Sugarcane Stillage Research Articles

Reduction of sugarcane stillage generation through Heat-Integrated Distillation and Evaporation (HIDiE)

Sugarcane stillage, or vinasse, is the most voluminous byproduct generated in ethanol production, with an average volume ratio of 12:1. Fertigation is the simplest worldwide destination for stillage, but stricter environmental regulations require its distribution over wider areas to avoid soil oversaturation, demanding thus expensive transportation infrastructure. While reducing disposed stillage is critical, current concentration systems are inefficient and require additional energy (steam) and dedicated evaporators, which are prohibitively expensive for most installed industries. This study demonstrates, through performance comparisons with conventional distillation systems (CS), that a novel system, here denoted as HIDiE (Heat-Integrated Distillation and Evaporation), efficiently reduces the volume of stillage still during the stripping step, requiring no additional equipment and resulting in a leaner and cheaper approach. Process simulations in ASPEN Plus V11 software were used to validate premises using thermodynamic analysis and mass and energy balances. HIDiE produces significantly less stillage (1.7 - 7.8 m3/ m3ethanol) than CS (5.4 - 14.5 m3/ m3ethanol) under same steam consumption. Using HIDiE for wine with alcoholic grades ranging from 6 to 14 %v/v can result in gains of 45.7–69.3 %. This novel process concept contributes to the expansion of the economic radius for stillage fertigation, implying significant savings for the industry and the environment.

Multi-stage process for mixed microbial culture production of polyhydroxyalkanoates from sugarcane stillage: Assessment of external nutrient supplementation

Sugarcane stillage is an abundant wastewater from ethanol production. It has drawn considerable interest as a potential feedstock for biotechnological processes aiming at the recovery of energy and value-added products. In this study we explored the use of stillage for the production of polyhydroxyalkanoates (PHA), which are microbial bioplastics with potential to replace conventional plastics in specific applications. As stillage is nutrient deficient, we investigated the impact of external nutrient supplementation on the selection of PHA-producing mixed cultures. Cultures selected under four different total-chemical-oxygen-demand-to-nitrogen ratios (COD.t/N) (15, 30, 40 and 80) were evaluated according to their PHA production performance and microbial composition. The experimental results demonstrated that the most favorable PHA production was achieved for the biomass selected under strict carbon-limiting conditions, with a COD.t/N ratio of 15. This resulted in an overall PHA volumetric productivity of 2.10 g PHA L−1 d−1, a maximum intracellular PHA content of 0.65 g PHA g VSS−1 and a PHA storage yield of 0.71 g CODPHA g CODH.Org−1. The resulting PHA was a copolymer of 3-hydroxybutyrate (73 %mol) and 3-hydroxyvalerate (27 %mol) monomers. The microbial consortium was enriched by members of the Brevundimonas genus, known PHA producers, with a relative abundance of 26.4 %.

Removal of organic pollutants from sugarcane stillage using UV-assisted Fenton process

Stillage or distillery wastewater have been reported as industrial effluent that are difficult to be treated as its discharge in the water bodies presents contamination with recalcitrant and non-degradable pollutants. Due to their complicated structure, stillage treatment process using traditional methods such as adsorption, coagulation, and flocculation is challenging. Fenton reaction has been found as an effective method to degrade these contaminants through hydroxyl radicals. In this study, the removal of pollutants in stillage was investigated using UV-assisted Fenton process. Experiments was conducted for 60 minutes in a batch reactor with initial pH of stillage 4.5, UV lamp of 395-400 nm, and constant speed of 250 rpm, while the dosages of H2O2 and Fe (II) were kept constant at 3.3 g/L and 0.6 g Fe/L, respectively. The profile of chemical oxygen demand (COD) removal, pH, temperature, and oxidation-reduction potential (ORP) was evaluated under three dilution factors of raw stillage (1/10; 1/25; and 1/50) during treatment process to investigate the effects of these parameters on treatment efficiency. It has been observed that initial COD of stillage had considerable effect on the performance of UV-photo-Fenton treatment, as higher dilution factor increases the removal efficiency of COD from stillage. The degradation of COD by UV-assisted Fenton was found to be suitably described by the pseudo-first-order kinetics. The results obtained from this work indicated that UV-Fenton can be introduced as a successful advanced treatment process for efficient degradation of stillage.

