Carbon emissions in aquaculture mainly stem from energy-intensive water exchange, the carbon footprint of feed production and transport, and greenhouse gas emissions (CO₂, CH₄, N₂O) from organic waste in the system. Studies have shown that bioflocs can produce extracellular polysaccharides via heterotrophic bacterial communities, aggregating organic particles in the water. These aggregates are consumed by cultured animals, reducing solid waste and preventing microbial decomposition that would release greenhouse gases, while also lowering feed requirements. Bioflocs further convert ammonia nitrogen into microbial nutrients, functioning as a micro-filtration system that stabilizes water quality, decreases organic wastewater discharge, and reduces reliance on energy-intensive recirculation equipment. Additionally, bioflocs promote butyrate production in the gut of cultured animals, suppressing pathogens and providing natural biocontrol, which minimizes antibiotic and drug use.
This project introduces a novel algae-bacteria symbiotic system. By adding a controlled proportion of autotrophic microalgae, photosynthesis consumes CO₂ and produces oxygen, supplying dissolved oxygen to heterotrophic bacteria and reducing aeration energy consumption and associated carbon emissions. Bioflocs are enhanced using sulfated fucoidans secreted by microalgae, which effectively bind bacterial cells and organic debris. Microalgae also provide high levels of unsaturated fatty acids and essential amino acids, increasing the nutritional value of bioflocs as a feed substitute. Using synthetic biology, microalgae will be engineered to improve flocculation efficiency beyond current bacterial-only bioflocs, while enhancing nutrition, antibacterial activity, and ammonia removal. Since precise control of carbon-to-nitrogen ratios, dissolved oxygen, and pH is critical, an artificial intelligence system will be developed. Using automated monitoring and deep learning algorithms, it will dynamically regulate biofloc density, ensuring ecosystem stability under near-zero water exchange conditions. Finally, on-site greenhouse gas monitoring equipment will measure carbon emissions across solid, liquid, and gas phases in aquaculture. The project will establish methodologies and field validation for algae-bacteria biofloc carbon reduction, creating the first domestically certified aquaculture carbon credit case in Taiwan.