Ethanol Production From Potato Peel Waste (2010) PDF

Waste Management 30 (2010) 1898–1902 Contents lists available at ScienceDirect Waste Management journal homepage: www...

Waste Management 30 (2010) 1898–1902 Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman Ethanol production from potato peel waste (PPW) D. Arapoglou a,1, Th. Varzakas b,*, A. Vlyssides c, C. Israilides a a Institute of Technology of Agricultural Products, National Agricultural Research Foundation, 1, Sof. Venizelou St., Lycovrissi, 14123 Athens, Greece b Technological Educational Institution of Kalamata, Department of Food Technology, Antikalamos, 24100 Kalamata, Greece c National Technical University of Athens, Department of Chemical Engineering, 9, Heroon Polytechniou St., Zographou 157 70, Greece a r t i c l e i n f o a b s t r a c t Article history: Considerable concern is caused by the problem of potato peel waste (PPW) to potato industries in Europe. Received 9 July 2009 An integrated, environmentally-friendly solution is yet to be found and is currently undergoing investi- Accepted 7 April 2010 gation. Potato peel is a zero value waste produced by potato processing plants. However, bio-ethanol pro- Available online 14 May 2010 duced from potato wastes has a large potential market. If Federal Government regulations are adopted in light of the Kyoto agreement, the mandatory blending of bio-ethanol with traditional gasoline in amounts up to 10% will result in a demand for large quantities of bio-ethanol. PPW contain sufficient quantities of starch, cellulose, hemicellulose and fermentable sugars to warrant use as an ethanol feedstock. In the present study, a number of batches of PPW were hydrolyzed with various enzymes and/or acid, and fer- mented by Saccharomyces cerevisae var. bayanus to determine fermentability and ethanol production. Enzymatic hydrolysis with a combination of three enzymes, released 18.5 g L 1 reducing sugar and pro- duced 7.6 g L 1 of ethanol after fermentation. The results demonstrate that PPW, a by-product of the potato industry features a high potential for ethanol production. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction the ethanol produced globally corresponds to fuel ethanol, 17% to beverage ethanol and 10% to industrial ethanol (Sanchez and With the inevitable depletion of the world’s energy supply, Cardona, 2008). there has been an increasing worldwide interest in alternative en- The EU directive (2003/30/EC) for bio-ethanol requires member ergy sources (Lin and Tanaka, 2006). In recent years, increasing re- states to establish legislation pertaining to the utilization of fuel search and development efforts have been directed towards the from renewable resources. In 2005, this utilization should cover commercial production of ethanol as the most promising biofuel 2% of the total fuel consumption. This quota is expected to increase from renewable resources. In many European countries the use to 5.75% in 2010 and beyond (Berna, 1998). In the EU the annual of bio-ethanol as an alternative fuel or gasoline supplement in bio-ethanol production was 2155 million liters in 2008 (USDA, amounts up to 15% is highly recommended (Mojovic et al., 2008). 2006). If Federal Government regulations are adopted based on Among the bioenergy crops used for fuel ethanol production, the Kyoto agreement, the mandatory blending of bio-ethanol with sugarcane is the main feedstock utilized in tropical countries such traditional gasoline in amounts up to 10% will result in a demand as Brazil and India. In North America and Europe, fuel ethanol is for large quantities of bio-ethanol. Many countries have imple- mainly obtained from starchy materials, especially corn. Countries mented, or are in the process of implementing, programs provid- with a significant agricultural-based economy may apply the cur- ing for the addition of ethanol to gasoline. Fuel ethanol production rent technologies for fuel ethanol fermentation. It is estimated that has increased remarkably due to the global demand to reduce oil feedstock accounts for about 20–55% of total production costs (Lin importation, thereby contributing towards boosting rural econo- and Tanaka, 2006; Del Campo et