Optimization of the production of neutral spirit from renewable yam and cassava starch substrates – A practical approach

The devastating impacts of climate change on our environment have led to increased research on mitigating these impacts, including fast-tracking original timeline for introduction and use of electric driven vehicles. Electric driven vehicles are considered the most promising and efficient way of securing the environment. However, research into partial or total replacement of energy derived from fossil fuels with renewable energy from plant materials such as neutral spirits (bioethanol) is ongoing. This study was carried out to further explore yam and cassava (tubers) starches as renewable raw materials for bioethanol production. The optimal processing conditions that will yield maximum neutral spirits from yam and cassava substrates were studied. Yam starch produced highest bioethanol in the range of 538–545 L of alcohol per tonne (LA/t) on a dry weight basis (dwb) than cassava starch that produced 508–513 LA/t when both substrates were processed at 142 °C. In contrast, cassava starch produced higher bioethanol in the range of 508–512 LA/t than yam starch that produced 409–416 LA/t when both substrates were processed at 85 °C. The reduced processing temperature of 85 °C caused huge loss of spirit yield (∼128 LA/t) for yam, but did not affect the spirit yield for cassava starch, thus saving cost (energy) for the industry. The use of viscosity reducing commercial enzymes such as β-glucanase (as practised in cereals processing) would be unnecessary in tuber starches processing to neutral spirits, and will further save costs for the industry.