad-inspired pollution filtration systems, and mimicking the fibers on the inside of a cow’s lungs to collect sulfur from the exhaust without water. If anyone has any ideas or resources around any of these threads please let me know!
