Bioenergy systems for the future 5 anaerobic biodigestion for enhanced bioenergy generation in ethanol biorefineries understanding the potentials of vinasse as a biofuel Bioenergy systems for the future 5 anaerobic biodigestion for enhanced bioenergy generation in ethanol biorefineries understanding the potentials of vinasse as a biofuel Bioenergy systems for the future 5 anaerobic biodigestion for enhanced bioenergy generation in ethanol biorefineries understanding the potentials of vinasse as a biofuel Bioenergy systems for the future 5 anaerobic biodigestion for enhanced bioenergy generation in ethanol biorefineries understanding the potentials of vinasse as a biofuel Bioenergy systems for the future 5 anaerobic biodigestion for enhanced bioenergy generation in ethanol biorefineries understanding the potentials of vinasse as a biofuel Bioenergy systems for the future 5 anaerobic biodigestion for enhanced bioenergy generation in ethanol biorefineries understanding the potentials of vinasse as a biofuel
Anaerobic biodigestion for enhanced bioenergy generation in ethanol biorefineries: Understanding the potentials of vinasse as a biofuel L.T Fuess*, M.L Garcia† *University of Sa˜o Paulo, Sa˜o Carlos, Brazil, †Sa˜o Paulo State University, Rio Claro, Brazil Abbreviations 2G AD BML BNDES BOD CC CGEE CHP COD CODsewage CODvinasse CONAB CR CRN CSV DDGS DOE EB EC EIA EP EPbagasse EPE second generation anaerobic digestion beet molasses Banco Nacional de Desenvolvimento Econ^ omico e Social (Brazilian Development Bank) biochemical oxygen demand combined cycle Centro de Gesta˜o e Estudos Estrategicos (Center of Strategic Studies and Management—Brazil) combined heat and power chemical oxygen demand COD of sewage COD of vinasse Companhia Nacional de Abastecimento (National Supply Company—Brazil) sewage-to-water return coefficient corn cassava distillers dried grains with solubles US Department of Energy energy balance consumed fossil energy US Energy Information Administration energetic potential energetic potential of bagasse Empresa de Pesquisa Energetica (Energy Research Company—Brazil) Bioenergy Systems for the Future http://dx.doi.org/10.1016/B978-0-08-101031-0.00005-3 © 2017 Elsevier Ltd All rights reserved 150 Bioenergy Systems for the Future EPvinasse EQP ERCOD ERP EtOH GHG HSW ICE IRR K LCL LHVCH4 LHVEtOH MRA MY NPV OLR PCCwater SGJ SJM SRB TC TKN TP TRS USD VPR ηel 5.1 energetic potential of vinasse equivalent population COD removal efficiency energy recovery potential ethanol greenhouse gas high-strength wastewater internal combustion engine internal rate of return potassium lignocellulosic materials lower heating value of methane lower heating value of ethanol minimum rate of attractiveness methane yield net present value organic loading rate per capita water consumption sugarcane juice sugarcane juice + molasses sulfate-reducing bacteria ton of cleaned sugarcane total Kjeldahl nitrogen total phosphorus total reducing sugars US dollar vinasse production rate electric conversion factor Introduction Biofuel industries, such as ethanol and biodiesel plants, may be considered the most representative examples of biorefineries, based on the application of different (bio) processes to efficiently obtain value-added products and bioenergy from a wide range of feedstocks (Poggi-Varaldo et al., 2014; Moraes et al., 2015) Focusing on ethanol production, important advantages must be considered, such as the worldwide technological consolidation of the process and the suitability for applying a series of crops, grown under different climatic conditions, as raw materials (Willington and Marten, 1982; Hill et al., 2006; Cavalett et al., 2012; Fuess and Garcia, 2014) In addition, depending on the type of feedstock, ethanol production may be coupled to sugar refining and electricity generation, which enables a more flexible use of the raw material Such interesting scenarios are particularly observed in sugarcane-based plants, so that the amount of total reducing sugars (TRS) directed to ethanol or sugar production depends intimately on their market price, whereas the residual lignocellulosic Anaerobic biodigestion of vinasse for enhanced bioenergy generation 151 material, that is, bagasse, is burned in cogeneration systems for both steam and electricity generation (BNDES and CGEE, 2008; Dias et al., 2013; Moraes et al., 2015) The efficient use of the raw material in ethanol plants is also strictly related to the proper management of the wastewater streams generated within the processes, so that special attention must be direct to vinasse Vinasse or stillage constitutes a highstrength dark-brown wastewater resulting specifically from the step of distillation, being characterized by some common compositional aspects regardless of the feedstock, including high levels of organic matter, solids, and acidic compounds (Espan˜a-Gamboa et al., 2011; Fuess and Garcia, 2014) Based on the highly polluting character of vinasse, Willington and Marten (1982) indicated that small-scale sugarcane-based distilleries (250 m3 of ethanol—EtOH—per day) may generate polluting loads equivalent to the ones observed for populations as high as million inhabitants Although vinasse generation rates depend directly on the type of feedstock and technological level of the processes, an average proportion of 10–15 L of vinasse per liter of produced ethanol is usually observed in ethanol plants (Willington and Marten, 1982; Cavallet et al., 2012; Moraes et al., 2015) For relatively large-scale sugarcane-based Brazilian distilleries (1000 m3EtOH dayÀ1, Dias et al., 2011), the annual volume of vinasse generated may reach up to 3.5 million cubic meters, based on an average sugarcane harvesting period of 232 days (CONAB, 2011) Such enormous value is of great interest in terms of environmental concern and energetic potential, as further discussed The reference literature includes a wide variety of approaches for the management of vinasse in ethanol plants Although prior studies presented direct discharge into water bodies and marine outfall as available options (Sheehan and Greenfield, 1980; Willington and Marten, 1982), the recent literature focus on the application of different (bio)technological approaches to vinasse, usually in an effort to reach environmental adequacy Studied processes include anaerobic (Mohana et al., 2009; Ferraz et al., 2016) and aerobic (de Bazu´a et al., 1991; Ferreira et al., 2011) digestion and conventional physical-chemical (Zayas et al., 2007; Rodrigues et al., 2014) and advanced oxidative processes (Sangave et al., 2007; Asaithambi et al, 2012) Alternatives applied to vinasse management also include incineration to ashes (Willington and Marten, 1982; Akram et al., 2015) and evaporation and concentration for producing animal feed and reducing costs with transportation (Wilkie et al., 2000; Pimentel et al., 2007; Murphy and Power, 2008); however, both cases demand expressive amounts of energy, hindering the global energy balance of the process Particularly, vinasse streams resulting from sugarcane processing are characterized by appreciable levels of nutrients, mainly potassium (Fuess and Garcia, 2014), which favors their direct land disposal through fertirrigation Fertirrigation constitutes virtually the sole management approach applied to vinasse in the Brazilian sugarcane-toethanol industry (BNDES and CGEE, 2008; Fuess and Garcia, 2014), leading to important reductions in the consumption of freshwater and mineral fertilizers (BNDES and CGEE, 2008; Sivaloganathan et al., 2013) However, the continuous soil application of vinasse may potentially generate a broad range of negative environmental impacts in the long term, such as soil salinization and structural destabilization, water bodies acidification, leaching of toxic compounds to groundwater, emissions of greenhouse gases (GHG), and release of unpleasant odors (Mohana et al., 2009; 152 Bioenergy Systems for the Future Oliveira et al., 2013; Fuess and Garcia, 2014; Moraes et al., 2015) GHG emissions and odors releasing result directly from the conversion of the biodegradable organic fraction found in vinasse by soil microbial populations, characterizing a second major drawback from fertirrigation, since the uncontrolled organic matter conversion associated to this practice leads to expressive bioenergy losses According to Palacio et al (2012), the energetic potential of ton of cleaned sugarcane (TC) is approximately 1718 Mcal, which is distributed as sugars (153 kg and 608 Mcal), bagasse with 50% moisture (216 kg and 598 Mcal), and straw with 15% moisture (165 kg and 512 Mcal) Given that the ethanol yield in autonomous distilleries, that is, TRS directed only for ethanol production, reaches usually 82.9 LEtOH TCÀ1 (Moraes et al., 2014), a fraction of about 421 