EXPERIMENTAL INVESTIGATION ON CASHEW NUT SHELL LIQUID AS A RENEWABLE FUEL IN DIESEL ENGINES: CHEMICAL PROPERTIES, EMISSIONS AND SUSTAINABILITY ASPECTS

The automotive sector is one of the main responsible of the carbon dioxide emitted into the atmosphere, with a share of approximately 17% of the total amount. This pushes the scientific and technical community to continuously develop new technological options to reduce the greenhouse gases emissions, without compromising the vehicle performance. Vehicle electrification and hybridization are apparently the best solutions, however their efficacy relies upon high penetration levels of renewables in the power grid, which is still far to be achieved in most countries. This aspect, together with the well-known issues related to battery manufacturing and social disequilibrium, imply that a fundamental role is likely to be still played by the Internal Combustion Engines (ICE) fed by renewable fuels at least in the near-medium term. In particular, the use of sustainable biofuels in blend or as substitutes of the conventional fossil fuels is one of the most attractive solutions. Unlike the vegetable oils commonly used for biodiesel production, cashew nut shell liquid (CNSL) is a waste material derived from the cashew agro-industry. The degummed CNSL considered in this work is cashew nut shell liquid which was treated to remove impurities, such as metals and residues, and distilled at high temperatures to obtain a high-grade fuel oil. The chemical analysis carried out in this work shows that it is a mixture of bio-derived phenolic compounds, mainly cardanol, cardol and 2-methylcardol, with a C15 saturated and unsaturated chain with one to three double bonds in the meta position (8, 11, or 14). In spite of the wide availability and promising properties of this feedstock for use as a fuel, there are only a few experimental analyses about the use of CNSL blended with Diesel in internal combustion engines. In order to fill this gap, the performance of a 3 litres Diesel engine fuelled with a blend of 98% of Diesel and 2% of CNSL are deeply characterized over a wide set of steady and transient operating conditions. The results show the engine performance and emissions of the CO2 and the main pollutants obtained using the blend in comparison with the pure fossil Diesel.