Ethanol production from sweet potato: The effect of ripening, comparison of two heating methods, and cost analysis

Abstract

Currently, biomass contributes to ∼14 % of global energy needs. Therefore, many studies and policies have been developed in order to expand the participation of renewable energy in the global energy matrix. In this context, ethanol has received substantial interest. This work investigates ways to improve efficiency in ethanol production from sweet potatoes, considering the costs that make the process potentially implementable. The following aspects were investigated: (i) conversion efficiency according to the post‐harvest time; (ii) influence of the heating method (water bath (conventional) and microwave) as well as the corresponding processing costs. The conversion efficiency increased significantly during sweet potato ripening, where the highest value was achieved 25 days after harvest. This is a very important result since it has a strong impact on the final cost. Among the heating methods, the conventional one was slightly superior in terms of conversion efficiency (9 % higher at 25 days) and also had better results regarding cost analysis. Among four designed scenarios, the largest cost difference was 17.5 %. Instead of a definitive elimination of microwave heating, the results should be analyzed to identify where the microwave heating should be improved in order to make it more attractive in the future.

A Simple Equation for Total Reducing Sugars (Trs) Estimation on Sweet Potato and Ethanol Yield Potential

“…Once the equation is available, it is possible to use it in different practical cases. Schweinberger et al (2016) used the equation presented here to simulate an ethanol micro plant. Then, several scenarios were evaluated varying the sweet potato moisture.…”

“…Several studies have been done on ethanol production from sweet potatoes, such as Cao et al (2011), Srichuwong et al (2012), and Zhang et al (2011), who carried out fermentations under high sweet potato concentrations, achieving an ethanol content of 15 -16% (v/v) (including Zhang et al (2011) who performed experiments on pilot and industrial scales). Schweinberger et al (2016) found that it is better to let the sweet potato ripen, leaving its own amylases to act; the best post-harvest period was 25 days. Dewan et al (2013) fermented a sweet potato broth using the bacterium Zymomonas mobilis.…”

Alcohol production from sweet potato (Ipomoea batatas (L.) Lam.) genotypes in fermentative medium

“…Among its priorities, preparation of the raw material to be used for the manufacturing and its own fermentation system must be highlighted. However, sweet potato in addition to sugar, also has starch; therefore, is necessary to convert the starch to sugars and ferment these, having to add cooking and saccharification procedures from root samples (Martins, Romanzini, Baldin, Trierweiler & Trierweiler, 2016 ;Oliveira et al, 2017).…”

Study of three drying methods in production of nutritious flours from the fermentation slurry of orange‐fleshed sweet potato

“…Approximately 90% of the world’s ethanol production comes from corn and sugar cane (Gupta & Verma, 2015); this has stimulated the research regarding alternative feedstocks, such as sweet potato. It has high starch content and favorable agronomic characteristics, so its application in ethanol production has been studied by several authors from different countries (Cao, Tian, Yao, & Yuan, 2011; Dewan, Li, Han, & Karim, 2013; Duvernay, Chinn, & Yencho, 2013; Huang et al., 2014; Lareo et al., 2013; Masiero, Peretti, Trierweiler, & Trierweiler, 2014; Schweinberger, Putti, Susin, Trierweiler, & Trierweiler, 2016; Srichuwong et al., 2012; Zhang et al., 2011). However, when more products are exploited in the process besides ethanol, the resources are better used, increasing profitability, and business safety.…”

“…Schweinberger et al. (2016) reduced the viscosity of a sweet potato mash by 81% using a pectinase. Although it was notable the degradation of the solid, when the wine was filtered, there were still 43% of the mass retained in the slurry.…”