Using the latest CCS and advanced fuels to help meet emissions targets
While shipowners are trying to determine the right path to obtain net-zero greenhouse gas (GHG) emissions by 2050, a new study envisions the use of carbon capture technology and e-methane and e-methanol fuels to achieve negative net-zero emissions.
In the concept study called CC-Meth by Mitsubishi Shipbuilding, a carbon capture and storage (CCS) plant would be installed on an ultra-large container ship (ULCS) that would burn either synthetic methane or methanol.
“Theoretically, you can combine blue hydrogen and captured CO2 and… create carbon-neutral methane or methanol,” explained Mitsubishi Shipbuilding deputy manager, strategic planning and operations Kazuki Saiki. The blue hydrogen would be produced using renewable energy –generated by wind, solar, water or geothermal energy - through electrolysis.
By operating the ship on carbon-neutral methane or methanol, in combination with the shipboard CCS plant, the vessel would yield net negative emissions.
“If we implement a methanation fuel system and carbon capture system on board, we theoretically make net negative solutions,” said Mr Saiki. “Remember, this methanation fuel is already carbon neutral, and if we collect the CO2 again, we can create theoretical net zero-emission conditions.” The idea behind the concept is to “trap” the CO2 in a closed-loop system, continuously reusing it and not releasing it into the atmosphere.
Mr Saiki discussed the concept study during Riviera Maritime Media’s Carbon capture for shipboard use and emissions monitoring webinar on 18 May. The webinar, sponsored by TECO2030 and supported by the Carbon Capture & Storage Association, was part of Carbon Capture & Storage Webinar Week, produced by LNG Shipping & Terminals and Marine Propulsion.
“The idea is to “trap” the CO2 in a closed-loop system, continuously reusing it and not releasing it into the atmosphere”
The study points out several challenges – both commercial and technical – for making the CCS concept a reality. One of those is that the additional energy required to run the entire shipboard CCS system would be almost 40% of the main engine power. “This is not small and does not include the diesel generator engines. It’s just maintenance,” he said.
For the study, the 20,000-TEU, methanol-fuelled box ship was equipped with a two-stroke MAN B&W dual-fuel 11G90ME-LGI engine, with a nominal operational rating of 49,500 kW. The CO2 emissions, including carbon capture, would be 766 tonnes per day and the system would require 37.7% of the engine’s power.
Additionally, the shipboard CCS system, between capture, liquefaction and storage, takes up an enormous amount of space on the ship. Mr Saiki also noted the system would result in the loss of almost 1,820 TEU s of containers – close to 10% of the ship’s capacity.
He said the capture plant and CO2 storage tanks were “huge” because if you burn one tonne of heavy-fuel oil it results in the release of three tonnes of CO2.
The CCS plant would capture about 95% of the CO2 emissions, but would result in a net CO2 reduction of about 80% because of the additional fuel consumption required to operate the plant.
“Onboard carbon capture is technically feasible, but, sadly, economically not,” said Mr Saiki. The implementation of a carbon tax or emissions trading scheme could provide impetus for the implementation of shipboard CCS. “We need to add economic incentives to shipowners, so that they can invest on this technology,” he said.
He noted that a compact shipboard CCS that captured a portion of CO2 emissions from a ship’s exhaust would be a possible solution for meeting IMO rules on EEDI or EEXI.
While he called the capex for shipboard CCS “a challenge”, he said that should drop over time. His bigger concern was shrinking the system’s footprint. Additionally, onshore and offshore storage capacity for CO2 is needed to underpin shipboard CCS, he noted.