Winner of the Excellence in Sustainability Steelie Award 2023
Rice is the staple food in South Korea. Every year, 3.8 million tonnes of rice are harvested, accounting for a staggering 87% of the national crop production. However, in our country, rice farming has inherent challenges.
First, soil that lacks calcium and magnesium has poor nutrient retention capacity, creating an unfavourable condition for crop growth. Second, the constant presence of water in flooded rice paddies interferes with the passage of oxygen into the soil. Lack of oxygen in soil is an ideal condition for anaerobic microorganisms that produce methane through the decomposition of organic matter. Silicate fertilizer can be a solution for these two obstacles.
Since 1973, we have supplied 14 million tonnes of blast furnace (BF) slag, a core ingredient of silicate fertilizer, to the farming industry. Thirty to forty percent of the slag generated during the BF ironmaking process is composed of calcium and magnesium, nutrients that prevent soil acidification. In addition, silica, a key rice stem nutrient, makes up 35% of BF slag.
Rice cultivation impacts the environment. In our country, flooded rice paddies are responsible for 21% (230,000 tonnes) of the annual national production of methane.
However, collaborative research with a university revealed that iron ions (Fe3+) found in BF slag can inhibit the activity of methanogens and reduce methane emissions in rice farming.
Additionally, the research has found that 1.5 tonnes of slag-based silicate fertilizer can slash methane emissions by 14% per hectare of rice paddy (27,000 tonnes of methane avoided from 2018 to 2022). Furthermore, by developing Fe-enhanced slag fertilizer, we achieved the dual benefit of recycling steelmaking by-products and enhancing avoided GHG emissions. With 2.5wt% iron content increase, this premium fertilizer cuts methane emissions by 33%, more than twice that of conventional slag fertilizers (14%). With the goal to maximise avoided GHG emissions, we intend to export Fe-enhanced fertilizers to other rice-producing Asian countries.