Investigating the Production of Multiple Bio-Products from Cassava Peel and Date Seed through an Integrated Biorefinery Approach

Abstract

The environmental damage from fossil fuels due to harmful emissions and the desire to find alternative sustainable energy sources led to this investigation of utilising biomass energy. Food wastes are considered one of the important sustainable sources of energy. Exploiting them in the production of energy may lead to avoiding the damage resulting from their accumulation. In this study, the possibility of exploiting the waste/unused product from cassava and date were explored as they are an important food used by many nations. Globally about 550 million metric tons of cassava and 9 million tons of dates are produced annually. Several bio-products can be produced from cassava peel starch and date seed oil, in addition, biogas can be produced through the anaerobic digestion process. The cassava peels have a considerable amount of starch and date seeds contain oil, so this study aims to explore the effect of starch and oil extracted from them on the quantity and quality of the resulting biogas. It also contributes to demonstrating the possibility of benefiting from producing bio-products from extracted starch and oil such as adhesive, biodiesel and glycerine. Overall this research has investigated the production of multiple bio-products from cassava peel and date seed using an integrated biorefinery approach. Cassava peel was treated by beating pre-treatment process to chop and slice the peel and extract the starch at the same time. The date seeds were treated using a grains and stones grinding machine. The digestate resulting from the anaerobic digestion was tested to determine starch and oil extraction effects on the resulting digestate. The influence of temperature, volatile solid and sludge quantity were investigated with the aid of Design of Experiments (DOE). An optimisation process was carried out to calculate the energy balance at the optimal results and evaluate the impact of the extraction process on the biogas and digestate produced, calculating the production costs of biodiesel, the adhesive and the preliminary analysis of process boundary, thus to evaluate its biorefinery applications. The study revealed that the influence of the starch on the biogas quantity and quality was quite low. Simultaneously, the oil extraction process contributed to the decrease in the amount of biogas and methane. The addition of cassava peels and date seeds before and after starch and oil extraction contributed to increase biogas and methane yields. The highest biogas volume obtained from the cassava peel, date seed and extracted oil date seed was 3830 ml, 4140 ml and 3534 ml respectively. The maximum methane per gram volatile solid added was 850 ml /g-VS, 1143.8 ml /g-VS and 949.6 ml /g-VS respectively. The percentage of oil extracted from date seeds was approximately 16% of the date seed weight, while the biodiesel and glycerine accounted for 79% and 9% of it. The starchbased adhesives showed high adhesion strength to the plywood and paperboard specimens. The laboratory tests of the resulting digestate proved that the anaerobic digestion process contains the necessary elements in fertiliser, so this test aims to gain more knowledge about the digestate. Overall, the study investigated the feasibility of an integrated biorefinery approach to the use of cassava peel and date seeds; to produce several bio-products and proper waste management with promising results.