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Project impact
The UK’s first large-scale wastewater heat recovery project enabled Borders College to reduce gas use, cut carbon emissions and modernise its heating infrastructure—with minimal capital outlay.
- A first in the UK: The first large-scale wastewater heat recovery project of its kind in the UK.
- 1 GWh of renewable heat generated annually.
- 180 tonnes of carbon emissions saved each year.
- Minimal capital outlay through an innovative funded heat supply model.
The challenge
Borders College wanted to reduce its reliance on gas and lower the carbon impact of heating its Galashiels campus.
The estate presented a significant challenge. Three very different buildings—including a Victorian textile mill—were served by five plant rooms containing ageing gas boilers.
The college needed a renewable solution that could work with its existing infrastructure without creating major disruption or requiring substantial upfront investment.
Finding the right solution
Several innovations were assessed:
- Biomass was ruled out because of fuel storage and delivery constraints.
- A connection to a local district heating network was considered too complex and slow.
Heat pumps offered the most practical route to converting local low-grade heat into usable energy.
A sewer running behind the college provided a reliable source of wastewater heat. Even during winter, the wastewater typically remained at around 20°C.
A heat exchanger captures this energy before heat pumps raise it to a suitable temperature. The heat is then distributed around the campus through an underground network, with the existing gas boilers retained as backup.
HI Group’s role
HI Group led the technical design and project management, bringing together the engineering, commercial and funding elements needed to make the project deliverable.
Our work included:
- Assessing the college’s heating demand.
- Designing the heat pump system, Energy Centre and underground heat network.
- Integrating the new system with five existing plant rooms.
- Coordinating access to the sewer with the local water authority.
- Advising stakeholders throughout design and pre-construction.
- Developing the commercial structure that reduced the college’s financial exposure.
We did more than simply design a low-carbon system. We helped create a commercially viable route to delivery.
Removing the financial barrier
The project used a funded heat supply model developed with HI Group’s corporate finance expertise.
Instead of making a major upfront capital investment, Borders College purchased heat through a commercial supply agreement.
This allowed the college to begin reducing emissions while limiting its capital commitment and transferring commercial risk to the technology and funding partners.
The result was a competitive heat price, lower financial exposure and access to renewable heating infrastructure that may otherwise have been difficult to fund.
The first of its kind in the UK
The project became the first in the UK to use wastewater heat recovery at this scale.
It combined:
- A heat pump retrofit integrated with existing heating systems.
- A fourth-generation, low-temperature heat network.
- Retained boiler infrastructure for resilience and future flexibility.
- A commercial model designed to reduce upfront cost and project risk.
The combination of innovative engineering and commercial finance turned an ambitious decarbonisation concept into a deliverable project.
Overcoming first-of-a-kind challenges
As a pioneering project, the system required several practical modifications:
Sewer debris
Additional screening and filtration were installed to manage wipes and other solid waste.
Lower summer flows
A recirculation solution allowed wastewater to pass through the system several times, improving heat extraction.
Extreme cold conditions
Automatic controls enabled the system to switch to gas backup when required.
Results
Since launching in December 2015, the system has:
- Generated approximately 1 GWh of renewable heat annually.
- Reduced carbon emissions by around 180 tonnes each year.
- Significantly reduced the college’s gas consumption.
- Delivered revenue savings with minimal capital outlay.
- Received the 2017 EAUC Green Gown Award for Newcomer of the Year.
- Received the 2017 Scottish Green Energy Award for Best Innovation.
- Hosted more than 300 visits during its first three years.
The project demonstrated that ageing and complex estates can be decarbonised without replacing every part of the existing heating infrastructure.
Building on success
Borders College has continued to explore opportunities to improve the system, including:
- Adding solar generation and battery storage to reduce grid electricity costs.
- Integrating the boiler plant with the heat network.
- Decommissioning satellite plant rooms to reduce servicing and maintenance costs.
Building on success
Borders College has continued to explore opportunities to improve the system, including:
- Adding solar generation and battery storage to reduce grid electricity costs.
- Integrating the boiler plant with the heat network.
- Decommissioning satellite plant rooms to reduce servicing and maintenance costs.
“Working with HI Group to deliver an innovative low-carbon heat solution for Borders College, I can thoroughly recommend them as an innovative leader in sustainability practice. From project inception to completion, their professionalism and flexibility ensured that we were able to significantly reduce our carbon footprint, while also realising revenue savings, and with minimal capital outlay.”
– Pete Smith, Principal & CEO, Borders College
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