Biomass powder, biogas and biosolid from microalgae processing: The technical, environmental and economic performance

The goal of this research was to quantify the energy demand, carbon footprint, and financial cost of microalgae biomass processing with solar drying to produce biomass powder and anaerobic digestion, which is preceded by heat treatment, to produce biogas and biosolids. Microalgae biomasses were produced from cultivation in open raceway ponds in nutrient regimes with the availability and limitation of nitrogen and phosphorus. The methods used in this study were life cycle assessment (LCA) and techno-economic analysis (TEA). The largest contribution in the Processing stage was from the microalgae biomass production, which accounted for 43-91 % of the indicator values in the base scenarios. The production of bioproducts from microalgae cultivation in scenarios of nutrient limitation, higher biomass productivity, electricity supply from a photovoltaic plant, and nutrient supply from on-site residual sources combined reduced up to 61 % in energy demand, 79 % in carbon footprint, and 47 % in financial cost compared to those of the base scenarios. Biomass powder is a competitive input for substituting fossil-based materials in plastic composites. Even though the biomass composition change from microalgae cultivation in nutrient limitation, methane loss reduction, and multiproduct coproduction favored the viability of anaerobic digestion in the assessed categories, the financial cost of biogas production must be reduced to increase its competitiveness compared to fossil fuels. Therefore, the proposed strategies in the evaluated scenarios should be combined to increase the eco-efficiency in an integrated microalgae biorefinery.