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There are currently no studies in the literature on the use of natural waste marble powder (WMP) resources as inexpensive sorbents for looping cycle CO2 capture. The high volume of marble production is associated with considerable amounts of WMP generated as byproduct during cutting and polishing procedures, which negatively impacts the surrounding environment. The main goal and innovative idea addressed in this study consists of investigating if solid wastes WMP from marble producer sources can be used as possible inexpensive and effective solid materials to be used as precursors of CaO-based sorbents in Ca-looping cycle CO2 post-combustion capture process. The cyclic carbonation–calcination reactions were experimentally studied in a laboratory-scale fixed-bed reactor unit for 10 and 20 cycles. The innovative and interesting results obtained show that Portuguese WMP represents a category of promising natural inexpensive solid sorbents to be used as effective CaO-based sorbents for looping cycle CO2 post-combustion capture, because of their increased CO2 carrying capacity and better cyclic stability with lower sorbent deactivation with the number of cycles, when compared with commercial CaCO3 reference sorbent precursor and with other natural and synthetic CaO-based sorbents, and other CaO-solid-based materials from industrial and natural wastes recovery, reported in the literature. The WMP resources have potential to be an economically attractive option thus contributing to reduce the cost of the Ca-looping cycle CO2 capture process, as well as to minimize the adverse environmental impacts of the high volume of WMP generated in the marble producers.

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Microalgae have emerged as potentially powerful platforms for the production of recombinant proteins and high-value products. Chlamydomonas reinhardtii is a potentially important host species due to the range of genetic tools that have been developed for this unicellular green alga. Transformation of the chloroplast genome offers important advantages over nuclear transformation, and a wide range of recombinant proteins have now been expressed in the chloroplasts of C. reinhardtii strains. This is often done in cell wall-deficient mutants that are easier to transform. However, only a single study has reported growth data for C. reinhardtii grown at pilot scale, and the growth of cell wall-deficient strains has not been reported at all. Here, we report the first pilot-scale growth study for transgenic, cell wall-deficient C. reinhardtii strains. Strains expressing a cytochrome P450 (CYP79A1) or bifunctional diterpene synthase (cis-abienol synthase, TPS4) were grown for 7 days under mixotrophic conditions in a Tris-acetate-phosphate medium. The strains reached dry cell weights of 0.3 g/L within 3-4 days with stable expression levels of the recombinant proteins during the whole upscaling process. The strains proved to be generally robust, despite the cell wall-deficient phenotype, but grew poorly under phototrophic conditions. The data indicate that cell wall-deficient strains may be highly amenable for transformation and suitable for commercial-scale operations under mixotrophic growth regimes.

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