Integration of a hemicelluloses extraction step into a forest biorefinery for production of green chemicals

Sustainable use of forest and agricultural resources will play an important role for solving urgent global challenges such as the enhanced green house effect and increasing demand for fossil fuels. The development of processes where lignocellulosic biomass can be refined to several different end-products in the same plant, i.e. a biorefinary, will be important in the development towards a more sustainable society where fossil fuels are replaced. To be able to compete with fossil resources, an efficient production of biomass based products is required in order to maximize overall process economics and to minimize negative environmental impact. One solution to increase profitability for forest biomass based plants can be production of value added derivatives produced through fermentation of sugars from hemicelluloses, extracted from lignocellulosic material. The first part of this thesis investigate the impact of hemicellulose pre-extraction on birch Kraft pulp properties. White liquor and water extractions of hemicelluloses from birch wood chips were performed under conditions compatible with Kraft pulping. The chips from select extractions were subject to subsequent Kraft pulping and the refined pulps were made into hand sheets. Several metrics for hand sheet strength properties were compared with a reference pulp made without an extraction step. This work also includes a demonstration of enzymatic hydrolysis and biological conversion of extracted xylan to succinic acid, a metabolite with the potential of a platform chemical. The study demonstrated that white liquor can be utilized to extract xylan from birch wood chips prior to Kraft cooking without decreasing the pulp yield and paper strength properties, while simultaneously impregnating cooking alkali into the wood chips. Alkaline conditions tested above pH 10 significantly degraded xylan and very low concentrations of xylose were obtained using any of the alkaline extractions. Water extractions resulted in the highest final concentration of xylose, 29.1 g/L; yielding fermentable liquor, but were found to negatively impact some pulp properties including decreases in compression strength, bursting strength, tensile strength and tensile stiffness while exhibiting minimal impact on elongation and slight improvement in tearing strength index. Since hot water extractions gave fermentable liquors, the next study was to integrate the production of green chemicals via hot water hemicellulose extraction of birch wood into a small-scale combined heat and power plant, in this case an externally fired gas turbine. The results show that the extracted wood chips would serve very well as a fuel for combustion and gasification processes due to the relatively high heating value. Most important, the extracted wood chips had low ash content and significantly lower concentrations of alkali metals. In addition a fermentable stream with a xylose concentration of 65 g/L was produced.The second part of this thesis was to optimise the production of the dicarboxylic acid, succinic acid, which can be produced via bioconversion as a renewable building block molecule for production of biodegradable solvents and polyesters. In this study the E. coli strain AFP184, which can ferment both five and six carbon sugars with a limited production of other organic acids was used. Earlier work using a high initial sugar concentration resulted in volumetric productivities of almost 3 g/L h, which is above estimated values for economically feasible production, and final succinic acid concentration was around 40 g/L. To further increase succinic acid concentrations, fermentations using NH4OH, NaOH, KOH, K2CO3, and Na2CO3 as neutralising agents were performed and compared. It was shown that substantial improvements could be made by using alkali bases to neutralise the fermentations. The highest concentrations and productivities were achieved when Na2CO3 was used, 77 g/L and 3 g/L h, respectively. A gradual decrease in succinate productivity was observed during the fermentations, which was shown to be due to succinate accumulation in the broth and not as a result of the addition of neutralising agent or the subsequent increase in osmolarity.Godkänd; 2010; 20100121 (jonhel); LICENTIATSEMINARIUM Ämnesområde: Biokemisk och kemisk processteknik/Biochemical and Chemical Engineering Examinator: Professor Kris A Berglund, Luleå tekniska universitet Tid: Fredag den 26 februari 2010 kl 10.15 Plats: C 305, Luleå tekniska universite

A multivariate analysis of aerobic growth conditions for E. coli strain AFP184 and the effects on anaerobic succinic acid productivity

