Environmental sustainability assessment of a microalgae raceway pond treating wastewater

4th International Congress on Sustainability Science & Engineering 26-29 May 2015 Environmental Sustainability Assessment of a Microalgae Raceway Pond Treating Wastewater from a Recirculating Aquaculture System From Upscaling to System Integration Sophie Sfez(a), Sofie Van Den Hende(b), Sue Ellen Taelman(a), Steven De Meester(a), Jo Dewulf(a) (a) Department of Sustainable Organic Chemistry and Technology, Ghent University, Coupure Links 653, B9000 Ghent, Belgium (b) Laboratory for Industrial Water and Eco-Technology (LIWET), Faculty of Bioscience Engineering, Ghent University, Graaf Karel de Goedelaan 5, B-8500 Kortrijk, Belgium Sustainable Pathways for Algal Bioenergy Introduction EnAlgae: INTERREG IVB North West Strategic Initiative (03/2011 – 06/2015) pilot scale algae cultivation sites (micro- and macroalgae) • In Roeselare, Belgium: Algae-based wastewater treatment plant, treating wastewater from a pikeperch recirculating aquaculture systems (RAS) Sustainable Pathways for Algal Bioenergy Introduction Aquaculture: fast growing sector competing for freshwater resources RASs: promising option to mitigate the environmental footprint of aquaculture systems Recirculating aquaculture system O2 UV Backwash Biofilters Fish ponds Drum filters wastewater Backwash supernatant Algae-based wastewater treatment system Fish sludge Anaerobic digestion Settling tank Water The MaB-floc technology tested in 2013 in Belgium at pilot scale to treat pikeperch aquaculture wastewater from the Aquaculture Research Center of Inagro (Belgium) Sustainable Pathways for Algal Bioenergy Introduction MaB-flocs: bioflocculating consortium of bacteria and microalgae As they grow, MaB-flocs need to be harvested, delivering a new source of biomass: valorisation as shrimp feed and anaerobic digestion were tested at pilot scale Industry needs insights to know which direction to take Goal of the study Goal 1: Assess the environmental footprint of a pilot MaB-floc SBR treating pikeperch culture WW and identify its improvement potential Goal 2: Forecast the most sustainable valorisation pathway for MaB-flocs in the framework of an integrated aquaculture waste treatment system at industrial scale Sustainable Pathways for Algal Bioenergy Studied MaB-floc based WWT plants Pilot MaB-floc SBR treating pikeperch wastewater (real case) Electricity Sunlight Land Flue gas Natural gas Heat MaB-floc raceway pond To stirring pumps Backwash supernatant Electricity MaB-floc liquor pond Area: 12 m2 Volume: 28 m3 Flow: 2.59 m3 day-1 Settling tank Supernatant MaB-floc liquor Effluent water Van Den Hende 2014 Sustainable Pathways for Algal Bioenergy Studied MaB-floc based WWT plants Pilot MaB-floc SBR treating pikeperch wastewater (real case) Hypothetical up-scaled cases (1000 m3 of WW treated per day): L: linearly up-scaled MaB-floc plant Natural gas Flue gas Heat 5m Blower To stirring pumps Electricity 50 m MaB-floc raceway pond Supernatant Sunlight Effluent Water Land 41 ponds Area: 245 m2 pond-1 Volume: 98 m3 pond-1 Flow: 24.5 m3 day-1 pond-1 Electricity Settling tank 41 reactors = 1ha of cultivation MaB-floc liquor Sustainable Pathways for Algal Bioenergy Studied MaB-floc based WWT plants Pilot MaB-floc SBR treating pikeperch wastewater (real case) Hypothetical up-scaled cases (1000 m3 of WW treated per day): L: linearly up-scaled MaB-floc plant S: linearly up-scaled MaB-floc plant with improved stirring system Propeller pump 22 W m-2 Paddle wheel 5.1 W m-2 Sustainable Pathways for Algal Bioenergy Studied MaB-floc based WWT plants Pilot MaB-floc SBR treating pikeperch wastewater (real case) Hypothetical up-scaled cases (1000 m3 of WW treated per day): L: linearly up-scaled MaB-floc plant S: linearly up-scaled MaB-floc plant with improved stirring system E: linearly up-scaled MaB-floc plant with Belgian electricity mix replaced by 100% wind energy Sustainable Pathways for Algal Bioenergy Studied