Periodic Reporting for period 1 - SusAlgaeFuel (Exploring the synergies between direct carbon-capture, nutrient recovery and next-generation purification technologies for cost-competitive and sustainable microalgal aviation fuel)
Reporting period: 2024-05-01 to 2025-10-31
Aviation is one of the most challenging sectors to decarbonise. While efficiency improvements and electrification will contribute to emissions reductions in short-haul transport, long-haul aviation will remain dependent on liquid hydrocarbon fuels for decades. Sustainable Aviation Fuels (SAFs) are therefore essential to achieving the European Green Deal and the EU’s legally binding climate-neutrality target for 2050. Under the ReFuelEU Aviation regulation, SAF blending must increase from 2% in 2025 to 64% by 2050, implying a rapid scale-up to several million tonnes of SAF by 2030.
Current SAF supply chains rely largely on waste oils and fats processed via the HEFA route, which face constraints in feedstock availability, sustainability and cost. Advanced biofuels and e-fuels remain capital- and energy-intensive. Microalgae offer a highly attractive alternative because they deliver high productivity, do not compete with food or land, and can grow on waste nutrients and captured CO2. However, high cultivation costs, microbial instability and energy-intensive downstream processing have so far prevented their large-scale deployment.
SusAlgaeFuel addresses these barriers through an integrated, circular microalgae-to-SAF platform linking waste valorisation, advanced cultivation control, low-energy biorefinery processing and fuel upgrading. The project is fully aligned with EU priorities on climate neutrality, circular economy and clean-energy industrial leadership.
The overall objective is to demonstrate a scalable and cost-competitive microalgae-based SAF pathway based on four core innovations:
(i). Use of liquid digestate and biogenic CO2 from anaerobic digestion (AD) as nutrient and carbon sources.
(ii). In-line monitoring, machine-learning-assisted process control and selective UV irradiation for stable algal cultures.
(iii). A low-energy cascading biorefinery based on autolysis and solvent recovery; and
(iv). Algae-specific thermocatalytic routes to HEFA-SPK and additional kerosene streams.
These technologies are integrated with TEA, LCA and sustainability certification. The project targets a 49% reduction in HEFA-SPK cost (from 12.3 to 6.3 USD/kg) and >60% GHG savings relative to fossil jet fuel. The pathway culminates in a TRL-5 pilot facility at an AD site in Ireland producing ≥10 kg lipids/year and demonstrating the potential to supply up to 20% of EU SAF demand in 2030.
Current SAF supply chains rely largely on waste oils and fats processed via the HEFA route, which face constraints in feedstock availability, sustainability and cost. Advanced biofuels and e-fuels remain capital- and energy-intensive. Microalgae offer a highly attractive alternative because they deliver high productivity, do not compete with food or land, and can grow on waste nutrients and captured CO2. However, high cultivation costs, microbial instability and energy-intensive downstream processing have so far prevented their large-scale deployment.
SusAlgaeFuel addresses these barriers through an integrated, circular microalgae-to-SAF platform linking waste valorisation, advanced cultivation control, low-energy biorefinery processing and fuel upgrading. The project is fully aligned with EU priorities on climate neutrality, circular economy and clean-energy industrial leadership.
The overall objective is to demonstrate a scalable and cost-competitive microalgae-based SAF pathway based on four core innovations:
(i). Use of liquid digestate and biogenic CO2 from anaerobic digestion (AD) as nutrient and carbon sources.
(ii). In-line monitoring, machine-learning-assisted process control and selective UV irradiation for stable algal cultures.
(iii). A low-energy cascading biorefinery based on autolysis and solvent recovery; and
(iv). Algae-specific thermocatalytic routes to HEFA-SPK and additional kerosene streams.
These technologies are integrated with TEA, LCA and sustainability certification. The project targets a 49% reduction in HEFA-SPK cost (from 12.3 to 6.3 USD/kg) and >60% GHG savings relative to fossil jet fuel. The pathway culminates in a TRL-5 pilot facility at an AD site in Ireland producing ≥10 kg lipids/year and demonstrating the potential to supply up to 20% of EU SAF demand in 2030.
During RP1 (M1–M18), SusAlgaeFuel established the scientific and technical foundations of the integrated microalgae-to-SAF system.
1. Waste-based cultivation and CO2 use.
Liquid digestate from AD plants was fully characterised and shown to be a robust nutrient source when combined with an ammonium-guided dilution and membrane-filtration strategy (10 and 1.2 µm). Using this approach, Nannochloropsis oceanica reached 0.95 g L⁻¹ biomass with ~43 wt% fatty acids at ~2% digestate at lab-scale. Scenedesmus strains also showed stable growth, demonstrating robustness across batches and species. A membrane-based CO2 delivery system was designed, built and operated successfully, validating bubble-free CO2 transfer.