Mcal is recovered through biofuel production, so that roughly 30% of the energetic content of the sugars (or 10% of the total sugarcane energetic potential) remains unconverted in vinasse In turn, the remaining energy fraction from ethanol production in annexed plants, that is, sugar and ethanol production, accounts for slightly more than 20% of the energy from sugars, based on average sugar and ethanol yields of 50.8 kgsugar TCÀ1 and 53.4 LEtOH TCÀ1 (Moraes et al., 2014) Such estimates not consider the amount of energy directed to cell growth in fermentative processes that may lead to slightly overestimated values Nevertheless, the values presented herein indicate that vinasse should be considered a highly energetic raw material from ethanol plants rather than a residual stream, with great potential toward the application of anaerobic processes Anaerobic digestion (AD) constitutes an effective alternative to the management of vinasse and other high-strength wastewaters (HSW), in order to concentrate important advantages compared with other treatment approaches The application of AD as the core technology in treatment plants enables associating reductions in the polluting load of effluents with the generation of bioenergy through biogas, a methane-rich gaseous blend resulting from the activity of several microbial populations under syntrophic associations The use of biogas as energy source in industrial plants should lead to a minimum-to-average energy recovery potential (ERP) of about 50%–60% (Borzacconi et al., 1995) In fact, a few studies on the energetic potential of vinasses from the corn-to-ethanol industry indicated reductions in the consumption of fossil fuels in the range of 43%–65% (Stover et al., 1984; Khanal, 2008; Agler et al., 2008; Cassidy et al., 2008; Schaefer and Sung, 2008) Therefore, considering the concept of biorefineries, the implementation of anaerobic processes provides a more efficient exploitation of the base raw material, with emphasis on the use of residues (by-products) as energy sources Numerous studies on the application of anaerobic processes to vinasses from different feedstocks are presented in the literature, such as sugarcane (Craveiro et al., 1986; Costa et al., 1986; Souza et al., 1992; Ferraz et al., 2016), beet (Braun and Huss, 1982; Boopathy and Tilche, 1991; Vlissidis and Zouboulis, 1993), corn (Stover et al., 1984; Agler et al., 2008; Lee et al., 2011; Andalib et al., 2012), cassava (Luo et al., 2009, 2010 and 2011), and cellulosic materials (Good et al., 1982; Callander et al., 1986 and 1987; Kaparaju et al., 2010) However, most reports are based on the use of bench-scale systems, so that some studies tend to superficially discuss the ERP of the biogas Parameters related to methane production are often characterized as complementary data for performance assessment, which is usually focused on organic matter removal In this context, wider energetic analyses are required to fully comprehend the potentials of Anaerobic biodigestion of vinasse for enhanced bioenergy generation 153 vinasse for bioenergy generation in the ethanol industry Thus, in this chapter, the potential of AD for bioenergy recovery in the ethanol industry is carefully considered, based on different approaches The energetic potential of vinasses from different feedstocks was calculated, in order to assess the ERP of methane (biogas) compared with the energy consumption in different steps from ethanol production The contribution from biogas energetic content to the energy balance of ethanol production was also considered Special attention was direct to the sugarcane-to-ethanol industry, based on the energetic self-sustaining character of such plants In this case, a detailed economic assessment was applied to assess the feasibility of implementing AD systems to the treatment of vinasse in large-scale distilleries 5.2 Vinasse characterization: Suitability for bioenergy generation Ethanol production is based mainly on two basic processes regardless of the feedstock, which include the fermentation of a sugar-rich substrate followed by the distillation of the fermented solution (Fig 5.1) Feedstock processing steps may differ according to the ready availability of reducing sugars, that is, the broth extracted from sugar-rich crops, such as sugarcane, beet, and sweet sorghum, may be directed employed in fermentation, whereas starch-rich (e.g., corn, cassava, and barley) and cellulosic materials require pretreatment steps (Fig 5.1) Ethanol production from sugar-rich feedstocks may be conducted using directly the sugars extracted from sugarcane (juice)—autonomous distilleries—or blends between the juice and molasses, a sucrose-rich concentrated residual solution from sugar production (Fig 5.1) In this case, distilleries are named annexed plants, which constitute most of ethanol plants in Brazil ($70%, Cavalett et al., 2012) Molasses may also be employed directly in ethanol production, such as in the Indian sugarcane-to-ethanol industry, where juice is used solely in sugar refining (Soam et al., 2015) Nevertheless, regardless of the feedstock and process characteristics, vinasse is generated specifically within the distillation step (Fig 5.1), presenting some interesting compositional aspects in terms of biodegradable organic matter Compositional characteristics for vinasses from different feedstocks are compiled in Table 5.1, usually indicating high values (>0.4) for the ratio between the biochemical (BOD) and chemical (COD) oxygen demands, that is, BOD/COD ratio, regardless of the feedstock This relation roughly describes the suitability of a given wastewater to biological process treatments, so that for values higher than 0.3–0.4, the biodegradable fraction may be considered high (von Sperling, 2007) Biodegradable organic compounds in vinasses result mainly from three sources: (i) residual fractions of nonconverted sugars, (ii) residual concentrations of nonrecovered ethanol, and (iii) fermentation of by-products, that is, metabolites excreted by yeasts and contaminant microorganisms, such as glycerol and organic acids (Wilkie et al., 2000; Dias et al., 2012) According to Wilkie et al (2000), every 1% of residual reducing sugars and ethanol may lead, respectively, to increments of about 16 and 20 gLÀ1 in the COD of vinasse Since such compounds are easily assimilated in anaerobic environments, the application of AD to vinasse theoretically enables obtaining high biogas production rates as a direct result from an efficient conversion of the organic matter 154 Bioenergy Systems for the Future Sugar-rich crops Starch-rich crops (sugarcane, sugar beet, sweet sorghum) (corn, cassava, cereals) Sugar extraction (milling or diffusion) Grinding Grinding Saccharification (enzymatic hydrolysis) Pretreatmenta Sugar production Lignocellulosic materials Molasses Enzymatic or acid hydrolysis Sugar-rich solution (broth) Fermentation Sugar Ethanol Distillation Vinasse Fig 5.1 Technological routes for ethanol production from different feedstocks Note: aIncludes the application of different physical-chemical and/or biological processes to disrupt vegetal fibers found in lignocellulosic materials, converting polysaccharides into fermentable sugars (Moraes et al., 2015) 5.3 5.3.1 Bioenergy generation from vinasse: Input data and estimates Energetic potential (EP) for vinasses from various feedstocks In short, EP constitutes the energy potentially recovered as biogas from the organic content found in vinasse In this study, the energetic analysis was initially applied to vinasses from various feedstocks: sugarcane (juice—SGJ—and blends of juice and molasses—SJM), beet molasses (BML), corn (CRN), cassava (CSV), and lignocellulosic materials (LCL) Table 5.2 compiles the raw data used in the estimates, Compositional characterization for vinasses from various feedstocks Feedstock BOD (g L1) COD (g L1) BOD/COD TKN (mg L1) TP (mg L1) K (mg L1) SO22 (mg L1) pH References Sugarcane (juice) 11.3–17.1 22.0–42.0 0.27–0.68 70–700 58–200 1473–2300 400–1300 3.5–4.6 Sugarcane (molasses) 25.0–60.0 51.2–100.0 0.38–0.61 450–1780 33–1500 1200–8900 3500–9500 3.4–5.0 Sugarcane (juice + molasses) 16.7–19.8 31.5–49.0 0.43–0.47 370–1603 9–200 1300–4600 420–3730 3.9–4.6 Costa et al (1986), Craveiro et al (1986), Driessen et al (1994), Ferreira et al (2011) Sheehan and Greenfield (1980), Costa et al (1986), Bories et al (1988), Driessen et al (1994), Goyal et al (1996), Prada et al (1998) Costa et al (1986), Souza et al (1992), Prada et al (1998), Siqueira et al (2013),Ferraz et al (2014) 155 Continued Anaerobic biodigestion of vinasse for enhanced bioenergy generation Table 5.1 Continued 156 Table 5.1 BOD (g L1) COD (g L1) BOD/COD TKN (mg L1) TP (mg L1) K (mg L1) SO22 (mg L1) pH References Beet (molasses) 27.5–44.9 45.0–115.8 0.49–0.63 