Anaerobic digestion of vinasse in fluidized bed reactors: Process robustness between two-stage thermophilic-thermophilic and thermophilic-mesophilic systems

Two-stage anaerobic digestion (AD) is a solution for the biodegradation of complex wastes, but the best association of temperatures between acidogenesis and methanogenesis is unclear. Our study investigated whether it is best to associate a thermophilic acidogenic reactor with a thermophilic or a mesophilic methanogenic reactor and results were compared to single-stage AD. The effect of increasing the organic loading rate (OLR from 2.7 to 24.7 kg COD/m3/d) in thermophilic and mesophilic second-stage methanogenesis of two-stage AD was also assessed. A thermophilic acidogenic reactor (R2-H2-Thermo) treating sugarcane stillage fed thermophilic (R2-CH4-Thermo) and mesophilic (R2-CH4-Meso) methanogenic reactors. A single-stage methanogenic thermophilic reactor was used as control (R1-CH4-Thermo). Reactors R2-CH4-Thermo and R2-CH4-Meso showed similar performance at OLR of 2.7–13.3 kg COD/m3/d, but the latter achieved the highest methane production rate at 24.7 kg COD/m3/d (3.2 L CH4/d/L – 78% higher than R2-CH4-Thermo). The two-stage system (R2-H2-Thermo + R2-CH4-Meso) achieved the best energetic yield: 5.5 kJ/g COD, which was 41% higher than the single-stage system. Operation of a second-stage reactor at mesophilic temperature is the most suitable for vinasse AD due to its flexibility, robustness, and stability of CH4 production, even in situations of organic overload and accumulation of toxic components. Digestate at ambient temperature is also more adequate for fertirrigation.

Sugarcane Stillage Treatment Using Direct Contact Membrane Distillation

Direct contact membrane distillation (DCMD) was evaluated as an alternative for the treatment of sugarcane stillage obtained in the bioethanol production process. First, a synthetic stillage solution was prepared in order to study the influence of the main operational parameters of DCMD in the permeate flux, as well as to analyze the separation of volatile components (such as ethanol and acetic acid) and the concentration of non-volatile components presented in the feed stream (sucrose and other salts). Secondly, an industrial sample of sugarcane stillage was treated using DCMD. The highest flux achieved was 13.4 kg/m2·h for a transmembrane temperature difference of 55 °C, reaching a recovery degree of 70% with a specific thermal energy consumption of 671 kWh/m3. Then, sugarcane stillage was concentrated until 60°Brix. A preliminary economic study was also presented, an estimated cost of 1.25 $ per m3 of recovered permeate was obtained without any heat integration or DCMD operational optimization. DCMD showed to be suitable for stillage disposal allowing to recuperate the permeate stream as process water (containing mainly water and a low concentration of volatile components) and the concentrated stillage as biofuel to be used in the steam boiler (for producing more energy making the process thermally sustainable) or for ferti-irrigation (for reducing the transportation cost due to the volume reduction).

Aconitic acid recovery from sugar-cane stillage: From the modeling of the anion-exchange step to the conception of a novel combined process

ABSTRACT Sugarcane stillage is rich in tri-carboxylic aconitic acid. To study its purification through anion-exchange, selectivity coefficients between aconitate and the major competing minerals were determined on a weak-base resin for different pH. Simulation of solutes separation in the column, using mass conservation equations and equilibrium theory, confirmed that resin in sulfate form and pH = 4.5 led to the best separation performances, and showed that a preliminary chloride removal up to 0.5 g L−1 was the most profitable to increase the ionic exchange capacity for aconitic acid. Demineralization of a real stillage by conventional electrodialysis followed by the optimized ion-exchange step led to an aconitic acid-rich extract.

