From October 1st to October 5th 2017, the “10th World Congress of Chemical Engineering” was held in Barcelona, Spain. More than 3000 delegates presenting and listening to more than 1500 oral communications led to event that managed to represent the chemical engineering and its thriving ideas and innovation as a whole. Due to the widespread topics, focus is put on the talks given by the members of the Waste2Fuels consortium.
Dr. Martin Miltner (TU Wien) presented “Membrane processes as the key technology in cascaded valorization of municipal organic waste” showing the newest findings in the practical efforts of Butanol enrichment from ABE fermentation broth by pervaporation. His colleague Florian Kirchbacher (TU Wien) put his focus on the optimization of a coupled pervaporation/distillation process to reduce energy demand of the purification process. The work was carried out using Aspen Plus® and showed potential energy savings of up to 50% and this could be even further improved by adopted membrane properties.
The “10th World Congress of Chemical Engineering” offered a very welcomed platform to present the newest insights gained in the Waste2Fuels project to a very broad audience. The discussions after the respective talks showed that interest in biofuels and particularly in biobutanol is very high and pointing to a bright future for this and upcoming projects in this field.
The 9th International Conference on Environmental Engineering and Management has been held from 6th to 9th of September 2017 in Bologna, Italy. The main topics focused on environmental sustainability and ways towards a circular economy. At the conference a wide range of fields where those aspect are of increased importance were represented. The practical research works presented focused on three main topics: environmental biotechnology, water and wastewater cycles and sustainable waste management and exploitation. Biotechnological aspects covered use and effects of different bacteria as well as algae, while the water section presented topics like removal from different pollutants (Cadmium, pharmaceutic compounds) as well as the production of valuable products from wastewater streams. The sustainable waste management section and exploitation section showed a wide variety of potential targets to be produced from waste streams but energy carriers like biohydrogen, biogas and biobutanol were well represented. The other topics focused more on theoretical approaches to waste management like life cycle analysis or process modelling.
The Waste2Fuels consortium made a strong showing at the conference and, although the conference spanned a wide field of topics, contacts made were very interesting and promising.
The “2nd Workshop on ABE Fermentation and Recovery” followed an event in July 2015 in Vienna but basically is the continuation of work initially started by Nasib Qureshi, Ian Maddox and Anton Friedl back in 1989 in New Zealand.
Around 15 researchers attended this workshop and discussed about ongoing projects, potential developments, implementation barriers and novel approaches to the topic. Works presented covered a broad range including biology and genomics of involved microorganisms, bioreactor design and downstream processing. Results from the project WASTE2FUELS as well the setup of the project itself have been presented by Anton Friedl, Richard Goerlitz and Antonio Marzocchella.
The Workshop was highly valuable for all attendees and will surely be perpetuated in the upcoming years.
The “5th International Scientific Conference on Pervaporation, Vapour Pervaporation and Membrane Distillation” has been held in June 2017 in Torun, Poland. This event has been combined with the “2nd Workshop on ABE Fermentation and Recovery” which was very fruitful as these membrane processes are promising techniques for a cost- and energy-efficient recovery of solvents from the ABE fermentation broth. Highly renowned personalities within the membrane society have been present as speakers like Dr. Richard Baker, Prof. Dr. Vladimir Volkov, Prof. Dr. Wojciech Kujawski and Dr. Erin Johnson. Industry was also present, amongst others Dr Martin Wolf and Dr. Rob de Lange from PERVATECH BV presented the company portfolio. Around 50 persons attended the conference, mostly from universities and research centres but also from various companies. A big share of presentations dealt with the recovery and enrichment of ABE components and other alcohols. Other topics covered hydrophilic dehydration of different feed solutions and of course the synthesis and characterisation of novel high-performance membrane materials. It has been concluded that membrane separation techniques, especially pervaporation and vapour permeation, will benefit from increasing market shares and a broadening field of applications in the near future. The 6th conference on the topic will take place in July 2019 in Gdansk, Poland.
Under the WP6, Industrial Scale-up, TU Wien is supporting WP 6 with simulation tasks for the overall process in Aspen Plus. Up to now, the focus was put mainly on potential in-situ recovery methods. The results generated in other work packages were used to develop simulation models for adsorption, stripping, pervaporation, distillation as well as coupled approaches.
The latest development was a solution-diffusion based multi-component model for pervaporation process developed for Aspen Plus and parameterized with characteristic membrane values gained through work package 3. Combination with distillation offers first estimates for potential energy savings of up to 50% compared to the traditional production route. Furthermore, effects of different membrane material on the butanol separation step were calculated.
UNIZAR has carried out combustion tests. Oxidation experiments of 1-butanol has been performed for different oxygen concentrations that go from fuel-rich to fuel-lean conditions.
The results showed:
Increasing the amount of oxygen in the reactor inlet causes a shift in the conversion onset of 1-butanol to lower temperatures.
