Evaluation Tool for the Environmental Design of Chemical Processes

Multicriteria analysis of sewage sludge-based biodiesel production

There is increasing attention on developing efficient processes including circular economy principles, and obtaining fuels from wastewater treatment feedstocks is among the most promising. As a wastewater treatment byproduct, sewage sludge is a source of lipids that can be converted to biodiesel in a transesterification process. Economic and environmental analysis have been applied to a 60 m3/h sewage sludge plant, exploring 32 process alternatives. Using solvent extraction from wet sewage sludge, the high cost associated with the drying step is skipped. The wet alternatives with low amounts of solvent and acid usage depicted higher performance compared to the dry ones. Incorporating additional extraction stages increases both the financial gains and environmental impacts. As a result, a multicriteria analysis is implemented to ascertain the optimum process based on different priorities. The case with 0.5:1 (v/v) of hexane to biomass ratio, 3-stage extractor, 60 min residence time and pH 4 was the optimum alternative in most criteria.

Microalgae-based biodiesel: a multicriteria analysis of the production process using realistic scenarios

Microalgae-based biodiesel has several benefits over other resources such as less land use, potential cultivation in non-fertile locations, faster growth and especially a high lipid-to-biodiesel yield. Nevertheless, the environmental and economic behavior for high scale production depends on several variables that must be addressed in the scale-up procedure. In this sense, rigorous modeling and multicriteria evaluation are performed in order to achieve optimal topology for third generation biodiesel production. Different scenarios and the most promising technologies tested at pilot scale are assessed. Besides, the sensitivity analysis allows the detection of key operating variables and assumptions that have a direct effect on the lipid content. The deviation of these variables may lead to an erroneous estimation of the scale-up performance of the technology reviewed in the microalgae-based biodiesel process. The modeling and evaluation of different scenarios of the harvesting, oil extraction and transesterification help to identify greener and cheaper alternatives.

Agile green process design for the intensified Kolbe-Schmitt synthesis by accompanying (simplified) life cycle assessment

In order to investigate the potential for process intensification, various reaction conditions were applied to the Kolbe-Schmitt synthesis starting from resorcinol. Different CO₂ precursors such as aqueous potassium hydrogencarbonate, hydrogencarbonate-based ionic liquids, DIMCARB, or sc-CO₂, the application of microwave irradiation for fast volumetric heating of the reaction mixture, and the effect of harsh reaction conditions were investigated. The experiments, carried out in conventional batch-wise as well as in continuously operated microstructured reactors, aimed at the development of an environmentally benign process for the preparation of 2,4-dihydroxybenzoic acid. To provide decision support toward a green process design, a research-accompanying simplified life cycle assessment (SLCA) was performed throughout the whole investigation. Following this approach, it was found that convective heating methods such as oil bath or electrical heating were more beneficial than the application of microwave irradiation. Furthermore, the consideration of workup procedures was crucial for a holistic view on the environmental burdens.

Microalgae-based biodiesel: economic analysis of downstream process realistic scenarios

Microalgae oil has been identified as a reliable resource for biodiesel production due to its high lipid productivity and potential cultivation in non-fertile locations. However, high scale production of microalgae based biodiesel depends on the optimization of the entire process to be economically feasible. The selected strain, medium, harvesting methods, etc., sorely affects the ash content in the dry biomass which have a direct effect in the lipid content. Moreover, the suitable lipids for biodiesel production, some of the neutral/saponifiable, are only a fraction of the total ones (around 30% dry base biomass in the best case). The present work uses computational tools for the modeling of different scenarios of the harvesting, oil extraction and transesterification. This rigorous modeling approach detects process bottlenecks that could have led to an overestimation of the potentiality of the microalgae lipids as a resource for the biodiesel production.