Thermal Pretreatment Research Articles

Biohydrogen production from solar and wind assisted AF-MEC coupled with MFC, PEM electrolysis of [formula omitted] and [formula omitted] fuel cell for small-scale applications

Small-scale biohydrogen production is a promising option to reduce GHG emissions for a sustainable H2 economy. Thus, solar and wind aided AF-MEC and MFC coupled with the electrolysis of H2O and a H2 fuel cell were developed. The integrated system uses a microwave oven for digestate pretreatment, and solar or wind energy sources to operate the electrical units. The results show that thermal pretreatment of AF digestate facilitated enzymes’ activities, while the highest energy efficiency recorded in MFC was attributed to the use of AF-MEC by-products as feedstock. The generated electricity by MFC in addition to solar or wind energy systems reduced the overall cost by eliminating AF-MEC separation and purification units for biohydrogen recovery. Renewable energy-powered PEMEC produced H2 and O2 and PEMFC generated electricity for the developed system in the absence of wind and sunlight. Energy efficiency >68.6% and H2 selling price <$5/kg which is cheaper than single electrolysis of H2O unit were recorded with a minimal CO2 by-product. By-product CO2 capture is recommended for an increase in electricity production from the MFC unit. In terms of service life and energy required for manufacturing, this developed system for energy conversation and storage outperforms lithium batteries by >10% efficiency.

Increasing the Biomethane Yield of Hazelnut By-Products by Low Temperature Thermal Pretreatment

Biomethane energy, which has the status of renewable energies, has the potential to be produced from all kinds of organic wastes, as well as from lignocellulosic materials, which are the most common in nature. In this study, hazelnut shells (HS), one of the hazelnut by-products, were used for biomethane production. In order to obtain higher yields from HS, thermal pre-treatments were applied at temperatures of 60°C, 80°C and 100°C. Pretreatment effects were controlled by lignocellulosic substance amount determinations. As a result of thermal pretreatment at 100°C for 2 h, cellulose and lignin removals occurred approximately 15% and 30%, respectively. While the cumulative biomethane yield of raw HS was 32.3 mL•g total solids (TS)‒1, the cumulative biomethane yields of 100°C pretreated HS were measured as 132.3 mL•gTS‒1. As a result of different pretreatment temperatures, different cumulative biomethane yield curves were successfully simulated with the Modified Gompertz equation and R2 values were found to be between 0.9962 - 0.9985.

Dominant lignan profiles and antidiabetic activity of thermally treated and non-treated burdock seeds

Burdock seeds (Fructus arctii) are used as a traditional medicine for cough, inflammation, detoxification, cancer and diabetes, usually as decoction obtained with seeds subjected to thermal pre-treatment. The present work aimed to perform the phytochemical characterization of the stir-baked and non-baked seeds of various Arctium lappa populations from nine localities. Arctiin was dominant compound in non-baked seeds ranging from 40.6–92.6 mg/g. Thermal treatment resulted in a significant transformation of phenolic compounds and arctigenin was prevalent in the baked samples with the content from 25.2–57.4 mg/g. The antidiabetic potential of baked and non-baked burdock seed extracts was further evaluated in vitro by inhibition of α-amylase and α-glucosidase activity, while molecular docking analysis was used to reveal the main molecular interactions underlying the inhibitory effects on these enzymes. In vitro study showed that stir-baked burdock seed extracts were stronger inhibitors of both enzymes compared to non-baked. The several extracts showed strong inhibition of both enzymes by almost or more than 60%, which was lower compared to acarbose (82.99% at a concentration of 1 mg/mL). Arctin and arctigenin were individually significantly stronger inhibitors of α-amylase and particularly α-glucosidase compared to burdock extracts and acarbose, and their activity was concentration dependent. Moreover, antidiabetic activity for the most active sample was determined in vivo using animals on high-fat and sucrose diet, where promising results were obtained. Briefly, after three months of administration of the stir-baked seed extract (100 mg/kg body weight), complete recovery from a hyperglycemic state was achieved. According to the obtained results A. lappa stir-baked seed extract is a potential drug with hypoglycemic action as indicated by in vitro, in vivo and in silico studies.

