# Impact of Combine Harvester Technological Operations on Global Warming Potential
## 3 Results and Discussion
### Results of the Telematics Data Analysis
However, other operations produced lower increases in GWP emissions, as follows:  
* Cereal threshing unit: 7.5%
* Straw chopper unit: 20.3%
* Cutter bar unit: 10.2%
* Grain unloading unit: 0.3%  
Figure 1: Hourly global warming potential (GWP) of a combine harvester (CH) in idle mode engaging different operational units (Eng = engine, Thr = threshing unit, Cho = straw chopper unit, Cut = cutter bar unit, and Unl = grain unloading unit, where \(n\) = engine crankshaft speed) in the 2019 tests. The value of each column is derived from an average of 20 replicates. Generally, maximum reductions should be made in the duration of idling; however, where this is not possible, engine speed should be reduced, and unused technological operations should thus be terminated. During the transport mode, the length of time and the GWP accounted for 13.2% and 8.8% of the totals, respectively. In 2019, the same field tests explored the relationships between engine speed, the use of technological operations, driving speed, and GWP Figure 2 provides the obtained results. According to the outcomes of the 2019 field test study, the absolute numerical value of the GWP increased commensurately with driving speed, while the GWP per km was reduced. The graphs in Figure 2 indicate that when the CH moves between fields, it is preferable to terminate any technological operations, reduce the engine speed, and increase the driving speed. The telematics data collected over a 5-year period from 67 CHs of the same model were compared with data from a specific CH obtained during field research. From the results given in Table 4 and Figure 1, the hourly GWP in idle mode can be potentially lower and equal to the 14.29 kg h\({}^{-1}\) achieved during the tests, although an analysis of the 5-year data revealed the value to be 22.54 kg h\({}^{-1}\). Considering that each CH spends an estimated average of 57.18 h year\({}^{-1}\) in idle mode, a potential GWP reduction of 471.7 kg year\({}^{-1}\) per machine is possible. This figure is even higher for the transport mode, for which the 5-year data provide an average hourly GWP of 63.84 kg h\({}^{-1}\). Switching off all technological gears, reducing the engine speed to 1690 min\({}^{-1}\), and driving at a speed of 8 km h\({}^{-1}\) can achieve a GWP of 44.91 kg h\({}^{-1}\) (Figure 2). The average time spent in the transport mode is 35.94 h year\({}^{-1}\), which allows for a potential GWP reduction of 680.3 kg year\({}^{-1}\). By optimizing the operation of CHs during their idling and transport modes, a potential GWP  
Figure 2: Relations between combine harvester (CH) speed in transport mode and global warming potential (GWP) in the 2019 tests (stubble height, 15 cm; soil moisture, 16.2%): \(B_{1}\)—All gears are switched off. Engine crankshaft speed \(n=1690\) min\({}^{-1}\)\(B_{2}\)—Gears engaged: header, threshing unit, and straw chopper. \(n=1690\) min\({}^{-1}\)\(B_{3}\)—All gears are switched off. \(n=2340\) min\({}^{-1}\)\(B_{4}\)—Gears are engaged: header, threshing unit, and straw chopper. \(n=2200\) min\({}^{-1}\)\(P_{1}\)—All gears are switched off. \(n=1690\) min\({}^{-1}\)\(P_{2}\)—All gears are switched off. \(n=2340\) min\({}^{-1}\) The value of each point was obtained from an average of 20 replicates. reduction of 1.15 t year\({}^{-1}\) per machine is achievable. It should be stressed that reductions in GWP will not only produce positive environmental impacts but also have direct financial benefits for farmers. The GWP per ton of wheat processed (Figure 3) was barely affected by changes to the speed of the threshing cylinder during threshing, particularly when the CH reached its optimal working speed (approx. 4-5 km h\({}^{-1}\)). At a harvesting speed of 1 km h\({}^{-1}\) with threshing cylinder rotational speeds of 850 and 950 min\({}^{-1}\), a 12.42% difference was noted in GWP. However, after reaching a maximum (and typical) harvesting speed of 5 km h\({}^{-1}\), the GWP difference was 3.88%.