56–4700 56–175 5500–10,030 1040–3716 4.6–6.7 Corn 26.9–68.6 60.0–129.3 0.42–0.56 755–2000 1170–4140 1100–5560 nd 3.3–4.6 Cassava 24.0–35.0 40.0–70.4 0.50–0.60 304–1440 83–400 nd nd 3.9–4.2 Cellulosic materials 13.2–27.6 22.5–61.3 0.45–0.52 95–2787 out/40 39 651–1800 3.6–6.3 Braun and Huss (1982), Boopathy and Tilche (1991), Vlissidis and Zouboulis (1993), Wilkie et al (2000), Lutoslawski et al (2011) Stover et al (1984), Wilkie (2008), Agler et al (2008), Alkan-Ozkaynak and Karthikeyan (2011), Nasr et al (2011), Andalib et al (2012) Luo et al (2009), (2010), and (2011); Wang et al (2011) Good et al (1982), Callander et al (1986) and (1987); Wilkie et al (2000) Parameters: BOD, biochemical oxygen demand; COD, chemical oxygen demand; TKN, total Kjeldahl nitrogen; TP, total phosphorus; K, potassium; SO2À , sulfate Note: nd, unavailable data Bioenergy Systems for the Future Feedstock Organic content (COD) AD performance OLR ERCOD MYa Crop (g L1) (kgCOD m23 d21) (%) (N m3 kg21 CODremoved) Sugarcane (juice) Reference Sugarcane (juice + molasses) Reference Beet (molasses) Reference Corn Reference Cassava Reference Lignocellulosic materials Reference 30.4 Wilkie et al (2000) 45.8 Costa et al (1986), Prada et al (1998) 55.5 Vlissidis and Zouboulis (1993) 60.2 Wilkie (2008) 62.2 Luo et al (2009), (2010), and (2011) 61.3 Wilkie et al (2000) 18.3 Costa et al (1986) 26.5 Souza et al (1992) 6.0 Vlissidis and Zouboulis 7.5 Agler et al (2008) 11.3 Luo et al (2009) 10.0 Good et al (1982) 76.0 0.329b 71.7 0.307 88.2 (1993) 92.2 0.330 85.1 0.258 84.4 0.316c 0.284 Anaerobic biodigestion of vinasse for enhanced bioenergy generation Table 5.2 Reference data on vinasse characterization and typical performance of AD systems applied to vinasses from various feedstocks Parameters: COD, chemical oxygen demand; OLR, organic loading rate; ERCOD, COD removal efficiency; MY, methane yield a Values corrected to standard temperature and pressure conditions (STP) if not indicated in the reference study b Temperature not indicated c Refer to eucalyptus wood hydrolysate 157 158 Bioenergy Systems for the Future including the compositional characteristics of vinasse (COD) and typical performance data on COD removal and methane production from AD systems reported elsewhere EP calculations were based on Eq (5.1), so that an average vinasse production rate (VPR) of 13 m3 mÀ3 EtOH was considered (BNDES and CGEE, 2008): EP ¼ VPR Á COD Á ERCOD Á MY Á LHVCH4 (5.1) In Eq (5.1), the terms EP, VPR, COD, ERCOD, MY, and LHVCH4 are, respectively, the energetic potential of vinasse (MJ mÀ3 EtOH), the average generation rate of vinasse À3 (13 m3 mÀ3 EtOH), the chemical oxygen demand of vinasse (kgCOD m ), the COD À1 removal efficiency (dimensionless), the methane yield (N m kgCODremoved), and the lower heating value of methane (50 MJ kgÀ1 or 35.72 MJ N mÀ3, Heywood, 1988) Performance data compiled in Table 5.2 refer to the application of thermophilic temperature conditions (50–55°C) to the reactors, which may be considered a feasible alternative for vinasses, based on two main advantages: (i) Vinasse is released from distillation columns at approximately 85–95°C (Dias et al., 2012; Moraes et al., 2015), naturally reaching the adequate temperature for the treatment without requiring energy inputs, and (ii) thermophilic systems may handle higher OLRs compared with mesophilic ones, which enables the use of more compact reactors and consequently improves the economics of full-scale anaerobic processes (Wilkie et al., 2000) 5.3.2 Energy recovery potential (ERP) and energy balance (EB) estimates Estimates on the ERP from biogas were based on an energy balance for the production of ethanol, in which the fossil energy used in feedstock processing and conversion into ethanol comprised system inputs, whereas the outputs corresponded to the EP previously calculated (Section 5.3.1) Eq (5.2) describes the calculations for the ERP (%), so that the terms EC and EP are, respectively, the amount of consumed fossil energy in À3 ethanol production (MJ mÀ3 EtOH) and the energetic potential of biogas (MJ mEtOH): ERP ¼ EP Á 100 EC (5.2) Table 5.3 depicts ranges of values obtained for EC in the reference literature, considering three distinct consumption categories: feedstock cultivation or agricultural phase, feedstock conversion in distilleries, and transport operations Energy demands in the agricultural phase account for the preparation of the cultivable area and the cultivation itself; the production and use of inputs, such as mineral fertilizers, alkalizing compounds, and soil conditioners; and the harvest (Salla et al., 2009, 2010a) In turn, feedstock processing, such as sugarcane milling or starch saccharification; fermentation; and distillation are the main energy-consuming steps in distilleries Transport operations include the transportation of the feedstock to ethanol plants and/or ethanol distribution Although the EP was estimated for vinasses from various feedstocks, the assessment of the ERP took into consideration only three types of crops, including Anaerobic biodigestion of vinasse for enhanced bioenergy generation 169 saccharification, the energy consumption in sugarcane mills is about 100% higher (Salla et al., 2009), characterizing the advantages of using self-generated steam as driving force in the plant In fact, energetic limitations observed in distilleries result directly from failures in the production and use of steam, which depends on the technological level of the processes (Silalertruksa and Gheewala, 2009; Turdera, 2013) Focusing on starch-based ethanol production chains, previous studies indicated similar ERP values for the biogas in relation to the consumption of fossil fuels in distilleries (43%–65%—Stover et al., 1984; Khanal, 2008; Agler et al., 2008; Cassidy et al., 2008; Schaefer and Sung, 2008), so that bioenergy production from biogas may be characterized as an attractive alternative compared with the other approaches used in such schemes, such as animal feed production In short, the high protein content remaining especially in vinasses from corn processing enables the recovery of their solid fraction as distillers dried grains with solubles (DDGS) after steps of centrifugation, evaporation, and drying, which increase the shelf life and reduce transportation costs of the material (Lee et al., 2011; Andalib et al., 2012; Westerholm et al., 2012) In terms of EP, about 1860 MJ mÀ3 of ethanol is saved through DDGS production (Pimentel et al., 2007), based on energy savings from conventional animal feed production processes (Fuess and Garcia, 2014) EP values estimated for corn and cassava vinasses submitted to anaerobic processes (6342–7320 MJ mÀ3 EtOH, Fig 5.2) are approximately 3.4- to 3.9-fold higher compared with the energy savings from DDGS production In addition, concentration steps require large amounts of energy, accounting for 30%–45% of the total EC in the ethanol plant (Westerholm et al., 2012), negatively impacting the energy balance of ethanol production chain (Andalib et al., 2012) The ERP of vinasse in relation to the global energy consumption in ethanol production reflects the considerable discrepancy observed for the consumption of fossil energy in feedstock processing steps, with values over 100% observed for sugarcanebased chains (106.1%–150.8%, Table 5.5 and Fig 5.3D) Compared with the use of corn, the slightly higher ERP values associated to cassava (36.5% vs 28.6%, Table 5.5) result from the lower EC in the agricultural phase, as previously discussed in this section In terms of the EB, the more favorable scenarios inherent to sugarcane distilleries supplied by bioenergy generated from bagasse associated lower gains to biogas energy inputs, which reached, however, yet expressive values The implementation of AD systems in distilleries processing SGJ and SJM could increase the EB of ethanol production, respectively, by 14.7% (7.48–8.54) and 19.3% (7.84–9.35) (Table 5.5 and Fig 5.5E) Considering starch-based chains, gains in EB could reach over 30%, that is, 0.83–1.11 and 1.22–1.59, respectively, for CRN and CSV (Table 5.5 and Fig 5.5E) The expressive influence of bioenergy generation from vinasse in such cases constitutes a direct result of the limitations for the use of additional bioenergy sources within the production chain of corn and cassava, so that the EP of vinasse is not “diluted” as observed for sugarcane-based schemes At this point, it is worth highlighting the positive impacts of AD over the corn-toethanol industry, as the input of biogas energy could lead to energetically selfsustaining systems, that is, EB > 1.0 Using similar calculation approaches, Agler et al (2008) and Lee et al (2011) indicated EB values, respectively, of 1.70 and 1.80 for the corn-to-ethanol production after introducing the AD