2. Bacterial control and monitoring.
Flow cytometry demonstrated that low digestate concentrations combined with filtration maintain algal dominance over bacteria. Optical sensing limitations caused by algal autofluorescence were mitigated using filtered UV-excited fluorescence, enabling future in-line bacterial monitoring. Two light-based control systems were developed: UV-C digestate disinfection and red/blue LED cultivation (450/660 nm).
3. Low-energy biorefinery.
Autolysis-assisted hybrid disruption (PEF or HPH) achieved <1 MJ kg⁻¹ dry biomass energy demand with up to 80% lipid recovery from wet biomass. High biomass and high biomass-to-solvent ratios using biphasic non-polar solvents confirmed feasibility of a low-energy, low-solvent biorefinery.
4. Fuel conversion.
Over 20 multifunctional catalysts were tested for HEFA-SPK, achieving >50% fatty-acid conversion. Thermo-catalytic reforming (TCR-HDO) was successfully applied to microalgae pellets, producing bio-oil from residues.
Together, these results provide the first integrated experimental proof linking digestate-based cultivation, microbial control, low-energy processing and fuel conversion readiness.
1. Waste-based cultivation and CO2 use.
Liquid digestate from AD plants was fully characterised and shown to be a robust nutrient source when combined with an ammonium-guided dilution and membrane-filtration strategy (10 and 1.2 µm). Using this approach, Nannochloropsis oceanica reached 0.95 g L⁻¹ biomass with ~43 wt% fatty acids at ~2% digestate at lab-scale. Scenedesmus strains also showed stable growth, demonstrating robustness across batches and species. A membrane-based CO2 delivery system was designed, built and operated successfully, validating bubble-free CO2 transfer.
2. Bacterial control and monitoring.
Flow cytometry demonstrated that low digestate concentrations combined with filtration maintain algal dominance over bacteria. Optical sensing limitations caused by algal autofluorescence were mitigated using filtered UV-excited fluorescence, enabling future in-line bacterial monitoring. Two light-based control systems were developed: UV-C digestate disinfection and red/blue LED cultivation (450/660 nm).
3. Low-energy biorefinery.
Autolysis-assisted hybrid disruption (PEF or HPH) achieved <1 MJ kg⁻¹ dry biomass energy demand with up to 80% lipid recovery from wet biomass. High biomass and high biomass-to-solvent ratios using biphasic non-polar solvents confirmed feasibility of a low-energy, low-solvent biorefinery.
4. Fuel conversion.
Over 20 multifunctional catalysts were tested for HEFA-SPK, achieving >50% fatty-acid conversion. Thermo-catalytic reforming (TCR-HDO) was successfully applied to microalgae pellets, producing bio-oil from residues.
Together, these results provide the first integrated experimental proof linking digestate-based cultivation, microbial control, low-energy processing and fuel conversion readiness.
SusAlgaeFuel has already achieved the state of the art in several critical areas.
The project demonstrated a true circular coupling of AD and microalgae, using liquid digestate and biogenic CO2 to produce high-lipid algal biomass with reproducibility across variable feedstocks—well beyond conventional wastewater cultivation.
A first quantitative framework for bacterial control in digestate-based algal systems was established, combining filtration, flow cytometry, UV-C treatment and selective illumination, together with spectroscopic sensing.
The validation of autolysis-assisted wet biorefinery achieving <1 MJ kg⁻¹ disruption energy and high lipid recovery addresses one of the largest energy bottlenecks in algal fuels.
Finally, SusAlgaeFuel demonstrated dual SAF pathways from one algal feedstock (HEFA-SPK from lipids and TCR-HDO fuels from residues), a capability not available in current SAF platforms.
Further progress toward impact will require pilot-scale operation, ASTM certification and TEA/LCA-guided optimisation.
The project demonstrated a true circular coupling of AD and microalgae, using liquid digestate and biogenic CO2 to produce high-lipid algal biomass with reproducibility across variable feedstocks—well beyond conventional wastewater cultivation.
A first quantitative framework for bacterial control in digestate-based algal systems was established, combining filtration, flow cytometry, UV-C treatment and selective illumination, together with spectroscopic sensing.
The validation of autolysis-assisted wet biorefinery achieving <1 MJ kg⁻¹ disruption energy and high lipid recovery addresses one of the largest energy bottlenecks in algal fuels.
Finally, SusAlgaeFuel demonstrated dual SAF pathways from one algal feedstock (HEFA-SPK from lipids and TCR-HDO fuels from residues), a capability not available in current SAF platforms.
Further progress toward impact will require pilot-scale operation, ASTM certification and TEA/LCA-guided optimisation.