Judit Martin
university of Valladolid
Judit Martín studied Chemical Engineering at University of Valladolid (Spain) and performed her final research project in the Department of Biocatalysis at Technical University of Hamburg (Germany). She joined to Environmental and Technology Group in the University of Valladolid as PhD student in 2014. Her work focuses on valorization of agro-food waste generating bio-energy and bio-products in processes with microalgae. She has collaborated as visiting researcher with groups from University of Wageningen (The Netherlands) and University of Novi Sad (Serbia).
The valorisation of residual biomass into a variety of bio-based products and bio-energy is a highly renowned concept defined as bio-refinery. The first bio-refineries focused precisely on low-added value. However, the microalgae application has attracted interest in recent years, not only because of the energy aspect yet its high-added value compounds. Despite this, bio-refinery of algae biomass is still in its early stage and, hence, demonstration of a feasible process must be needed, making practical implementations of experimental data related to up and downstream efficiencies.
In the present, the valorisation of microalgae biomass grown in pig manure wastewater treatment was evaluated, involving sequential extraction based on a bio-refinery concept. CO2 supercritical was applied on microalgae biomass to extract lipids. Two solid fractions were obtained: residual biomass and extracted lipid fraction. Residual biomass was used as substrate for subcritical water tests to extract proteins mainly and carbohydrates, and raw material was also used to determine the feasibility of CO2 extraction. In the last place, the residue recovered after this process could be used as a bio-fertilizer. For this purpose, CO2 extraction tests were performed at 100, 200 and 300 bars, and 40 and 60ºC. While subcritical water experiments were carried out at 100, 130, 160 and 190ºC for 10 min.
In this study, the chemical composition of freeze-dried microalgae biomass was 5.12% of lipids, 44.03% of proteins and 31.16% of carbohydrates. The CO2 assays proved to extract almost all the lipid content (up to 81%), detecting an important impact on yields by increasing pressure and temperature. After that, 300 bar and 60ºC were the best conditions and, hence, its exhausted solid was used for subcritical water extraction. The CO2 pretreated biomass reported the highest solubilisations at 190ºC, achieving 33% of released protein yields, and 67% of released sugar yields; detecting greater effect on carbohydrates than proteins. In contrast, the untreated raw material accounted higher results at low temperatures and, yet lower than found by exhausted material. Finally, the composition of solids after subcritical water extractions, with NPK higher than 7% (w/w) and C/N lower than 15, allows their use as fertilizers.
Bioenergy and biofuels , Biomass conversion technologies