of vinasse; 170 Bioenergy Systems for the Future however, both studies used a reference EB value of 1.26 (scheme without AD) Shapouri et al (2003) and Hill et al (2006) also reported favorable energy balances for the corn-based ethanol industry (respectively, 1.34 and 1.25) without including biogas production, so that such positive values may be explained by considering the recovery of other coproducts, such as DDGS (Shapouri et al., 2003) In fact, studies indicate that obtaining favorable energetic scenarios in the corn-to-ethanol industry depends directly on coproducts recovery; otherwise, the input of fossil fuels reaches higher levels compared with the EP of ethanol Pimentel (2003) and Pimentel and Patzek (2005) estimated fossil inputs 29% higher than the energetic content of the produced ethanol from corn, that is, EB ¼ 0.71, which comprises a value similar to the one obtained herein for production chains without vinasse AD (0.83, Table 5.5 and Fig 5.3F) Therefore, vinasse AD may be considered an essential technological approach to enable the characterization of the corn-based ethanol as a renewable energy source, once the establishment of positive energy balances comprises one of the main pillars for the production of a given biofuel (Hill et al., 2006) At last, regardless of the feedstock used in ethanol production, estimates presented herein highlight the potential of vinasse as a bioenergy source, indicating the suitability of anaerobic processes as the core treatment technology in ethanol industry 5.4.3 Technological assessment of AD plants in sugarcane-based distilleries Details on environmental and energetic aspects associated to the implementation of AD systems in sugarcane-based distilleries are compiled in Table 5.6 Fig 5.4 also depicts information on energetic aspects of the technological assessment, in order to compare bioenergy generation from biogas with hydro- and thermoelectric sources Estimated polluting loads for vinasses from autonomous and annexed plants were equivalent to populations over million inhabitants (Table 5.6), reaching approximately 2.5-fold the Brazilian population when considering global generation data from the 2014/2015 sugarcane harvesting Although expressive reductions on the organic polluting load of vinasse could be obtained (>90 tonCOD seasonÀ1, Table 5.6) through biogas recovery, the residual organic fraction would yet lead to polluting potentials equivalent to populations over million inhabitants Such values highlight the importance of applying both AD as the core treatment technology in distilleries and further treatment approaches (e.g., aerobic processes) to comply with environmental and/or wastewater reuse normative instructions Particularly, wastewater reuse constitutes an essential requirement for a highly efficient use of raw materials in biorefineries In this context, reductions in the organic content may provide a more environmental-friendly final destination for vinasse through fertirrigation, as high nutrient levels may be yet found in biodigested vinasses (Moraes et al., 2015) This characteristic results from the negligible nutrient removals observed in anaerobic environments (Chernicharo, 2007), so that this limitation may be positively used when considering the management of vinasse With respect to energetic aspects, interesting scenarios confirmed the suitability of vinasse as a biofuel Electricity generation from biogas could reach up to Anaerobic biodigestion of vinasse for enhanced bioenergy generation 171 Table 5.6 Environmental and energetic aspects from AD systems in sugarcane-based distilleries Parameter Annual vinasse generation (m3 seasonÀ1) Annual organic polluting load—raw vinasse (tonCOD seasonÀ1) Equivalent population—raw vinasse (inhab) Annual avoided organic polluting loadtreated vinasse (tonCOD seasonÀ1) Equivalent population—biodigested vinasse (inhab) Annual methane production (N m3 seasonÀ1) Annual electricity production (MWh seasonÀ1) Power generated (MW) Energetic potentiala (MJ mÀ3 EtOH) Energetic potentialb (MJ mÀ3 EtOH) a b Autonomous distillery Annexed distillery 2014/2015 harvesting 4.3Á106 2.8Á106 371.8Á106 130.7Á103 128.2Á103 11.3Á106 5.2Á106 5.1Á106 481.3Á106 99.3Á103 91.9Á103 8.6Á106 1.2Á106 1.4Á106 115.5Á106 32.7Á106 28.2Á106 2.8Á109 139.5Á103 120.3Á103 11.9Á106 25.1 3522 1515 21.6 4716 2028 2274.5 3497 1504 In terms of the total biogas energy content In terms of electricity production (ηel ¼ 0.43) 139.5Á103 MWh seasonÀ1 depending on the distillery type (Table 5.6) Using a residential electricity consumption of 163 kWh monthÀ1 as reference (average for Brazilian conditions—EPE, 2014) and assuming a number of three inhabitants per residence, the electricity generated within AD plants in large-scale distilleries could supply populations of about 290,000 and 330,000 inhabitants, respectively, for annexed and autonomous plants Despite the lower organic content found in vinasses from juice (Table 5.4), the volume of wastewater generated in autonomous plants is approximately 1.5-fold higher compared with annexed schemes, which may explain the differences in electricity generation depicted in Table 5.6 (120.3 Â 103 vs 139.5 Â 103 MWh) Furthermore, experimental data usually associate higher MY values, that is, higher energy extraction levels, for vinasses from juice (Costa et al., 1986; Souza et al., 1992), as specific compositional characteristics from molasses, such as higher salt levels, may stress anaerobic populations, leading to slightly lower methane productions Nevertheless, wider energetic analyses indicate that the total electricity potentially generated from vinasse AD in the 2014/2015 Brazilian sugarcane harvesting period (11.9 Â 106 MWh, Table 5.6) could account for almost 15% of the total electric production from the largest hydropower plants in the world (Itaipu and Three Gorges Dams, Fig 5.4) Moreover, comparatively to bagasse burning in Brazilian biorefineries, an increment of over 60% of the electricity exported to the grid (2014 data) could be achieved from bioenergy recovery through biogas Electricity generation (million MWh) 172 (A) Bioenergy Systems for the Future 98.8a 100 a 87.7 Electricity generation (AD) 75 Total recoverable energy (AD) 50 32.6b 25 27.7 b 19.4 11.9 100 13.6% 12.0% AD contributionc (%) 36.5% 75 61.3% 50 25 Itaipu Damd (B) Three Gorges Damd Total thermoelectricity Exported generatione thermoelectricity Fig 5.4 Bioenergy generation from biogas compared with hydro- (Itaipu and Three Gorges Dam) and thermoelectric (bagasse burning) sources: (A) Overall energy production and (B) electric power replacement potential for biogas References/Notes: aItaipu Binacional (2014); bUNICA (2016); cIn terms of electricity generation; dItaipu Binacional (2014); eTotal thermoelectricity generation includes total amounts of both self-consumed (13.2 Â 106 MWh) and exported electricity to grid (19.4 Â 106 MWh) in Brazilian sugarcane-based biorefineries in 2014 (UNICA, 2016) (Fig 5.4), increasing revenues with bioelectricity sales In terms of the total thermoelectricity production from bagasse, which includes both self-consumed and exported amounts, the observed increment could reach almost 40% (Fig 5.4) Finally, the economic feasibility of implementing AD systems in large-scale distilleries could be confirmed, regardless of the process, that is, autonomous or annexed plants Fig 5.5 summarizes data obtained for the economic assessment, including investment costs and IRR and NPV values Although higher investment costs were estimated for the installation of both AD treatment and power plants in autonomous distilleries (52.34 vs 48.48 USD million, Fig 5.5), an overall analysis indicated better scenarios for such a case compared with annexed schemes, based on higher IRR and NPV values (12.36% vs 11.51% and 17.00 vs 11.86 USD million, respectively, Fig 5.5) and a slightly lower discounted payback time (11.0 vs 12.6 years) The Anaerobic biodigestion of vinasse for enhanced bioenergy generation 12.36% AD system Power plant IRR MRA 13 12 60 11.51% $24.64 45 11 $21.25 10 30 $27.70 IRR (%) Investment (million USD) 75 173 $27.18 15 8.76% (A) Autonomous distillery Annexed distillery 30 NPV (million USD) 15 10 12 –15 14 16 18 20 22 24 26 Project lifetime (year) –30 Autonomous distillery –45 Annexed distillery (B) –60 Fig 5.5 Economic assessment for the implementation of AD systems in autonomous and annexed sugarcane-based distilleries: (A) investment costs and internal rate of return (IRR) and (B) net present value (NPV) Note: MRA, minimum rate of attractiveness observed differences are due to the better performance in terms of methane production in AD systems applied to sugarcane juice, leading to a higher annual revenue with electricity sales in autonomous plants (13.37 vs 11.53 USD million) Such