Ethanol production from sorghum milling wastes
Nigeria is the world's second largest sorghum producer, producing 6.5 million metric tonnes per year. The accumulated wastes from sorghum processing are potentially suitable for bioethanol production.
Sorghum bran is an underutilised waste from the sorghum milling process in Nigeria. It contains relatively high amounts of starch and protein, indicating that it is a suitable substrate for fermentative conversion into value-added products.
Sorghum is processed by soaking and wet milling to obtain bran, which is a typical processing technique in Nigeria. The sorghum bran is soaked and milled to separate the sorghum bran from the starch. The starch is the main product, while the residual sorghum bran is hydrolysed by enzymes or acids to generate a sugar-rich hydrolysate. The hydrolysate is fermented to produce bioethanol by yeast fermentation. The waste yeast, together with the unfermented solid wastes, can be used as high-protein animal feed. The University of Ilorin achieves a bioethanol production yield of 0.151 g bioethanol per g sorghum bran. It is estimated that if all the sorghum bran produced in Nigeria were used, the bioethanol produced could provide 17% of Nigeria's annual transport fuel needs.
Market deployment considerations
Unverified industrial scale