The novel application of polyoxometalates for achieving sludge deep dewatering using low-temperature thermal hydrolysis pretreatment

Traditional thermal hydrolysis pretreatment (THP) for sludge deep dewatering is energy-intensive and poses the risk of generating bio-toxic substances that affect downstream wastewater treatment processes. To address these challenges, this study introduces the novel application of polyoxometalates (POMs) in THP to achieve sludge deep dewatering at lower temperatures. Specifically, under the optimal conditions with a POMs dosage of 1.0 mM/g VSS and a THP temperature of 140 °C, a reduction of 30.36%, 88.31%, and 55.04% in WC, SRF, and CST, respectively, was achieved compared to 20-RS-THP. Further analysis revealed that both the acidity and the biological effect of POMs played the dominant role in enhancing sludge dewatering. Spectroscopic techniques and molecular simulations revealed changes in protein structure during THP induced the POMs-proteins interaction. Results revealed that at lower THP temperatures (<80 °C), POMs induced protonation of functional groups in amino acid residues, strengthening electrostatic interactions. As temperatures increased (80–140 °C), more binding sites in hydrophilic amino acid residues became available for hydrogen bonding with POMs. This interaction led to structural changes in proteins, facilitating water liberation and the formation of sludge colloidal aggregates with improved drainage channels. However, at higher temperatures (140–180 °C), the exposure of hydrophobic sites, the loss of hydrophilic amino acids, and the occurrence of the Maillard reaction in proteins partially offset POMs' binding effects. Moreover, the development of magnetized POMs-based materials may offer sustainability and economic benefits for POMs-based sludge treatment and disposal technologies.

Optimization of methane production from solid tuna waste: Thermal pretreatment and co-digestion

Fish canning industries generate large amounts of solid waste during their processing operations, creating a significant environmental challenge. Nonetheless, this waste can be efficiently and sustainably treated through anaerobic digestion. In this study, the potential of biogas production from anaerobic digestion of thermally pretreated and co-digested solid tuna waste was investigated. The thermal pretreatment of raw fish viscera resulted in a 50 % increase in methane yield, with a production of 0.27 g COD-CH4/g COD added. However, this pretreatment did not lead to a significant increase in biogas production for cooked tuna viscera. When non-thermally pretreated raw viscera was tested, a large accumulation of volatile fatty acids and long chain fatty acids was observed, with levels reaching 21 and 6 g COD/L, respectively. On the other hand, anaerobic co-digestion of cooked tuna viscera with fat waste significantly enhanced methane production, achieving 0.87 g COD-CH4/g COD added. In contrast, co-digestion of cooked tuna viscera with dairy waste and sewage sludge resulted in notably lower yields of 0.36 and 0.46 g COD-CH4/g COD added, respectively. These results may be related to the C/N ratio, which was found to be within the optimal range for anaerobic digestion only in the tuna and fat waste co-digestion assay.

Effects of different thermal and thermochemical pretreatments on the anaerobic digestion of algal biomass cultivated in urban wastewater and collected with and without chemical coagulants

Algal biomass cultivated in wastewater treatment systems is a promising feedstock for biogas production through anaerobic digestion. However, its rigid cell wall inhibits the hydrolysis of intracellular substances and limits its anaerobic digestibility. To improve anaerobic biodegradability, this study investigated the effects of different thermal and thermochemical pretreatments on the performance of anaerobic digestion of the obtained biomass. High-rate algal ponds fed with UASB effluent treating domestic sewage were used to grow algal biomass. Two methods were used for biomass harvesting: a physical method, through filtration, and a physico-chemical method, using coagulants, Tanfloc SL and Aluminum Sulfate (Al2(SO4)3). Three types of biomasses were obtained, one without coagulant (AB-P), one with Tanfloc (AB-T), and one with Al2(SO4)3 (AB-AS), which were subjected to different thermal and thermochemical pretreatments. Fourier-transform infrared spectroscopy analysis confirmed the effectiveness of the pretreatment methods, showing modifications in the structures of proteins, carbohydrates, and lipids in the microalgae cells. The alkaline thermochemical pretreatment (90 °C-3 h-pH 11) of AB-AS resulted in higher organic matter solubilization, with a 32 % increase in soluble COD. This pretreatment also resulted in the highest biogas yield, producing 460.64 mL CH4.gVS−1, with a 229 % increase, and the highest maximum production rate, with Rmax = 78.98 mL CH4.gVS−1.day−1. Acidic thermochemical pretreatments that resulted in biomass with pH ≤ 4.2 inhibited biogas production. In terms of energy, the best pretreatment was 78 °C-7 h on AB-P, with an EROI of 2.20, which demonstrates a surplus of energy. These findings underscore the potential for optimizing the anaerobic digestibility of algal biomass, thus contributing to more efficient and sustainable biogas production.

