This research project endeavours to pioneer a biological solution for mitigating carbon dioxide (CO2) emissions from effluent gases produced by bioenergy combustion systems. The primary focus is on converting the captured CO2 into carbon-negative energy carriers, specifically emphasizing the photosynthetic conversion of biogenic CO2 into energy-rich biomass. The transformation of this biomass into widely used renewable energy carriers, such as biocrude and biogas, is targeted, with an additional emphasis on enriching these carriers with renewable hydrogen to achieve carbon circularity. The project is structured to address key aspects, including; efficient biogenic CO2 capture from effluent systems, development of resilient microalgae strains to enhance resistance to flue gas toxicity, novel biomass pre-treatment methods for cell disruption and nitrogen removal (concurrent production of biostimulants), and improvements in the efficiency and sustainability of hydrothermal liquefaction (biocrude), anaerobic digestion (biogas) and hydrogenotropic conversion of CO2 to biomethane. The ultimate goal is to validate the viability of the developed direct CO2 fixation methods through integration with effluent systems at a pilot scale, reaching TRL5. This multifaceted approach underscores the project's commitment to advancing sustainable and efficient methods for biogenic CO2 fixation and subsequent conversion into renewable energy carriers. To assess the economic viability, a detailed techno-economic analysis of the proposed carbon capture and use solution will be conducted. Furthermore, sustainability and social impact assessments will be performed, taking into account circular economy principles and addressing social, economic, and environmental aspects in alignment with the priorities outlined in the European Green Deal.