2020 Sulfur Cap

Effective January 1, the International Maritime Organization (IMO) has imposed a cap on sulfur emissions that the organization announced in 2016. The sulfur cap of 0.50% m/m (mass/mass), revising the former 3.5% cap, will affect about 70,000 ships worldwide.

Sulfur emissions have many harmful effects, most notably acid rain, which damages crops, is harmful to animals, and raises the acidity of the oceans. The decision to limit sulfur emissions was needed, but I wanted to look at how ship owners and manufacturers would achieve this seemingly drastic drop in standards. I found out that there are multiple ways to limit sulfur emissions, so I wanted to highlight a couple of the popular ones.

First, owners could simply switch to a low sulfur content fuel. This is essentially the same fuel they currently use but it’s pre-treated to remove a lot of the sulfur. This fuel is about 25% more expensive, and there are supply concerns if many users make the switch. There is also the issue of how the fuel burns. It may technically be the same fuel, but it burns hotter and affects lubrication needs for the engine. No easy fix here.

Another route would be to switch to gas or methanol as fuel. Again, this affects lubrication and changes exhaust temperatures, and it’s also very expensive to buy a new engine or to retrofit a current engine to be able to use these types of fuel.

Finally, one of the more popular ideas is the use of scrubbers. Scrubbers are devices that are added after the engine in the exhaust system. The scrubber uses water (seawater or treated fresh water) to treat the exhaust and remove most of the sulfur. There are three types of scrubbers: open loop systems, closed loop systems, and hybrid systems.

Open loop systems treat the exhaust and then release the waste into the ocean. This is a simple system, costs the least amount of money, and takes the least amount of time to install.

Closed loop systems treat the exhaust and then store the waste to be discharged later at port or treatment facility. These systems cost more, and you need more space to store the wastewater, which, as you can imagine, is a problem in the marine shipping industry.

Hybrid systems treat the exhaust, and then you can either store the waste or you can discharge the waste into the sea. This is handy when the port or area of the sea doesn’t allow waste discharge. The waste can be stored until the ship is in an area of the sea or at a port where discharge is allowed.

Scrubbers sound great until you think about the fact that the sulfur we were worried about being released into the air and causing acid rain – which acidifies the oceans – just gets dumped directly into the sea. Ship owners have thought about this, too, and they fear that soon there will be further regulations passed that will govern the waste from scrubbers as well.

The solution to pollution, should not be dilution.