Effects of the Organic Loading Rate on Polyhydroxyalkanoate Production from Sugarcane Stillage by Mixed Microbial Cultures.

Stillage is an abundant wastewater from the sugarcane ethanol industry. It is rich in fermentable substrates and presents low-nutrient content, constituting a promising substrate for polyhydroxyalkanoate (PHA) production by mixed microbial cultures (MMC). This work assessed the enrichment of a PHA-accumulating MMC from acidified sugarcane stillage in a sequencing batch reactor under increasing organic loading rates (OLR) and no external nutrient supplementation. The OLR was increased from 1.0 to 7.1kg COD m-3day-1 in four steps. A PHA-producing MMC with high storage response was selected in all experimental conditions. The volumetric biomass productivity and the maximal PHA storage capacity increased continuously with the OLR, reaching 0.061g VSS L-1h-1 and 0.49g PHA g VSS-1, respectively. The highest observed PHA storage yield (0.60g CODPHA g COD.t-1) and specific PHA storage rate (0.169g CODPHA g of CODX h-1) were obtained for the OLR of 4.5kg COD m-3day-1. The PHA produced was a co-polymer of 3-hydroxybutyrate (86-77%mol) and 3-hydroxyvalerate (14-23%mol). The performance of the biomass enrichment was comparable to those attained with other agro-industrial wastewaters, indicating the potential of acidified sugarcane stillage as a feedstock for MMC PHA production.

Improvement of Sugarcane Stillage (Vinasse) Anaerobic Digestion with Cheese Whey as its Co-substrate: Achieving High Methane Productivity and Yield.

This study investigated methane production in an anaerobic sequencing batch biofilm reactor (AnSBBR) by co-digesting sugarcane vinasse and cheese whey. The assessment was based on the influence of feed strategy, interaction between cycle time and influent concentration, applied volumetric organic load (OLRA), and temperature over system stability and performance. The system showed flexibility with regard to the feed strategy, but the reduction of cycle time and influent concentration, at the same OLRA, resulted in lower methane productivity. Increasing organic load, up to the value of 15.27gCODL-1day-1, favored the process, increasing methane yield and productivity. Temperature reduction from 30 to 25°C resulted in worse performance, although increasing it to 35°C provided similar results to 30°C. The best results were achieved at an OLRA of 15.27gCODL-1day-1, cycle time of 8h, fed-batch operation, and temperature of 30°C. The system achieved soluble COD removal efficiency of 89%, methane productivity of 208.5molCH4m-3day-1 and yield of 15.76mmolCH4gCOD-1. The kinetic model fit indicated methanogenesis preference for the hydrogenotrophic route. At the industrial scale estimative, considering a scenario with a sugarcane ethanol plant with ethanol production of 150,896m3year-1, it was estimated energy production of 25,544MWhmonth-1.

Thermophilic hydrogen and methane production from sugarcane stillage in two-stage anaerobic fluidized bed reactors

This study evaluated the feasibility of H2 and CH4 production in two-stage thermophilic (55 °C) anaerobic digestion of sugarcane stillage (5,000 to 10,000 mg COD.L−1) using an acidogenic anaerobic fluidized bed reactor (AFBR-A) with a hydraulic retention time (HRT) of 4 h and a methanogenic AFBR (AFBR-S) with HRTs of 24 h–10 h. To compare two-stage digestion with single-stage digestion, a third methanogenic reactor (AFBR-M) with a HRT of 24 h was fed with increasing stillage concentrations (5,000 to 10,000 mg COD.L−1). The AFBR-M produced a methane content of 68.4 ± 7.2%, a maximum yield of 0.30 ± 0.04 L CH4.g COD−1, a production rate of 3.78 ± 0.40 L CH4.day−1.L−1 and a COD removal of 73.2 ± 5.0% at an organic loading rate (OLR) of 7.5 kg COD.m−3.day−1. In contrast, the two-stage AFBR-A system produced a hydrogen content of 23.9 ± 5.6%, a production rate of 1.30 ± 0.16 L H2.day−1.L−1 and a yield of 0.34 ± 0.08 mmol H2.g CODap−1. Additionally, the decrease in the HRT from 18 h to 10 h in the AFBR-S favored a higher methane production, improving the maximum methane content (74.5 ± 6.0%), production rate (5.57 ± 0.38 L CH4.day−1.L−1) and yield (0.26 ± 0.06 L CH4.g COD−1) at an OLR of 21.6 kg COD.m−3.day−1 (HRT of 10 h) with a total COD removal of 70.1 ± 7.1%. Under the applied COD of 10,000 mg L−1, the two-stage system showed a 52.8% higher energy yield than the single-stage anaerobic digestion system. These results show that, relative to a single-stage system, two-stage anaerobic digestion systems produce more hydrogen and methane while achieving similar treatment efficiencies.