Thermally enhanced solid-liquid separation process in food waste biorefinery: modelling the anaerobic digestion of solid residues.

The biochemical valorization potential of food waste (FW) could be exploited by extracting decreasing added-value bio-based products and converting the final residues into energy. In this context, multi-purpose and versatile schemes integrating thermal and biochemical conversion processes will play a key role. An upstream thermal pretreatment + solid-liquid separation unit was here proposed to optimize the conversion of the liquid fraction of FW into valuable chemicals through semi-continuous fermentation process, and the conversion of the residual solid fraction into biomethane through anaerobic digestion. The solid residues obtained after thermal pretreatment presented a higher soluble COD fraction, which resulted in higher methane production with respect to the raw residues (0.33 vs. 0.29 Nm3CH4 kg-1VSfed) and higher risk of acidification and failure of methanogenesis when operating at lower HRT (20d). On the contrary, at HRT = 40 d, the pretreatment did not affect the methane conversion rates and both tests evidenced similar methane productions of 0.33 Nm3CH4 kg-1VSfed. In the reactor fed with pretreated residue, the association of hydrogenotrophic methanogens with syntrophic bacteria prevented the acidification of the system. Modelling proved the eligibility of the FW solid residues as substrates for anaerobic digestion, given their small inert fractions that ranged between 0% and 30% of the total COD content.

Rice straw anaerobic co-digestion: Comparing various pre-treatment techniques to enhance biogas production

Study investigates rice straw size impact on co-digestion with four pre-treatments: thermal, hydrogen peroxide, combined thermal and hydrogen peroxide, and hydrogen peroxide followed by thermal treatment. Rice straw is divided into four sizes: 3–5 cm, 1–2 cm, 5–10 mm, and 300 μm. Co-substrates, sewage sludge, and chicken manure are used at a 20 % total solids concentration. Pre-treatment effects on rice straw and volatile fatty acid content post-digestion are assessed by quantifying cellulose, hemicellulose, and lignin content. Thermal pre-treatment, particularly on 1–2 cm-sized rice straw, demonstrates the highest efficacy with biogas production of 389 mL/g-VS. Preferred rice straw sizes for adaptability are ranked: 1–2 cm > 5–10 mm > 3–5 cm > 300 μm. However, pre-treatment fails to enhance biogas production compared to the control, attributed to structural deterioration, accelerated hydrolysis, elevated VFA levels, methanogenic inhibition, and increased hemicellulose content. Co-digestion is recommended over pre-treatment for rice straw anaerobic digestion.

Municipal wastewater for energy generation: a favourable approach for developing nations

This study focuses on understanding municipal wastewater (MWW) constituents and assessing technological options to harness the energy content of wastewater in developing countries. There are numerous research studies related to water treatment technologies and wastewater energy value. However, it remains to be seen which perspectives actually make technology adoption feasible. This study explores and presents the potential for some viable and innovative MWW treatment plant (WWTP) systems as a paradigm shift towards resource recovery, energy neutrality and the production of renewable energy by WWTPs. Various cost-effective opportunities related to operational strategies, plant redesign and the upgrading of current WWTPs that can foster self-reliant communities were visualised. Thermal and chemical pretreatments, sequential batch reactors, anaerobic membrane fluidised bioreactors, ammonia-based aeration control and combined heat and power systems can collectively contribute to energy recovery by WWTPs, ranging from 85 to 111%. The study suggests that upgrading the system to become an energy self-reliant water treatment system outweighs the multimode costs associated with health and ecological damages by reducing diseases, pollution and poor productivity regimes.

Influence of Thermal Pretreatment on Lignin Destabilization in Harvest Residues: An Ensemble Machine Learning Approach

The research on lignocellulose pretreatments is generally performed through experiments that require substantial resources, are often time-consuming and are not always environmentally friendly. Therefore, researchers are developing computational methods which can minimize experimental procedures and save money. In this research, three machine learning methods, including Random Forest (RF), Extreme Gradient Boosting (XGB) and Support Vector Machine (SVM), as well as their ensembles were evaluated to predict acid-insoluble detergent lignin (AIDL) content in lignocellulose biomass. Three different types of harvest residue (maize stover, soybean straw and sunflower stalk) were first pretreated in a laboratory oven with hot air under two different temperatures (121 and 175 °C) at different duration (30 and 90 min) with the aim of disintegration of the lignocellulosic structure, i.e., delignification. Based on the leave-one-out cross-validation, the XGB resulted in the highest accuracy for all individual harvest residues, achieving the coefficient of determination (R2) in the range of 0.756–0.980. The relative variable importances for all individual harvest residues strongly suggested the dominant impact of pretreatment temperature in comparison to its duration. These findings proved the effectiveness of machine learning prediction in the optimization of lignocellulose pretreatment, leading to a more efficient lignin destabilization approach.