al., 2006), based on the total mies and improving air quality. The world ethyl alcohol produc- estimated cost of USD 0.40/l of ethanol produced. Furthermore, tion has reached approximately 51,000 million liters, whereas intensive research on the utilization of lignocellulosic biomass as the USA and Brazil are the main producers. On average, 73% of feedstock has been conducted over recent years. Any further increase in ethanol production will necessarily involve the use of feedstock rather than corn grain due to limited supplies. Feed- stocks are typically grouped under the heading ‘‘biomass” and * Corresponding author. Tel.: +30 2721045281; fax: +30 2721045234. E-mail addresses: [email protected] (D. Arapoglou), [email protected] include agricultural residues, wood, municipal solid waste and (Th. Varzakas), [email protected] (A. Vlyssides). dedicated energy crops (Kim and Dale, 2004; Stichnothe and 1 Tel.: +30 2102845940; fax: +30 2102852521. Azapagic, 2009). Biomass is seen as an interesting energy source 0956-053X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.wasman.2010.04.017  D. Arapoglou et al. / Waste Management 30 (2010) 1898–1902 1899 for several reasons, the main reason being the contribution 2006). Enzymes afford numerous advantages compared to acidic provided by bioenergy to sustainable development (Sanchez and hydrolysis because they work under mild conditions, are biode- Cardona, 2008). Resources are often available locally, and conver- gradable, improve yields, reduce energy, water consumption and sion into secondary energy carriers is feasible without high capital the amount of by-products (Israilides et al., 2008). The strategy investments (Lin and Tanaka, 2006). for the use of enzymes in the production of bio-ethanol from starch The problem of the management of potato peel waste (PPW) includes two stages: liquefaction and saccharification. In liquefac- causes considerable concern to the potato industries in Europe, tion a-amylase, obtained either from thermoresistant bacteria thus implying the need to identify an integrated, environmen- such as Bacillus licheniformis or from engineered strains of Esche- tally-friendly solution. Potato peel is a zero value waste from pota- richia coli or Bacillus subtilis are used to decrease viscosity in the to processing plants. slurry or produce dextrins. In saccharification the enzymes use While consumption of potatoes has decreased, processed prod- dextrins to make glucose (Sanchez and Cardona, 2008). ucts such as French fries, chips, and puree have experienced grow- In this paper we present a new PPW hydrolysis with a specific ing popularity (ZMP, 2000). Losses caused by potato peeling range combination of enzymes and/or hydrochloric acid, subsequently from 15% to 40% their amount depending on the procedure applied, fermented by Saccharomyces cerevisae var. bayanus to determine i.e. steam, abrasion or lye peeling (Scieber et al., 2001). Plants peel fermentability and ethanol production. The novelty of the the potatoes as part of the production of crisps, instant potatoes approach lies in the application of the specific enzyme mix, which and similar products. The produced waste is 90 kg per Mg of influ- includes a cellulolytic enzyme, aiming at the highest possible ent potatoes and is apportioned to 50 kg of potato skins, 30 kg fermentable sugar release for the production of ethanol. starch and 10 kg inert material. The downstream processing in the potato crisp industry is illustrated in the following general flowchart of Fig. 1 (Vlyssides et al., 2007). 2. Materials and methods The PPW contains sufficient quantities of starch, cellulose, hemicellulose, lignin and fermentable sugars to warrant use as Samples of PPW were supplied to the Biotechnology Laboratory an ethanol feedstock. Starch is a high yield feedstock for ethanol of the National Agricultural Research Foundation (N.AG.RE.F.) in production, but its hydrolysis is required to produce ethanol by Greece and were dried. Moisture was determined by oven drying fermentation. Starch was traditionally hydrolyzed by acids, but at 105 °C to a constant weight. Total sugars and total carbohy- the specificity of the enzymes, their inherent mild