A Cheap & Easy Way To Reduce Carbon Emissions From Ships

It is pretty well known that the ships that ply the oceans of the world, transporting cargos of every type and dimension, are a significant source of emissions that are not climate friendly. In all, ships are responsible for more carbon dioxide emissions than air travel. But there is a lot of other nasty stuff that escapes from all those smokestacks. Depending on the fuel their engines run on, they can include soot (fine particulates), oxides of nitrogen, and sulfur dioxide. You really don’t want to put your face over one of those smokestacks and take a deep breath.

The problem originated with the engines that have been powering those ships for generations. The oldest of them burn bunker oil — the sludge that is left over when refineries have extracted all the useful products they can from petroleum. It is so thick, it needs to be heated to make it flow from the fuel tanks to the engines. You might think, “Well, why don’t they just switch to a cleaner fuel?”

The answer is, those marine diesel engines don’t have a crankcase filled with lubricating oil like in a standard internal combustion engine. Instead, the oily fuel itself provides all the internal lubrication needed. Not only that, bunker oil is cheap, so switching to cleaner fuels would make shipping more expensive. In a business where costs are figured to the hundredth of a penny per ton/mile, that is not news managers want to hear.

Ships can be retrofitted with more modern engines that burn cleaner fuel, but the process can cost a half million dollars or more. It also requires the ship be taken out of revenue service for many months, so not only is money going out the door to pay for the retrofit, there is no money coming in to offset the lost revenue.

Seabound Carbon Capture System

There are a number of strategies proposed to clean up emissions from ships — electrification, sails, green ammonia, biomethane — and they all have pluses and minuses. In London, a new company called Seabound says it has a way to capture some of those emissions in a low tech and affordable way.

“Shipowners face mounting pressure to reduce greenhouse gas emissions from new global regulations, customers, and shareholders, but have limited viable options. Future fuels are decades away, efficiency solutions insufficient, and slow steaming just pushes off the inevitable,” the company says on its website.

“Seabound’s onboard carbon capture system is proven and ready today. Shipping drives 90% of the world’s economy. Shipowners who want to capture a competitive edge and lead the industry’s decarbonization now have an ocean-ready option with Seabound.”

The Seabound system basically consists of steel containers roughly the size of standard shipping containers. Inside are quicklime pellets about the size of cherries. A ship’s exhaust is piped into the container where carbon dioxide reacts with the quicklime, turning it into limestone.

It has been a few years since I took chemistry in high school, so I turned to Wikipedia to update my understanding of quicklime, which is also known as calcium oxide. Wikipedia says it is typically made by the thermal decomposition of limestone or seashells that contain calcium carbonate (CaCO3) in a kiln. When the kiln is heated to more than 825 °C (1,517 °F), a molecule of  carbon dioxide is released, leaving quicklime behind. This reaction has been known to humans since prehistoric times and is one of the precursors to cement.

Quicklime is made in commercially significant amounts. The largest producer is China, which makes about 170 million tons of  the stuff every year. The US is second at about 20 million tons. Shhhh…..don’t tell the Big Guy or he will declare a quicklime emergency!

A Dedication To The Climate

The creative force behind the Seabound technology is Alisha Fredriksson, a young entrepreneur who got the idea after reading a report from the Intergovernmental Panel on Climate Change that detailed the global implications of 1.5ºC vs. 2ºC of warming. “That’s when I realized that everyone around the world will be affected by the climate crisis, and so if I cared about large scale social impact, the best thing I could do would be to help tackle it,” she told Emma Bryce of The Guardian recently.

Quicklime is used to capture carbon emissions at many large industrial facilities. Fredriksson and her co-founder, Roujia Wen, came up with the idea of scaling down one of those systems to fit aboard a ship. Early tests showed positive results. The pair made a prototype, which attracted about $4 million in funding from investors. Some of the money came from shipping companies themselves. “It all happened really quickly. Suddenly we had money, and we had to go build it,” said Fredriksson. “I think people were ready for a solution.”

A succession of prototypes have taken Fredriksson from Seabound’s testing facility in East London to shipyards in Turkey, and then to the deck of a ship carrying 3200 containers through the Suez canal. What that journey showed is that a Seabound unit can capture 78% of all the carbon from a ship’s exhaust and 90% of the sulfur.

The latest prototype is being built to the dimensions of a standard 20ft (5.9 meter) shipping container, so that it can seamlessly slot in with cargo on deck, Fredriksson says. The design allows the stacking of several containers like regular cargo, and enables the ship to incrementally increase carbon capture in line with its journey length and decarbonization goals. Once a ship docks, the container sized units can be offloaded and replaced with other containers packed with fresh quicklime.

Too Good To Be True?

If this all sounds too good to be true, it is. CleanTechnica readers, being better informed than most, know that when limestone is heated, it gives off copious amounts of carbon dioxide. In addition, heating the kiln to the required temperature also produces lots of carbon dioxide. Those are problems that bedevil the cement industry. If we take limestone, convert it into quicklime, and it becomes limestone again as it captures carbon dioxide, is there any net gain?

As part of the search for low carbon cement, companies are experimenting with using renewable energy instead of fossil fuels to heat kilns and are developing methods to capture the carbon dioxide that gets released so it doesn’t enter the atmosphere. “There isn’t currently a large quantity of green lime available globally, however there are many companies in the lime industry that are working on producing this — both large incumbents and various startups.” Fredriksson said.

Not everyone is impressed with the Seabound approach. “The potential for short-term use of carbon-capture retrofits on existing vessels should not become a justification to extend the lifespan of fossil fuels or delay the shift to truly sustainable alternatives,” Blánaid Sheeran of Opportunity Green, a nonprofit organization focused on gaps in global climate policy, told The Guardian.

In April, at a meeting of the International Maritime Organization, UN member states agreed to a landmark deal that will start charging ships for every ton of emissions above a certain threshold, which will gradually incentify shipping companies to adopt low carbon fuels. Seabound believes its technology will fit well in this new regulatory program. “We can grow the amount of carbon capture as the regulations ramp up,” she said, and added that the Seabound technology can begin cleaning up ships now as green fuels filter through the industry later.

Fredriksson said the Seabound technology is cost effective, and her company already has a commitment from one shipping company to fit the first full-scale containers on to its ships later this year. Asked what her vision of the future is, she said, “It would be that we’re on hundreds to, hopefully, thousands of ships, and we’ve got hubs in all the major ports around the world.” That is unlikely to happen unless and until the problem of making quicklime affordable and green is solved.