Anaerobic Digestion for Renewable Energy Production
Anaerobic Digestion (AD) has become a core process in the treatment of sewage sludge and organic wet waste, generating renewable energy to improve the sustainability and indeed the energy efficiency of municipal and industrial wastewater treatment plants. The anaerobic process converts waste streams into biogas providing both heat and electrical power to support the other processes and treatment operations on wastewater treatment plants, whilst generating energy from a sustainable source and simultaneously reducing reliance on fossil fuels.
With advancements in efficiency, modern AD technology has become even more efficient in the generation of energy from waste streams supporting circular economy principles and increasing resource recovery.
How does Anaerobic Digestion work?
Anaerobic Digestion is a natural process that breaks down organic material in the absence of oxygen, using microorganisms to convert it into biogas and digestate. This normally takes place in a gas-tight vessel, often referred to as a Digester or Reactor. Here is a simple overview of the process:
- Bacteria inside the digester break down the organic material into smaller molecules, such as sugars and fatty acids.
- Other microorganisms, called archaea convert these molecules into biogas, which mainly comprises methane.
- The biogas collected can be used as a renewable energy source, often harnessed through Combined Heat & Power (CHP) systems to generate both electricity and heat.
- The remaining digestate can be treated and used as fertiliser (biofert) or processed further to recover valuable components.
Anaerobic Digestion Plant Management
Managing an Anaerobic Digestion plant requires specialist skills and knowledge to ensure the highest standards of safety and maximise the production of valuable biogas for energy and heat.
Maximising Energy Production
CAW has a proven track record in designing, building, and operating AD plants to maximise energy production. By optimising feedstock management, process control, and system efficiency, we enhance biogas yield. We integrate both established technologies and newer, more advanced solutions like Ephyra®. Our expertise ensures highly efficient gas capture and utilisation across the sites we operate and maintain.
Managing Safety
Safety is at the core of our approach to the design, construction and operation of AD systems. We implement rigorous gas monitoring, explosion risk control, and H₂S management to mitigate hazards. Our commitment to safety is reinforced through ongoing investment in Operational and Process Safety training, robust procedures, and proactive risk management, ensuring compliance with health, safety, and environmental regulations.
Sludge and Biosolids Management
CAW’s expertise in sludge handling and biosolids management is built on years of operating Ireland’s largest wastewater treatment plant at the Ringsend WwTW together with Advanced Sludge Treatment Facilities at Sligo and Waterford. Our experience in designing, building, and operating Advanced Sludge Treatment and Biosolids Management Facilities has refined our approach to dewatering, stabilisation, and nutrient recovery, optimising resource use while minimising waste. Advanced processes such as Pasteurisation, Thermal Hydrolysis and Ephyra® further enhance the treatment of sludge streams maximising resource recovery for reuse.
Types of Anaerobic Digestion
Traditional Anaerobic Digestion (AD) typically operates in single or multi-stage digesters under mesophilic (35-40°C) or thermophilic (50-55°C) conditions. While effective for energy production, traditional AD requires a high volume of organic matter and substantial investment, which has limited its adoption across Ireland.
However, advancements in AD technology have led to the development of Ephyra®, which generates 20-30% more biogas and improves sludge breakdown compared to traditional methods. Ephyra uses a multi-compartment reactor to shorten retention times and increase biogas yield, all within a compact footprint that makes it ideal for retrofitting or integration into existing treatment plants.
With extensive experience in both traditional and Ephyra® AD technologies, CAW is well-positioned to support the design, build, and operation of these systems.
Anaerobic Digestion Plant Design and Build
Our project engineering team is committed to enhancing the performance and sustainability of the AD plants we design, build, and operate. By continuously identifying opportunities to improve efficiency and reduce operating costs, we help maximise biogas yield and resource recovery. For example, CAW are currently identifying opportunities in further optimising the AD plants and associated assets we operate to assist our Clients in achieving 2030 GHG emission targets.
While Anaerobic Digestion offers a sustainable solution for organic waste management, challenges such as process stability, gas handling, and digestate management require careful optimisation. Our expertise ensures a balance between sustainability, efficiency, and long-term operational reliability.
CAW Managed Sites
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