The simplest everyday acts—like carrying groceries home in plastic bags—can leave a trail of carbon footprints with potentially devastating impacts on our planet. Within the chemical industry, over half of all greenhouse gas (GHG) emissions come from the basic processes to make just two groups of products: ammonia-based fertilisers for farming, and oxygen-containing chemicals (oxygenates) for plastics.
“We make large volumes of ammonia and oxygenates due to how pervasive they are in modern life,” commented Wan Ru Leow, a Scientist at A*STAR’s Institute of Sustainability for Chemicals, Energy and Environment (ISCE2). “Unfortunately, both products use manufacturing processes with high carbon footprints, leading to a global release of 0.9 billion tonnes of carbon dioxide (CO2) each year.”
Leow explained that hydrogen gas, a key ingredient in ammonia, is currently extracted from methane using high-temperature reactions that directly create CO2 and are often powered by fossil fuels. Likewise, to turn hydrocarbons into oxygenates calls not only for energy-intensive heating and cooling, but inefficient reactions where up to 20 percent of a hydrocarbon feedstock may be lost as waste CO2.
Previous studies have shown that electrolysers—devices that use electricity, rather than heat, to facilitate chemical reactions—can reduce GHG emissions from chemical manufacturing processes, sparking a greener future for the industry. Leow joined forces with international collaborators to explore the potential of electrolysers that coupled two processes: electrified hydrocarbon-to-oxygenate conversion, and water-to-hydrogen evolution reactions.
Through a thorough life-cycle assessment, Leow and colleagues aimed to weigh up the approach’s efficiency and measure their GHG emissions versus traditional manufacturing methods. They found that by carefully tuning manufacturing conditions for optimal hydrocarbon-to-oxygenate conversion, they could cut the GHG emissions involved in making ammonia and oxygenates by up to 88 percent.
To their surprise, the team also found the coupled systems to substantially slash GHG emissions even without using clean energy sources such as wind or solar power. Emissions were reduced by up to 39 percent even with power grids using primarily fossil fuel-based electricity, such as those found in China and the United States.
A conceptual diagram for how electrolyser systems can cut carbon emissions in ammonia and plastics manufacturing. Apart from replacing fossil fuel-based inputs with renewable energy, electrolysers that couple two chemical processes (e.g., hydrocarbon-to-oxygenate conversion and hydrogen evolution from water) can make more efficient use of both energy and industrial feedstocks.
©️ A*STAR Research
“This is important as low-carbon electricity is still limited in most industrialised countries today,” said Leow, adding that as around 20 percent of global chemical sites manufacture both ammonia and oxygenates on-site, these facilities represent prime targets for implementing electrolyser technologies.
The study provides much-needed insights and opportunities that Leow hopes will spur positive change in tomorrow’s chemical manufacturing industries and encourage the scientific community to further develop such ‘carbon-lite’ manufacturing processes.
Moving forward, the team is positioning themselves to tackle other areas for improvement in the chemical industry, such as the development of greener hydrocarbon building blocks to pave the way for a carbon-neutral future.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Sustainability for Chemicals, Energy and Environment (ISCE2).