Effect of the Pretreatment on the Properties of Cement-Based Recycled Powder

Three pretreatment methods including calcination, carbonization, and a carbonization-calcination combined pretreatment were studied to understand the pretreatment mechanisms for cement-based recycled powder (CRP). The mineral and microstructure of the CRP sample were investigated through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermal gravity (TG) analysis, and scanning electron microscopy (SEM) after exposure to different thermal temperatures (400 °C, 600 °C, and 800 °C), carbonization times (6 h, 1 d, and 3 d), and pre-carbonization for 1 d followed by heating at 800 °C. The results showed that the optimal thermal pretreatment temperature was approximately 720–800 °C. Through the process of calcination, the C-S-H, Ca(OH)2, and CaCO3 minerals in the CRP sample underwent decomposition to produce CaO or C2S. During carbonation, the pretreatment not only results in the increased production of CaCO3 owing to the reaction of the C-S-H gel and Ca(OH)2 with CO2, but also enhances its properties and the strength of chemical bond between CaCO3 and the post-hydration products. Both CaCO3 and CaO were present after the combined pretreatment, which indicates that the CaCO3 mineral formed superior stability after it had been pre-carbonated. Due to fewer impurities in CRP, the positive effect of the pretreatment on CRP was significantly better than that on recycled powder derived from construction and demolition waste.

Effect of ultrasound-ethanol immersion, microwave and starch-blanching pretreatments on drying kinetics, rehydration, and quality properties of beetroot chips

Abstract For the first time, the impact of ultrasound-ethanol immersion as a non-thermal pretreatment (NTPT) and coating-blanching in starch solutions as a thermal pretreatment (TP) on the convective drying of beetroot was evaluated. The beetroot was exposed to ethanol immersion (E), ultrasound (U), and ultrasound-ethanol immersion (UE). Besides, TP pretreatment was performed by blanching the beetroot at steam (SB), water (WB), starch-coating solutions, and microwave (M). The hot air drying was conducted at 90 °C and air velocity of 1.2 m/s. The maximum decreases in the drying time were observed at UE30 (64.29 %) and the sample blanched at native corn starch solution (60.17 %). Moisture diffusion coefficients ranged from 0.851 to 2.312 × 10−9 m2/s. The friction drag force, convective heat, and mass transfer coefficients were 2.840 × 10−6 N, 59.368 W/m2 K, and 0.0492 m/s, respectively. The thermal conductivity, specific heat, and density ranged from 0.464 to 0.615 W/m. K, 3164–4071 J/kg. K, and 798.9 to 1055.9 kg/m3, respectively. The maximum values of rehydration ratio at non-thermal (NTPT) and thermal pretreatments (TP) were observed at U30 and the sample blanched at the modified starch solution (MCS), respectively. The total phenolic contents of the NTP sample decreased while those for the TP samples increased due to boosted polyphenol synthesis at high temperatures. Both U and E samples caused a decrease in the total antioxidant activity, while they increased the anthocyanin content of beetroot samples. Pretreatments reduced the hardness owing to changes in the microstructure of the sample. U, E, and M pretreatments increased the brightness of samples, and the minimum color change compared with control samples was observed by UE30 pretreatment. The UE and blanching at a starch solution could be selected for improving the drying characteristics of beetroots at an industrial scale.

Study of the Mechanism of Hydrolysis of Hemicellulose from Lignocellulose during Alkali Thermal Pretreatment by Density Functional Theory and Experiment.

The covalent bond fracture of hemicellulose leads to hemicellulose hydrolysis during lignocellulosic alkali thermal pretreatment, which has not previously been reported. Density functional theory was used to study the mechanism of hydrolysis of the hemicellulose model compounds under alkali conditions. There are four reaction paths for xylose formation, among which the reaction path with the lowest energy barrier is that in which the nucleophile captures H30 to generate water. The deprotonated hydroxyl group attacks the carbon on the glycoside bond, resulting in the cleavage of the glycoside bond and the formation of a new carbon-oxygen covalent bond, with an energy barrier of 154.2 kJ/mol. The nucleophile further attacks the glycosidic bond to form a new xylose residue with an energy barrier of 111.9 kJ/mol. When the glycosidic bond breaks, the orbital interaction with the largest proportion causes the transfer of ∼0.511 electron from the glycosidic bond oxygen to the deprotonated hydroxy oxygen. In situ Fourier transform infrared spectroscopy is used for the identification of functional groups during the alkali thermal pretreatment. As the temperature increases, the feasibility of the reaction increases. This study lays a theoretical foundation for the development of the alkali thermal pretreatment of lignocellulose.