values offset the higher investment and operating costs (respectively, 52.34 USD million and 3.23 USD million per year) estimated for autonomous plants It is important highlighting that the economic assessment considered only incomes obtained with the sales of electricity generated from biogas, that is, revenues from ethanol and sugar sales were not included Therefore, the scenarios observed indicate that AD power plants applied to sugarcane vinasse may economically self-sustain regardless of the process type, reinforcing the application of AD as a suitable approach as the core treatment technology in distilleries The literature may be considered scarce in terms of economic data regarding the installation of AD plants in distilleries Moreover, reported data depend strictly on the reference values assumed in estimates, such as ethanol and vinasse production rates and economic parameters, leading to a considerable wide range of values 174 Bioenergy Systems for the Future Nevertheless, a few cases should be considered for referencing purposes Based on the US corn-to-ethanol industry, Schaefer and Sung (2008) indicated that bioenergy recovery from biogas could lead to savings of about 10 USD million in plants with annual ethanol productions of 360 Â 106 l Such value is quite similar to the ones obtained for electricity annual revenues in this study (13.37 vs 11.53 USD million), despite the different assumptions considered in each case In turn, Nandy et al (2002) indicated annual savings of about 460,000 USD in molasses-based distilleries (90 m3EtOH dayÀ1) due to reductions in fuel oil consumption, based on the generation of thermal energy from biogas burning in boilers Particularly, this study is characterized as one of the few cases reporting data from full-scale AD systems applied to vinasse, considering the operation of two 4500 m3 fixed-bed digesters producing about 13.8–14.8 Â 103 m3 of biogas ($60%–65% of methane) per day Considering the Brazilian case, Nogueira et al (2015) estimated an installation cost of about 2.12 USD million for an AD power plant with capacity to generate MW of electricity The installation cost reported by such authors is proportional to the values obtained herein; as for power capacities of 22–25 MW, the estimated cost increased by a factor of about 23–24, reaching 48.48–52.34 USD million (Fig 5.5) 5.5 Outlook: Prospects for AD as the core treatment technology in ethanol plants Results obtained herein clearly highlight the potential of vinasse as a biofuel in ethanol distilleries, also characterizing the suitability of AD as the core treatment approach in such plants However, a few restrictions still hinder the implementation of full-scale treatment systems for bioenergy recovery from vinasse, as reference/comparative data on such type of large-scale operation may be considered scarce Although the literature concentrates a considerable number of studies exploring the potentials of anaerobic processes applied to vinasses from various feedstocks since the 1970s, useful data on the application of full-scale digesters to vinasse may be found only in a few cases, such as in the study of Nandy et al (2002), as previously highlighted in Section 5.4.3 In this context, prospects for implementing AD systems in distilleries in the short-term are based mainly on two approaches, including initially the conduction of studies to define adequate operating conditions for each type of vinasse Published data should be used to direct such studies, providing a kickoff to define the conditions tested in each case in a systematic and organized way Such step should also include a complete compositional characterization of vinasse, which is imperative to measure potentials and drawbacks of the processes Although vinasses present common characteristics, with high organic matter and acidity levels, particular aspects resulting from specific raw materials and processing steps may lead to different responses of AD systems, such as a fast acidification potential in sugar-rich streams and enhanced sulfide generation in processes coupled to sugar production Simultaneously to such fundamental investigations, energetic assessments through estimates and/or simulation based-studies are also required in the short term, providing decision makers of the ethanol production sector with critical information on the Anaerobic biodigestion of vinasse for enhanced bioenergy generation 175 available approaches for bioenergy recovery from biogas in distilleries In addition to electricity generation, biogas streams obtained from vinasse AD may be directed to different uses, such as diesel replacement in automotive engines (Souza et al., 2012; Moraes et al., 2014), thermal energy production from biogas burning in boilers (Nandy et al., 2002; Salomon et al., 2011; Moraes et al., 2014) and direct injection into natural gas grids as biomethane, that is, purified biogas (Moraes et al., 2015) Particularly, Moraes et al (2014) indicated that diesel replacement could be a more profitable alternative for the use of biogas in distilleries compared with electricity production in engines and cogeneration of electricity and heat in industrial boilers However, among the potential uses for biogas, electricity production seems to maximize its exploitation in ethanol plants, based on the technological development associated to available prime movers and also on the relatively simple infrastructure for electricity sales, which already exist in most Brazilian sugarcane-based distilleries Some recent studies also bring relevant estimates on scenarios for bioenergy recovery from vinasse in the Brazilian sugarcane-to-ethanol (Salomon and Lora, 2009; Salomon et al., 2011; Moraes et al., 2014) and US corn-to-ethanol (Agler et al., 2008; Schaefer and Sung, 2008; Lee et al., 2011) industries Nandy et al (2002) and Barrera et al (2016) also reported critical studies regarding options for the management of vinasse using AD as the core treatment step, discussing perspectives, respectively, for the Indian and Cuban ethanol industries The association between data from both experimental investigations and scenario prediction should enable designing robust anaerobic treatment plants in the long term, ideally leading to an efficient exploitation of vinasse as a bioenergy source The accumulated knowledge on anaerobic processes observed in recent years, regarding especially the advances on microbiological aspects, must also be considered to support the implementation of full-scale systems in distilleries In addition to scientific aspects, a few considerations regarding environmental and financial factors should be considered, using the Brazilian sugarcane-to-ethanol sector as reference The proved polluting potential of vinasse should be used as a guide to more restrictive laws in terms of its proper management, defining criteria for both treatment and disposing (fertirrigation) systems (Fuess and Garcia, 2014) In short, restrictions in application dosages, especially in terms of organic matter, would naturally lead to the implementation of treatment systems in distilleries, in an effort to comply with environmental adequacy In turn, financial incentives from the government also constitute essential aspects to enhance the attractiveness of implementing AD plants in distilleries (Salomon and Lora, 2009; Moraes et al., 2015), based on subsides and funding programs mainly to reduce investment costs and provide a higher profitability from bioenergy sales According to Salomon and Lora (2009), the lack of a national biogas program and difficulties associated to the commercialization of carbon credits are two of the main limitations for the dissemination of anaerobic processes as an attractive choice for the management of vinasse within the ethanol industry Such aspects are imperative to characterize the technical and economic feasibility of AD compared with fertirrigation, also considering the environmental benefits and the energy recovery capacity associated to the process, as discussed in detail in this study 176 Bioenergy Systems for the Future Finally, considering a wider analysis, anaerobic processes are fully inserted into the concept of biorefineries, which are based on the conversion of a given raw material into a wide range of value-added products, such as chemicals and biofuels, and direct generation of energy (Poggi-Varaldo et al., 2014; Moraes et al., 2015) Compared with other available approaches, AD enables a more efficient use of raw materials, as the treatment plants may be characterized as additional feedstock processing steps to enhance energy extraction from residual organic compounds Recent studies also discuss on the feasibility of obtaining value-added bioproducts—for example, biohydrogen, organic acids, and biopolymers—from AD