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- Current pretreatment technologies for the development of cellulosic ethanol and biorefineriesPublication . Silveira, Marcos H. Luciano; Morais, Ana Rita C.; Lopes, André; Olekszyszen, Drielly Nayara; Lukasik, Rafal M.; Andreaus, Jurgen; Ramos, Luiz PereiraLignocellulosic materials, such as forest, agriculture, and agroindustrial residues, are among the most important resources for biorefineries to provide fuels, chemicals, and materials in such a way to substitute for, at least in part, the role of petrochemistry in modern society. Most of these sustainable biorefinery products can be produced from plant polysaccharides (glucans, hemicelluloses, starch, and pectic materials) and lignin. In this scenario, cellulosic ethanol has been considered for decades as one of the most promising alternatives to mitigate fossil fuel dependence and carbon dioxide accumulation in the atmosphere. However, a pretreatment method is required to overcome the physical and chemical barriers that exist in the lignin–carbohydrate composite and to render most, if not all, of the plant cell wall components easily available for conversion into valuable products, including the fuel ethanol. Hence, pretreatment is a key step for an economically viable biorefinery. Successful pretreatment method must lead to partial or total separation of the lignocellulosic components, increasing the accessibility of holocellulose to enzymatic hydrolysis with the least inhibitory compounds being released for subsequent steps of enzymatic hydrolysis and fermentation. Each pretreatment technology has a different specificity against both carbohydrates and lignin and may or may not be efficient for different types of biomasses. Furthermore, it is also desirable to develop pretreatment methods with chemicals that are greener and effluent streams that have a lower impact on the environment. This paper provides an overview of the most important pretreatment methods available, including those that are based on the use of green solvents (supercritical fluids and ionic liquids).
- Green chemistry and biorefineries: common future?Publication . Carvalho, V.; Relvas, F.; Lopes, André; Morais, Ana Rita C.; Silva, Sara P. Magalhães da; Mata, Ana C.; Roseiro, Luisa B.; Lukasik, Rafal M.Green Chemistry and Biorefinery concepts are two approaches helping to develop new and more sustainable processes.The implementation of both methodologies impels to fossil-independent future with bioeconomy based on natural feedstock like biowaste and industrial by-products. The development of technologies for valorisation of these resources is a key role of society in the creation of sustainable and more environmentally friendly future. Shortly after the Rio Declaration on Environment and Development, Anastas and Warner presented 12 Principles of Green Chemistry but more a decade before Trevor Kletz in his Jubilee lecture entitled “What you don’t have, can’t leak” draw the frames in which scientific and industrial work should be performed. This basis of green chemistry created a fundament for further development and implementation of Anastas and Warner principles of green chemistry. One of these frames is integration of green chemistry principles in the biorefinery concept. The biorefinery is an industrial facility (or network of facilities) that cover an extensive range of combined technologies aiming to full sustainable transformation of biomass into their building blocks with the concomitant production of biofuels, energy, chemicals and materials, preferably of value added products. One of the principles of green chemistry is the use of more sustainable solvents. Some examples of them are ionic liquids (ILs) and supercritical fluids (scF). This work will demonstrate the successful examples of lignocellulosic biomass valorisation using green solvents answering the question regarding the feasibility of future biorefineries made in a greener manner.
- Integrated conversion of agroindustrial residue with high pressure CO2 within the biorefinery conceptPublication . Morais, Ana Rita C.; Mata, Ana C.; Lukasik, Rafal M.Sustainable production of energy and other added-value products from biomass-derived polysaccharides is a key challenge of an efficient biorefinery facility. Most technologies for biomass processing are energy demanding and use significant amounts of chemicals and catalysts. The need to develop a process which is devoid of all these shortcomings associated with conventional processes is emphasized. A new approach is demonstrated for an integrated wheat straw biorefinery using a green technology, highpressure CO2–H2O, to produce oligosaccharides from hemicellulose fraction and to enhance the cellulose digestibility for the enzymatic hydrolysis. Over the range of reaction conditions (130, 215, 225 °C and 0 to 54 bar of CO2), CO2 adds value to the process by in situ formation of carbonic acid that leads to higher dissolution of hemicellulose into xylo-oligosaccharides and xylose and to the use of less energy in comparison with water-only technologies. Without an additional chemical catalyst, high-pressure CO2–H2O out performed hydrothermal reactions and gave much higher total sugars yield for wheat straw (as high as 84% in comparison with 67.4% with auto-hydrolysis at a 10 °C higher temperature). Apart from the results obtained for valorisation of hemicellulose fraction, both chemical and physical effects of CO2 coupled to enzymatic hydrolysis resulted in a glucan conversion to glucose yield of 82%, which consists of 26% improvement over those obtained during auto-hydrolysis. The influence of the high pressure reaction on the processed solid was examined by spectroscopic methods (namely Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy). The obtained results suggest that the high pressure CO2-based method is a very promising alternative technology allowing integrated biomass processing within the biorefinery concept.
