The pyrolysis behavior of wheat straw and mallee residue and resulting gases, liquids, and chars were examined. The specific heat and thermal conductivity of both species were measured using computer-aided thermal analysis at heating rates of 10 and 100 °C/min to a temperature of 1000 °C. The sample decomposition was also measured by thermogravimetry. Gas chromatography detected evolved gases, and the bio-oils were characterized using GC-MS. Chars were examined using FTIR, proximate, and ultimate analysis. Both species initially displayed endothermic behavior, followed by rapid decomposition and fluctuating specific heat and thermal conductivity between 250 and 500 °C. Oxides of carbon were the primary gases evolved, with small amounts of hydrocarbons and hydrogen. The bio-oils predominantly contained oxygenated aromatics and organic acids, and the chars had high fixed carbon and low sulfur. In all instances approximately half of the product output was liquid. Straw produced 14% gas and 32% solid at 500 °C, whereas mallee produced 13% gas and 36% solid. At 1000 °C the proportions of solid decreased and gas increased. The efficiency of pyrolysis to 500 °C, assuming no losses, was around 96% for both species. At 1000 °C the efficiency decreased, with pyrolysis of mallee slightly more efficient than for straw.
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Second generation liquid biofuels from lignocellulosic feedstocks are part of a suite of solutions to peak oil and a safe climate economy. Biofuels have technological advantages over electrification for applications with minimal refuelling or recharging options such as air travel, shipping, agriculture and low or intermittent frequency trucking and rail. We examined a fuel production concept combining slow pyrolysis chars and superfine commutation. Char is micronised and suspended in diesel or water to create a reduced cost, quality and energy density liquid biofuel. Process yields and efficiencies were derived from a review of the slow pyrolysis char, coal commutation and combustion literature and used to develop theoretical estimates of process performance. Char structure and composition were also reviewed in the context of commutation and management of ash and alkalis in the fuel. The paper concluded that char based fuels had potential applications where cost was critical, but quality was not, such as diesel engines for agriculture, trucks, trains, shipping and backup electricity supply. Char water fuels increase safety by being non-flammable and are environmentally benign, a valuable trait in sensitive environments such as coastal shipping.
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