Analysis of energy return on investment of dry anaerobic digestion for low water alperujo with oxidative, thermal and alkaline pretreatments

AbstractAnaerobic digestion processes for biogas generation using alperujo have been the subject of intensive studies suggesting that phenolic compounds act as microbial inhibitors in anaerobic digestion. Pretreatments are needed to reduce the effects of phenolic compounds and improve biogas production, especially for dry anaerobic digestion. However, industrial‐scale implementation of these pretreatments is challenging, and it is unclear whether the improvement in biogas production justifies the energy expended on pretreatment. This study examines the energy analysis of dry anaerobic digestion and three alternative pretreatments: alkaline, oxidative and thermal. Results indicate that thermal pretreatment at 80°C with added water reduces phenolic compounds in alperujo by 35.4%. Meanwhile, pretreated with hydrogen peroxide in alkaline medium had the highest methane productivity (205 mL CH4/gVS). Even so, thermal pretreatment was only one with an energy return on investment greater than 1, signifying the necessity for energy analysis to ensure the viability of pretreatment processes.

Metabolic mechanism of thermal pretreatment combined with ethanol pre-fermentation to enhance anaerobic digestion of food waste: A comprehensive analysis of key enzyme-encoding genes

Ethanol pre-fermentation (EP) can enhance methanogenic efficiency and facilitate food waste (FW) hydrolysis, while ensuring anaerobic digestion (AD) system stability. FW contains high-water content, and thermal pretreatment (TP) can significantly enhance solids and soluble organic matter content. The study focused on investigating the mechanism of TP combined with EP (TP-EP) on the AD of FW. The results showed that TP-EP enriched hydrolyzing and acid-producing bacteria, as well as the methanogens Methanosarcina, and Methanothrix. Consequently, the degradation rates of soluble chemical oxygen demand, volatile fatty acids, and cumulative methane yield exhibited an increase of 9.54%, 5.94%, and 20.42%, respectively, in comparison to the control. EP promoted carbohydrate metabolism, while TP promoted amino acid metabolism and enhanced energy metabolism by enriching F-type ATPase and NADHase. When combined as TP-EP, the processes integrated the advantages and promoted substrate hydrolysis and energy metabolism while enhancing methanogenic metabolism.

Review of Melanoidins as By-Product from Thermal Hydrolysis of Sludge: Properties, Hazards, and Removal

Melanoidins, as macromolecular heterogeneous organic polymers, are produced from the Maillard reaction between amino and carbonyl groups during the thermal hydrolysis pretreatment (THP) of sludge. The brown color and recalcitrance of melanoidins pose a serious threat to wastewater treatment systems, such as invalidating UV disinfection and decreasing the efficiency of anaerobic digestion; thus, they have gradually received much concern in recent years. However, currently the study on THP-origin melanoidins is limited by a lack of reliable extraction and quantification methods. This paper presents a comprehensive review of the physical, chemical, and biological properties of melanoidins from different sources to fill the research gap on THP-origin melanoidins. The adverse effects of melanoidins on the management of wastewater and sludge are discussed, and for the first time, special attention is paid to the potential environmental hazards of THP-origin melanoidins to natural ecosystems. The removal technologies of melanoidins are summarized and compared as well. Finally, the suggested areas that future studies should focus on are provided. This review is dedicated to providing guidance on melanoidin research and management for the better development of the THP industry.

Maximizing Bio-Hydrogen and Energy Yields Obtained in a Self-Fermented Anaerobic Bioreactor by Screening of Different Sewage Sludge Pretreatment Methods