- Selective hydrolysis of wheat straw hemicellulose using high-pressure CO2 as catalystPublication . Relvas, F.; Morais, Ana Rita C.; Lukasik, Rafal M.The processing of wheat straw using high-pressure CO2–H2O technology was studied with the objective to evaluate the effect of CO2 as catalyst on the hydrothermal production of hemicellulose-derived sugars either as oligomers or as monomers. Also, the reduction of the crystallinity of the cellulose-rich fraction was assessed. Over a range of reaction conditions (0 to 50 bar of initial CO2 pressure and 0 to 45 minutes of holding time, at T ¼ 180 C), the addition of CO2 to water-based processes led to the in situ formation of carbonic acid, which allowed us to obtain a higher dissolution of wheat straw hemicellulose. Furthermore, this approach led to a xylo-oligosaccharide (XOS) rich fraction, yielding 79.6 g of XOS per 100 g of the initial xylan content (at 50 bar of initial CO2 pressure and 12 min of residence time) while the water-only process gave only 70.8 g of XOS per 100 g of initial xylan content. Furthermore, for higher pressures of CO2, a decrease in oligosaccharide content was found and was counterbalanced by production of monomer sugars, achieving a maximum of 5.7 g L1 at the severest condition.
- Green metrics evaluation of isoprene production by microalgae and bacteriaPublication . Matos, Cristina T.; Gouveia, Luisa; Morais, Ana Rita C.; Reis, Alberto; Lukasik, Rafal M.Isoprene is a key intermediate compound for the production of synthetic rubber and adhesives and is also used as a building block in the chemical industry. Traditionally, isoprene is obtained from crude oil during the refinery process. Nevertheless, plants and animals are also able to synthesize this important compound. This work compares two renewable approaches for isoprene production: by photosynthetic organisms (autotrophic microalgae/cyanobacteria) and by heterotrophic organisms (bacteria). These are two alternative pathways for the conventional isoprene production obtained from the petrochemicalbased refinery process, which were assessed in this work using green metrics. Their performance was evaluated in terms of: material efficiency, energy efficiency, economic evaluation and land use. A 10-tonne scale was chosen to perform the green metrics evaluation for both biological processes leading to isoprene. For each process, a comparison was made between a scenario considering the highest isoprene produced reported in the literature and a scenario considering the maximum theoretical stoichiometric isoprene productivity.
- Kinetic modeling of hemicellulose-derived biomass hydrolysis under high pressure CO2–H2O mixture technologyPublication . Relvas, F.; Morais, Ana Rita C.; Lukasik, Rafal M.This work is focused on the development of kinetic models of hydrolysis of hemicellulose-derived wheat straw under high-pressure CO2.H2O technology. The experiments were performed at fixed temperature (180.C), varying pressure from 0 (water-only reaction), 20, 35 to 50 bar of initial CO2 pressure and reaction times varied from 0 to 45 min. The three accurate kinetic models allowed to describe the effect of reaction conditions mainly hitherto not studied CO2 pressure and reaction time on the concentration of intermediate compounds such as xylose and arabinose in both oligomer and monomer form as well as final compounds e.g. acetic acid, furfural and other degradation products. Modeling demonstrated that addition of CO2 plays an important role in kinetics study of hemicellulose fraction hydrolysis being the fastest step the polysaccharides f hydrolysis into sugars in oligomer form. Even negligible amount of CO2 (20 bar of initial pressure) improves the initial kinetic constant of aforementioned reaction by almost 40% in comparison to water-only process. Depletion of oligosaccharides ' concentration and counterbalanced production of monomer sugars were found for longer reaction times, achieving maximum faster for CO2 assisted than CO2 free processes. Moreover, the increase of initial CO2 pressure demonstrated to be highly efficient in enhancement of the kinetic constants of all reactions occurring in the liquors. The developed models demonstrated a good fitting to the experimental data albeit the complex composition of raw material as well as the multistep analytical process.