MaB-floc based WWT plants Pilot MaB-floc SBR treating pikeperch wastewater (real case) Hypothetical up-scaled cases (1000 m3 of WW treated per day): L: linearly up-scaled MaB-floc plant S: linearly up-scaled MaB-floc plant with improved stirring system E: linearly up-scaled MaB-floc plant with Belgian electricity mix replaced by 100% wind energy M: linearly up-scaled MaB-floc plant with MaB-floc productivity improved by 30% Sustainable Pathways for Algal Bioenergy Studied integrated system Three scenarios are compared: Valorisation of MaB-flocs as shrimp feed Treated backwash supernatant released in the sewage system Pikeperch Backwash Settling RAS wastewater Fish sludge Maize silage MaB-floc liquor Raceway ponds Digester Valorisation as shrimp feed Dewatering Heat Biogas CHP Drying Electricity Digestate Heat Milling Shrimp feed Electricity to the grid Soil conditioner Valorisation of MaB-flocs as biogas Treated backwash supernatant released in the sewage system Pikeperch Backwash RAS wastewater Settling Raceway ponds MaB-floc liquor Soil conditioner Valorisation as biogas Digestate Dewatering Digester Biogas Fish sludge CHP Maize silage Heat Electricity to the grid Sustainable Pathways for Algal Bioenergy Studied integrated system Three scenarios are compared: Valorisation of MaB-flocs as shrimp feed Valorisation of MaB-flocs as biogas Baseline scenario Backwash supernatant released in the sewage system Pikeperch Backwash Settling wastewater RAS Electricity to the grid Fish sludge Heat Heat Digester Maize silage Biogas CHP Electricity Digestate MaB-flocs plants are integrated: Natural gas Flue gas Heat Soil conditioner 5m Blower To stirring pumps Electricity Plant L (linearly up-scaled plant) 50 m MaB-floc raceway pond Supernatant Sunlight Effluent Water Land Electricity Settling tank 41 reactors = 1ha of cultivation MaB-floc liquor Plant SEM (plant L with the improvements implemented Natural gas Flue gas Heat 5m Blower To stirring pumps Electricity 50 m MaB-floc raceway pond Supernatant Sunlight Effluent Water Land Electricity Settling tank 41 reactors = 1ha of cultivation + + + MaB-floc liquor Sustainable Pathways for Algal Bioenergy Env Sustainability Analysis Life Cycle Assessment (LCA), ISO standards 14040 & 14044 Functional unit Syst boundaries Production of kg TSS MaB-floc liquor Goal 2: SA of the integration of MaB-floc based WWTP in an aquaculture system Treatment of m3 of wastewater Goal and scope definition Cradle-to-gate Foreground Pilot: site data Data from up-scaled system Up-scaled: pilot data + plant + ecoinvent v 2.2 literature + literature Inventory analysis Background ecoinvent v 2.2 + system literature Resource consumption (CEENE 2013) resource efficiency analysis Global warming potential (IPCC 2007) air emission efficiency analysis Marine and freshwater eutrophication (ReCiPe 2013) Impact assessment water emission efficiency analysis Sustainable Pathways for Algal Bioenergy Interpretation Goal 1: comparison of the MaB-floc based WWTP LCA results: environmental sustainability of the MaB-floc based WWTP Total CEENE: 848 MJ kg-1 MaB-floc TSS Resource footprint (CEENE results) 450 350 300 250 200 150 100 50 S E M P Land resource L S E M P L Fossil fuels S E M P Metal ores L S E M P Minerals L S E M P Nuclear energy L S E M P L S E M Water resources Abiotic renewable resources Electricity consumption - stirring pumps Electricity consumption - other pumps Electricity consumption - flue gas blower Heating of the pond M L S P Pilot MJex,CEENE kg-1 MaB-floc TSS 400 Direct Land occupation Infrastructure Direct phosphorus emissions to water Direct nitrogen emissions to water Sustainable Pathways for Algal Bioenergy LCA results: environmental sustainability of the MaB-floc based WWTP Total CEENE plant L: 278 MJ kg-1 MaB-floc TSS Resource footprint (CEENE results) 450 -77% -69% 350 300 250 200 150 100 50 S E M P Land resource L S E M P L Fossil fuels S E M P Metal ores L S E M P Minerals L S E M P Nuclear energy L S E M P L S E