The University of Sheffield has unveiled a 20 m high ‘catalytic poem’ mounted on a wall at the university, overlooking the A57. The poem, In Praise of Air by Simon Armitage, has been printed on a giant banner coated with photocatalytic titanium dioxide (TiO2).
Light shining on the photocatalyst excites electrons in the TiO2 molecule, which then react with oxygen in the air to form oxygen free radicals. The highly reactive free radicals then react with water in the air to form peroxide, which then oxidise pollutants, forming harmless by products. Nitrogen oxides (NOx) are converted to soluble nitrate, and volatile organic compounds (VOCs) are converted into fatty acids and soaps.
One square meter of treated material can remove around 2g of NOx per day, with the banner itself removing NOx equivalent to that released by a bus, or around 20 cars per day. The daily average traffic flow on the A57 adjacent to the banner was 14,789 in 2012; therefore, the poster will remove the NOx from just 0.001% of the traffic flow.
Although this project has highlighted the issue of poor air quality in the UK, it is unlikely that the use of catalytic surfaces will improve air quality, and trials carried out in the UK investigating the impact of NOx reducing paint have been inconclusive (LAQM Helpdesk, 2010). The technology works; however, given the large volumes of air that need to be cleaned, it is unlikely to be effective in reducing ambient concentrations of air pollutants. The only way to clean up the air is to not pollute in the first place.
In Praise of Air by Simon Armitage.
I write in praise of air. I was six or five
when a conjurer opened my knotted fist
and I held in my palm the whole of the sky.
I’ve carried it with me ever since.
Let air be a major god, its being
and touch, its breast-milk always tilted
to the lips. Both dragonfly and Boeing
dangle in its see-through nothingness…
Among the jumbled bric-a-brac I keep
a padlocked treasure-chest of empty space,
and on days when thoughts are fuddled with smog
or civilization crosses the street
with a white handkerchief over its mouth
and cars blow kisses to our lips from theirs
I turn the key, throw back the lid, breathe deep.
My first word, everyone’s first word, was air.