Viability of Using Glycerin as a Co-substrate in Anaerobic Digestion of Sugarcane Stillage (Vinasse): Effect of Diversified Operational Strategies

Vinasse, from sugar and ethanol production, stands out as one of the most problematic agroindustry wastes due to its high chemical oxygen demand, large production volume, and recalcitrant compounds. Therefore, the viability of using glycerin as a co-substrate in vinasse anaerobic digestion was tested, to increase process efficiency and biogas productivity. The effect of feeding strategy, influent concentration, cycle length, and temperature were assessed to optimize methane production. Glycerin (1.53% v/v) proved to be a good co-substrate since it increased the overall methane production in co-digestion assays. CH4 productivity enhanced exponentially as influent concentration increased, but when temperature was increased to 35°C, biogas production was impaired. The highest methane productivity and yield were achieved using fed-batch mode, at 30°C and at an organic loading rate of 10.1kgCODm-3day-1: 139.32molCH4m-3day-1, 13.86molCH4kgCODapplied, and 15.30molCH4kgCODremoved. Methane was predominantly produced through the hydrogenotrophic route. In order to treat all the vinasse produced by a mid-size sugar and ethanol plant, nine reactors with 7263.4m3 each would be needed. The energy generated by burning the biogas in boilers would reach approximately 92,000MWh per season and could save up to US$ 240,000.00 per month in diesel oil demand.

Methane Production by Co-Digesting Vinasse and Whey in an AnSBBR: Effect of Mixture Ratio and Feed Strategy.

The most common approach to deal with vinasse (sugarcane stillage) is fertigation, but this technique compromises soil structure and surrounding water bodies. A possible solution is to transport vinasse to local cheese whey producers and perform the co-digestion of these wastewaters together, reducing their organic load and generating bioenergy. Therefore, this study investigated the application of an AnSBBR (anaerobic sequencing batch biofilm reactor) operated in batch and fed-batch mode, co-digesting vinasse and whey at 30°C. The effect of influent composition and feeding strategy was assessed. In all conditions, the system achieved high organic matter removal (approximately 83%). Increasing the percentage of vinasse from 0 to 100% in the influent resulted in a decrease in methane productivity (76.3 to 51.1 molCH4 m-3 day-1) and yield (12.7 to 9.1 molCH4 kgCOD-1), but fed-batch mode operation improved reactor performance (73.0 molCH4 m-3 day-1 and 11.5 molCH4 kgCOD-1). From the kinetic metabolic model, it was possible to infer that, at the best condition, methane is produced in a similar way from the acetoclastic and hydrogenotrophic routes. A scheme of four parallel reactors with a volume of 16,950m3 each was proposed in the scale-up estimation, with an energy recovery estimated in 28,745MWh per month.

