Optimisation of Bioethanol Production in a Potato Processing Industry

Abstract

Nowadays, there is a requirement for industries to eliminate carbon from their energy mix and substitute it with greener options. This calls for investment in efforts to facilitate the scaling up of technical advancements. Because of the huge amount of waste, a life cycle strategy has been used by industries, especially the food industry, to lessen the environmental impact of their products. One of the sectors that burdens the environment with a significant amount of waste is the potato processing industrial sector. The current study focuses on the valorisation of all the potato processing waste streams (potato peels, potato tubers and slices, starch and low-quality chips) towards bioethanol production at a pilot level. After their physico-chemical characterisations, several experimental trials were performed in order to determine the optimum pretreatment and hydrolysis conditions for each waste stream. Acid hydrolysis, alkaline hydrolysis and hydrothermal pretreatment were examined when no pretreatment resulted in low ethanol yields (below 60%). The optimum results that were obtained were applied in a pilot plant of 200L to examine the upscaling factor. It was verified that upscaling by 1000 times generates comparable and, in some cases, greater results. From the integration of the results and the mass balances of a typical potato processing company, a full-scale implementation plan was also set up, where it was calculated that around 2 m3 bioethanol per week could be produced.

Exploring the Potential of Potato Peels for Bioethanol Production through Various Pretreatment Strategies and an In-House-Produced Multi-Enzyme System

“…Several studies have explored the potential of potato peels for biofuel production, including biogas [6,7,54], bioethanol [8,[55][56][57][58][59], and xanthan gum [7]. Felekis et al [8] achieved the highest ethanol concentration of 9 ± 0.9 g/L by pretreating potato peels with 1% w/v NaOH for 6 h at 50 • C, using commercial enzyme preparations.…”

“…Several studies have explored the potential of potato peels for biofuel production, including biogas [6,7,54], bioethanol [8,[55][56][57][58][59], and xanthan gum [7]. Felekis et al [8] achieved the highest ethanol concentration of 9 ± 0.9 g/L by pretreating potato peels with 1% w/v NaOH for 6 h at 50 • C, using commercial enzyme preparations. Achinas et al [54] investigated the anaerobic digestion of potato peels with and without dilute H 2 SO 4 pretreatment, observing improved biogas production with pretreatment.…”

“…Potatoes, scientifically known as Solanum tuberosum, are a widely consumed staple food globally, either in their natural form or processed into various products such as chips, fries, mashed potatoes, and dehydrated products. However, during processing, a significant portion of the raw potato, ranging from 20% to 50%, is discarded as waste, primarily in the form of peels [5][6][7][8]. Potato peels consist of approximately 55% cellulose, 12% hemicellulose, and 14% lignin [9], along with varying amounts of starch and pectin.…”

“…Converting this waste into value-added products can address the issue of waste disposal and provide a promising solution to enhance the biofuel sector [12]. In recent years, there has been increasing interest in utilizing potato waste, including potato starch residue, waste potato mash, and potato peels, as feedstocks for bioethanol production [4,[6][7][8]11,[13][14][15][16][17]. Generally, the conversion of native biomass into bioethanol involves four stages: pretreatment, enzyme-catalyzed hydrolysis to generate fermentable sugars, fermentation to produce bioethanol, and product recovery [18][19][20][21].…”

“…Enzyme-mediated hydrolysis also offers other advantages, such as lower energy consumption, mild conditions, and no corrosion. However, the use of a suitable combination of multiple enzyme systems with high specificity and costeffectiveness remains a challenge for commercial applications [8,[24][25][26]. Since potato peels contain cellulose, hemicelluloses, starch, and pectin, an enzyme cocktail consisting of carbohydrases, including endo-1,4-β-D-glucanase, exo-1,4-β-D-glucanase, β-1,4-glucosidase, endo-β-1,4-xylanase, endo-β-1,4-β-D-mannanase, α-amylase, gluco amylase, and pectinase, can be utilized to saccharify the biomass into free sugars.…”