Discarded newspapers, disposable nappies and old cotton T-shirts might be rubbish to you but to Dr Marie Tuohy they represent valuable raw materials. All can be converted into sugars which can be used in dozens of ways, from energy production to drugs manufacture.
Dr Tuohy works in the Department of Biochemistry at NUI Galway and in the university's Environmental Change Institute. She also heads the Molecular and Glyco Biotechnology Research Group which involves 14 graduate students and two post doctorates.
Her research focuses on turning trash into resources by finding ways of reducing all types of waste but particularly by turning paper and other cellulose-based substances into sugars. The key to this work lies with a number of enzymes, found in a fungus, that enable this complex breakdown.
"We are focusing on carbohydrate-modifying enzymes from fungal sources and are interested in cloning the genes and characterising the enzymes," she explained. "We then want to find applications for them."
Paper waste is a particular problem around the world. Once dumped into landfill it degrades very slowly and the bacteria that reduce it tend to emit methane, a powerful greenhouse gas.
"What we want to do is look at the other angle; we can take this waste and use enzymes to reduce it."
Breaking down paper and cellulose materials, including plant waste, using enzymes would have a number of advantages, she explained. "In practical terms it could save 70 to 75 per cent of the landfill space."
Methane production would be reduced but the single greatest advantage is that when these enzymes are used, the cellulose breaks down into "waste" that can be taken off and used as a valuable raw material.
A number of sugar forms come off in a liquid syrup that is easily recovered. Much of the remaining residue is lignan, a tar-like substance. It is a polyphenotic compound used by the plant as a form of protection, but it can be burned as fuel or broken down further by methane forming bacteria.
"This is where the economic benefits of waste kick in," she said. "The sugar syrups can be subsequently fermented to bioethanol, green motor fuel, and other chemical feedstocks by yeast and fungi, while the lignan-rich residues represent an important source of thermal energy and agricultural fertilisers."
Bio-ethanol is simply alcohol, produced by straightforward fermentation and distillation. All that is needed is a cheap source of sugars and the resultant alcohol can be added to petrol for motor fuel. The sugars could also be used in drug manufacture when used as a feedstock for yeasts in fermentation or to feed bacteria or fungi in a reactor.
The fungus involved in the work actually produces a collection of 15 to 20 enzymes important to the breakdown process, Dr Tuohy said. "We found it on a compost heap. We knew if it was living in the heap it was breaking down the compounds."
The research team isolated and purified the enzymes and characterised a number of them. Their actions were studied as individual proteins but also as collections in various groups. The enzymes alone can reduce the paper faster than the natural fungus, she said.
"To make the process more valuable we have cloned the gene for some of the key enzymes." The team mixed and matched the various enzymes as a way to achieve particular types of waste breakdown. For example they can be used for total cellulose reduction or waste newsprint can be de-inked while retaining the cellulose fibres in paper recycling.
The team is also looking at other uses for the enzymes in textile manufacture and processing, in functional foodstuffs and novel food processing technologies.
Dr Tuohy believes that between two-thirds and three-quarters of the paper volume could be recovered as sugars and much of the remainder as lignans, leaving very little residue for landfill other than ash. Bandages, fabrics and other cellulose-containing wastes could be sterilised by heating while at the same time being reduced by heat-resistant fungal enzymes. This process would greatly reduce landfill and eliminating the risk of infection from this material.