M Water resources Abiotic renewable resources Electricity consumption - stirring pumps Electricity consumption - other pumps Electricity consumption - flue gas blower Heating of the pond M L S P Pilot MJex,CEENE kg-1 MaB-floc TSS 400 Direct Land occupation Infrastructure Direct phosphorus emissions to water Direct nitrogen emissions to water Sustainable Pathways for Algal Bioenergy LCA results: environmental sustainability of the MaB-floc based WWTP Re CiPe 2013 - Freshwater eutrophication 1,E-02 Re CiPe 2013 - Marine eutrophication 28% 34% 36% 1,E-02 kg Neq kg MaB-floc TSS 8,E-03 6,E-03 4,E-03 2,E-03 0,E+00 S 1,E-02 8,E-03 6,E-03 4,E-03 2,E-03 0,E+00 E Pilot L S 25 20 15 10 E Pilot L S Electricity consumption - other pumps Electricity consumption - flue gas blower Heating of the pond M Electricity consumption - stirring pumps S L Pilot Pilot 67% 90% 97% 75% kg CO2 eq kg-1 MaB-floc TSS 1,E-02 1,E-02 kg Peq kg-1 MaB-floc TSS 30 2,E-02 67% 85% 91% 1,E-02 IPCC 2007 - Climate change Direct Land occupation Infrastructure Direct phosphorus emissions to water Direct nitrogen emissions to water E M Sustainable Pathways for Algal Bioenergy LCA results: environmental sustainability of the Integrated systems Baseline scenario Pikeperch Backwash Settling wastewater RAS Backwash supernatant released in the sewage system Electricity to the grid Fish sludge Heat Heat Digester Maize silage Biogas CHP Electricity Digestate Soil conditioner Scenario - valorisation of MaB-flocs as shrimp feed Treated backwash supernatant released in the sewage system Pikeperch Backwash Settling RAS wastewater Raceway ponds Fish sludge MaB-floc liquor Digester Maize silage Valorisation as shrimp feed Dewatering Heat Biogas CHP Drying Electricity Digestate Heat Shrimp feed Milling Electricity to the grid Soil conditioner Scenario - valorisation of MaB-flocs as biogas Treated backwash supernatant released in the sewage system Pikeperch Backwash RAS wastewater Settling Raceway ponds MaB-floc liquor Soil conditioner Valorisation as biogas Digestate Dewatering Digester Biogas Fish sludge CHP Maize silage Heat Electricity to the grid Sustainable Pathways for Algal Bioenergy LCA results: environmental sustainability of the Integrated systems Resource footprint1 - 133% - 101% Left bar: Right bar: Avoided processes CEENE results without abiotic renewable resources Sustainable Pathways for Algal Bioenergy LCA results: environmental sustainability of the Integrated systems Freshwater eutrophication Marine eutrophication (ReCiPe 2013) (ReCiPe 2013) Left bar: Carbon footprint (IPCC 2007) Right bar: Avoided processes Sustainable Pathways for Algal Bioenergy Conclusion MaB-floc technology: stirring has the highest contribution to most impact categories Integrated aquaculture waste treatment system: • Potential to compete with the baseline scenario and contribute to a sustainable connection of the water-food-energy nexus in the aquaculture sector • Valorizing MaB-flocs into shrimp feed: overall more sustainable than into biogas Bottleneck: EU legislation Future research: • Improvement of LCA with more complete data on nutrient cycle (measurements needed) • Focus on the improvement of the energy efficiency of the system, rather than of MaB-flocs productivity Sustainable Pathways for Algal Bioenergy Thank you! Sophie.Sfez@UGent.be +32 (0) 264 99 27 Sustainable Pathways for Algal Bioenergy ... aquaculture wastewater from the Aquaculture Research Center of Inagro (Belgium) Sustainable Pathways for Algal Bioenergy Introduction MaB-flocs: bioflocculating consortium of bacteria and microalgae As... sustainable valorisation pathway for MaB-flocs in the framework of an integrated aquaculture waste treatment system at industrial scale Sustainable Pathways for Algal Bioenergy Studied MaB-floc based... MaB-flocs as biogas Treated backwash supernatant released in the sewage system Pikeperch Backwash RAS wastewater Settling Raceway ponds MaB-floc liquor Soil conditioner Valorisation as biogas Digestate