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Cotton stalks and cotton ginning trash both present management problems for growers and processors within the cotton industry. One option, now being considered, is to use these materials to produce ethanol fuel. One of the biggest influences on the viability of producing ethanol, however, is the cost of the material used.
To identify if cotton wastes were viable feedstocks, a model of the cost to collect and transport cotton stalks and ginning trash was developed on a spreadsheet. Two variables were allocated triangular probability distributions: the biomass yield (tonne per hectare), and the biomass transport weight (tonne per transport unit). Sensitivity analysis was carried out by varying the contract rates, transport rates, and transport distance.
The best collection method identified, was to forage harvest the cotton stalks into boll buggies, and transport it (over an assumed 50 km) compacted as modules or pallets; costing $30-$40/tonne, ($0.10-$0.13/litre of ethanol produced). Sensitivity analysis indicated the contract rates had the biggest effect on collection costs, transport rates had the least effect, and increasing the transport distance to 100 km increased the cost of the best collection method by $6.00/tonne ($0.02/litre of ethanol produced).
It was concluded that given the collection costs identified and current estimates of plant economics, the operation of a lignocellulosic ethanol production plant using cotton stalks or cotton ginning trash, was a viable proposition.