Feasibility of biohydrogen production by co-digestion of vinasse (sugarcane stillage) and molasses in an AnSBBR

Abstract This work studied the feasibility of biohydrogen production by co-digestion of vinasse/molasses in an AnSBBR operated with mechanical stirring (30°C and 200 rpm). Hydrogen production by co-digestion of vinasse/sucrose was also studied to verify the performance of the process with a known co-substrate with easy degradation. The effects of influent composition (vinasse/sucrose and vinasse/molasses), influent concentration (3000 and 4000 mgCOD.L-1) and cycle time (3 and 4 h) on performance indicators were evaluated using stability, organic matter removal efficiency, molar hydrogen yield, productivity and biogas composition. The condition with vinasse/molasses in the influent that showed the best results was obtained with a 3-hour cycle time, influent concentration of 3000 mgCOD.L-1 and composition of 33% vinasse and 67% molasses. The molar productivity in this condition was 3.8 molH2.m-3.d-1 with a hydrogen molar fraction of 16% (and a methane molar fraction of 14%). A first order kinetic model was fitted efficiently to the best conditions.

Biomethane generation in an AnSBBR treating effluent from the biohydrogen production from vinasse: Optimization, metabolic pathways modeling and scale-up estimation

Abstract A study was performed regarding the production of methane by an AnSBBR treating wastewater coming from a biohydrogen production process using vinasse (sugar cane stillage). The reactor operated with recirculation of liquid phase in sequencing batch and fed-batch mode. The influence of the applied volumetric organic load (AVOL) was examined by varying influent concentration between 1000 and 4500 mgCOD L−1 (1.5–6.6 kgCOD m−3 d−1). Increasing AVOL resulted in a decrease in organic matter removal efficiency and in an increase in methane productivity. The highest productivity (133.1 molCH4 m−3 d−1) was obtained in fed-batch operation at the highest AVOL. Methane productivity and yield were always higher for fed-batch operation. From the kinetic metabolic model, it was possible to infer that methane is mainly produced via the acetoclastic route in batch mode and via both acetoclastic and hydrogenotrophic routes in fed-batch mode. Energy production of the two-stage system (acidogenic/biohydrogen-methanogenic/methane) was 13.6 kJ per gram of applied COD, which corresponds to a 38.8% increase compared to the traditional one-stage system (methanogenic/methane). The scale-up assessment (based on industrial production and performed with best condition data) proposed an operation of six parallel hydrogen-producing reactors of 6076 m3 each followed by four parallel methane-producing reactors of 1720 m3 each.

Lignocellulose-derived thin stillage composition and efficient biological treatment with a high-rate hybrid anaerobic bioreactor system.

BackgroundThis study aims to chemically characterize thin stillage derived from lignocellulosic biomass distillation residues in terms of organic strength, nutrient, and mineral content. The feasibility of performing anaerobic digestion on these stillages at mesophilic (40 °C) and thermophilic (55 °C) temperatures to produce methane was demonstrated. The microbial communities involved were further characterized.ResultsEnergy and sugar cane stillage have a high chemical oxygen demand (COD of 43 and 30 g/L, respectively) and low pH (pH 4.3). Furthermore, the acetate concentration in sugar cane stillage was high (45 mM) but was not detected in energy cane stillage. There was also a high amount of lactate in both types of stillage (35–37 mM). The amount of sugars was 200 times higher in energy cane stillage compared to sugar cane stillage. Although there was a high concentration of sulfate (18 and 23 mM in sugar and energy cane stillage, respectively), both thin stillages were efficiently digested anaerobically with high COD removal under mesophilic and thermophilic temperature conditions and with an organic loading rate of 15–21 g COD/L/d. The methane production rate was 0.2 L/g COD, with a methane percentage of 60 and 64, and 92 and 94 % soluble COD removed, respectively, by the mesophilic and thermophilic reactors. Although both treatment processes were equally efficient, there were different microbial communities involved possibly arising from the differences in the composition of energy cane and sugar cane stillage. There was more acetic acid in sugar cane stillage which may have promoted the occurrence of aceticlastic methanogens to perform a direct conversion of acetate to methane in reactors treating sugar cane stillage.ConclusionsResults showed that thin stillage contains easily degradable compounds suitable for anaerobic digestion and that hybrid reactors can efficiently convert thin stillage to methane under mesophilic and thermophilic conditions. Furthermore, we found that optimal conditions for biological treatment of thin stillage were similar for both mesophilic and thermophilic reactors. Bar-coded pyrosequencing of the 16S rRNA gene identified different microbial communities in mesophilic and thermophilic reactors and these differences in the microbial communities could be linked to the composition of the thin stillage.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0532-z) contains supplementary material, which is available to authorized users.

