Engineers from West Virginia University (WVU) have developed a new production process for a carbon-neutral battery made from liquid ammonia. The new process fixes nitrogen extracted from the air with hydrogen extracted from water - no carbon involved. Ammonia produced in this way can also be used as fertiliser, thereby reducing demand for the Haber-Bosch process.
The Haber-Bosch process has remained the predominant means to chemically fix nitrogen and produce agricultural fertilisers despite being responsible for 1-2% of global energy consumption and 3% of global emissions. The Haber-Bosch process is very energy intensive and extracts hydrogen from methane (natural gas fossil fuel). The new production process developed by WVU, in constrast, is much less energy intensive and can be used as an energy vector for renewables, helping decarbonise the energy sector.
While renewable energy sources offer low-to-zero carbon emissions, they cannot offer constant energy production nor currently meet demand fluctuations. Batteries can store surplus energy generated from renewables and release the energy when there’s demand. Lithium-ion batteries are the most popular alternative to traditional lead-acid batteries but concerns over resource scarcity have lead researchers to explore alternative technologies. Indirect hydrogen storage media, such as ammonia and methanol, are currently being considered as such alternatives. Only ammonia is carbon-free.
However – just because it’s carbon-free doesn’t mean it’s emission free. Nitrogen can form atmospheric nitrous oxide (N2O), a greenhouse gas roughly 300 times more potent than CO2. And, if the ammonia is used as a fertiliser, runoff can pollute waterways and lead to eutrophication. Additionally, extracting hydrogen from water in areas of water insecurity (such as California) may not be viable, and hydrogen could instead be extracted from methane – a greenhouse gas 30 times more potent than CO2 – making ammonia carbon negative.
If ammonia batteries are going to be the future of carbon-neutral electricity, their impacts beyond carbon must be considered.