Martin Clemesha of Braskem (Brazil) reminded us that Brazil had the world’s best climate for growing sugar cane and was therefore the best place for producing biofuels and biopolymers. Once again the land-use issue was dealt with thoroughly. 1 hectare of land can produce 77 tonnes of cane which can make 6700 liters of ethanol or 3 tonnes of ethylene or polyethylene per year. Braskem’s capacity for PE, now 200,000 tonnes/year represented 2% of Brazil’s total ethylene production or 0.02% of Brazilian arable land.
On a cradle to factory gate basis, the “I’m green” PE had a negative Global Warming Potential of -2.15kgs CO2/kg PE. The by-products of ethanol production, vinasse liquor and bagasse solids, both contribute to this benefit. The vinasse liquor (13 litres per litre of ethanol produced) is phosphorous-rich and used for irrigation, replacing some petro-fertilisers which would otherwise be needed. The bagasse (cane minus the sugar) is burnt in the power station providing more than enough electricity for the process. Overall, the process uses 1/5th of the fossil carbon used for petro-PE production.
Bio-LDPE is now available alongside the linear-low and high density grades. Illustrations of new applications included Huggies diapers in Asia.
Asked about the costs of the bio-PE Mr Clemesha said it would be a long time before they could compete with petro-PE. They had made massive investments and “I’m Green” would be a premium product for a long time. He could not say how much more expensive it would be but commented that it could well be the cheapest bio-plastic. Could the bagasse be used in composites? No, it was susceptible to rotting.
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