Egypt faces significant challenges in managing its sewage sludge generated in large quantities from wastewater treatment plants. This study investigates the feasibility of utilizing sewage sludge as a renewable resource for hydrogen production through anaerobic digestion at the 100 L bioreactor level. Hydrogen is considered a promising alternative energy source due to its high energy content and environmental benefits. To optimize the microbial degradation process and maximize hydrogen production from sewage sludge, a specialized pretreatment is necessary. Various pretreatment methods have been applied to the sewage sludge, individually and in combination, to study the bio-hydrogen production from sewage sludge. The four methods of treatment were studied in batch assays as a pilot scale. Thermal pretreatment of sewage sludge significantly increases bio-hydrogen production yield compared to other sewage sludge pretreatment methods, producing the highest H2 yield (6.48 LH2/g VS). In general, the hydrogen yield of any type of pretreated inoculum was significantly higher than the untreated inoculum. At the same time, alkaline pretreatment improved the hydrogen yield (1.04 LH2/g VS) more than acid pretreatment (0.74 LH2/g VS), while the hydrogen yield for the combination of pretreatments (shock alkali pretreatment) was higher than both (1.73 LH2/g VS), On the other hand, untreated sewage sludge (control) had almost no hydrogen yield (0.03 LH2/g VS). The self-fermented anaerobic bioreactor improved sewage sludge utilization, increased bioenergy yields, and seems to be promising for treating complex wastes at this scale.

Life cycle analysis of anaerobic digestion processes of poultry litter

This article presents results of life-cycle assessment of anaerobic digestion processes of poultry litter (PL) preceded or not by thermal pretreatment (autohydrolysis). For this, the environmental impact categories, greenhouse gas (GHG) emissions, eutrophication, and soil acidification were evaluated using the ReCiPe Midpoint (H) method. Based on primary data provided by a partner company, life-cycle inventories were constructed for three forms of poultry waste management: i. disposal of in natura PL into the soil, which is the commonly used management technique; ii. anaerobic digestion of in natura PL; and iii. thermal pre-treatment by autohydrolysis of PL before its anaerobic digestion. It is concluded that anaerobic digestion of PL reduces GHG emissions compared to the “business as usual” scenario of soil disposal. The use of digestate (liquid fraction generated by PL anaerobic digestion) as soil fertilizer would result in avoided GHG emissions of 34%, while thermal pre-treatment by autohydrolysis of PL prior to its anaerobic digestion would result in a slightly lower reduction (27%) in GHG. Anaerobic digestion of in natura PL would also reduce the eutrophication potential by 98.2% (kg eq PO4-3/t litter) and the acidification potential by 98.4% (kg eq SO2/t litter) compared to its soil disposal. These results show that anaerobic digestion is a more sustainable way to manage PL than its environmental discharge.

Bio-based production of medium-chain carboxylic acids from food waste and sludge without chemical addition: The pivotal role of mix ratio and pretreatment

Medium-chain carboxylates such as caproic acid, have a plethora of applications, ranging from food additives to bioplastics, and can be produced via microbial chain elongation (CE), a process that can be more sustainable than conventional production routes. During CE short fatty acids accept electrons from donors as lactate or ethanol elongating into medium-chain carboxylates with higher economic value and easier recoverability. Nowadays, waste activated sludge (WAS) and food waste (FW) are the most abundant waste steams generated in European cities impacting dramatically on environment, society, and economic sectors. A novel sustainable biotechnology is here proposed to produce marketable caproic acid from mixed WAS and FW with in-situ self-formed lactate without buffering agents addition. Different mix ratios between WAS and FW, and thermal pretreatment strategies were compared by fermentation batch tests. The production of lactate as electron donor (ED), together with acetate and butyrate, and hydrogen assured high production of caproate only in presence of thermal pretreated WAS, able to reduce the potential risk of lactate accumulation and drop in pH. The findings of this study demonstrate that the initial soluble carboydrate/protein ratio significantly affected the pH of the fermentation broth in the first hours of fermentation, and that only using FW and pretreated WAS mixed using a ratio of 60/40 in terms of volatile solids, CE pathway and lactate utilization as ED were promoted obtaining the highest percentage of caproate (about 21% of the total produced carboxylic acids; 2 gCOD/L).

Anaerobic digestion of distillery wastewater and napier grass: Characterization and process performance parameters

The BOD/COD ratio of napier grass (NG) + distillery wastewater (DWW) was found to be 0.4982, which reflected that the biodegradability of organic material is high and can be degraded and treated efficiently via biological processes. Moreover, further reductions in total solids (TS) and volatile solids (VS) were observed after thermal pretreatment at temperatures of 60°C and 100°C. VS/TS ratio also increased from 0.8767 to 0.9508 indicating a more significant proportion of organic matter are favorable for biogas production. This was evidenced by the resulting removal efficiencies ranging from 15% to 32% and 23% to 42%, for TS and VS, respectively. Overall, the study reported relevant effects of the application of thermochemical pretreatment in the process performance parameters in anaerobic digestion.