Biogas upgrading is no longer an exclusive preserve of the large-sized plants. Andrew Parsons of biomethane firm Bennamann explores the possibilities coming into view.
AD systems typically comprise one to three digesters – large, round towers with dome covers – where organic matter is broken down by anaerobic bacteria to produce biogas. These plants have been designed primarily for electricity generation, often with heat as a by-product.
It’s been widely adopted but, oddly, much of its production capacity has remained under-used.Many AD plant operators report that they could produce more gas than they use. This excess capacity represents not just lost potential revenue but missed opportunities for carbon reduction and resource efficiency.
Why the mismatch between biogas production, capacity and usage? Many plants were intentionally built with excess capacity to ensure they wouldn’t fall short on electricity production. However, this oversizing, coupled with limitations in generator capacity or demand, often leads to excess biogas being unused.
A key breakthrough: scalable biogas upgrading
Recent technological advances now offer solutions to this issue. Companies, including Bennamann, have developed compact, skid-mounted biogas upgrading systems that can process smaller volumes of excess biogas. These units, similar in size to a 12-foot shipping container, are designed to upgrade biogas to high-purity biomethane.
The Bennamann Biocycle process, for instance, can take biogas containing 50-70% biomethane and upgrade it to as high as 99% biomethane. This technology is particularly noteworthy for its scalability and ease of integration into existing AD infrastructure, requiring minimal additional investment from plant operators.
Being able to efficiently upgrade biogas to biomethane opens up new applications and markets. The key benefits:
1. Enhanced carbon reduction: Capturing and using methane is obviously preferable to allowing it to remain unused. At COP26 150 countries signed a pledge to reduce emissions of methane by 30 per cent by 2030.
2. Circular economy in action: AD technology, especially when coupled with biogas upgrading, exemplifies the principles of a circular economy. It transforms waste – be it agricultural residues, food waste, or sewage – into valuable resources: energy and fertilizer. This closed-loop system reduces the need for landfills, overflowing slurry pits and incineration while producing renewable energy.
3. Decarbonising transport: Biomethane can be used as a renewable transport fuel, potentially powering vehicles such as heavy goods vehicles, buses, and agricultural machinery. This application is particularly significant given the challenges of decarbonising the transport sector, especially for heavy vehicles where electrification may not be feasible.
4. Soil health and carbon sequestration: The digestate produced as a by-product of AD is a nutrient-rich biofertilizer. When applied to agricultural land, it not only reduces the need for synthetic fertilizers but also contributes to soil carbon sequestration, further enhancing the carbon negativity of the AD process.
Policy landscape outlook
Supportive policy frameworks and market incentives are also germane to the viability of the approach. In the UK, for instance, the Renewable Transport Fuel Obligation (RTFO) provides Renewable Transport Fuel Certificates (RTFCs) for biomethane production. Notably, biomethane produced from true waste products like food waste or animal slurry qualifies for double the RTFC value to that from purpose-grown energy crops.
This incentive structure aligns with broader waste management and sustainability goals, encouraging the processing of waste through AD plants. It also creates a financial incentive for AD operators to invest in biogas upgrading technologies, potentially transforming what was once a cost centre into a profit-generating asset. Bennamann offers a service whereby it can claim the RTFCs on behalf of the plant, further simplifying the process for farmers and contractors while maximising the potential benefits.”
AD 2.0 and beyond
The potential for scalable biogas upgrading in the UK and globally is substantial. In the UK alone, over half of existing AD plants are potentially suitable for this technology. This presents significant opportunities not just for waste management and renewable energy sectors, but also for rural economies and the broader goal of national carbon reduction.
Looking ahead, several trends are likely to shape the future of AD technology:
1. Integration with other renewables: AD plants could play a crucial role in balancing the intermittency of solar and wind power, providing a stable, on-demand source of renewable energy.
2. Smart AD plants: The integration of AI and IoT technologies could optimise AD processes, predicting and managing biogas production based on various factors including feedstock composition and energy demand.
3. Diversification of feedstocks: Research into new feedstocks, including algae and specific energy crops, could further enhance the efficiency and sustainability of AD systems.
4. Carbon capture: Combining AD with carbon capture technologies could create negative-emission systems, where CO2 is not just reduced but actively removed from the atmosphere.
A new paradigm?
Advances in anaerobic digestion and biogas upgrading represent more than just an incremental improvement in waste management technology. They signal a paradigm shift in how we view and manage organic waste streams, transforming them from a problem to be solved into a valuable resource.
For policymakers, this technology offers a powerful tool in the pursuit of circular economy principles and climate change mitigation. For industry leaders, it presents new opportunities for sustainable business practices and potential revenue streams. And for environmental professionals, it provides a concrete example of how innovative technologies can bridge the gap between waste management and renewable energy production.
As we continue to grapple with the dual challenges of waste management and climate change, the role of advanced AD technologies in creating local, sustainable energy sources is set to grow. By enabling more efficient use of our resources and reducing our carbon footprint, these innovations are not just shaping the future of waste management – they’re contributing to the broader transition towards a more sustainable and resilient society.
The journey towards AD 2.0 is well underway.As we move forward, continued research, investment and policy support will be essential to fully realise the promise of AD 2.0 technology and its role in building a more sustainable future.