through the decoupling between the acidogenic and methanogenic phases of the process, which will greatly enhance resource recovery within the plants (Poggi-Varaldo et al., 2014) Such aspects justify the interests on the application of AD to residual streams from biofuel industries, in an effort to enhance the energy balance ratio and the profitability of the processes 5.6 Concluding remarks The detailed energetic assessment presented herein confirms the suitability of anaerobic processes as the core step for vinasse management in ethanol plants, regardless of the feedstock considered Bioenergy generation from biogas could fully supply sugarcane-based plants, whereas for corn- and cassava-based processes, reductions of about 30%–35% in the total fossil energy consumption could be achieved The expressive suitability for bioenergy recovery from residual solid (bagasse) and liquid (vinasse) streams explains the more favorable energetic scenarios observed for sugarcane-based processes Nevertheless, in terms of the energy balance for ethanol production, the recovered energy from biogas could enhance the energetic output of starch-based processes by over 30% (0.83–1.11 and 1.22–1.59, respectively, for corn and cassava), leading to energetically self-sustaining production chains in the case of the corn-to-ethanol industry Focusing on the sugarcane-to-ethanol industry, results confirmed the economic feasibility of implementing AD systems in large-scale distilleries, with slightly better results for autonomous plants due to the better performance in terms of methane production from sugarcane juice compared with blends of juice and molasses Annual revenues with electricity sales could reach over 10 USD million in both autonomous and annexed distilleries Comparatively to fertirrigation, the application of AD to vinasse could have prevented an energy loss of about 12 million MWh in the 2014/2015 Brazilian sugarcane harvesting period, which corresponds to almost 15% of the hydroelectricity generated from Itaipu Dam in the referred period Such expressive values characterize some of the several advantages of implementing anaerobic processes as the core treatment steps in ethanol plants, so that vinasse may be characterized as a highly energetic biofuel Acknowledgments The authors are grateful to the Sa˜o Paulo Research Foundation (FAPESP), grant number 2010/04101-8, and to the Brazilian National Council for Scientific and Technological Development (CNPq), grant 470010/2013-4, for supporting the development of this study Anaerobic biodigestion of vinasse for enhanced bioenergy generation 177 References Agler, M.T., Garcia, M.L., Lee, E.S., Schlicher, M., Angenent, L.T., 2008 Thermophilic anaerobic digestion to increase the net energy balance of corn grain ethanol Environ Sci Technol 42, 6723–6729 Akram, M., Tan, C.K., Garwood, R., Thai, S.M., 2015 Vinasse—a potential biofuel—cofiring with coal in a fluidised combustor Fuel 158, 1006–1015 Alkan-Ozkaynak, A., Karthikeyan, K.G., 2011 Anaerobic digestion of thin stillage for energy recovery and water reuse in ethanol plants Bioresour Technol 102, 9891–9896 Andalib, M., Hafez, H., Elbeshbishy, E., Nakhla, G., Zhu, J., 2012 Treatment of thin stillage in a high-rate anaerobic fluidized bed reactor (AFBR) Bioresour Technol 121, 411–418 Asaithambi, P., Susree, M., Saravanathamizhan, R., Matheswaran, M., 2012 Ozone assisted electrocoagulation for the treatment of distillery effluent Desalination 297, 1–7 Barrera, E.L., Rosa, E., Spanjers, H., Romero, O., De Meester, S., Dewulf, J., 2016 A comparative assessment of anaerobic digestion power plants as alternative to lagoons for vinasse treatment: life cycle assessment and exergy analysis J Clean Prod 113, 459–471 Barth, D., Monteiro, A.R.S., Costa, M.M., Virkaj€arvi, I., Sacon, V., Wilhelmsom, A., 2014 DesinFix TM 135 in fermentation process for bioethanol production Braz J Microbiol 45, 323–325 Binacional, Itaipu, 2014 Relato´rio de sustentabilidade—2014 Sustainability report—2014 (in Portuguese) https://www.itaipu.gov.br/sites/default/files/RS-2014-Port-2.pdf (Accessed 11 December 2015) BNDES, CGEE, 2008 Bioetanol de cana-de-ac¸u´car: energia para o desenvolvimento sustenta´vel (Bioethanol from sugarcane: energy for sustainable development), first ed BNDES, Rio de Janeiro (in Portuguese) Boddey, R.M., Soares, L.H.B., Alves, B.J.R., Urquiaga, S., 2008 Bioethanol production in Brazil In: Pimentel, D (Ed.), Biofuels, Solar, and Wind as Renewable Energy Systems Springer, Netherlands, pp 321–356 Boopathy, R., Tilche, A., 1991 Anaerobic digestion of high strength molasses wastewater using hybrid anaerobic baffled reactor Water Res 25, 785–790 Bories, A., Raynal, J., Bazile, F., 1988 Anaerobic digestion of high-strength distillery wastewater (cane molasses stillage) in a fixed-film reactor Biol Waste 23, 251–267 Borzacconi, L., Lo´pez, I., Vin˜as, M., 1995 Application of anaerobic digestion to the treatment of agroindustrial effluents in Latin America Water Sci Technol 32 (12), 105–111 Braun, R., Huss, S., 1982 Anaerobic filter treatment of molasses distillery slops Water Res 16, 1167–1171 Callander, I.J., Clark, T.A., Mcfarlane, P.N., 1986 Anaerobic digestion of stillage from a pilot scale wood-to-ethanol process: II Laboratory-scale digestion studies Environ Technol Lett 7, 397–412 Callander, I.J., Clark, T.A., Mcfarlane, P.N., 1987 Anaerobic digestion of wood ethanol stillage using upflow anaerobic sludge blanket reactor Biotechnol Bioeng 30, 896–908 Camiloti, P.R., Mockaitis, G., Rodrigues, J.A.D., Damianovic, M.H.R.Z., Foresti, E., Zaiat, M., 2014 Innovative anaerobic bioreactor with fixed-structured bed (ABFSB) for simultaneous sulfate reduction and organic matter removal J Chem Technol Biotechnol 89, 1044–1050 Cassidy, D.P., Hirl, P.J., Belia, E., 2008 Methane production from ethanol co-products in anaerobic SBRs Water Sci Technol 58, 789–793 178 Bioenergy Systems for the Future Cavallet, O., Junqueira, T.L., Dias, M.O.S., Jesus, C.D.F., Matelatto, P.E., Cunha, M.P., Franco, H.C.J., Cardoso, T.F., Maciel Filho, R., Rossell, C.E., Bonomi, A., 2012 Environmental and economic assessment of sugarcane first generation biorefineries in Brazil Clean Techn Environ Policy 14, 399–410 Chen, Y., Cheng, J.J., Creamer, K.S., 2008 Inhibition of anaerobic digestion process: a review Bioresour Technol 99, 4044–4064 Cheng, K.Y., Ho, G., Cord-Ruwisch, R., 2012 Energy-efficient treatment of organic wastewater streams using a rotatable bioelectrochemical contactor (RBEC) Bioresour Technol 126, 431–436 Chernicharo, C.A.L., 2007 Anaerobic reactors IWA Publishing, London CONAB, 2011 A gerac¸a˜o termoeletrica com a queima bagac¸o de cana-de-ac¸u´car no Brasil: ana´lise desempenho da safra 2009-2010 (Thermoelectric generation from sugarcane bagasse burning in Brazil: performance assessment of the 2009/2010 harvesting CONAB, Brası´lia (in Portuguese) http://www.conab.gov.br/OlalaCMS/uploads/arquivos/ 11_05_05_15_45_40_geracao_termo_baixa_res.pdf (Accessed 26 May 2015) CONAB, 2015 Acompanhamento da safra brasileira: cana-de-ac¸u´car (Monitoring of the Brazilian crop: sugarcane) fourth survey, April/2015, CONAB, Brası´lia (in Portuguese) http://www conab.gov.br/OlalaCMS/uploads/arquivos/15_04_13_08_49_33_boletim_cana_portugues 1o_lev_-_15-16.pdf (Accessed 08 February 2016) Costa, F.J.C.B., Rocha, B.B.M., Viana, C.E., Toledo, A.C., 1986 Utilization of vinasse effluents from an anaerobic reactor Water Sci Technol 18 (12), 135–141 Craveiro, A.M., Soares, H.M., Schmidell, W., 1986 Technical aspects and cost estimations for anaerobic systems treating vinasse and brewery/soft drink wastewaters Water Sci Technol 18 (12), 123–134 Dai, D., Hu, Z., Pu, G., Li, H., Wang, C., 2006 Energy efficiency and potentials of cassava fuel ethanol in Guangxi region of China Energy Convers Manag 47, 1686–1699 de Bazu´a, C.D., Cabrero, M.A., Poggi, H.M., 1991 Vinasses biological treatment by anaerobic and aerobic processes: laboratory and pilot-plant tests Bioresour Technol 35, 87–93 Dias, M.O.S., Cunha, M.P., Jesus, C.D.F., Rocha, G.J.M., Pradella, J.G.C., Rossell, C.E.V., Maciel Filho, R., Bonomi, A., 2011 Second generation ethanol in Brazil: can it compete with electricity production? Bioresour Technol 102, 8964–8971 Dias, M.O.S., Junqueira, T.L., Jesus, C.D.F., Rossell, C.E.V., Maciel Filho, R., Bonomi, A., 2012 Improving bioethanol production – comparison between extractive and low temperature fermentation Appl Energy 98, 548–555 Dias, M.O.S., Junqueira, T.L., Cavalett, O., Pavanello, L.G., Cunha, M.P., Jesus, C.D.F., Maciel Filho, R., Bonomi, A., 2013 Biorefineries for the production of first and second generation ethanol and electricity from sugarcane Appl Energ 109, 72–78 DOE, 2016 Alternative fuels data center: global ethanol production US Department of Energy, Energy