Consumption in sugarcane harvesters

The mechanized harvesting of sugar cane represents around 30% of the total production costs of this crop. Reducing this percentage is possible, as long as simple aspects such as machine adjustments, correct engine rotation and ideal harvesting speed are observed. 

One of the most important activities in agriculture is harvesting, which represents around 30% of all costs involved. This is due to its high added value, which can be understood as the most expensive operation in the production process due to the high energy demand. In order to have a greater return on all investments made during the production cycle of a crop, whatever it may be, the harvest must be carried out within the quality standards required by the operation's managers. In order to optimize this process we must have at hand some information related to the energy performance of the harvesters or, in other words, fuel consumption, as we can manage this mechanized agricultural system and make more logical and judicious decisions, aiming at rationalization and sustainability. of mechanized sugar cane harvesting.

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Even though there is a high cost with mechanized sugarcane harvesting, it presents itself as a viable alternative, due to its operational capacity being greater than that of semi-mechanized harvesting (popularly called manual harvesting), as there are labor laws that value ergonomics. of rural workers when manual cutting occurs and, also, due to the reduction of environmental impacts caused by the burning of raw sugarcane.

In this context, high fuel consumption becomes the biggest aggravating factor in the energy sustainability of harvesting, in which around 30L/h to 60L/h are consumed per harvester, with these values ​​fluctuating in mechanized sugarcane harvesting in spacings of 1,50m and 0,90m x 1,50m, and follow the following estimates (Table 1):

Due to this high amount spent on energy demand, evaluating the safety and comfort of those who will operate the harvester is essential, as it is a way to avoid additional costs related to the operator's health. We must, therefore, apply ergonomic evaluation criteria and prioritize projects that allow perfect human-machine interaction to be established, as the operational capacity and efficiency of agricultural work depend on the conditions under which they are carried out and, together with these factors, is associated with energy demand of the harvest, which may increase due to operator stress or discomfort. An operator in a pleasant environment is able to better operate and control the machine during routine work operations, resulting in greater energy efficiency.

The correct adjustment and use of the harvester in different working conditions are important allies in reducing fuel consumption and, in this sense, we can mention some important aspects.

The variation of the engine's working speed must be in accordance with the needs, seeking the minimum consumption range, related to the productivity of the sugarcane field. For example, studies show that in low-productivity sugarcane fields, reducing work rotation significantly reduces the harvester's fuel consumption, due to this automatic control.

Working with the appropriate harvesting speed depending on the size of the sugarcane field is another aspect that needs to be observed.

Spacing between harvested rows affects the amount of fuel used throughout the harvest, associated with sugarcane productivity (flow of harvested plant material).

The basal cutting mechanism with automatic control of the cutting height aims to avoid contact of the discs and knives with the ground, thus reducing the resistance to the harvester's movement.

Adjusting the working rotation of the primary extractor depending on the working day is also another important factor. In drier periods of the day, the rotation can be reduced and maintain efficiency in cleaning plant and mineral material.

It is known that some factors depend on the reality of the producer or the production unit, which is why we must always look for the best cost-benefit ratio, so that, after all, we have a more economical and even more sustainable process, since there is less pollutant emission. , due to less burning of diesel oil, which is a goal that everyone strives to achieve.

In this context, assuming that the energy demand of mechanized sugarcane harvesting is influenced during the operation, the Agricultural Mechanization Laboratory (LMA) at UFV/Viçosa and the Agricultural Machinery and Mechanization Laboratory (Lamma) at Unesp/ Jaboticabal aimed in this work to evaluate the energy demand of a sugarcane seedling harvester throughout the harvest, through statistical process control.

The test was carried out in the agricultural area of ​​a sugar cane factory close to the geodetic coordinates: latitude 20º01’ S and longitude 48º56’ W, with an average altitude of 516 meters. The average slope of the agricultural area of ​​the production unit where the test was carried out was 5%, with the predominant climate being Aw, according to the Köeppen classification. The size of the sugarcane field was evaluated using a standard right-angled triangle, according to the methodology proposed by Ripoli (1996), in which 25%, 39% and 36% of stalks were lying, bedded and erect, respectively. The variety harvested was RB85-5453, being in the second cut. The average productivity of the harvested area throughout the harvester monitoring was 90,91Mg/ha.

The harvester used had the following technical characteristics: 6090T PowerTech (Tier III) engine, with nine liters, 251kW (342hp), with four valves per cylinder, being equipped with the Field Cruise system, engine rotation control and wheelsets. treadmills with a gauge of 1,88m. This harvester did not have an automatic steering system (autopilot) during operation. The machine harvests only one row of crops, spaced 1,50 m apart. This harvester had been in use for two years, with different amounts of engine hours (2.700) and elevator hours (2.240) worked.

The experimental design was carried out based on the statistical process control methodology, throughout a day shift, with an eight-hour working day, totaling 50 sample points, being collected approximately every nine minutes. The variables or quality indicators evaluated were: work speed, hourly fuel consumption, effective power and specific energy consumption per unit area. Hourly fuel consumption was collected using the front column monitor, inside the harvester, in which fuel consumption was quantified using specific sensors installed on the machine (input and output of the fuel flow).

The results were evaluated through statistical process control, using type I control charts (individual values), which have a central line (general average), as well as upper and lower control limits, defined as LSC and LIC, calculated based on the standard deviation of the variables - for LSC, mean plus three times the standard deviation, and for LIC, mean minus three times the deviation, when greater than zero (Montgomery, 2009). Regardless of the assumption of data normality, control charts were designed to monitor the process, with analysis and knowledge of the process being essential for decision making (Montgomery, 2009).

Hourly fuel consumption showed process instability throughout the mechanized harvesting of sugarcane seedlings (Figure 1), that is, there are non-random causes influencing the harvesting of seedlings. In this sense, the possible explanation could be due to the greater quantity of raw material inside the machine, which increased the power demand of the harvester engine for the complete processing of this plant material, at these points outside the upper limit of control.

Voltarelli (2013), when evaluating the quality of mechanized agricultural processes, reports that the instability of a quality indicator can unsatisfactorily represent the performance of the operation or a service performed, but knowledge and the correct interpretation for each situation become fundamental for adequate management of the operation, in order to make it sustainable.

Finally, the energy consumption of fuel during the mechanized harvesting of sugar cane has high variability due to the dynamism of the conditions that the machine must withstand, therefore the real-time quantification of this quality indicator during harvesting becomes an effective means to maintain agricultural quality and also provides greater control of the harvesting process by managers of production units.

Murilo Aparecido Voltarelli, UFV/Viçosa; Rouverson Pereira da Silva, Unesp/Jaboticabal; Wilson de Almeida Orlando Junior, UFV/Viçosa; Carla Segatto Strini Paixão, Unesp/Jaboticabal

Article published in issue 173 of Cultivar Máquina