Processes for biobutanol production from renewable resources

Abstract

The impact of petroleum fuel emissions and more rapid diminishing petroleum reserves have increased the research for alternative biofuel sources. In this scenario, recently is rising the biorefinery concept. A biorefinery is a facility that produces fuels, power, heat, and value-added chemicals from conversion. The study carried out during the present Ph.D. program aimed at investigating the butanol production process by fermentation from renewable resources. The activities, in order to pursue the biorefinery concept, were articulated according to three paths :i)Feedstock market and techno-economic feasibility assessment of butanol production; ii)Biomass Pretreatment; iii)Butanol production and characterization of the ABE fermentation process. These studies were carried out at the Enco Engineering Consulting Company, at the of Western Ontario Canada and at the Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale of the University of Naples 'Federico II'. Waste to energy: feedstocks market assessment The cost of the substrate represents about 60% of the overall production cost for a fermentation process. For this reason, feedstock available at high mass rate, with a constant availability over the year and low cost is a key issue for the success of the butanol production. A survey of potential waste biomass for butanol production was proposes. The maximum butanol production rate from each has been estimated taking into account the feedstock availability rate, the average composition and the butanol yield. Furthermore, a study aiming at investigating the techno-economic feasibility of butanol production from lignocellulosic was carried out. A potential flowsheet to produce butanol by conversion of a lignocellulosic has been simulated by means of the software Aspen Plus®. The production process has been splitted into three sections: the upstream section, the fermentation section, and the butanol recovery section. Particular attention has been paid to the upstream process. The upstream units have been analysed according the approximated cost-estimation methods integrated with the simulation software Aspen Plus®. Biomass Pretreatment A new class of solvents DES (Deep Eutectic Solvent) has been investigated to obtain fermentable sugars from corncob. Corncob, a byproduct of corn grain production, is currently being used as a potential feedstock for cellulosic ethanol production in the United States, as it has a low lignin and high carbohydrate contents. DESs exhibit similar physico-chemical properties to ionic liquids, but they are environmentally friendlier and much cheaper. The pretretated corncob was characterized in term of lignin content, inhibitors concentration, crystallinity index and enzymatic digestibility. Butanol production and characterization of the ABE fermentation process The study was aimed at the assessment of the butanol production by C. acetobutylicum. Xylose and lactose are used as carbon source. Xylose is one of the mains components of the lignocellulose hydrolysates, lactose is used to mime cheese-whey, a wastewater stream released from the cheese industry. In order to optimize a continuous biofilm reactor, which is characterized by a heterogeneous cell population, the kinetics of acidogenic and solventogenic cells are investigated. Acids production by acidogenic cells and butanol production by solventogenic cells were investigated using different reactor configurations: CSTR under controlled pH and CSTR with microfiltration unit respectively. Operating conditions of the continuous tests were selected to maximize the butanol production and butanol selectivity.