Biomaqua project: Energetic valorisation of microalgae

Abstract

Introduction: Microalgae have been described as high potential source of biomass for energy production especially considering their lipid content and the high yield of production. Biomaqua is a collaborative project developed by the technological centres Ainia, Cidaut and Gaiker, which aims to evaluate integrated alternatives for sustainable microalgae production and its energetic valorisation. The project considers the use of gas and liquidwastes streams for producing microalgae and different alternatives of energetic valorisationofmicroalgaebyusingnot only the lipids but thewhole biomass components. Methods: Microalgae has been selected from collections and natural environments. Wastewater and digestate have been evaluated as main sources of nutrients for microalgae cultivation. Batch cultures have been conducted in 2 and 5 L photobioreactors. Continuousmicroalgae cultures have been developed in tubular (270 L) and bags (100 L) photobioreactors (both of them designed and constructedwhiting theproject). Assays ofmicroalgae biomethanation potential have been carried out in 2.0 L batch digesters. All along the project a Life Cycle Analysis (ACV) has been conducted in order to evaluate the global sustainability of the compared alternatives. Results: 13 microalgae strains have been evaluated and 3 selected including Chlorella and Scenedesmus. Under the defined conditions, noneof the continuousmicroalgae cultures have shown higher densities than 0.6 g dm/L or lipid contents higher than 8.0% dm. However, medium productivities have been measured about 13.5 g dm/day. Main culturing bottlenecks have been found in avoiding contaminations and increasing lipid productivities. The results of biomethanation potential have shown a medium biogas production (228 NL/kg SV) with elevated methane content (67.4%) and 90.0% of total the biogas production reached before 20 days. Discussion: Among major results, ACV indicates that under integrated defined scenario, biogas could be considered as interesting alternative for complementary microalgae valorisation.