When Scottish Water set the ambitious target of reaching net zero by 2040, five years ahead of Scotland’s national goal, it put methane firmly in the spotlight. Methane is around 80 times more potent than carbon dioxide over a 20-year period, making it one of the most pressing greenhouse gases to tackle. The urgency was stressed at COP26 in Glasgow in 2021, where more than 100 countries signed a pledge to cut global methane emissions by 30% this decade.

For wastewater utilities, methane is a stubborn problem. Even after biogas is captured from anaerobic digestion, dissolved gas and microscopic bubbles remain in the sludge. Once the sludge moves on to storage or dewatering, that methane escapes to the atmosphere, wasting energy potential and harming the climate. Addressing these hidden emissions offers a quick and practical win in the race to decarbonise.

That’s where ELOVAC® comes in.

 

From Pilot to Proof

ELOVAC® is a vacuum degassing system that removes dissolved and entrapped gas from digested sludge. At the same time, it enables controlled phosphate precipitation with magnesium chloride, reducing struvite scaling issues and improving dewaterability. In late 2021, Scottish Water hosted a two-month demonstration of the technology at Nigg Wastewater Treatment Works (WwTW), near Aberdeen.

The trial confirmed that the system could be operated stably under full-scale conditions at Nigg. Over the 11-week demonstration, ELOVAC® consistently delivered the performance expected, proving that the concept is not only technically sound but also robust enough for day-to-day operation in a live treatment works. Crucially, the pilot was run at realistic flow rates, treating the full sludge stream rather than a side stream, giving confidence that the results can be replicated when scaled permanently.

What stood out most was the combination of climate and operational benefits. Alongside the clear evidence of methane capture, the trial showed how the technology can integrate seamlessly with existing sludge treatment infrastructure. By working directly in line with digesters, ELOVAC® adds value without requiring complex redesigns or major site disruption, making it a practical option for other utilities aiming to decarbonise their operations.

Independent testing by Aqua Enviro added further reliability, particularly in analysing the impact on dewatering performance with their dewaterability optimisation (DOT) equipment.

The results were clear:

• Greenhouse gas impact: ELOVAC® captured methane equivalent to 463 tonnes of CO₂e per year based on a CO₂ over 20 years: 84. That’s the same as taking 200 cars off the road, putting solar panels on over 1,000 homes, or planting 46,000 trees annually.
• Energy recovery: The captured methane can be fed back into the combined heat and power (CHP) engines, offsetting the plant’s own electricity use and even producing a surplus. The calculations showed an energy-positive operation, generating more electricity than the unit consumed.
• Operational benefits: An improvement in dewatering performance (0.5–1% dry solids) was observed in controlled tests, with the potential to reduce polymer use and minimise struvite scaling in downstream equipment.

While the dewatering improvements were less financially significant at Nigg due to low transport costs, the climate benefit was undeniable. For Scottish Water, this was a practical, real-world solution to one of its biggest carbon challenges.

 

The Bigger Picture: Why It Matters

Methane is not just another greenhouse gas. Its short-term warming potential makes it a critical lever for near-term climate action. The Intergovernmental Panel on Climate Change (IPCC) estimates that reducing methane emissions could help the world avoid 0.3°C of warming by 2040. At a time when every fraction of a degree matters, technologies that can cut methane today are vital.

By targeting methane, Scottish Water is addressing a greenhouse gas with far greater short-term impact than CO₂, and doing so ahead of many peers in the sector.

 

The Next Step: Full-Scale Delivery

The next phase of the project is now well underway. A full-scale ELOVAC® unit is being built for Nigg, designed to treat the entire sludge flow at the site. Unlike the pilot, this will be a permanent installation, fully WIMES compliant and integrated into Scottish Water’s existing infrastructure. Delivery is scheduled for later this year, with commissioning expected in early 2026.

By moving from a temporary trial to a fully engineered plant, the project marks a decisive step forward: a proven technology becoming part of everyday operations, with measurable climate benefits delivered at scale.

 

A Model for the Industry

For the wider water sector, the story at Nigg shows how pilot projects can scale into business-as-usual. Many utilities across the UK and Europe are grappling with the same methane challenge. The Nigg trial proves that technologies like ELOVAC® are not just experimental, they are deployable, reliable, and capable of delivering measurable impact at scale.

By capturing gas that would otherwise slip through the net, utilities can:

• Cut their direct emissions in line with national and corporate net zero targets.
• Improve resilience against energy price volatility by generating additional renewable electricity.
• Demonstrate leadership on one of the most pressing climate issues of the decade.

It also highlights the role of collaboration. Scottish Water’s willingness to host an innovative technology, combined with Eliquo’s engineering expertise, shows how partnerships can accelerate progress. Neither organisation could have achieved this outcome alone.

 

Looking Ahead

As we prepare to commission the full-scale installation at Nigg, the project offers a powerful example of how innovation moves from idea to impact. From a containerised demo plant on site in 2021 to a permanent, operational asset in 2025, the journey shows that tackling climate change in wastewater treatment is not just theory, it’s happening now.

 

ELOVAC® demo plant available for on-site trials

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