Refrigerated vehicles an overlooked source of ultrafine particles

New research by Zemo Partnership on behalf of the Department for Transport has highlighted the often overlooked danger of emissions from refrigeration units on vans and HGVs.

The new research builds on that published in February 2024 and includes the results of tests on diesel auxiliary transport refrigeration units (auxTRU).

Regulations covering emissions from such units only came into effect in January 2019, so Zemo examined emissions from units that came into use both before and after that date. 

They also examined emissions under different conditions: chilled, frozen and multi-temperature) and at different ambient temperatures. The tests were carried out on both HGVs and vans 

The refrigeration components fitted to HGVs and vans increase average CO2 emissions by 11% compared with standard vehicles without such units.

One of the main objectives of the new research was to greater understand more abut the particles being emitted and in especially their size. Of particular concern was the proportion of emitted matter that falls into the ultrafine category, those with diameters no greater than 100 nm.

The results showed that the proportion of the particles in the ultrafine category varied between 57-93%, with an average of 82%. However, the majority of tests produced ultrafine proportions in the range 75-90%.

In the original research, it was found that a van carrying a refrigeration unit would emit an additional 54 kt of tailpipe CO2 compared with those without a fridge. They also consume around 20 million litres of extra fuel, 0.3% of the total fuel burned by vans.

A final stage of the report, due to be completed later this winter, will assess alternative technologies to reduce emissions from TRUs on-board vehicles as fleets transition away from operating on diesel.

Zemo project manager Emily Stevens said: ‘This latest research confirms that there is a significant issue in terms of emissions arising from the presence of refrigeration units on vehicles, particularly in terms of their impact on local air quality.

‘The final stage of the study aims to provide further evidence and useful recommendations for operators and policymakers to reduce their negative impacts.’

The full report can be read here.