Abstract
The UK national atmospheric emissions inventory estimates of construction industry emissions use a top-down approach, based on fuel consumption and employment. It estimates that the sector is the 2nd largest emitter of PM 2.5 (14%) and 4th largest emitter of NO X (7%). In this study, we have adopted a bottom-up approach to assess emissions of NO X from the sector and show that emissions are 39% higher than the existing estimates. By developing a novel fleet turnover model to predict the population and emission standard of construction machinery up to 2025, we demonstrate a significant shift in the quantity and types of machines used. The overall uncertainty of the model was calculated to be 55%. Applying the estimated uncertainties to the model, in 2018, the non-road mobile machinery fleet in the UK emitted 36.6 ± 10.0 kilo-tonnes of NO X , whilst the NAEI estimated 33.2 kilo-tonnes for the same sector. For the subsequent years 2019 and 2020, the NAEI estimate was within the model’s uncertainty prediction—28.0 kilo-tonnes compared with 32.7 ± 8.9 kilo-tonnes for 2019 and 23.2 kilo-tonnes compared with 29.5 ± 8.1 kilo-tonnes for 2020. Overall, the size of the non-road mobile machinery fleet in the UK is predicted to reduce by 4% in 2025 compared to 2018. Furthermore, the introduction of Stages IV and V emission regulations for new machines will lead to a 58% reduction in fleet NO X emissions over the same period. These emission regulations are targeted at the larger, more polluting machines, with smaller machines not required to meet tighter emissions standards under Stage V. As a result, mini-excavators are the most common machines and consequently become the dominant source of NO X emissions from the fleet, contributing 55% in 2025. Therefore, tighter emissions regulations, or the uptake of battery power in the form of electrification, for these small machines would yield significant emissions reductions. Graphical Abstract