Launched in 2016, this project is testing safer alternatives to creosote for preserving wooden electricity poles. Accelerated weathering trials with the new preservatives match creosote’s durability over decades, offering an environmentally friendly, cost-effective solution for maintaining a reliable electricity network.
The Challenge
Creosote has traditionally been used to preserve wooden overhead electricity poles in the UK, extending their lifespan up to 60 years.
However, creosote is potentially carcinogenic, which led for its ban for DIY in 2003 and stricter rules for industrial use. As creosote is now likely to be banned altogether, the urgency to find a safer alternative is growing.
Preservative treated wooden poles are still essential for electricity distribution networks. This is due to their affordability, ease of use and much better environmental profile compared to other materials such as steel, concrete and GRP.
Treated wooden poles are environmentally friendly when sourced responsibly and blend well with their surroundings. Their flexibility also helps them withstand a variety of weather conditions.
What Happened?
This project launched in November 2016. Three extensions, supported by the EIC, expanded the insights gained from this Network Innovation Allowance (NIA) project, with final reporting expected in November/December 2026.
This is a collaborative project is led by SP Energy Networks and includes Northern Powergrid, Scottish and Southern Electricity Networks, and Electricity North West (ENW). In 2017 UK Power Networks joined the project following ENW’s withdrawal.
A unique test bed incorporating wooden stakes, treated with selected preservatives, soil, enhanced temperature and artificial rainfall was constructed to simulate 10 years of field weathering/decay for every year of testing.
Testing Included:
Stake Test: This operated for six years, the equivalent of 60 years of field testing. This was completed in 2024
Round Timber Test: To test timbers more representative of real field poles, the round timber test started in 2023 using pre-leached treated timbers to build on stake test results (with addition of a further preservative type). This is Ssheduled for completion in 2026; the four-year trial equates to 40 years in field.
Solutions and Results
1. The trials are progressing well. The results of the stake trial indicated that the selected new preservatives are as effective as creosote over the test period (equivalent to 36 to 42 years in the field)
2. These results are in-line with the preservative manufacturers’ long term efficacy claims
3. The acceleration factor, based on the decayed and disintegrating condition of untreated stakes was less than planned. Due to a lack of nitrogen in the original test environment, each year was equivalent to six to seven years in the field, rather then the planned 10.
4. Results for the ongoing round timber trial demonstrate similar efficiency for the new preservatives, with none of the treated rounds showing any decay after two years, despite the opposite being found in all untreated timbers.
The project has therefore been successful in allowing for rapid assessment of preservative effectiveness, simulating decades of field exposure over a substantially reduced period of time.
What’s Next?
1. The round timber trial is proceeding and due to complete in 2026
2. This extension will allow for a more comprehensive evaluation of preservative efficiency, simulating 40 years of field exposure for representative timber sizes
3. The trial will assess both external and internal decay, providing insights into the treatment process and preservative performance in representative timbers
4. By including a new candidate for creosote replacement, this trial also offers a broader choice of preservatives. With existing infrastructure and resources, the extension is cost-effective and promises valuable outcomes.