Search

Phosphogypsum (CaSO4) is produced as a waste by-product during phosphoric acid production in the fertilizer industry. Only 15% of worldwide phosphogypsum production is recycled, while 85% is stored in the vicinity of factories as huge piles resulting in environmental and health hazards. An extensively studied biotransformation of phosphogypsum to calcium carbonate or calcite (CaCO3) using sulfate reducing bacteria (SRBs) is a prolonged process and results in the formation of extremely hazardous H2S gas. Here we report for the first time a novel approach for biotransformation of phosphogypsum to CaCO3 using urease producing Lysinibacillus sphaericus strain GUMP2. The strain could effectively transform phosphogypsum to crystalline, bead-shaped CaCO3 precipitates. In a batch reactor with the PG loading rate of 60 g/L, 100% biotransformation was observed within seven days. After calcite recovery, the ammonium sulfate formed in the supernatant was recovered by precipitation. Urease-producing L. sphaericus strain GUMP2 could be used to remove the hazardous phosphogypsum from the environment by converting it to the industrially useful CaCO3 and ammonium sulfate, a valuable agricultural fertilizer. This novel and sustainable approach could be a promising solution for the hazardous phosphogypsum in the phosphoric acid industries. [ABSTRACT FROM AUTHOR]

Marine biorefineries, based on macroalgal (seaweed) feedstocks, could provide sustainable alternative sources of food, energy, and materials. Green macroalgae, with their unique chemical composition, can contribute to marine biorefinery systems associated with a wide range of potential products. This review discusses the challenge of developing industrially relevant and environmentally-friendly green seaweed biorefineries. First, we review potential products from green seaweeds and their co-production, the key element in an integrated biorefinery. Second, we discuss large-scale cultivation, hydrothermal treatments, fermentation, anaerobic digestion, and emerging green solvents, pulsed electric field, microwave, and ultrasound processing technologies. Finally, we analyse the main polysaccharides in green seaweeds: sulfated polysaccharides, starch, and cellulose, as products of a cascading biorefinery, with emphasis on applications and technological challenges. We provide a comprehensive state-of-the-art review of green seaweed as feedstock for the biorefinery, analysing opportunities and challenges in the field. [ABSTRACT FROM AUTHOR]