The objective of the project was the creation of a de-oiled cashew nut-shell fraction that is suitable for energy production in pellet form. Among Norges Vel’s activities is transformation of the cashew sector in Mozambique, aiming to increase useability of the residual bio-mass that is created in processing cashew kernels. One particular aim, that was addressed in this project, is the transformation of the cashew husks, or cashew nut shells, into fuel pellets. Previous attempts of pressing cashew nut shells into pellets have failed, most likely due to the presence of residual oil-like fraction, that prevents the pellets from binding and being transportable.
Due to restrictive travel policies, work was started at WFBR ahead of a visit, which unfortunately had to be cancelled in the end, as travel policies did not ease up in time. The raw material, pressed cashew nut shells, was made available via Norges Vel, who sourced it directly from Mozambique.
De-oiling on the cashew nut shells was done using consecutive ethanol extractions at room temperature. Analysis of total phenolic content, dry matter and ash content was carried out. Parallel analysis showed small starch content, so no further attempt of starch recovery was made. An external analysis of energy content showed a reduce in energy after extraction, but enough residual energy left to maintain an attractive pellet. Post-extraction the solids appeared markedly drier and better fit for pelleting, which is tested outside of BRISK. All experiments were conducted in the laboratories of WFBR. Apart from the cancelled visit due to external circumstances, the opportunity was a great success, showing a possible opportunity to turn a large, currently underused material stream, into portable energy pellets, with large potential impact for the local communities in Africa.
Fig 1.
Starting biomass – cashew nut shell cake, which has been pressed to remove most phenolics, but retains an “oily” guise.
Fig 2.
Cashew nut shell cake after extraction of phenolic phase with ethanol. Visibly drier and ready to be pressed into pellets.
Fig 3.
Extraction set-up: Cashew nut shell cake in a permeable membrane which is perfused by ethanol. Deliberate simplicity to maintain a high feasibility level in remote African locations without need for investment.