reaction condi- drates were estimated by the colorimetric method of Dubois tions and the absence of secondary reactions have led to the wide- et al. (1956). Protein was estimated by the Kjeldahl method by spread use of amylases as catalysts in this process. Starch multiplying residual nitrogen (N) by 6.25. Fat was determined by processing is a technology utilizing enzymatic liquefaction and the Soxhlet method (AOAC, 1995). Heavy metal analysis was per- saccharification, which produces a relatively clean glucose stream formed by atomic absorption according to the standard methods that is fermented to ethanol by Saccharomyces yeasts (Gray et al., for examination of water and wastewater, (APHA, 1989). Starch Fig. 1. Diagram of the potato crisps manufacturing and production of liquid wastes. 1900 D. Arapoglou et al. / Waste Management 30 (2010) 1898–1902 was quantified with the Kit. Cat. No. 10207748035, Böehringer 2.3.2. PPW hydrolysis by enzymes Mannheim/R-Biopharm. Ethanol was measured with the Böehrin- Two grams of dry potato peel waste (PPW) was mixed with ger Mannheim/R-Biopharm, Kit. Cat. No. 10 176 290 035. The 100 ml distilled water. The mixture was treated with enzymes in degree of polysaccharide degradation was estimated by quantify- two or three steps. The first step, liquefaction, was carried out with ing the amount of reducing sugars formed during enzymatic or Ternamyl 120 L at 85 °C and pH 6.0 for 1 h, or with Liquozyme Su- acidic hydrolysis. Reducing sugars were determined as glucose pra at 55 °C, pH 5.5 and reaction time 20 h. The second step, sac- by using dinitrosalicylic acid (DNS) reagent at optical density charification, was carried out at 44 °C, pH 4.6 for 2.5 h reaction 575 nm, by the method described by Miller (1959). time with Viscozyme. An extra step with Celluclast to degrade cel- lulose was carried out at 50 °C, pH 5 for 2 h reaction time. At the 2.1. Microorganism end of each stage, the enzyme was deactivated with boiling in a water bath at 95 °C, pH 4.6 and for 10 min. S. cerevisae var. bayanus from the Wine Institute (N.AG.RE.F.) The enzyme combinations tested were the following: collection was used for the fermentation of hydrolyzed potato peel waste (PPW), and was maintained on a malt agar slant. The agar a. Liquozyme Supra (L) 1% (v/w) and Viscozyme (V) six FBGU. slant consisted of malt extract (3 g L 1), yeast extract (3 g L 1), b. Ternamyl 120 L (T) 0.24 KNU and Viscozyme (V) six FBGU. peptone (5 g L 1), agar (20 g L 1) and distilled water (up to 1 L). c. Ternamyl 120 L (T) 0.48 KNU and Viscozyme (V) 12 FBGU. For the inoculum, the culture was grown aerobically in 250 ml d. Ternamyl 120 L (T) 2.4 KNU and Viscozyme (V) 12 FBGU. flasks in a shaking water bath at 32 °C for 48 h. The liquid media e. Ternamyl 120 L (T) 0.24 KNU, Viscozyme (V) six FBGU, Cellu- consisted of yeast extract (3 g L 1), peptone (3.5 g L 1), KH2PO4 clast (C) 0.5%. (2 g L 1), MgSO4
7H2O (1 g L 1), (NH2)2SO4 (1 g L 1), glucose f. Ternamyl 120 L (T) 0.24 KNU, Viscozyme (V) 12 FBGU, Cellu- (10 g L 1) and distilled water. Six percent of inoculum was used clast (C) 1%. for the fermentation of PPW. g. Ternamyl 120 L (T) 0.24 KNU, Viscozyme (V) 24 FBGU, Cellu- clast (C) 2%. 2.2. Acidic hydrolysis 2.4. Ethanol fermentation of PPW hydrolyzates In the present study HCl was used to achieve acidic hydrolysis. Hydrochloric acid is usually used for complete hydrolysis of plant Starch hydrolyzates obtained by both enzymatic and acidic origin carbohydrates to simple reducing sugars, with no adverse ef- hydrolysis, were subjected to ethanol fermentation by a 48 h old fects on the material. To an 250 ml Erlenmeyer flask with fermen- culture of Saccharomyces cereviciae var. bayanus under anaerobic tation trap, 40 g of PPW containing 85% moisture, 6 g dry matter agitated conditions (pH 5.0, 32 °C, 100 rpm) in a 250 ml Erlen- (15%) and 52.09% starch per dry weight, was added together with meyer flask with fermentation trap. The inoculum was 6% (v/v) 0.5% NH4NO3, 0.1% peptone and 120 ml HCl 0.5 M. The mixture and fermentation was carried out for 2 days. was sterilized at 121 °C for 15 min. During sterilisation the carbo- hydrates from potato peel were transformed into fermentable