- Ionic liquids as a tool for lignocellulosic biomass fractionationPublication . Lopes, André; João, Karen; Morais, Ana Rita C.; Bogel-Lukasik, Ewa; Lukasik, Rafal M.Lignocellulosic biomass composes a diversity of feedstock raw materials representing an abundant and renewable carbon source. In majority lignocellulose is constituted by carbohydrate macromolecules, namely cellulose and hemicellulose, and by lignin, a polyphenilpropanoid macromolecule. Between these biomacromolecules, there are several covalent and non-covalent interactions defining an intricate, complex and rigid structure of lignocellulose. The deconstruction of the lignocellulosic biomass makes these fractions susceptible for easier transformation to large number of commodities including energy, chemicals and material within the concept of biorefinery. Generally, the biomass pre-treatment depends on the final goal in the biomass processing. The recalcitrance of lignocellulose materials is the main limitation of its processing once the inherent costs are excessively high for the conventional pre-treatments. Furthermore, none of the currently known processes is highly selective and efficient for the satisfactory and versatile use, thus, new methodologies are still studied broadly. The ionic liquid technology on biomass processing is relatively recent and first studies were focused on the lignocellulosic biomass dissolution in different ionic liquids (ILs). The dissolution in IL drives to the structural changes in the regenerated biomass by reduction of cellulose crystallinity and lignin content contrasting to the original biomass. These findings provided ILs as tools to perform biomass pre-treatment and the advantageous use of their specific properties over the conventional pre-treatment processes. This review shows the critical outlook on the study of biomass dissolution and changes occurred in the biomass during this process as well as on the influence of several crucial parameters that govern the dissolution and further pre-treatment process. The review of currently known methods of biomass fractionation in IL and aqueous-IL mixtures is also discussed here and perspectives regarding these topics are given as well.
- Chemical and biological-based isoprene production: Green metricsPublication . Morais, Ana Rita C.; Dworakowska, Sylwia; Reis, Alberto; Gouveia, Luisa; Matos, Cristina T.; Bogdal, Dariusz; Lukasik, Rafal M.Green metrics is a methodology which allows the greenness of either new or already existing processesto be assessed. This paper is a part of a special issue devoted to green metrics in which this methodologyis applied to different processes to assess bio and petrochemical routes. In this work, green metrics wereused as a tool to validate and compare the petrochemical and biological processes of isoprene production.The Sumitomo process has been selected for this comparison as it is beneficial because of it using lessexpensive C1components as well as the fact that it has lower investment costs for a single-step process. The production of isoprene through a modified Escherichia coli bacterial process has been selected forcomparison with the fossil pathway. The green metrics evaluation was performed for both processes toproduce isoprene and to target 50,000 tonnes of isoprene yearly. Although, the calculated costs for the bio-isoprene are slightly higher than the actual market price ofits fossil counterpart, the results obtained reveal that the bacteria-based isoprene production is able to substitute the petrochemical process, with material and energy efficiency. This conclusion has also beenproved by the increasing number of industrial interest in bioisoprene. The challenge comes from the landuse needed for the production of a carbon source which might be solved by the use of waste and residueswhich are rich in carbohydrates or lignocellulosic biomass which can be converted to simple sugars.
- Insight into the high-pressure CO2 pre-treatment of sugarcane bagasse for a delivery of upgradable sugarsPublication . Fockink, Douglas, H.; Morais, Ana Rita C.; Ramos, Luiz Pereira; Lukasik, Rafal M.ABSTRACT: This work provides an insight into sugarcane bagasse pre-treatment carried out with greener and more sustainable CO2/H2O system. Temperatures and residence times at a fixed initial CO2 pressure were studied to verify their effects on pre-treatment efficiency with regard to the chemical composition of both water-soluble and water-insoluble fractions as well as to the susceptibility of the latter to enzymatic hydrolysis at high total solids. Also, trends in enzymatic hydrolysis were analysed in function of biomass crystallinity. This work provides an integrated approach in the analysis of upgradable sugars that are released as a result of pre-treatment and enzymatic hydrolysis. At optimal pre-treatment conditions, 17.2 g.L-1 sugars were released in the water-soluble fraction mainly as pentoses in monomeric and oligomeric forms. The enzymatic hydrolysis of solids produced at these pre-treatment conditions gave 76.8 g.L-1 glucose in the substrate hydrolysate. The overall sugar yield delivered in both pre-treatment and enzymatic hydrolysis was 73,9 mol%. These results were compared to the chemical effect of hydrothermal and/or physico-chemical effects of N-2-aided hydrothermal processes and showed that the greener processing of biomass pre-treatment with CO2 is advantageous for the integrated valorisation of industrial residues and delivery of upgradable sugars within the biorefinery concept.
- Carbon dioxide in biomass processing: contributions to the green biorefinery conceptPublication . Morais, Ana Rita C.; Lopes, André; Lukasik, Rafal M.The 21st century is witnessing a huge demand of fossil reserves coupled with a rapid reduction in readily and economically reachable oil feedstocks.The present energy demand is not fulfilled from fossil fuel sources, making the world exposed to geopolitical risk. Furthermore, concerns regarding the security of the supply chain and the environmental impacts have resulted in an ever-increasing shift of global energy policies to seek alternative technologies and sustainable sources of energy, materials, chemicals, and value-added products. Recently, the need for development of an economy based on renewable resources has been recognized by society, and diverse R&D activities have started to be funded to accomplish this aim. However, generation of bioproducts based on sustainable supply chains poses vast challenges for an eco-based economy.The simplest way to provide a supportable supply chain is through the employment of renewable biomass feedstocks, which is the only sustainable option to substitute for fossil fuel resources, as sources of organic compounds over a relatively short time scale and with limitless supply.
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