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."

PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
Life and Style
ebookNow available in paperback
ebooks
ebookPart of The Independent’s new eBook series The Great Composers
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

    Tradewind Recruitment: KS2 Teacher

    Negotiable: Tradewind Recruitment: My client is a two form entry primary schoo...

    Tradewind Recruitment: English Teacher

    Negotiable: Tradewind Recruitment: My client is an excellent, large partially ...

    Tradewind Recruitment: Science Teacher

    £90 - £140 per day: Tradewind Recruitment: I am currently working in partnersh...

    Tradewind Recruitment: Year 3 Primary Teacher

    £100 - £150 per day: Tradewind Recruitment: Year 3 Teacher Birmingham Jan 2015...

    Day In a Page

    Isis hostage crisis: The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power

    Isis hostage crisis

    The prisoner swap has only one purpose for the militants - recognition its Islamic State exists and that foreign nations acknowledge its power, says Robert Fisk
    Missing salvage expert who found $50m of sunken treasure before disappearing, tracked down at last

    The runaway buccaneers and the ship full of gold

    Salvage expert Tommy Thompson found sunken treasure worth millions. Then he vanished... until now
    Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

    Homeless Veterans appeal: ‘If you’re hard on the world you are hard on yourself’

    Maverick artist Grayson Perry backs our campaign
    Assisted Dying Bill: I want to be able to decide about my own death - I want to have control of my life

    Assisted Dying Bill: 'I want control of my life'

    This week the Assisted Dying Bill is debated in the Lords. Virginia Ironside, who has already made plans for her own self-deliverance, argues that it's time we allowed people a humane, compassionate death
    Move over, kale - cabbage is the new rising star

    Cabbage is king again

    Sophie Morris banishes thoughts of soggy school dinners and turns over a new leaf
    11 best winter skin treats

    Give your moisturiser a helping hand: 11 best winter skin treats

    Get an extra boost of nourishment from one of these hard-working products
    Paul Scholes column: The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him

    Paul Scholes column

    The more Jose Mourinho attempts to influence match officials, the more they are likely to ignore him
    Frank Warren column: No cigar, but pots of money: here come the Cubans

    Frank Warren's Ringside

    No cigar, but pots of money: here come the Cubans
    Isis hostage crisis: Militant group stands strong as its numerous enemies fail to find a common plan to defeat it

    Isis stands strong as its numerous enemies fail to find a common plan to defeat it

    The jihadis are being squeezed militarily and economically, but there is no sign of an implosion, says Patrick Cockburn
    Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action

    Virtual reality: Seeing is believing

    Virtual reality thrusts viewers into the frontline of global events - and puts film-goers at the heart of the action
    Homeless Veterans appeal: MP says Coalition ‘not doing enough’

    Homeless Veterans appeal

    MP says Coalition ‘not doing enough’ to help
    Larry David, Steve Coogan and other comedians share stories of depression in new documentary

    Comedians share stories of depression

    The director of the new documentary, Kevin Pollak, tells Jessica Barrett how he got them to talk
    Has The Archers lost the plot with it's spicy storylines?

    Has The Archers lost the plot?

    A growing number of listeners are voicing their discontent over the rural soap's spicy storylines; so loudly that even the BBC's director-general seems worried, says Simon Kelner
    English Heritage adds 14 post-war office buildings to its protected lists

    14 office buildings added to protected lists

    Christopher Beanland explores the underrated appeal of these palaces of pen-pushing
    Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

    Human skull discovery in Israel proves humans lived side-by-side with Neanderthals

    Scientists unearthed the cranial fragments from Manot Cave in West Galilee