Invention: Ammonia storage to reduce NOx
A team of Danish researchers developed a method for storing ammonia in solid form by binding it with a compacted metallic salt. Their innovation opens up possibilities for the energy-rich chemical to be used as a safe hydrogen source for fuel cells and hydrogen-powered cars. More importantly, it can be employed as part of systems that remove as much as 99% of the mono-nitrogen oxides from diesel engine exhaust.
Ammonia is like an unco-operative superhero. It has potential to do good
- if it weren't so temperamental. Release a steady trickle of ammonia gas into
the exhaust system of a diesel engine, and potentially harmful mono-nitrogen
oxides (NO
and NO2 - collectively known as NOx) are reduced to
harmless water vapour and nitrogen. But storing the noxious and caustic
chemical is bulky (as a gas), expensive (as a liquid) or both (freezing it to a
solid).
Compact, convenient storage for ammonia appeared unlikely until a team of Danish scientists led by Johannessen and Quaade put their heads together and developed an entirely new way to tackle the problem. They discovered how to get certain metal salts, such as strontium chloride, to absorb ammonia like a sponge. In fact, through their process a 100-gram cube of this solid can fit into the palm of one's hand yet contain up to 50 grams of solid ammonia - the equivalent of 60 litres of ammonia gas.
Societal benefit
Johannessen, Quaade and co-researchers, who include Claus Hviid Christensen, Jens Kehlet Nørskov and Rasmus Zink Sørensen, have built a business around fighting pollution. Their solid-form ammonia product, marketed under the name AdAmmine, has a number of potential applications. It could be used as a storage device for hydrogen, for instance. That hydrogen, once removed, could then act as a propellant in either an internal combustion engine or in an electric fuel cell. At the moment, however, AdAmmine is most commonly used to neutralise NOx emissions from diesel engines, reducing them by as much as 99% - far beyond what competing technologies can offer.
The team's invention stands to disrupt the status quo. Current urea-based exhaust-scrubbers only start putting out cleaner emissions at temperatures upwards of 200°C. That is not a problem when driving longer distances because engines have time to heat up, but in short-distance city driving, such temperatures are rarely reached. Systems that use AdAmmine begin neutralising NOx pollutants in one-fifth of the time, and if the technology becomes an industry standard for exhaust scrubbing, it has the potential to make the air in and around cities cleaner and safer to breathe.
Economic benefit
The advantage of having fewer pollutants in the air is hard to appraise financially. A French Senate committee report estimates that the total effects of all air pollution (not just cars) cost the country some EUR 100 billion annually, citing reduced health as the major expense. It is fair to say that reducing diesel-engine-related smog through technologies such as AdAmmine would have a positive effect on pollution-related costs because transportation makes up about 44% of all NOx pollution.
Assessing the impact of AdAmmine on the automotive market is easier. Already, Amminex has had four successful investment rounds and is reported to have EUR 5.1 million in equity. Its roughly EUR 4.3 million in annual revenue is reinvested, so Amminex is not yet turning a profit, but the company is planning big. It wants to offer an alternative that would replace current AdBlue diesel-scrubbing systems, whose numbers are expected to triple in Europe by 2025.
