Real-world emissions from non-road mobile machinery in London

The 2016 London atmospheric emissions inventory estimates that, the construction sector contributes 34% of the total PM 10 and 7% of the total NO X – the largest and 5 th largest sources, respectively. Recent on-road light duty diesel vehicle emission tests have shown significant differences between real-world NO X emissions compared with results from laboratory based regulatory tests. The aim of this study was therefore to quantify the ‘real-world’ tail-pipe NO X, CO 2, and particle emissions, for 30 of the most commonly used construction machines in London under normal working conditions. The highest NO X emissions (g/kWh) were from the older engines (Stage III-A ~4.88 g/kWh and III-B ~4.61 g/kWh), these were reduced significantly (~78%) in the newer (Stage IV ~1.05 g/kWh) engines due to more advanced engine management systems and exhaust after treatment. One Stage IV machine emitted NO X similar to a Stage III-B machine, the failure of this SCR was only detectable using PEMS as no warning was given by the machine. Higher NO X conformity factors were observed for Stage IV machines, due to the lower NO X emission standards, which these machines must adhere to. On average, Stage III-B machines (~525 g/kWh) emitted the lowest levels of CO 2 emissions, compared to Stage III-A (~875 g/kWh) and Stage IV (~575 g/kWh) machines. Overall, a statistically significant (~41%) decrease was observed in the CO 2 emissions (g/kWh) between Stage III-A and III-B machines, while no statistically significant difference was found between Stage III-B and IV machines. Particle mass measurements, which were only measured from generators, showed that generators of all engine sizes were within their respective Stage III-A emission standards. A 95% reduction in NO X and 2 orders of magnitude reduction in particle number was observed for a SCR-DPF retrofitted generator, compared to the same generator prior to exhaust gas after-treatment strategy.