Algal-Bacterial Aerobic Granular Sludge Shows Great Potential in Reducing Greenhouse Gas Emissions

Strategic Insights -

Research conducted by the Shanghai Academy of Environmental Sciences has shed new light on the potential of algal-bacterial aerobic granular sludge (AGS) in reducing greenhouse gas (GHG) emissions. According to the study, AGS has shown significant potential in reducing GHG emissions compared to traditional activated sludge processes. However, the study also highlighted the need to understand nitrous oxide (N2O) and methane (CH4) emissions in AGS systems, as these gases remain poorly understood.

The research, which was funded by several organizations, including the Science and Technology Commission of Shanghai Municipality, aimed to investigate N2O, CO2, and CH4 emission characteristics and explore non-CO2 GHG emission mitigation potential using photosynthetically fixed carbon in algal-bacterial AGS systems. The study found that N2O emission factors fluctuated significantly, ranging from 0.4% to 3.0%, and exhibited no correlation with algae contents, extracellular polymeric substance contents, or nutrient removal efficiencies.

Key Takeaways:

  • Algal-bacterial aerobic granular sludge (AGS) has shown significant potential in reducing GHG emissions compared to traditional activated sludge processes.
  • N2O and CH4 emissions in AGS systems remain poorly understood and require further investigation.
  • The study found that N2O emission factors fluctuated significantly, ranging from 0.4% to 3.0%, and exhibited no correlation with algae contents, extracellular polymeric substance contents, or nutrient removal efficiencies.
  • The reduced CO2 emission in AGS systems shows a strong positive correlation (R-2 = 0.88) with Chlorophyll-a content, primarily due to enhanced photosynthetic activity.
  • The study concluded that non-CO2 GHG emissions in ALGAL-bacterial aerobic granular sludge needs to be mitigated.

Statistics:

  • N2O emission factors in AGS systems ranged from 0.4% to 3.0%.
  • The reduced CO2 emission in AGS systems showed a strong positive correlation (R-2 = 0.88) with Chlorophyll-a content.
  • CH4 emissions in AGS systems were offset by photosynthetically fixed carbon when Chlorophyll-a achieved 11.1 mg/g-MLVSS.

Sources:

  • "Photosynthetically Fixed Carbon Neutralizes Nitrous Oxide and Methane Emissions for a Carbon-negative Algal-bacterial Aerobic Granular Sludge Process." Journal of Water Process Engineering, 2025;76.
  • Xiaoyong Qian, Shanghai Academy of Environmental Sciences, Shanghai 200233, People's Republic of China.
  • Shanghai Academy of Environmental Sciences.
  • Elsevier, Radarweg 29, 1043 Nx Amsterdam, Netherlands.