sug- ars due to acid hydrolysis. After sterilisation the pH was corrected 2.5. Statistical analysis to 4.15 with NaOH (1 M). Samples were taken at random in triplicate runs. The results 2.3. Enzymatic hydrolysis were calculated as the average (means) of three separate measure- ments of each run. The means were compared with Students t-test 2.3.1. Enzymes at a probability level of p = 0.05. The selection of Student’s t-test for For the enzymatic hydrolysis of PPW the following enzyme comparison of the means was chosen due to the fact that the dis- preparations from Novozymes A/S, Denmark, were used: tribution of t statistic is relatively stable for population that posses not only a normal probability distribution but also a non-normal  Viscozyme L (V). Viscozyme is a cell wall degrading enzyme mount-shaped one. complex from Aspergillus aculeatus. The activity of Viscozyme L was 120 Fungal Beta-Glucanase Units (FBGU)/ml. One FBG is 3. Results and discussion the amount of enzyme required under standard conditions (30 °C, pH 5.0, reaction time 30 min) to degrade barley a-glucan Dry potato peel waste (PPW) composition is given in Table 1. to reducing carbohydrates with a reduction power correspond- Soluble sugar, reducing sugar and starch are part of total carbohy- ing to 1 lmol glucose/min. drates. Lignin was not estimated. As shown, potato peel waste  Ternamyl 120 L (T). Ternamyl 120 L is a heat-stable amylase (PPW) had a high starch content (52% d.w.) but the fermentable from B. licheniformis. The enzyme activity was 120 KNU/g (kilo reducing sugar was very low (0.6% d.w.). For this reason, any novo units of a-amylase). KNU is the amount of enzyme required to break down 5.26 g of starch per hour according to Table 1 Novozyme’s standard method for the determination of Chemical composition of potato peel waste (PPW). a-amylase.  Liquozyme Supra (L). Liquozyme Supra is a heat-stable a-amylase Parameters Dry weight (%) from Bacillus lichneniformis. The enzyme activity was 200 Moisture % 85.06 KNU/g. Total carbohydrate 68.7 Total soluble sugar 1  Celluclast 1.5 L (C). Celluclast 1.5 L is a liquid cellulase prepara- Reducing sugar 0.61 tion with an enzyme activity of 1500 NCU/g. One Novo Cellulase Starch 52.14 Unit (NCU) is the amount of enzyme which, under standard Nitrogen 1.3 conditions, degrades carboxymethylcellulose to reducing carbo- Protein (Ntot 6.25a) 8 hydrates with a reduction power corresponding to 1 lmol glu- Fat 2.6 Ash 6.34 cose per minute. It is produced by submerged fermentation of a a selected strain of Trichoderma reesei. Lignin was not estimated.  D. Arapoglou et al. / Waste Management 30 (2010) 1898–1902 1901 1 Fig. 2. Ethanol production (g L ) of soluble fermentable sugar from acidic hydrolysis of PPW. fermentation of the raw material is not practical and an initial PPW carbohydrates to fermentable reducing sugars was tested. hydrolysis (acidic or enzymatic) of carbohydrates is necessary. The use of Ternamyl released 4.65 g L 1, the Liquozyme 4.03 g L 1 and Viscozyme only 0.7 g L 1. Ternamyl and Liquozyme 3.1. Ethanol production from PPW are enzymes for starch liquefaction, and Viscozyme is used in sac- charification. These results indicate that the saccharification stage 3.1.1. Acidic hydrolysis alone was inadequate and a preliminary liquefaction stage was re- After acidic hydrolysis the total amount of sugars was quired. For this reason, the use of enzyme combination was neces- 19.37 g L 1 while the fermentable reducing sugar was 18.15 g L 1, sary for an effective hydrolysis of PPW. corresponding to 0.36 g released sugar per g of raw dry PPW. At Table 2 shows the reducing sugar released after enzymatic the end of fermentation total sugars were 4.34 g L 1 and ferment- hydrolysis, the remaining reducing sugar after fermentation by able reducing sugars 4.06 g L 1. Therefore, the reducing sugars con- S. cerevisae var. bayanus, as well as sugar consumed for fermenta- sumed were 14.08 g L 1. The final pH at the end of fermentation tion. Due to lower release of reducing sugar and high reaction time was 3.89. (20 h), the use of Liquozyme was rejected for starch liquefaction Fig. 2 shows the evolution of ethanol production (g L 1) during and