Nutshell

The SMEs participating in the NUTSHELL-project approached Avans to assist them in evaluating the pyrolytic extraction of valuable oils from Cashew Nut Shell (CNS). CNS is waste generated in the production of edible cashew nut. For the 2017 the predicted cashew nuts crop yield is 3 million tons; resulting to 2 million tons of CNS waste. CNS contains circa 30-35% brown viscous liquid, called Cashew Nut Shell Liquid (CNSL) , this is a natural resin containing valuable components, for example cardanol, cardol and anacardic acid. CNSL and its derivatives have several industrial uses as biobased additives, polymeric building blocks and biodiesel. Part of the CNSL can be extracted during the roasting process prior to separating the shell and nut kernel. The shell waste still has a relatively high CNSL concentration that can be isolated by solvents or pressing (expeller). Expeller process is simple and not capital-intensive; therefore it is commonly used in a small scale production. The main disadvantages of the method are the relatively high energy consumption and its low oil recovery, the level of oil in the press-cake remains 3 to 5%. The residual oil produces harmful gases in burning hence hindering the use as fuel. Also the resulting cake is too dense to be further processed to charcoal or other useful application; hence forming a significant waste stream. One of the main advantages of the pyrolysis route as envisaged by the SME partners is using the total CNS biomass.

The objective of this project is to study a process where in the pyrolytic isolation of CNSL oils is achieved and the remaining cake can be further pyrolysed to form charcoal or biochar.