The world's population is increasing, and the developing world's economies are expanding. Demand for fuel is always on the rise(Guo 2013). The major problem of fossil fuels is higher carbon emission and depletion of oil reserves(Ishola et al. 2020). The primary drivers of alternative fuels are sustainable development and environmental preservation(Justin Abraham Baby et al., 2021). Because of its superior performance and benefits of renewable, clean, degradable,pollution-free, non-toxic, biodiesel is often regarded as the most viable alternative energy source to petroleum diesel(Gohain et al. 2017; Zhang et al. 2020). Fatty acid methyl ester is another name of biodiesel. It can be made by transestrifying renewable sources such as vegetable oil, animal fats with short-chain alcohol in the presence of a catalyst.(Bastos et al. 2020; Guo et al. 2020).
Two different catalysts used to synthesize biodiesel are homogeneous and heterogeneous catalysts. homogeneous catalysts like sulphuric acid, sodium, and potassium hydroxides are highly active. However, their industrial applications are limited due to the side reaction of saponification, equipment corrosion, and separation complexity (Qu et al. 2020). heterogeneous catalysts have attracted widespread attention due to their advantages. non-toxic to the equipment(Chen et al. 2020), easily separable from the biodiesel product, which improves biodiesel quality and reduces post-treatment cost(Naik and Meivelu 2020). heterogeneous base catalyst is more efficient than heterogeneous acid catalyst as they catalyze the reaction 4000 times faster than heterogeneous acid catalyst (Sahani et al. 2020). the major drawback of heterogeneous catalysts is that it requires high temperature and pressure for acidic heterogeneous catalysts, low acid value feedstock for basic catalysts, and high cost for immobilized enzymatic catalysts(Khandan and Saffarzadeh-Matin 2020).
The main drawback of using edible oils as biodiesel feedstock is their high cost, dependence on food price(Pikula et al. 2020).in the present study, cashew nut seed shell is used for the production of biodiesel. India is the second-largest producer, processor, and exporter of cashews in the world(Deepanraj et al., 2021). Cashew cultivation now covers a total area of 0.70 million hectares of land, producing over. 0.40 million M.T. of raw cashew nuts annually(Padmanaban et al. 2014). The cashew nut is separated from the fruit, washed, sun-dried, and roasted to extract the cashew nut and separate the cashew kernel. The nut has a shell of about 1/8th inch thickness inside, which is a soft honeycomb structure. The extractable oil is called cashew nut shell liquid and has numerous applications in the polymer industry such as friction lining, paints, and varnishes, rubber compounding resins, cashew cement, biocomposite, the monomer for polymers, etc. (Lubi and Thachil 2000; Smith Jr et al. 2003; Subbarao et al. 2011). Cashew Nut Shell Liquid (CNSL) is a useful cashew industry byproduct. The cashew nutshell contains 20% CNSL. The oil can be extracted by roasting the cashew kernel or by using an oil extraction method such as solvent extraction. Untreated CNSL is a dark reddish-brown liquid that is viscous and vesicant. Despite the fact that CNSL has a wide range of applications in the polymer area,(Taiwo 2015), few studies have been conducted on the feasibility of the oil as a feedstock for biodiesel preparation. Here focus is two fold, using cashewnut shell biomass which is an agriculture waste as an easily available biochar and using CSNL which is a cheap, non edible natural oil as a biodiesel source. Thus the entire cost of production can be significantly reduced.