Ternamyl was selected with higher hydrolysate reducing sugar PPW hydrolyzate fermentation. The maximum ethanol produced and shorter reaction time (1 h). was 6.97 g L 1 after 48 h fermentation, subsequently leveling off The results indicate that higher enzyme concentration leads to to 60 h with a slight decrease thereafter. The product yield Y p/s higher fermentable reducing sugar content. Obviously, the same (g of product/g of sugar consumed) was 0.463 (or 46.3%). This cor- conversions could be achieved with lower enzyme concentration, responds to 92.6% of the max theoretical yield obtained when the although requiring longer times. The longer exposure of the en- substrate is pure glucose (Bryan, 1990). zyme to high temperatures (85 °C for Ternamyl), needed for gelati- nization of the starch granules and to achieve a good susceptibility to enzyme action could lead to slight enzyme deactivation (Mojo- 3.1.2. Enzymatic hydrolysis vic et al., 2006). The degree of hydrolysis of native starch of PPW depends on On the other hand, treatment of PPW with Celluclast increased factors such as substrate concentration, type and concentration the release of reducing sugars significantly (p < 0.05), due to of the enzyme used, and the process conditions such as pH, the additional cellulose degradation. The increase of Celluclast temperature, etc. Firstly, the ability of each enzyme to degrade Table 2 Fermentable reducing sugars released after enzymatic hydrolysis of PPW with various enzyme combinations, reducing sugar (g L 1) at the end of fermentation and Table 3 1 fermentable sugar during fermentation. Ethanol production (g L ), yield and % of maximum theoretical yield, during PPW fermentation. Enzyme combinations Hydrolysate Reducing Consumed 1 reducing sugar after sugar Enzyme combinations Ethanol (g L ) Y (p/s) % Max theoretical sugar fermentation yield a L-1% and V-6U 14.06 ± 0.67a 1.46 ± 0.12 12.60 ± 0.33 a L-1% and V-6U 5.86 ± 0.15a 0.462 92.40 b T-0.24U and V-6U 10.27 ± 0.98b 1.09 ± 0.22 9.18 ± 0.17 b T-0.24U and V-6U 4.19 ± 0.10b 0.459 91.80 c T-0.48U and V-12U 16.82 ± 1.01c 1.82 ± 0.19 15.00 ± 1.14 c T-0.48U and V-12U 7.00 ± 0.06c 0.467 93.38 d T-2.4U and V-12U 14.68 ± 1.20a 1.61 ± 0.31 13.07 ± 0.99 d T-2.4U and V-12U 6.05 ± 0.23a 0.460 92.10 e T-0.24U and V-6U 16.99 ± 1.17c 2.03 ± 0.53 14.96 ± 1.25 e T-0.24U and V-6U and C- 6.89 ± 0.47c 0.456 91.24 and C-0.5% 0.5% f T-0.24U and V-12U 18.32 ± 1.23d 2.11 ± 0.28 16.21 ± 1.54 f T-0.24U and V-12U and C- 7.58 ± 0.24c 0.463 92.54 and C-1% 1% g T-0.24U and V-24U 18.48 ± 0.65d 1.93 ± 0.31 16.55 ± 0.85 g T-0.24U and V-24U and C- 7.50 ± 0.28c 0.458 91.64 and C-2% 2% L: Liquozyme. L: Liquozyme. T: Ternamyl. T: Ternamyl. V: Viscozyme. V: Viscozyme. C: Celluclast. C: Celluclast. a,b,c,d a,b,c, Different superscripts are statistically significant, p = 0.05. Different superscripts are statistically significant, p = 0.05. 1902 D. Arapoglou et al. / Waste Management 30 (2010) 1898–1902 concentration from 1% to 2% did not lead to any significant increase study. Moreover, the availability of manufacturers to become in- of reducing sugar (p > 0.05). The enzyme combination with the volved in this project and to devote resources to its implementa- highest release of reducing sugar was (g) Ternamyl 0.24 tion will provide a significant contribution. KNU + Viscozyme 24 FBGU + Celluclast 2% with a rate of 18.48 g L 1 that corresponded to 0.92 g released sugar per g of Acknowledgements raw dry PPW. Using this combination, at the end of fermentation the reducing sugars were 1.93 g L 1. Therefore, the sugars con- The authors wish to thank Mrs. Malli Basiliki and Mrs. sumed were 16.55 g L 1 (Table 2). In all treatments the non-fer- Chaidemenaki Katerina for their valuable help in the analytical mented sugar at the end of fermentation was very low. The work. consumed sugar during fermentation was very high (up to 89%), indicating the high ability of S. cerevisiae var. bayanus to bioconvert References reducing sugars. Table 3 shows the ethanol production (g L 1), product yield Y American Public Health Association (APHA), 1989. Standard Methods for the Examination of Water and Wastewater, 17th ed., Washington, DC. p/s (g of product/g of sugar