Estimating the elemental biomass composition of Desmodesmus sp. cultivated in sugarcane stillage

Cultivating algae on various stillage types present an alternative to current stillage application for fertirrigation of the sugarcane. The objective of this study was to determine how algal concentration, nutrient removal efficiency and elemental composition of Desmodesmus sp. algae change in response to different (raw and digested) types of stillage. Algal biomass was cultivated and harvested at laboratory scale. Obtained concentrations were 0.5 g/L and 0.3 g/L for Desmodesmus sp. grown in raw and digested stillage, respectively. At these concentrations, total carbon (TC) and total nitrogen (TN as Total Kjeldahl Nitrogen or N-TKN) removal from stillage medium accounted 39.78% and 5.58% for raw; 20.83% and 5.43% for digested stillage, respectively. The Desmodesmus sp. used in the present study contained high carbon and oxygen content, similar to other algal species. Calcium, phosphorus, and sulfur were the three most abundant inorganic elements. Both biomasses were free of chlorine and with the low content of potassium. The phosphorous content in both biomasses was in the range of 6.03%-6.84%, which could classify these biomasses as useful plant nutrients.

Operational strategies for long-term biohydrogen production from sugarcane stillage in a continuous acidogenic packed-bed reactor

The use of packed-bed reactors for biohydrogen production often results in performance losses in the short term because of the negative effects of operational factors, such as biomass accumulation and inadequate pH conditions. Because packed-bed systems constitute a promising technology for biohydrogen production, studies on continuous hydrogen production over the long term must be carefully conducted by applying proper operational strategies. Therefore, this study assessed continuous biohydrogen production in a packed-bed reactor operated under thermophilic conditions (55 °C) using sugarcane stillage as the substrate. The results indicated that the acidogenic reactor presented a capacity for recovering from performance losses, regardless of their cause, and maintaining continuous hydrogen production rates under long-term operation (240 days). pH proved to be a key factor for obtaining continuous hydrogen production, and the optimal results were observed in a pH range from 5.1 to 5.2. Furthermore, an optimal specific organic loading rate of 6.3–6.4 g carbohydrates g−1 volatile suspended solids d−1 was observed, and this value is consistent with the results of previous studies focused on hydrogen production from fermentative systems.

Color Removal from Anaerobically Digested Sugar Cane Stillage by Biomass from Invasive Macrophytes

The ability of untreated and acid-treated biomass from Pistia stratiotes (PL and APL, respectively) and Eichhornia crassipes (ELS and AELS, respectively) to remove color from anaerobically digested sugar cane stillage (ADS) was investigated. The effects of pH (3–8), particle size (< 0.75, 0.75–1, 1–4 mm), and biomass concentration (5–15 g/L) on decolorization of ADS were assessed using untreated biomass. After acid modification of biomass (acid-treated), the effects of pH (3–8), biomass concentration (6–10 g/L), time (20–480 min), and ADS dilution (non-diluted, 1:2, 1:10, 1:20) on color removal from ADS were evaluated. Scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR) analyses were also performed. A clear effect of particle size on ADS decolorization was found (21.04 ± 0.75 and 27.87 ± 0.30 % for 0.75–1 and <0.75 mm, respectively, for ELS; 31.65 ± 0.23 and 37.82 ± 0.53 for 1–4 and 0.75–1 mm, respectively, for PL). Decolorization also increased when the untreated biomass concentration was higher (15.41 ± 0.3 and 27.89 ± 0.2 % for 5 and 10 g/L, respectively, for ELS; 15.61 ± 0.11 and 33.06 ± 1.09 % for 5 and 10 g/L, respectively, for PL). The use of acid-treated biomass enhanced the effect of pH on color removal (48.30 ± 1.27 and 12.96 ± 0.27 % for pH of 3 and 7, respectively, for AELS; 47.11 ± 1.72 and 6.62 ± 0.21 % for pH of 3 and 7, respectively, for APL). The highest rate of color removal obtained using acid-treated biomass was 55.58 ± 1.82 and 56 ± 0.77 % for AELS and APL, respectively. The FTIR spectra analysis suggested the electrostatic attraction between protonated carboxylic groups on biomass and anionic colored compounds as being one of the adsorption mechanisms for ADS decolorization. The use of dry biomass from invasive macrophytes is an effective alternative for color removal from ADS.

