2004 IRISH SCIENTIST YEAR BOOK

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Institute of Technology Carlow
Linda Jennings
Sugar beet – a renewable fuel feedstock

Postgraduate researcher, Siobhan Wheatley, working on the Renewable Fuels project at IT Carlow

With the inevitable depletion of the world's petroleum supply, there has been an increasing worldwide interest in alternative, non-petroleum-based sources of energy. A growing source of transportation fuel worldwide is fermentation derived bioethanol. As well as reducing green-house gases, bioethanol produces less harmful emissions during combustion than its fossil fuel equivalents. Bioethanol is produced from a wide variety of raw materials – including cornstarch, sugar cane and lignocellulosic waste materials. The main cost element in bioethanol production is the feedstock. The use of alternative types of biomass as a source of carbohydrates for fermentation to ethanol has been studied by many investigators worldwide. Potential cheap feedstocks include lignocellulosic biomass from urban and industrial waste and from wood/agricultural residues. Researchers at the Institute of Technology Carlow have investigated the conversion of a variety of waste materials to ethanol – including grasses, cereal straws, newspaper and waste office paper. This research has now been expanded to include sugar processing waste.

1.34 million tonnes of sugar beet are grown in Ireland each year by 3,700 growers based mainly in the southeast of the country. The sugar beet is processed at two plants, one in Carlow and one in Mallow, which yields 200,000 tonnes of sugar. The main byproducts of sugar processing are molasses and sugar beet pulp. The Carlow factory produces 25,000 tonnes of molasses and 80,000 tonnes of sugar beet pulp annually. Molasses and pulp are currently used as animal feed. However, as pulp and the molasses contain substantial amounts of carbohydrates, they have potential as a raw material for the production of fuel ethanol or bioethanol. Molasses contains 50% sucrose, with smaller amounts of fructose and glucose. Sugar beet pulp contains approximately 30% cellulose, 30% hemicellulose, and 30% pectin.

The research at Carlow is concentrating on the enzymatic hydrolysis of the sugar beet pulp to its constituent monomeric sugars – which include glucose, fructose, mannose, galactose, xylose and arabinose. While technology for fermentation of single sugars (particularly glucose) is very well developed, the fermentation of complex mixtures of sugars which include pentoses is not. The use of unconventional fermenting microorganisms to maximize ethanol production is being investigated. The ultimate aim is to work towards the development of new microbial strains with improved properties for the conversion of such waste-derived sugar hydrolysates to ethanol.

Contact: Dr Linda Jennings, Department of Health & Science, Institute of Technology Carlow;
Tel: 059-9170531; E-mail: [email protected]