A NOVEL TOA-GLYCEROL BASED EXTRACTION - RE-EXTRACTION PROCESS FOR THE SEPARATION OF CHEMICALS PRODUCED BY ACIDOGENIC FERMENTATION OF BIOMASS

Acidogenic fermentation of biomass for the production of ethanol and acetic, propionic, butyric and lactic acids is a promising technology, in the sense that germ free conditions are not required, very diversified, less pretreated and cheap biomass can be used, and the molecules produced and their esters are consumed on a large scale by industries. The product recovery, separation and concentration steps downstream of the biomass transformation remain, however, a major challenge for the industrial application of acidogenic fermentation which produces very dilute (concentrations of only a few percent) and complex aqueous solutions of acids and ethanol. A novel extraction - re-extraction process for the recovery of ethanol and acetic, propionic, butyric and lactic acids from acidogenic fermentation broths is presented which is based on the transfer of the acids and ethanol to a glycerol phase via an intermediate solvent phase. Tri-n-octylamine based solvents are chosen in the first, extraction step of the process for their preferential extraction of acids. In the second, re-extraction step, the acids are extracted from the intermediate solvent with glycerol, opening perspectives for the transformation of glycerol into short chain esters, directly using the acids recovered. The novel TOA-based extraction – glycerol-based re-extraction process is experimentally investigated. First, butyric acid aqueous model solutions are tested. Next, the behavior with real fermentation broths is studied. The extraction re-extraction performance is observed to depend strongly on the solvent and on the operating conditions. The influence of the most important process parameters, such as the pH, the temperature, the composition of the aqueous phase is measured. For the first extraction step (water/TOA system), the distribution coefficient of butyric acid is seen to increase significantly with decreasing pH of the aqueous solution. The pH after extraction is linearly related to the pH before extraction. Furthermore, the extraction efficiency is seen to increase with decreasing temperature. Inversely, for the second extraction step (TOA/glycerol system), the extraction efficiency is seen to increase with increasing temperature. The simultaneous presence of butyric and acetic acids is shown not to affect the extraction of the individual acids

Changing climate shifts timing of European floods

A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale

Changing climate shifts timing of European floods

A warming climate is expected to have an impact on the magnitude and timing of river floods; however, no consistent large-scale climate change signal in observed flood magnitudes has been identified so far. We analyzed the timing of river floods in Europe over the past five decades, using a pan-European database from 4262 observational hydrometric stations, and found clear patterns of change in flood timing. Warmer temperatures have led to earlier spring snowmelt floods throughout northeastern Europe; delayed winter storms associated with polar warming have led to later winter floods around the North Sea and some sectors of the Mediterranean coast; and earlier soil moisture maxima have led to earlier winter floods in western Europe. Our results highlight the existence of a clear climate signal in flood observations at the continental scale

Multi-Scale Modeling of Plastic Waste Gasification: Opportunities and Challenges

Among the different thermo-chemical recycling routes for plastic waste valorization, gasification is one of the most promising, converting plastic waste into syngas (H2+CO) and energy in the presence of an oxygen-rich gas. Plastic waste gasification is associated with many different complexities due to the multi-scale nature of the process, the feedstock complexity (mixed polyolefins with different contaminations), intricate reaction mechanisms, plastic properties (melting behavior and molecular weight distribution), and complex transport phenomena in a multi-phase flow system. Hence, creating a reliable model calls for an extensive understanding of the phenomena at all scales, and more advanced modeling approaches than those applied today are required. Indeed, modeling of plastic waste gasification (PWG) is still in its infancy today. Our review paper shows that the thermophysical properties are rarely properly defined. Challenges in this regard together with possible methodologies to decently define these properties have been elaborated. The complexities regarding the kinetic modeling of gasification are numerous, compared to, e.g., plastic waste pyrolysis, or coal and biomass gasification, which are elaborated in this work along with the possible solutions to overcome them. Moreover, transport limitations and phase transformations, which affect the apparent kinetics of the process, are not usually considered, while it is demonstrated in this review that they are crucial in the robust prediction of the outcome. Hence, possible approaches in implementing available models to consider these limitations are suggested. Finally, the reactor-scale phenomena of PWG, which are more intricate than the similar processes—due to the presence of molten plastic—are usually simplified to the gas-solid systems, which can result in unreliable modeling frameworks. In this regard, an opportunity lies in the increased computational power that helps improve the model’s precision and allows us to include those complexities within the multi-scale PWG modeling. Using the more accurate modeling methodologies in combination with multi-scale modeling approaches will, in a decade, allow us to perform a rigorous optimization of the PWG process, improve existing and develop new gasifiers, and avoid fouling issues caused by tar