Efficiency & Renewable Energy http:\\www.afdc.gov/data/10331 (Accessed 11 January 2016) Driessen, W., Tielbaard, M.H., Vereijken, T.L.F.M., 1994 Experience on anaerobic treatment of distillery effluent with the UASB process Water Sci Technol 30 (12), 193–201 EIA, 2015 Monthly energy review, December 2015 DOE/EIA-0035(2015/12) US Energy Information Administration, Washington, DC http://www.eia.gov/totalenergy/data/ monthly/pdf/mer.pdf (Accessed 11 January 2016) EPE, 2014 Anua´rio estatı´stico de energia eletrica 2014—ano base 2013 (2014 Statistical yearbook of electricity—2013 baseline year) EPE, Rio de Janeiro http://www.epe.gov.br/ AnuarioEstatisticodeEnergiaEletrica/Anu%C3%A1rio%20Estat%C3%ADstico%20de% 20Energia%20El%C3%A9trica%202014.pdf (Accessed 11 January 2016) Anaerobic biodigestion of vinasse for enhanced bioenergy generation 179 Espan˜a-Gamboa, E., Mijangos-Cortes, J., Barahona-Perez, L., Dominguez-Maldonado, J., Herna´ndez-Zarate, G., Alzate-Gaviria, L., 2011 Vinasses: characterization and treatments Waste Manag Res 29, 1235–1250 Ferraz Jr., A.D.N., Wenzel, J., Etchebehere, C., Zait, M., 2014 Effect of organic loading rate on hydrogen production from sugarcane vinasse in thermophilic acidogenic packed bed reactors Int J Hydrogen Energy 39, 16852–16862 Ferraz Jr., A.D.N., Koyama, M.H., Arau´jo Jr., M.M., Zaiat, M., 2016 Thermophilic anaerobic digestion of raw sugarcane vinasse Renew Energy 89, 245–252 Ferreira, L.F.R., Aguiar, M.M., Messias, T.G., Pompeu, G.B., Lopez, A.M.Q., Silva, D.P., Monteiro, R.T., 2011 Evaluation of sugac-cane vinasse treated with Pleurotus sajor-caju utilizing aquatic organisms as toxicological indicators Ecotox Environ Safe 74, 132–137 Fuess, L.T., Garcia, M.L., 2014 Implications of stillage land disposal: a critical review on the impacts of fertigation J Environ Manag 145, 210–229 Good, P., Moudry, R., Fluri, P., 1982 Use of fixed film and CSTR reactor for anaerobic treatment of stillage of wood hydrolysate Biotechnol Lett 4, 595–600 Goyal, S.K., Seth, R., Handa, B.K., 1996 Diphasic fixed-film biomethanation of distillery spent wash Bioresour Technol 56, 239–244 Graboski, M.S., 2002 Fossil energy use in the manufacture of corn ethanol Prepared for the US National Corn Growers Association http://www.oregon.gov/energy/P-I/Biomass/docs/ FORUM/FossilEnergyUse.pdf (Accessed 15 June 2015) Heywood, J.B., 1988 Internal combustion engine fundamentals, first ed McGraw-Hill, New York Hill, J., Nelson, E., Tilman, D., Polasky, S., Tiffany, D., 2006 Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels Proc Natl Acad Sci U S A 103, 11206–11210 Kaparaju, P., Serrano, M., Angelidaki, I., 2010 Optimization of biogas production from wheat straw stillage in UASB reactor Appl Energ 87, 3779–3783 Khan, A.S., Fox, R.W., 1982 Net energy analyses of ethanol production from sugarcane in Northeast Brazil Biomass 2, 213–221 Khanal, S.K., 2008 Anaerobic biotechnology for bioenergy production: principles and applications, first ed Blackwell Publishing, New Delhi Kim, S., Dale, B.E., 2005 Environmental aspects of ethanol derived from no-tilled corn-grain: nonrenewable energy consumption and greenhouse gas emissions Biomass Bioenerg 28, 475–489 Lamonica, H.M., 2007 Produc¸a˜o de vapor e eletricidade – a evoluc¸a˜o setor sucroalcooleiro (Production of steam and electricity – the evolution of the sucro-alcohol sector) In: II Workshop de Gesta˜o de Energia e Resı´duos na Agroindu´stria Sucroalcooleira.12-13 June 2007, Pirassununga, SP, Brazil Lavigne, A., Powers, S.E., 2007 Evaluating fuel ethanol feedstocks from energy policy perspectives: a comparative energy assessment of corn and corn stover Energ Policy 35, 5918–5930 Le, L.T., van Ierland, E.C., Zhu, X., Wesseler, J., 2013 Energy and greenhouse gas balances of cassava-based ethanol Biomass Bioenerg 51, 125–135 Lee, P.H., Bae, J., Kim, J., Chen, W.H., 2011 Mesophilic anaerobic digestion of corn thin stillage: a technical and energetic assessment of the corn-to-ethanol industry integrated with anaerobic digestion J Chem Technol Biotechnol 86, 1514–1520 Leng, R., Wang, C., Zhang, C., Dai, D., Pu, G., 2008 Life cycle inventory and energy analysis of cassava-based fuel ethanol in China J Clean Prod 16, 374–384 Lens, P.N.L., Visser, A., Janssen, A.J.H., Hulshoff Pol, L.W., Lettinga, G., 1998 Biotechnological treatment of sulfate-rich wastewaters Crit Rev Environ Sci Tec 28 (1), 41–88 180 Bioenergy Systems for the Future Liu, B., Wang, F., Zhang, B., Bi, J., 2013 Energy balance and GHG emissions of cassava-based fuel ethanol using different planting modes in China Energ Policy 56, 210–220 Luo, G., Xie, L., Zhou, Q., 2009 Enhanced treatment efficiency of an anaerobic sequencing batch reactor (ASBR) for cassava stillage with high solids content J Biosci Bioeng 107, 641–645 Luo, G., Xie, L., Zou, Z., Wang, W., Zhou, Q., Shim, H., 2010 Anaerobic treatment of cassava stillage for hydrogen and methane production in continuously stirred tank reactor (CSTR) under high organic loading rate (OLR) Int J Hydrogen Energy 35, 11733–11737 Luo, G., Xie, L., Zhou, Q., Angelidaki, I., 2011 Enhancement of bioenergy production from organic wastes by two-stage anaerobic hydrogen and methane production process Bioresour Technol 102, 8700–8706 Lutoslawski, K., Ryznar-Luty, A., Cibis, E., Krzywonos, M., Mis´kiewicz, T., 2011 Biodegradation of beet molasses vinasse by a mixed culture of micro organisms: effect of aeration conditions and pH control J Environ Sci 23, 1823–1830 Macedo, I.C., 1992 The sugar cane agro-industry – its contribution to reducing CO2 emissions in Brazil Biomass Bioenerg 3, 77–80 Macedo, I.C., 1998 Greenhouse gas emissions and energy balances in bio-ethanol production and utilization in Brazil (1996) Biomass Bioenerg 14, 77–81 Macedo, I.C., Seabra, J.E.A., Silva, J.E.A.R., 2008 Green house gases emissions in the production and use of ethanol from sugarcane in Brazil: the 2005/2006 averages and a prediction for 2020 Biomass Bioenerg 32, 582–595 Metcalf & Eddy, Inc., 2003 Wastewater engineering: treatment and reuse, fourth ed McGrawHill, Inc., New York Mohana, S., Acharya, B.K., Madamwar, D., 2009 Distillery spent wash: treatment technologies and potential applications J Hazard Mater 163, 12–25 Moraes, B.S., Junqueira, T.L., Pavanello, L.G., Cavalett, O., Mantelatto, P.E., Bonomi, A., Zaiat, M., 2014 Anaerobic digestion of vinasse from sugarcane biorefineries in Brazil from energy, environmental, and economic perspectives: profit or expense? Appl Energ 113, 825–835 Moraes, B.S., Zaiat, M., Bonomi, A., 2015 Anaerobic digestion of vinasse from sugarcane ethanol production in Brazil: challenges and perspectives Renew Sust Energ Rev 44, 888–903 Murphy, J.D., Power, N.M., 2008 How can we improve the energy balance of ethanol production from wheat? Fuel 87, 1799–1806 Nandy, T., Shastry, S., Kaul, S.N., 2002 Wastewater management in a cane molasses distillery involving bioresource recovery J Environ Manag 65, 25–38 Nasr, N., Elbeshbishy, E., Hafez, H., Nakhla, G., Hesham, M., El Naggar, M.H., 2011 Biohydrogen production from thin stillage using conventional and acclimatized anaerobic digester sludge Int J Hydrogen Energy 36, 12761–12769 Nguyen, T.L.T., Gheewala, S.H., Garivait, S., 2007a Energy balance and GHG-abatement cost of cassava utilization for fuel ethanol in Thailand Energ Policy 35, 4585–4596 Nguyen, T.L.T., Gheewala, S.H., Garivait, S., 2007b Full chain energy analysis of fuel ethanol from cassava in Thailand Environ Sci Technol 41, 4135–4142 Nguyen, T.L.T., Gheewala, S.H., Garivait, S., 2008 Full chain energy analysis of fuel ethanol from cane molasses in Thailand Appl Energ 85, 722–734 Nogueira, C.E.C., Souza, S.N.M., Micuanski, V.C., Azevedo, R.L., 2015 Exploring possibilities of energy insertion from vinasse biogas in the energy matrix of Parana´ State Brazil Renew Sust Energy Rev 48, 300–305 Anaerobic biodigestion of vinasse for enhanced bioenergy generation 181 Oliva-Neto, P., Dorta, C., Carvalho, A.F.A., Lima, V.M.G., Silva, D.F., 2013 The Brazilian technology of fuel ethanol fermentation—yeast inhibition factors and new perspectives to improve the technology In: Mendez-Vilas, A (Ed.), Materials and Processes for Energy: Communicating Current Research and Technological Developments Formatex, Badajoz pp 371–379 Oliveira, M.E.D., Vaughan, B.E., Rykiel Jr., E.J., 2005 Ethanol as fuel: energy, carbon dioxide balances, and ecological footprint Bioscience 55, 593–602 Oliveira, B.G., Carvalho, J.L.N., Cerri, C.E.P., Cerri, C.C., Feigl, B.J., 2013 Soil greenhouse gas fluxes from vinasse application in Brazilian sugarcane areas Geoderma 200–201, 77–84 Palacio, J.C.E., Angarita, E.E.Y., Lora, E.E.S., Venturini, E.J., 2012 Cogerac¸a˜o a partir de resı´duos na indu´stria de biocombustı´veis: sucroalcooleira e de biodiesel (Cogeneration