consumed) and percentage of the max- AOAC, 1995. Official Methods of Analysis of AOAC International. In: Cunniff, P. (Ed.), imum theoretical yield, with the use of various enzyme combina- 16th ed. AOAC International, Arlington, Virginia, USA. tions. In all enzyme treatments, S. cerevisae produced high Berna, G., 1998. Integrated biomass system. Office for Official Publications of the EC, Luxembourg, p. 27. quantities of ethanol (6.0–7.6 g L 1), with the exception of combi- Bryan, W., 1990. Solid-state fermentation of sugars in sweet sorghum. Enzyme nation (b) resulting in lower ethanol production (4.2 g L 1). The Microbial Technology 12, 437–442. product yield Y p/s (g of product/g of sugar consumed) was about Del Campo, I., Alegria, I., Zazpe, M., Echeverria, M., Echererria, I., 2006. Diluted acid hydrolysis pretreatment of agri-food wastes for bioethanol production. 0.46. In all cases the product yield corresponded up to 91% of the Industrial Crops and Products 24, 214–221. max theoretical yield. Dubois, M., Gills, K.A., Hamilton, J.K., Rebers, P.A., Smith, F., 1956. Colorimetric The results indicate that the critical parameters for ethanol pro- method for determination of sugars and related substances. Analytical Chemistry 28, 350–356. duction from PPW were the enzyme combination, the dose and the Gray, A.K., Zhao, L., Emptage, M., 2006. Bioethanol. Current Opinion in Chemical residence time of hydrolysis. After liquification and saccharifica- Biology 10, 141–146. tion, fermentation by S. cerevisae converted sugars to high yields Israilides, C., Vlyssides, A.G., Arapoglou, D., Varzakas, Th., Marchant, R., Vlysides, A.A., 2008. Integrated management of potato starch wastes. In: Proceedings of of ethanol. the Waste and Resource Management – A Shared Responsibility (Waste 2008), September 16–17, 2008, Stratford-Upon-Avon, UK, No. 36. 4. Conclusions Kim, S., Dale, B.E., 2004. Global potential bioethanol production from wasted crops and crop residues. Biomass and Bioenergy 26, 361–375. Lin, Y., Tanaka, S., 2006. Ethanol fermentation from biomass resources: current state It is evident that enzymatic hydrolysis of PPW liberates a higher and prospects. Applied Microbiology and Biotechnology 69, 627–642. amount of fermentable reducing sugar compared to hydrochloric Miller, G.L., 1959. Use of dinitro-salicylic acid reagent for determination of reducing sugar. Analytical Chemistry 31, 426–428. acidic hydrolysis. The enzyme combination featuring the highest Mojovic, L., Nikolic, S., Rakin, M., Vukasinovic, M., 2006. Production of bioethanol release of reducing sugar, was (g) Ternamyl 0.24 KNU + Viscozyme from corn meal hydrolyzates. Fuel 85, 1750–1755. 12 FBGU + Celluclast 1% with 18.48 g L 1. With this combination, at Sanchez, O., Cardona, C., 2008. Trends in biotechnological production of fuel ethanol from different feedstocks. Bioresource Technology 99, 5270–5295. the end of fermentation the reducing sugars were 1.93 g L 1. Scieber, A., Stintzing, F.C., Carle, A., 2001. By-products of plant food processing as a Therefore, the sugars consumed were 16.55 g L 1. Ethanol produc- source of functional compounds – recent developments. Trends in Food Science tion was 7.58 g L 1 and ethanol yield corresponded to 91.6% the and Technology 1, 401–413. max theoretical yield. Stichnothe, H., Azapagic, A., 2009. Bioethanol from waste: life cycle estimation of the greenhouse gas saving potential. Resources, Conservation and Recycling 53, The results demonstrated that PPW, a by-product of the potato 624–630. industry, could be efficiently utilized for ethanol production with USDA, 2008. Foreign Agricultural Service. Gain Report No. E48063. simultaneous reduction of waste by-product. The production of Vlyssides, A., Barampouti, S., Mai, E., 2007. Waste minimization in potato processing industry. In: XI International Waste Management and Landfill Symposium, 1–5 ethanol from PPW represents an alternative, readily manageable October 2007, Sardinia, Italy. option; the feasibility of implementing this technique will be fur- ZMP, 2000. ZMP – Marktbilanz Kartoffeln. ZMP (Zentrale Markt- und ther investigated by means of a larger scale technico-economical Preisberichtsstelle GmbH), Bonn.