Exhaust gases emissions from agricultural tractors : state of the art and future perspectives for machinery operators

Due to the increased attention paid to environmental sustainability, the environmental concerns that come from agricultural operations are of increasing worldwide importance. For agricultural operations, one of the most important issues focuses on exhaust gases emissions released from tractors during fuel combustion. In particular, the increasing interest is in reducing the emissions of pollutants from exhaust gases to improve air quality. This review aims to analyse the recent scientific literature with respect to the solutions adopted to control exhaust gases emissions from agricultural tractors, and similar self-propelled machines, and to highlight the improvements about the possibilities of reducing these pollutants during field operations. Twenty-four studies were analysed. Of these, most researches focused on the more recent tractor engine designs (emission Stage 3A or Tier 3), and most of the instrumentation included power-take-off dynamometers, portable gas analysers, electronic control units for the monitoring of machinery parameters and fuel flowmeters. Some studies analysed the effects of different fuel blends (33.3%), while only few studies analysed the environmental burden of field operations considering the variation in exhaust gases (16.7%). The most important interventions that were found in these studies regarded the need for increasing fuel efficiency, introducing technical solutions with respect to the recent emission limits and, consequently, to reduce pollutant emissions, as well as introducing biofuel blends. This latter area can be less effective than the other solutions because the composition of blends can also increase some exhaust gases, mainly CO2 and NOX.