Science: King of the solvent substitute

LOOK ON the label of a popular brand of decaffeinated coffee and you will see it is made using "Nature's natural effervescence". This is a neat piece of marketing to explain the use of supercritical carbon dioxide in the manufacturing process.

"The marketing men probably decided that the word supercritical would frighten the general public," says Dr Steve Howdle, a research chemist at Nottingham University. "But carbon dioxide is far healthier than the dry cleaning solvents which were once used instead."

Howdle and his colleagues are examining what happens when carbon dioxide is compressed to about 70 times normal atmospheric pressure. Under those conditions it becomes "supercritical" and the gas takes on some of the properties of a liquid. It can then be used as a solvent to carry out chemical reactions and make new materials. As an alternative to harmful organic compounds like carbon tetrachloride, it has potential applications in a range of industrial processes. Extracting the caffeine out of coffee beans is one of the first to be used on a commercial scale, but there are many others in the pipeline.

The big advantage of carbon dioxide is that when the taps on a pressure vessel are opened it changes back into a gas and floats harmlessly away, leaving behind a clean, dry product. When liquid organic solvents are used a small residue always remains. The characteristic smell of a new car is caused by the solvents used in making the plastic trimmings. The residue may be harmful to human health and the ozone layer.

Using supercritical carbon dioxide does not contribute to the Greenhouse effect, and much of the gas used is a natural by-product of the brewing industry. In the Nottingham team there are 30 scientists looking at new applications for the technology.

Howdle became interested in this field while an undergraduate in Manchester 12 years ago. He heard a lecture on new solvents given by Martyn Poliakoff. He had been hoping to do some form of postgraduate study and went up to Professor Poliakoff after the lecture and asked for a job.

He said: "What I like about it that I am taking real problems that people are having to deal with and looking for new ways round them." As a Royal Society University research fellow, Howdle is encouraged to collaborate with scientists abroad. He is working with a group of Russian scientists in using carbon dioxide to make plastics for medical implants. Some people fitted with dental plates for false teeth, he points out, find they are unable to wear them because residues of conventional solvents can cause allergies.

Increasingly stringent legislation has led to bans on some solvents and will increase the pressure on industry to develop more environmentally friendly processes. "The challenge is not just to develop a greener process, we must also try to make it better, cheaper, easier or more controllable."

Have you tried new the Independent Digital Edition apps?
Life and Style
ebookNow available in paperback
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

ES Rentals

    iJobs Job Widget
    iJobs General

    Recruitment Genius: Electronic Service Engineer - Television & HI-FI

    £17000 - £21000 per annum: Recruitment Genius: Engineers for field & bench ser...

    Recruitment Genius: Digital Designer - Award Winning Agency

    £30000 - £40000 per annum: Recruitment Genius: A fantastic opportunity for a t...

    Recruitment Genius: Project Manager

    £35000 - £50000 per annum: Recruitment Genius: This global provider of call ce...

    Recruitment Genius: Customer Service and Business Support Assistant

    Negotiable: Recruitment Genius: By developing intimate relationships with inte...

    Day In a Page

    Blundering Tony Blair quits as Middle East peace envoy – only Israel will miss him

    Blundering Blair quits as Middle East peace envoy – only Israel will miss him

    For Arabs – and for Britons who lost their loved ones in his shambolic war in Iraq – his appointment was an insult, says Robert Fisk
    Fifa corruption arrests: All hail the Feds for riding to football's rescue

    Fifa corruption arrests

    All hail the Feds for riding to football's rescue, says Ian Herbert
    Isis in Syria: The Kurdish enclave still resisting the tyranny of President Assad and militant fighters

    The Kurdish enclave still resisting the tyranny of Assad and Isis

    In Syrian Kurdish cantons along the Turkish border, the progressive aims of the 2011 uprising are being enacted despite the war. Patrick Cockburn returns to Amuda
    How I survived Cambodia's Killing Fields: Acclaimed surgeon SreyRam Kuy celebrates her mother's determination to escape the US

    How I survived Cambodia's Killing Fields

    Acclaimed surgeon SreyRam Kuy celebrates her mother's determination to escape to the US
    Stephen Mangan interview: From posh buffoon to pregnant dad, the actor has quite a range

    How Stephen Mangan got his range

    Posh buffoon, hapless writer, pregnant dad - Mangan is certainly a versatile actor
    The ZX Spectrum has been crowd-funded back into play - with some 21st-century tweaks

    The ZX Spectrum is back

    The ZX Spectrum was the original - and for some players, still the best. David Crookes meets the fans who've kept the games' flames lit
    Grace of Monaco film panned: even the screenwriter pours scorn on biopic starring Nicole Kidman

    Even the screenwriter pours scorn on Grace of Monaco biopic

    The critics had a field day after last year's premiere, but the savaging goes on
    Menstrual Hygiene Day: The strange ideas people used to believe about periods

    Menstrual Hygiene Day: The strange ideas people once had about periods

    If one was missed, vomiting blood was seen as a viable alternative
    The best work perks: From free travel cards to making dreams come true (really)

    The quirks of work perks

    From free travel cards to making dreams come true (really)
    Is bridge the latest twee pastime to get hip?

    Is bridge becoming hip?

    The number of young players has trebled in the past year. Gillian Orr discovers if this old game has new tricks
    Long author-lists on research papers are threatening the academic work system

    The rise of 'hyperauthorship'

    Now that academic papers are written by thousands (yes, thousands) of contributors, it's getting hard to tell workers from shirkers
    The rise of Lego Clubs: How toys are helping children struggling with social interaction to build better relationships

    The rise of Lego Clubs

    How toys are helping children struggling with social interaction to build better relationships
    5 best running glasses

    On your marks: 5 best running glasses

    Whether you’re pounding pavements, parks or hill passes, keep your eyes protected in all weathers
    Joe Root: 'Ben Stokes gives everything – he’s rubbing off on us all'

    'Ben Stokes gives everything – he’s rubbing off on us all'

    Joe Root says the England dressing room is a happy place again – and Stokes is the catalyst
    Raif Badawi: Wife pleads for fresh EU help as Saudi blogger's health worsens

    Please save my husband

    As the health of blogger Raif Badawi worsens in prison, his wife urges EU governments to put pressure on the Saudi Arabian royal family to allow her husband to join his family in Canada