Reducing carbon emissions from roads, rail and shipping requires a range of solutions to be implemented simultaneously. In the case of cars, reducing trips altogether (by making it easier for people to walk and cycle and improving public transport), switching vehicle fuels, and making the most of the vehicles already on the road will all have to play their part. None of these solutions are sufficient by themselves.
The UK will ban the sale of new diesel and petrol passenger cars by 2030. The future of passenger vehicles will be electric. But recent parts supply issues and the high carbon costs of building electric vehicles could delay the climate benefits of the switch.
To get the most out of existing gasoline and diesel-burning vehicles — and the carbon invested in making them — drivers and manufacturers can reduce emissions of a class of compounds called nitrogen oxides, which are linked to respiratory disease in smog, by better treating exhaust fumes . That way, the communities most affected by air pollution can at least be protected until harmful vehicle emissions are eventually eradicated.
My research team is developing a new generation of catalytic converters—devices that fit into exhaust pipes to reduce the release of toxic gases. Inspired by chemical reactions observed on the surfaces of extremely hot planets like Venus, we’ve produced a synthetic material that could improve air quality.
From Venus to Car Exhaust
Sunlight destroys carbon dioxide (CO2) in the planet’s atmosphere, producing carbon monoxide (CO). Not fast enough to avoid climate change, but fast enough for an atmosphere like Venus to contain more carbon dioxide than we observe there.
Our group studies the effects of meteoric material (dust from space) in the atmosphere. We made an iron silicate powder that replicates this dust to accelerate the conversion of CO to CO2. That’s what the first catalytic converters in cars were designed to do, because CO is a poisonous gas.
This got us thinking about whether the material could help tackle other problems, such as nitrogen oxide pollution in the air of many UK cities exceeding legal limits. Poor air quality caused by vehicle exhaust kills tens of thousands of people every year.
We found that the powder not only removes both CO and nitrogen oxide emissions, but also converts nitrogen dioxide (NO2, a specially regulated noxious gas) into harmless molecular nitrogen (N2) and water at room temperature.
Catalysts installed in modern diesel vehicles to treat nitrogen oxide (NOx) emissions can only work at exhaust temperatures above 150°C. Even if your car uses an additive fluid to reduce NOx emissions, it’s less likely to work at slow speeds when the exhaust is cooler. This is when vehicles emit the most nitrogen dioxide — usually in traffic jams, where the most polluted air collects.
Catalytic converters that can remove nitrogen oxides may still be important when the grid is decarbonized enough to charge millions of electric vehicles. For example, natural gas fuel in industrial furnaces is likely to be replaced by hydrogen.
Unlike hydrogen buses and cars, which generate energy through reactions in fuel cells, larger applications such as steel mill furnaces will burn hydrogen fuel directly. This high-temperature combustion converts molecular nitrogen in the air into nitrogen oxide pollution, which needs to be removed.
That’s why we’re excited to have developed a prototype emissions converter that will work in most situations and has the potential to radically reduce toxic emissions from internal combustion engines and other sources in the future.
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