If fossil fuels are to be removed as the main raw material for production of fuels and chemicals an economically competitive process based on renewable resources is required. Succinic acid, produced by microbial fermentation of renewable feed stocks, can substitute chemicals based on benzene and other intermediate petrochemicals for production of polyester and solvents. Other chemicals that can be produced from succinic acid are food ingredients, fuel additives and plant growth stimulants. The micro organism used for succinic acid production in this project is the bacterium Escherichia coli strain AFP184. This strain has been metabolically modified to increase the succinic acid production. The process in this project is a dual-phase fermentation which constitute of an aerobic growth phase and an anaerobic succinic acid production phase. After transition to anaerobic conditions the cells starts to produce succinic acid in large quantities using glucose as the main carbon source. Formation of succinic acid requires CO2 input and hence the process does not contribute to any atmospheric CO2 accumulation. The media used for all the fermentations is a low cost media based on corn steep liquor. Corn steep liquor is an industrial by-product from wet milling of maize and it contains nutrients needed for the cells. The use of E. coli strain AFP184 for fermentative succinic acid production can provide a stable process where the productivity of succinic acid is high and the productivity of other mixed acid fermentation products are low or non. The use of a low cost media makes the strain AFP184 a suitable candidate for large scale succinic acid production. In order to optimize the growth phase of AFP184 and to get knowledge if a fluctuation within certain domains of four controlled variables will affect biomass production and further succinic acid production, a designed experiment was used. Using design of experiment (DOE) data was collected from the growth phase and analyzed with multivariate data analysis. The controlled variables that were varied in chosen domains were stirring (400 rpm to 1200 rpm), airflow (2 vvm to 10 vvm), temperature (32 °C to 42 °C) and pH (5.5 to 7.5). The responses in the designed experiment were eight different organic acids, dry cell weight, specific growth rate, viable cells and glucose consumption. The results from the analysis were validated by additional experiments, where also the effect on the anaerobic succinic acid production phase was evaluated. From the analysis of the designed experiment it was shown by additional experiments that the growth rate and cell viability could be increased and the acetic acid formation decreased. The controlled variables temperature and pH could be varied in the chosen domain to produce biomass with moderate acetic acid concentration at the chosen time of transition from aerobic to anaerobic conditions. The additional experiments also showed during the anaerobic succinic acid production phase that productivity and yield of succinic acid decreased compared with the three centre point runs from the designed experiment and that could depend on the physiological state of the cells at the time of transition.Validerat; 20101217 (root

Integration of a hemicellulose extraction process into a biomass based heat and power plant

The development of processes where lignocellulosic biomass can be refined to several different end-products in the same plant, i.e. a biorefinery, will be important in the development towards a more sustainable society where fossil fuels are replaced. This paper presents the idea to integrate the production of green chemicals via hot water hemicellulose extraction of birch wood (hardwood) into a small-scale combined heat and power plant (CHP), in this case an externally fired gas turbine. A techno-economically successful concept could provide the option to turn a small- to medium scale CHP plant into a small- to medium scale biorefinery. The results show that the extracted wood-chips would serve very well as a fuel for combustion and gasification processes due to the relatively high heating value, low ash content and significantly lower concentrations of alkali metals. Under the assumed economic conditions, electricity can be produced to a cost in the range of €85.6 to €196.2 per MWhel and a fermentable feedstock stream with a xylose concentration of 65 g/L to a cost in between €0.44 to €4.15 per kg xylose depending on plant size and number of annual operational hours.Godkänd; 2009; Bibliografisk uppgift: CD; 20091109 (joakim

Production of value added chemicals from xylan extraction in a Kraft pulp mill and the effect on pulp quality

In the Kraft process hemicelluloses are lost in the cooking procedure to the black liquor stream, which is subsequently burnt in the recovery boiler to recover cooking chemicals and to produce steam and energy. Hemicelluloses have a low heating value compared to lignin and therefore recovery of hemicelluloses at an earlier stage of the Kraft process followed by biochemical conversion into high value-added products might offer a much better economic opportunity. In collaboration with the research and development department of Smurfit Kappa Kraftliner AB, Piteå, Sweden, alkali and water extractions of birch wood were performed under conditions compatible with the Kraft process, at different times, temperatures and alkali charges. The extraction conditions were set in a range suitable with the current pulp process at Smurfit Kappa Kraftliner. The requirements for process configurations, based on either hot water or alkali extraction were also explored. The xylan yields from different extraction trials were measured and the chips from those extraction trials were cooked, refined and turned into sheets of paper. The effects on paper quality were compared with a reference pulp made from the same wooden chips. Recovered xylans from water extracted birch wood chips were subjected to secondary hydrolysis, enzymatic or sulphuric acid. Detoxification of the hydrolysate with active carbon and regulation of pH were performed before fermentation. Fermentation of the xylose hydrolysate to succinic acid was demonstrated by the use of the succinic acid producer Escherichia coli AFP184.Godkänd; 2008; Bibliografisk uppgift: Sider: 204; 20081125 (jonhel)</p