Seaweed on your plate, carbon out of the air: Korea's 'black semiconductor' pulls its weight

Gim — the dried seaweed sheets that have long been a staple of the Korean table — is drawing fresh attention as a carbon sink in an era of climate crisis, with researchers now working to quantify just how much CO2 the crop can absorb.

According to South Chungcheong Province, Seocheon-gun and the Ministry of Oceans and Fisheries, gim converts carbon dioxide into organic matter through photosynthesis, absorbing CO2 throughout its growth cycle.

The Korea Environment Corporation said last year that, as of October 2024, one ton of gim absorbs 4.92 tons of carbon dioxide — nearly five times its own weight in carbon.

Building on that figure, Seocheon-gun announced Thursday that its gim farms produced 47,851 tons of the seaweed last year, reducing carbon dioxide emissions by 235,426.9 tons in the process. That figure accounts for 95.4 percent of the county's total emissions reduction of 246,879 tons and is nearly double the original target of 127,587 tons.

Extrapolating from last year's national gim output of 718,000 tons, analysts estimate the crop absorbed roughly 3.53 million tons of CO2 across the country.

According to the Greenhouse Gas Inventory and Research Center under the Ministry of Climate, Environment and Energy, South Korea's total greenhouse gas emissions in 2023 stood at 707.2 million tons. Based on that figure, gim aquaculture could account for roughly 0.5 percent of the country's total emissions reduction.

Research to pin down the scale of gim's carbon absorption more precisely is already underway. South Chungcheong Province has been conducting a study focused on waters off Seocheon since March.

The Marine Science Research Institute at Gunsan University, which is carrying out the research, plans to measure CO2 absorption by farmed gim and develop a numerical model showing how absorption rates vary with light and water temperature, with results expected by the end of this year.

Wando-gun in South Jeolla Province, which accounts for more than half of the country's total seaweed output, is also pursuing what it calls a "Wando-style ocean pension" — a scheme to distribute revenue generated through seaweed blue-carbon trading directly to local residents.

Gim and other seaweeds were recognized as new carbon sinks by the Intergovernmental Panel on Climate Change at its 63rd plenary session last October.

Meanwhile, according to the Ministry of Oceans and Fisheries, gim exports surpassed $100 million in 2010, crossed $700 million in 2021, and last year set an all-time record of $1.13 billion.