Résumé
Amidst growing concerns regarding energy supply and environmental degradation, biofuels from cashew nut shells (CNS) are emerging as promising alternatives to petrodiesel. However, some inherent issues exist with cashew nutshell liquid (CNSL) properties for direct use in diesel engines. This review analyses the current developments in improving the fuel properties of CNSL as fuel for diesel engines. Furthermore, the fuel characteristics of the CNSL biofuels and the performance and emission characteristics of diesel engines powered by biofuels (and blends) are investigated. Current developments for improving the fuel properties of CNSL, such as vacuum catalytic and thermal cracking, involve the production of biofuels with properties that match those of diesel fuels. This review shows that up to 20% (v/v) biofuel achieves a performance similar to that of diesel. CNSL biofuels may require modification of injection pressure and injection timing of the engine and preheating of the fuel. Further, fuel blends with up to 20% CNSL, at an injection pressure of 20 MPa or preheated to 70°C (injection timing of 19° before top dead centre), successfully yielded high thermal efficiencies (up to 29.32%) in diesel engines, alongside lower emission characteristics. The current development for producing CNSL biofuels necessitates high temperatures, thereby increasing operational costs. This review suggests technical CNSL as a potential substitute for heavy fuel oil in low-speed stationary diesel engines or boilers. This could help reduce the environmental impact of cashew nutshell and the dependence of processing units on petroleum products.