Lubricants (Nov 2023)
Olive Pomace Oil as a Chainsaw Lubricant: First Results of Tests on Performance and Safety Aspects
Abstract
The total loss lubrication system that is typical of chainsaws is responsible for a massive dispersion in the agro-forestry environment of highly impactful pollutants, mostly of fossil origin, often well known as carcinogenic substances, which, in addition to presenting a risk to the environment, represent an important risk factor for human health, especially for chainsaw users. During its use, the chain lubricant is dispersed from the guide bar tip in the form of droplets and aerosol, or it is adsorbed on wood residues and sawdust. Then, it is subjected to drift, settles on the ground and vegetation, and can hit the operators, who, after prolonged exposures, can suffer both irritation of the respiratory tract and dermal absorption. Such a risk factor is often amplified by the widespread use of less-expensive, sometimes illegal alternatives, such as exhausted motor oils. To mitigate said negative effects, a process has been in progress for several years that is aimed at replacing conventional lubricants with synthetic or biobased oils with increasing biodegradability. As a contribution to this process, a study has been started on the possibility of using refined olive pomace oil (ROPO) as a base stock for the formulation of a totally biodegradable chainsaw lubricant. On purpose, to improve its properties of viscosity and adhesivity, such an oil was added with a biodegradable thickening agent, obtaining four formulations with different viscosity. After a lab test and a preliminary cutting test on firewood, the formulation with 2% of thickener resulted in being the best, and 3.0 g kg−1 of tert-butylhydroquinone (TBHQ), a food-grade antioxidant, was then added to form the final formulation (F2) to be compared, in the subsequent four test sessions, to a biodegradable commercial chain lubricant (SB). The tests were carried out without changing the chainsaw setting, on different wood species, both in forest and, with the aim of increasing the repeatability of tests conditions and comparability of results, at a fixed point. The fluids’ performances were mainly evaluated based both on the operators’ opinions and on the measurements of the chain–bar temperatures and of saw chain wear related to a predefined number of cuts. As to the destiny of the fluid dispersed during cutting, the overall dispersion was assessed by considering the average working time, the consumption of chain lubricant, and the forest area cut down daily. Eventually, the amounts of inhalable and respirable dust particles as vectors of oil residues were quantified by means of personal air samplers worn by the operators and analyzed to determine any differences in the concentration of metallic elements. The test results evidenced chain temperatures that were 0.5, 4.9, and 12.5 °C higher with F2 relating to SB, respectively, in the cutting of trunks of fresh Pinus, Eucalyptus, and dry Pinus. They were accompanied by chain weight losses of 89.5% and 35% higher with F2 relating to SB, respectively, in cutting tests of Turkey oak and Poplar. Such a greater wear, however, apparently did not affect the saw chain’s cutting efficiency with F2, since the operators declared that they did not notice any difference between the performances of the two fluids at the time of comparison. The effects of higher wear on the chain lifetime, any deriving risks for the operator’s safety, and the possibility to reduce the wear levels observed with F2 will be explored in a further study, e.g., through different settings of the lubricating system of the chainsaw. The results of the analyses of the air-sampled dust residues that were evidenced with F2 showed lower concentrations of respirable and inhalable particles and of some metallic elements (Al, Mg, and Ca) than those with SB. This behavior probably depends on the different interaction between sawdust and the two fluids, which differ according to their chemical–physical characteristics (different viscosity, composition, and additives). However, it represents a positive factor in favor of the use of the ROPO-based lubricant, emphasized by the total biodegradability of its residues that are possibly contained in the dust inhaled by the operators.
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