Unignorable Emissions and Potential Health Effects of Unregulated Pollutants from Nonroad Engines Using Greener Fuels - A Review

Nonroad mobile machinery such as construction equipment, agricultural machinery, ships, and generators emit significant pollutants. Countries worldwide have implemented stringent emission regulations targeting pollutants like CO, HC, NO_x, and PM. However, these machines also emit unregulated pollutants such as PAHs, VOCs, POPs, and metals, which severely impact human health and the atmosphere. A key strategy to reduce these emissions is using green fuels, including biodiesel, oxygenated fuels, metal additives, hydrogen, and ammonia. This paper analyzes the impact of these fuels on non-road machinery emissions of unregulated pollutants. Results indicate that green fuels can reduce some harmful emissions but may increase others. Biodiesel and oxygenated fuels significantly reduce PAHs and soot emissions, but their effect on VOCs varies with fuel type and engine load. Metal additive fuels effectively reduce EC/OC, smoke, and particle number emissions but may increase total PAHs and BaPeq emissions. Currently, research on using metal additive fuels, hydrogen, and ammonia in generators is limited, focusing mainly on biodiesel and oxygenated fuels. Similarly, studies on unregulated emissions from ships using clean fuels are scarce. Most research concentrates on PAHs, PN, and EC/OC emissions, with less focus on POPs, N_2O, VOCs, and metal components.