The stoichiometry also affects to the temperature of formation of products and the temperature where they reach their maximum concentration.
Increasing stoichiometry influences the hydrocarbons concentrations obtained (CH4, C2H6 and C4H8) that are produced in low amounts.
The kinetic model of different hydrocarbons and alcohols reactions developed by UNIZAR has been updated with a subset for describing the oxidation of 1-butanol. There is good agreement between the experimental and simulated results.
Under the WP3 (ABE fermentation and solvent recovery), since the last status update TU Wien has conducted extensive research regarding different membrane materials as well as potential membrane module designs for the separation of ABE from fermentation broth. The focus was put on commercially available PDMS (polydimethylsiloxane) and newly developed POMS (polyoxymethylsiloxan) membranes by different vendors. Flat sheet modules were tested for both materials while hollow fiber modules were only considered for PDMS membranes as they are not commercially available yet for POMS.
Influence of temperature, glucose and salt concentration on separation performance was tested. While an increase in temperature led to improved results, addition of glucose and ammonia chloride did not show negative impacts in the relevant concentration range. Both materials showed promising results although certain differences exist. POMS offers slightly higher butanol selectivity but PDMS has a slightly higher permeance and therefore overall higher flux. Which option is preferable must be further researched in the context of the overall process and its energy demand in the final upgrading steps.
Concluding, it was possible to show solvent enrichment from 1.5 wt% BuOH up to 31.5 wt% in a single upgrading step while also considering the influence of potential secondary components in the fermentation broth.
In the WP4 (Catalytic conversion of ethanol to butanol), bio-ethanol can be catalytically converted into butanol through alcohol dimerization called Guerbet reaction. This reaction is promoted by catalysts with a suitable combination of both acid and basic sites. Furthermore, addition of an active metal can favor the initial dehydrogenation of the alcohol to form the carbonyl intermediate.
In the first year g-Al2O3, hydroxyapatite and MgO were synthesized as powders to obtain high surface area supports for dispersion of Ruthenium or Nickel. Textural, acid and basic properties of the three supports and redox properties of the metals were characterized in order to optimize the catalyst formulation. Ni/MgO and Ru/MgO provided the best butanol yields and were chosen to be upgraded to catalytic pellets for operation in the pre-pilot scale rig.
The activity of the second year was focused on the dispersion of Ni or Ru on commercial pellets following two main routes: i) deposition of metals on MgO pellets ii) deposition of metals on MgO-coated g-Al2O3 pellets. Reduction of volume of catalytic bed can be achieved provided that a uniform dispersion of the metal is obtained according to route i) or surface area of MgO is significantly enhanced by deposition onto alumina according to route ii). After determination and optimization of the technique for production of the best performing catalytic pellets a suitable amount of catalyst will be supplied to HELBIO (Task 4.3) for the pre-pilot scale operation.
Under the WP1, (Selection of renewable feedstock for ABE fermentation), the following tasks have been performed:
Between two and three pretreatment methods have been proposed by ITACyl for each of the four agrofood wastes. These methods allow an equilibrium between maximal sugar release and minimal generation of fermentation inhibitors in the hydrolysates.
Common fermentation inhibitors for the four agrofood wastes have been identified by BIOPOX, TOMSA, ITACyL with GC-MS and an analytical method for inhibitor quantification by HPLC-UV has been developed. Several detoxification methods for the hydrolysates obtained have been compared.
BIOPOX and CNR-IRC have performed activities on enzymatic hydrolysis of agrofood wastes by different enzymes, as well as reactor operation conditions, which are being optimised. In addition, the new cellulosome enzymes obtained in WP2 will be evaluated soon for their ability to hydrolyse agrofood wastes.
Specifically, the hydrolysis of lignocellulosic biomass catalyzed by cellulase cocktails is a heterogeneous process and includes several phenomena: liquid-solid mass transfer, enzymes adsorption on biomass, cellulose and hemicellulose hydrolysis. Process design asks for reliable cellulase kinetic models. Semi-mechanistic models can be used to describe the heterogeneous process. Kinetic characterization of the commercial cellulases cocktail Cellic CTec2 (Novozymes) has been carried out through three semi-mechanistic models in order to provide reliable tools for further rational design of reactors for enzymatic hydrolysis of lignocellulosic biomass.
In particular, a study related to the kinetic characterization of the enzymatic hydrolysis is needed in order to obtain a useful tool able to maximize the sugar release depending on the composition of the pretreated biomass during enzymatic hydrolysis. A kinetic characterization of the main used commercial cocktail Cellic CTec2 on apple residues pretreated with NaOH, HCl and laccases has been carried out.
Kinetic parameters showed faster rate of hydrolysis for the samples with the lower lignin content that were obtained after alkaline pretreatment.
Alternative and cheap nutrient sources for solventogenic bacteria are being assessed by BEUTH. The suitability of these nutrients will be validated by fermenting real hydrolysates.