from residues in biofuel industry: sucro-alcohol and biodiesel) In: Lora, E.E.S., Ventnurini, O.J (Eds.), Biocombustı´veis Interci^encia, Rio de Janeiro, pp 811–895 (in Portuguese) Papong, S., Malakul, P., 2010 Life-cycle energy and environmental analysis of bioethanol production from cassava in Thailand Bioresour Technol 101, S112–S118 Pimentel, D., 2003 Ethanol fuels: energy balance, economics, and environmental impacts are negative Nat Resour J 12, 127–134 Pimentel, D., Patzek, T.W., 2005 Ethanol production using corn, switchgrass, and wood; biodiesel production using soybean and sunflower Nat Resour Res 14, 65–76 Pimentel, D., Patzek, T.W., 2008 Ethanol production: energy and economic issues related to US and Brazilian sugarcane In: Pimentel, D (Ed.), Biofuels, Solar and Wind as Renewable Energy Systems Springer, Netherlands, pp 357–371 Pimentel, D., Patzek, T.W., Cecil, G., 2007 Ethanol production: energy, economic, and environmental losses Rev Environ Contam Toxicol 189, 25–41 Poggi-Varaldo, H.M., Munoz-Paez, K.M., Escamilla-Alvarado, C., Robledo-Narva´ez, P.N., Ponce-Noyola, M.T., Calva-Calva, G., Rı´os-Leal, E., Galı´ndez-Mayer, J., EstradaVa´zquez, C., Ortega-Clemente, A., Rinderknecht-Seijas, N.F., 2014 Biohydrogen, biomethane and bioelectricity as crucial components of biorefinery of organic wastes: a review Waste Manage Res 32, 353–365 Prada, S.M., Guekezian, M., Sua´rez-Iha, M.E.V., 1998 Metodologia analı´tica para a determinac¸a˜o de sulfato em vinhoto (Analytical methodology for the determination of sulfate in vinasse) Quim Nova 21, 249–252 (in Portuguese) Prakash, R., Henham, A., Bhat, I.K., 1998 Net energy and gross pollution from bioethanol production in India Fuel 77, 1629–1633 Procknor, C., 2009 Energia eletrica a partir da vinhac¸a (Electric energy from vinasse) Revista da Sociedade dos Tecnicos Ac¸ucareiros e Alcooleiros Brasil (J Sugar Alcohol Tech Brazil Soc) Solutions plant (in Portuguese) http://www.unica.com br/opiniao/show.asp?msgCode¼{2FA3CE2B-6B5C-43E9-A64A-B1A71A491EEF} (Accessed 14 December 2015) Rodrigues, I.J., Fuess, L.T., Biondo, L., Santesso, C.A., Garcia, M.L., 2014 Coagulationflocculation of anaerobically treated sugarcane stillage Desalin Water Treat 52, 4111–4121 Salla, D.A., Furlaneto, F.P.B., Cabello, C., Kanthack, R.A.D., 2009 Avaliac¸a˜o energetica da produc¸a˜o de etanol utilizando como materia-prima a cana-de-ac¸u´car (Energy evaluation of the etanol production using as raw-material the sugar cane) Cienc Rural 39, 2516–2520 (in Portuguese) Salla, D.A., Furlaneto, F.P.B., Cabello, C., Kanthack, R.A.D., 2010a Estudo energetico da produc¸a˜o de biocombustı´vel a partir milho (Energetic study of ethanol production from the corn crops) Cienc Rural 40, 2017–2022 (in Portuguese) 182 Bioenergy Systems for the Future Salla, D.A., Furlaneto, F.P.B., Cabello, C., Kanthack, R.A.D., 2010b Ana´lise energetica de sistemas de produc¸a˜o de etanol de mandioca (Manihot esculenta Crantz) (Energetic analysis of the ethanol production systems of cassava (Manihot esculenta Crantz)) R Bras Eng Agric Ambiental 14, 444–448 (in Portuguese) Salomon, K.R., Lora, E.E.S., 2009 Estimate of the electric energy generating potential for different sources of biogas in Brazil Biomass Bioenerg 33, 1101–1107 Salomon, K.R., Lora, E.E.S., Rocha, M.H., del Omo, O.A., 2011 Cost calculations for biogas from vinasse biodigestion and its energy utilization Sugar Ind 136, 217–223 Sangave, P.C., Gogate, P.R., Pandit, A.B., 2007 Combination of ozonation with conventional aerobic oxidation for distillery wastewater treatment Chemosphere 68, 32–41 Schaefer, S.H., Sung, S., 2008 Retooling the ethanol industry: thermophilic anaerobic digestion of thin stillage for methane production and pollution prevention Water Environ Res 80, 101–108 Shapouri, H., Duffield, J.A., Graboski, M.S., 1995 Estimating the net energy balance of corn ethanol Agricultural Economic Report 721, US Department of Agriculture, Washington, DC http://www.ers.usda.gov/media/926108/aer721.pdf (Accessed 26 May 2015) Shapouri, H., Duffield, J.A., Wang, M., 2003 The energy balance of corn ethanol revisited T ASAE 46, 959–968 Sheehan, G.J., Greenfield, P.F., 1980 Utilisation, treatment and disposal of distillery wastewater Water Res 14, 257–277 Silalertruksa, T., Gheewala, S.H., 2009 Environmental sustainability assessment of bio-ethanol production in Thailand Energy 34, 1933–1946 Siqueira, L.M., Damiano, E.S.G., Silva, E.L., 2013 Influence of organic loading rate on the anaerobic treatment of sugarcane vinasse and biogas production in fluidized bed reactor J Environ Sci Heal A 48 (13), 1707–1716 Sivaloganathan, P., Murugaiyan, B., Appavou, S., Dharmaraj, L., 2013 Effect of dilution of treated distillery effluent (TDE) on soil properties and yield of sugarcane AJPS 4, 1811–1814 Soam, S., Kumar, R., Gupta, R.P., Sharma, P.K., Tuli, D.K., Das, B., 2015 Life cycle assessment of fuel ethanol from sugarcane molasses in northern and western India and its impact on Indian biofuel programme Energy 83, 307–315 Soares, L.H.B., Alves, B.J.R., Urquiaga, S., Boddey, R.M., 2008 Balanc¸o energetico na produc¸a˜o de bioetanol de mandioca (Manihot esculenta Crantz) (Energy balance for bioethanol production from cassava (Manihot esculenta Crantz)) Embrapa Abrobiologia, Seropedica Circular Tecnica 23, (in Portuguese) Souza, M.E., Fuzaro, G., Polegato, A.R., 1992 Thermophilic anaerobic digestion of vinasse in pilot plant UASB reactor Water Sci Technol 25 (7), 213–222 Souza, S.N.M., Borsoi, A., Santos, R.F., Secco, D., Frigo, E., Silva, M.J., 2012 Production potential of biogas in sugar and etanol plants for use in urban buses in Brazil J Food Agric Environ 10 (1), 908–920 Stover, E.L., Gomathinayagam, G., Gonzalez, R., 1984 Use of methane gas from anaerobic treatment of stillage for fuel alcohol production In: Proceedings of the 39th Industrial Waste Conference 8-10 May 1984, West Lafayette, Indiana Ann Arbor Science/Boston Butterworth, Stoneham, MA, pp 57–63 Turdera, M.V., 2013 Energy balance, forecasting of bioelectricity generation and greenhouse gas emission balance in the ethanol production at sugarcane mills in the state of Mato Grosso Sul Renew Sust Energ Rev 19, 582–588 UNICA, 2016 A bioeletricidade da cana em nu´meros—fevereiro de 2016 (Bioelectricity from sugarcane in numbers—February 2016) UNICA, Sa˜o Paulo/Brası´lia http://www.unica com.br/download.php?idSecao¼17&id¼6703271 (Accessed 11 January 2016) Anaerobic biodigestion of vinasse for enhanced bioenergy generation 183 Vlissidis, A., Zouboulis, A.I., 1993 Thermophilic anaerobic digestion of alcohol distillery wastewaters Bioresour Technol 43, 131–140 von Sperling, M., 2007 Wastewater characteristics, treatment and disposal, first ed IWA Publishin, London Wang, W., Xie, L., Chen, J., Luo, G., Zhou, Q., 2011 Biohydrogen and methane production by co-digestion of cassava vinasse and excess sludge under thermophilic condition Bioresour Technol 102, 3833–3839 Westerholm, M., Hansson, M., Schn€urer, A., 2012 Improved biogas production from whole stillage by co-digestion with cattle manure Bioresour Technol 114, 314–319 Wilkie, A.C., 2008 Biomethane from biomass, biowaste and biofuels In: Wall, J.D., Harwood, C.S., Demain, A (Eds.), Bioenergy ASM Press, Washington, DC, pp 195–205 Wilkie, A.C., Riedesel, K.J., Owens, J.M., 2000 Stillage characterization and anaerobic treatment of ethanol stillage from conventional and cellulosic feedstocks Biomass Bioenerg 19, 63–102 Willington, I.P., Marten, G.G., 1982 Options for handling stillage waste from sugar-based fuel ethanol production Resour Conserv 8, 111–129 Worley, J.W., 1992 Energy analysis of ethanol production from sweet sorghum Bioresour Technol 40, 263–273 Yang, Q., Chen, G.Q., 2012 Nonrenewable energy cost of corn-ethanol in China Energ Policy 41, 340–347 Yang, Q., Chen, B., Ji, X., He, Y.F., Chen, G.Q., 2009 Exergetic evaluation of corn-ethanol production in China Commun Nonlinear Sci Numer Simulat 14, 2450–2461 Zayas, T., Romero, V., Salgado, L., Meraz, M., Morales, U., 2007 Applicability of coagulation/ flocculation and electrochemical processes to the purification of biologically treated vinasse effluent Sep Purif Technol 57, 270–276 ... substrates into more easily assimilable organic compounds, so that the fractions not uptaken by yeasts remain as residual organic compounds in vinasse Vinasses from Anaerobic biodigestion of vinasse. .. generation (m3 seasonÀ1) Annual organic polluting load—raw vinasse (tonCOD seasonÀ1) Equivalent population—raw vinasse (inhab) Annual avoided organic polluting loadtreated vinasse (tonCOD seasonÀ1)... difficulties associated to the commercialization of carbon credits are two of the main limitations for the dissemination of anaerobic processes as an attractive choice for the management of vinasse within