Air quality implications of coal-ammonia co-firing

Japan is currently gearing up to begin replacing coal with ammonia (NH3) as an alternative to burning coal as the burning itself does not emit greenhouse gases and it is relatively easier, cheaper, and safer to transport than hydrogen. For these reasons, it is believed to be a green alternative to coal combustion and G7 climate ministers have tentatively agreed to the plans. However, the current commonly used method of production of ammonia is a significant source of greenhouse gas emissions as it involves the burning of fossil fuels, which leads to emissions of carbon dioxide. Furthermore, to satisfy the demand for ammonia, it will need to be imported using ships that are also powered by this fuel. 

The Centre for Research on Energy and Clean Air (CREA) has published a report on the impact of coal-ammonia co-firing at Japan’s Hekinan Thermal Power Station.

The findings of the report show that, ultimately, the co-firing of ammonia will affect emissions of several different species (PM2.5, SO2, NO2, NH3), from multiple different activities, such as production, transport, and  combustion, and the changes in total emissions have the potential to affect atmospheric concentrations of PM2.5 and human health, as well as emissions of greenhouse gases, which are contributing to climate change. 

Emissions of PM 2.5 and its precursor species (NO 2 , SO 2 , and NH 3 ) at Unit 4 of the Hekinan Thermal Power Station

Note: For each of the three fuel mix scenarios, we show emissions of PM 2.5 (red bar) SO 2 (green bar), NO 2 (orange bar), NH 3 (blue bar) from all activities (production + transport, + combustion), and total pollutant emissions (PM 2.5 + SO 2 + NO 2 + NH 3 ) from combustion only (black star). Sources: Data used to create this figure is taken from Koplitz et al. (2017), European Environment Agency (2021), Balcome et al (2022) and DieselNet (2023).

CREA’s report includes primary research specifically associated with the Hekinan Thermal Power Station, Japan’s largest thermal power station, which is currently undergoing an ammonia co-firing trial and so is under the spotlight. 

Key findings

  • Fine Particles (PM2.5) are an atmospheric pollutant that are responsible for thousands of premature deaths in Japan each year, and millions worldwide.
  • We estimated total emissions of PM2.5 and precursor gases at Unit 4 of Hekinan Thermal Power Station, where 0 %, 20 % and 50 % of the energy demand is met by NH3 (and the remaining energy demand is met by coal).
  • We found that total emissions of PM2.5 and precursor gases increase by 67 % when NH3 displaces 20 % of the energy demand, and by 167 % when NH3 displaces 50 % of the energy demand.
  • These large increases in total emissions are due to the emissions of the PM2.5 precursor gas NH3, which are released during the shipping and combustion of this fuel.
  • The increased total emission will likely lead to increased PM2.5 concentrations and an even larger public health burden of this pollutant.

Following this research, which reveals the risks to human health and the environment in an ammonia co-firing energy transition, the Centre for Research on Energy and Clean Air (CREA) urges the Japanese government to invest in renewable energy sources such as solar and wind.

The press release and report are also available in Japanese.

Lauri Myllyvirta, Lead Analyst, CREA; Jamie Kelly, Air Quality Analyst, CREA