Microbial fuel cells (MFCs) and microalgae–bacteria consortia represent two renewable and promising technologies of growing interest that enable wastewater treatment while obtaining high-value-added products. This study integrates MFCs and microalgae production systems to treat animal slurry, aiming to remove and recover organic and inorganic components while generating energy and producing biomass. The MFCs effectively eliminated Chemical Oxygen Demand (COD), organic nitrogen, and a portion of the suspended solids, achieving a maximum voltage of 195 mV and a power density of 87.03 mW·m⁻². After pre-treatment with MFCs, the slurry was diluted to concentrations of 10%, 50%, and 100% and treated with microalgae–bacteria consortia. The results showed a biomass production of 0.51 g·L⁻¹ and a productivity of 0.04 g·L⁻¹·day⁻¹ in the culture fed with 10% slurry, with significant removal efficiencies: 40.71% for COD, 97.76% for N-NH₄₊, 39.66% for N-NO₂⁻, 47.37% for N-NO₃⁻, and 94.37% for P-PO₄⁻³. The combination of both technologies allowed for obtaining a properly purified slurry and the recovery of nutrients in the form of bioelectricity and high-value biomass. Increasing the concentration of animal slurry to be treated is essential to optimize and scale both technologies.

This study investigates the viability of a native Scenedesmus sp. strain for use in a 50 L bubble column photobioreactor designed to reduce greenhouse gas emissions under simulated spring, extreme summer, and winter conditions. The experiments were conducted by placing the reactor in a controlled climatic chamber, which allowed us to regulate the temperature, light intensity, and day–night cycles throughout the entire experiment. The results showed that under simulated spring conditions (a maximum temperature of 22 °C), the algal culture grew continuously for 61 days. Under extreme summer conditions (a maximum temperature of 39 °C), an initial drop in cell density was followed by recovery and continued growth over 75 days, although biomass production was 35% lower. Under winter conditions (a maximum temperature of 10 °C), the culture failed, indicating the need to prevent temperatures below 10 °C. In terms of biomass production, the culture densities achieved were 1.04 g L⁻¹ and 0.68 g L⁻¹ in the spring and summer trials, respectively. The Scenedesmus sp. strain demonstrated high carbon capture efficiency, tolerance to extreme heat, and sustained growth without the need for fresh medium or pH adjustments for over 60 days during spring and extreme summer conditions, confirming its potential for outdoor applications.

Microalgal biomass is increasingly valued in industrial and agricultural sectors due to its bioactive compounds. However, large-scale production remains costly, mainly due to nitrogen fertilizer expenses. A promising sustainable alternative is co-cultivation with N₂-fixing bacteria, capable of supplying biologically available nitrogen. In this study, Chlorella vulgaris was grown in synthetic medium with and without nitrogen, as well as in co-culture with three different N₂-fixing bacteria in nitrogen-free medium. Microalgal growth was assessed by dry weight, Fv/Fm ratio, and flow cytometry, which also allowed evaluation of population dynamics and cell viability. Biomass composition (proteins, carbohydrates, lipids, chlorophyll, and carotenoids) was analyzed under all conditions. Co-cultures in nitrogen-free medium showed comparable biomass productivity to nitrogen-supplemented controls, although Fv/Fm values indicated physiological stress in some cases. Moreover, the agricultural potential of the resulting biomass and supernatants was evaluated through germination bioassays using lettuce seeds. All cultures tested at 0.2 g·L^-1 significantly improved the germination index. Also, applying the culture supernatant (biomass removed) also yielded positive effects, with GI increases exceeding 40 %. These results suggest that co-cultivation with N₂-fixing bacteria can support efficient microalgal production while generating biomass and supernatants with biostimulant potential, contributing to sustainable agriculture and circular bioeconomy strategies.

Pig slurry management has emerged as a pressing environmental challenge in the context of rapid population growth and intensified livestock production, highlighting the need for sustainable recovery technologies. While microalgae–bacteria (MB) systems offer promising opportunities for nutrient recycling, the high turbidity of raw pig slurry (PS) typically limits their direct application. This study proposes an innovative two-step treatment that combines microbial fuel cells (MFCs) with MB consortia to enhance both pollutant removal and resource recovery from raw PS with COD levels exceeding 18,000 mg·L⁻ ¹ . Unlike conventional designs relying on perfluorinated membranes, the MFCs employed an ionic liquid [N _{8-10,8–10,8–10,1} ⁺ ][Cl ⁻ ] as a proton exchange medium, achieving 50% of COD removal and generating 57.27 ± 10.99 mW·m⁻ ² . The effluent was subsequently treated with MB consortia, yielding biomass productivities of 0.1 to 0.2 g·L⁻ ¹ ·day⁻ ¹ , comparable to chemical fertilizer-based controls. Cell density with pre-treated and untreated pig slurry also matched control levels. In pollutant recovery, the combined microbial fuel cell and microalgae-bacteria treatment achieved up to 67% recovery of COD, over 99% of N-NH ₄ ⁺ , and between 65 and 85% of P-PO ₄ ³⁻ . These findings highlight the potential of integrating MFCs with MB consortia as a strategy for raw pig slurry management, t-ransforming waste into renewable energy and bioresources. Key points: • Pig slurry is transformed into biomass and bioenergy using sustainable technologies • Microalgae-bacteria consortia enhance nutrient recovery and water treatment • Ionic liquid microbial fuel cells support energy generation and COD reduction Graphical