• Energy Research

Abstract This work aims to evaluate the water footprint of microalgae cultivation in a closed pilot-scale multi-tubular photobioreactor, taking into account the life cycle stages of reactor construction and its operation for microalgae cultivation, on a gate-to-gate approach. The data was obtained from real production conditions complemented with data from the literature and life cycle inventory databases. Results indicate that the total water footprint lies in the range of 2.4-6.8 m3/kg dry biomass, being the PBR operation stage responsible for the largest contribution (> 60 %), mainly due to water consumption associated to electricity and nutrients production for the PBR operation.

Abstract This work aims to evaluate the water footprint of microalgae cultivation in a closed pilot-scale multi-tubular photobioreactor, taking into account the life cycle stages of reactor construction and its operation for microalgae cultivation, on a gate-to-gate approach. The data was obtained from real production conditions complemented with data from the literature and life cycle inventory databases. Results indicate that the total water footprint lies in the range of 2.4-6.8 m3/kg dry biomass, being the PBR operation stage responsible for the largest contribution (> 60 %), mainly due to water consumption associated to electricity and nutrients production for the PBR operation.

This work evaluates the possibility of using spent coffee grounds (SCG) for biodiesel production and other applications. An experimental study was conducted with different solvents showing that lipid content up to 6 wt% can be obtained from SCG. Results also show that besides biodiesel production, SCG can be used as fertilizer as it is rich in nitrogen, and as solid fuel with higher heating value (HHV) equivalent to some agriculture and wood residues. The extracted lipids were characterized for their properties of acid value, density at 15 °C, viscosity at 40 °C, iodine number, and HHV, which are negatively influenced by water content and solvents used in lipid extraction. Results suggest that for lipids with high free fatty acids (FFA), the best procedure for conversion to biodiesel would be a two-step process of acid esterification followed by alkaline transesterification, instead of a sole step of direct transesterification with acid catalyst. Biodiesel was characterized for its properties of iodine number, acid value, and ester content. Although these quality parameters were not within the limits of NP EN 14214:2009 standard, SCG lipids can be used for biodiesel, blended with higher-quality vegetable oils before transesterification, or the biodiesel produced from SCG can be blended with higher-quality biodiesel or even with fossil diesel, in order to meet the standard requirements.

This work evaluates the possibility of using spent coffee grounds (SCG) for biodiesel production and other applications. An experimental study was conducted with different solvents showing that lipid content up to 6 wt% can be obtained from SCG. Results also show that besides biodiesel production, SCG can be used as fertilizer as it is rich in nitrogen, and as solid fuel with higher heating value (HHV) equivalent to some agriculture and wood residues. The extracted lipids were characterized for their properties of acid value, density at 15 °C, viscosity at 40 °C, iodine number, and HHV, which are negatively influenced by water content and solvents used in lipid extraction. Results suggest that for lipids with high free fatty acids (FFA), the best procedure for conversion to biodiesel would be a two-step process of acid esterification followed by alkaline transesterification, instead of a sole step of direct transesterification with acid catalyst. Biodiesel was characterized for its properties of iodine number, acid value, and ester content. Although these quality parameters were not within the limits of NP EN 14214:2009 standard, SCG lipids can be used for biodiesel, blended with higher-quality vegetable oils before transesterification, or the biodiesel produced from SCG can be blended with higher-quality biodiesel or even with fossil diesel, in order to meet the standard requirements.

Developing clean and renewable energy resources ranks as one of the greatest challenges facing mankind in the medium to long term. The issues associated with developing non-fossil energy are intimately connected with economic development and prosperity, quality of life and global stability, and require smart strategies for sustainable development. This study presents a relative sustainability assessment of biodiesel, taking into account its full life cycle with the main goal of comparing alternative feedstocks, either currently used or promising for future use such as microalgae. A set of sustainability metrics relevant for biodiesel is identified using only the data available in the literature and taking into account all the three dimensions of sustainability: environmental, societal, and economic. Although this study does not attempt to identify which feedstock or process is the best, its procedural suggestions may be valuable to practitioners and policy makers seeking to identify the best alternatives. The conclusions, however, are limited by the availability and the quality of the data used in the analyses.

Developing clean and renewable energy resources ranks as one of the greatest challenges facing mankind in the medium to long term. The issues associated with developing non-fossil energy are intimately connected with economic development and prosperity, quality of life and global stability, and require smart strategies for sustainable development. This study presents a relative sustainability assessment of biodiesel, taking into account its full life cycle with the main goal of comparing alternative feedstocks, either currently used or promising for future use such as microalgae. A set of sustainability metrics relevant for biodiesel is identified using only the data available in the literature and taking into account all the three dimensions of sustainability: environmental, societal, and economic. Although this study does not attempt to identify which feedstock or process is the best, its procedural suggestions may be valuable to practitioners and policy makers seeking to identify the best alternatives. The conclusions, however, are limited by the availability and the quality of the data used in the analyses.