(580f) Technoeconomic Study of AB Synthesis for Biobutanol Production
The ethical issues involving first generation biofuels have led to focus on obtaining biofuels from agricultural residues. Corn being the major crop in the world, results in the fact that corn stover is widely available. However, in the case of biobutanol, the yield has been low due to the fact that together with biobutanol, ethanol and acetone are typically obtained. Thus, this work is divided in two parts: the first part is devoted to the experimental evaluation of the lignocellulosic biomass degradation. In the second one, a technoeconomic study of a new production process is described. The novelty of this work relies on the scale up of AB fermentations, that does not produce ethanol, (Qureshi et al., 1999). In addition, in-situ recovery techniques such as evaporation are also included at the process to make it economically competitive with conventional fuels and bioethanol.
In the first stage of the work, comprehensive evaluation of the experimental conditions to break down switchgrass and corn stover from Castille and Leon region (Spain) has been performed. The study considers both pretreatment and hydrolysis. With regards to pretreatment, several physio-chemical techniques such as acid (H2SO4), alkali (using KOH or NH4OH), ultrasounds processing, surfactants or organic solvents are tested. With regard toÂ hydrolysis, various enzyme cocktails were used. It turns out that corn stover reaches the highest yield, 677.00 mg of sugars by gram of biomass, when it is pretreated using a diluted sulfuric acid solution 0.5% v/v, autoclaving the mixture during 90 min at 121 ÂºC with no sonication stage. The hydrolysis method is set up at 50 ÂºC and 150 rpm with a solid loading of 2.5 % w/v and a ratio of enzymes/biomass of 400 and 440 Âµl/g of NS50013 (cellulose complex) and NS50010 (Î²-glucosidase cocktail) respectively. The sugar recovery obtained is competitive with current best available technologies i.e. (Sundaram and Muthykumarappan, 2016).
In a second stage, we synthesize a process for the production of biobutanol from corn stover including the use of novel technologies such as pervaporation to improve the yield from biomass and reducing the by-products by means of AB fermentation. The processes consists of four sections, pretreatment, hydrolysis, fermentation-pervaporation system and product purification. We use the experimental results to determine the yield of the pretreatment and hydrolysis. A hybrid simulation using EXCEL to develop black box kind of models for the experimentally validated units and ChemCAD has been performed to evaluate the technoeconomic feasibility of this process.
The results show an investment of 186 MMâ?¬ and a butanol production cost of 1.09 â?¬/kg for a 27 kt/y plant. The yield to butanol is 0.21 kg/kg of biomass resulting, altogether, in a fuel closerÂ to become competitive versus second generation bioethanol and fossil based fuels in terms of yield and cost.
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