Abstract
ABSTRACT Sweet potato is an attractive feedstock for ethanol production due to its high starch content and favorable agronomic characteristics. This paper proposes a simple equation to estimate the total reducing sugars (including glucose from starch) in sweet potatoes based on their moisture content (low cost and simple measurement). It allows the calculation of the ethanol production potential of a given sweet potato mash. According to the equation, the ethanol potential increases non-linearly with increasing concentrations of sweet potato mash in the fermenting medium (w/v), reaching a constant value for high concentrations (22 % of ethanol to 10 kg: L of a sweet potato with a moisture content of 66 %). Additionally, the ethanol yield potential is very sensitive to the sweet potato moisture, increasing linearly when the moisture decreases. We emphasize that the relations proposed in this paper can be used by other researchers, who can apply them to their specific cases.
Highlights
Fossil fuels supply around 82% of the current world energy demand (Gupta and Verma, 2015)
This paper focuses on the Total Reducing Sugars (TRS) content of the sweet potato, i.e., glucose and fructose, which are the substrates converted into ethanol, assuming the ideal condition that all starch is hydrolyzed into glucose
The starch content is one of the main factors that determine the final ethanol production, since the sweet potato is mainly composed of starch and moisture
Summary
Fossil fuels supply around 82% of the current world energy demand (Gupta and Verma, 2015). Ethanol is not a new alternative, but its production is centered in two countries, USA ~ 60% and Brazil ~ 30%, and mainly from two feedstocks: corn (USA) and sugarcane (Brazil) (Gupta and Verma, 2015). To increase the ethanol production, advantageous alternative feedstocks should be considered. Sweet potato roots have high starch content, 20 - 30% (w/w), which makes them a promising alternative (Srichuwong et al, 2012). The sweet potato presents several agronomic advantages, such as the capability to grow in poor soils, drought resistance, high multiplication rate, short growth cycle, and low illness and plague incidence. The roots rapidly cover the soil and they protect it from erosive rains, as well as against possible weed problems (Lareo et al, 2013)
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