Continuous thermophilic hydrogen production and microbial community analysis from anaerobic digestion of diluted sugar cane stillage

The aim of this study was to promote biohydrogen production in an thermophilic anaerobic fluidized bed reactor (AFBR) at 55 °C using a mixture of sugar cane stillage and glucose at approximately 5000–5300 mg COD L−1. During a reduction in the hydraulic retention time (HRT) from 8, 6, 4, 2 and 1 h, H2 yields of 5.73 mmol g CODadded−1 were achieved (at HRT of 4 h, with organic loading rate of 52.7 kg COD m−3 d−1). The maximum volumetric H2 production of 0.78 L H2 h−1 L−1 was achieved using stillage as carbon source. In all operational phases, the H2 average content in the biogas was between 31.4 and 52.0%. Butyric fermentation was the predominant metabolic pathway. The microbial community in accordance with the DGGE bands profile was found similarity coefficient between 91 and 95% without significant changes in bacterial populations after co-substrate removal. Bacteria like Thermoanaerobacterium sp. and Clostridium sp. were identified.

Organic loading rate impact on biohydrogen production and microbial communities at anaerobic fluidized thermophilic bed reactors treating sugarcane stillage

This study aimed to evaluate the effect of high organic loading rates (OLR) (60.0-480.00 kg COD m(-3)d(-1)) on biohydrogen production at 55°C, from sugarcane stillage for 15,000 and 20,000 mg CODL(-1), in two anaerobic fluidized bed reactors (AFBR1 and AFBR2). It was obtained, for H2 yield and content, a decreasing trend by increasing the OLR. The maximum H2 yield was observed in AFBR1 (2.23 mmol g COD added(-1)). The volumetric H2 production was proportionally related to the applied hydraulic retention time (HRT) of 6, 4, 2 and 1h and verified in AFBR1 the highest value (1.49 L H2 h(-1)L(-1)). Among the organic acids obtained, there was a predominance of lactic acid (7.5-22.5%) and butyric acid (9.4-23.8%). The microbial population was set with hydrogen-producing fermenters (Megasphaera sp.) and other organisms (Lactobacillus sp.).

Sugar Cane Stillage: A Potential Source of Natural Antioxidants

Biorefinery of sugar cane is the first economic activity of Reunion Island. Some sugar cane manufactured products (juice, syrup, molasses) have antioxidant activities and are sources of both phenolic compounds and Maillard Reaction Products (MRP). The study aimed to highlight the global antioxidant activity of sugar cane stillage and understand its identity. Chromatographic fractionation on Sephadex LH-20 resin allowed the recovery of a MRP-rich fraction, responsible for 58 to 66% of the global antioxidant activity according to the nature of the sugar cane stillage (DPPH test), and a phenolic compounds-rich fraction for 37 to 59% of the activity. A good correlation was recorded between the antioxidant activity of the sugar cane stillage and its content in total reducing compounds amount (Folin-Ciocalteu assay), among them 2.8 to 3.9 g/L of phenolic compounds (in 5-caffeoylquinic acid equivalent). Preliminary experiments by HPLC-DAD-MS allowed to identify several free phenolic acids and gave clues to identify esters of quinic acids.