Improve Biogas Production Research Articles

Improved biogas production from tobacco processing waste via biochar-assisted thermophilic anaerobic digestion

Tobacco processing generates large amounts of waste, which can potentially serve as feedstock for the biogas production by anaerobic digestion (AD) technology. In this study, the thermophilic AD of flue-cured tobacco leaf waste with a high solid content was conducted, and the effects of biochar on biogas production at different organic loads were evaluated. The fermentation performance and microbial community with biochar addition (BAT) and without biochar addition (WBA) were thoroughly compared to explore the biochar-mediated enhancement mechanisms. Biochar addition enhanced methane production by 1.12–1.20 fold at the tested organic loads. Fermenting a low organic load (seed sludge/feedstock ratio: 2.0) in the BAT had the highest methane yield (120.4 mL/g-volatile total solids). Biochar addition significantly shortened the lag period of methane production and increased the methane production rate with an increasing organic load. The cellulolytic and fermentative bacterial genus Hydrogenispora, polysaccharide-degrading and syntrophic acetate-oxidizing bacterial genus norank_o_MBA03, and hydrogenotrophic methanogens were crucial for thermophilic flue-cured tobacco leaf digestion. Biogas production was enhanced by Hydrogenispora and Methanoculleus enrichment. These results demonstrate effective methane production from flue-cured tobacco leaves via biochar-assisted thermophilic fermentation with a high solid content and provide a useful reference for tobacco waste treatment.

ANAEROBIC DIGESTION OF BREWER’S SPENT GRAIN WITH BIOCHAR – BIOGAS PRODUCTION KINETICS AND PROCESS EFFICIENCY

Biochars made from brewer’s spent grain were added to the anaerobic digestion of brewer’s spent grain to enhance the methane fermentation process and improve biogas production. In research, the effect of biochars made at 300, 450, and 600 °C and doses of 1-8% added to anaerobic digestion was tested. The biochemical biogas potential tests in mesophilic conditions were performed. The tests took 28 days, the biogas yield for each reactor varied from 500-650 ml×gVS-1, and around 60% substrate degradation was obtained. For each test, the kinetics parameters using the first-order model were determined. The constant biogas production rate (k), and the biogas production rate (r) varied from 0.05-0.08 d−1, and 42-60 ml×(gVS×d)−1 respectively. Though the differences in biogas production turned out to be statistically insignificant (p<0.05) due to the high disappearance in obtained data and conflicting effects, the response surface area analysis showed that biochar made at 450 °C at the share of 1-4% could be used to maximize biogas production. Nevertheless, supplementation with biochar needs to be done carefully since in many cases, a reduction in biogas production was observed

Assessing machine learning tools for methane emission prediction from POME treatment in Malaysia

Abstract Palm oil mill effluent (POME) treatment is an anthropogenic activity contributing to global warming through methane emission. The inability to address this issue would deem true the catastrophic impacts of global temperatures exceeding 2 °C as was predicted by the Intergovernmental Panel on Climate Change (IPCC) in 2015. Little research and development exist on GHGs monitoring and methane emissions in POME treatment facilities as opposed to research on improving biogas production. A methane emission prediction tool based on machine learning models and tools can address this problem and consequently facilitate the development of efficient carbon neutrality approaches in POME treatment plants. In this study, six regression models were explored alongside their kernels using eight predictors, linking towards methane emission volume. The best model found was support vector machine (SVM), producing performance metrics for R2 and RMSE with values of 0.45 and 0.749, respectively.

Dynamic modelling the effects of ionic strength and ion complexation on trace metal speciation during anaerobic digestion

Dosing trace metals into anaerobic digestors is proven to improve biogas production rate and yield by stimulating microorganisms involved in the metabolic pathways. Trace metal effects are governed by metal speciation and bioavailability. Though chemical equilibrium speciation models are well-established and widely used to understand metal speciation, the development of kinetic models considering biological and physicochemical processes has recently gained attention. This work proposes a dynamic model for metal speciation during anaerobic digestion which is based on a system of ordinary differential equations aimed to describe the kinetics of biological, precipitation/dissolution, gas transfer processes and, a system of algebraic equations to define fast ion complexation processes. The model also considers ion activity corrections to define effects of ionic strength. Results from this study shows the inaccuracy in predicting trace metal effects on anaerobic digestion by typical metal speciation models and the significance of considering non-ideal aqueous phase chemistry (ionic strength and ion pairing/complexation) to define speciation and metal labile fractions. Model results show a decrease in metal precipitation and increase in metal dissolved fraction and methane production yield with increase in ionic strength. Capability of the model to dynamically predict trace metal effects on anaerobic digestion under different conditions, like changing dosing conditions and initial iron to sulphide ratio, was also tested and verified. Dosing iron increases methane production and decreases hydrogen sulphide production. However, when iron to sulphide ratio is greater than 1, methane production decreases due to increase in dissolved iron which reaches inhibitory concentration levels.

Thermal hydrolysis of sewage sludge: Improvement in biogas generation and prediction of global warming potential.

Anaerobic digestion (AD) is a prominent treatment method for the sludge produced from sewage treatment plants. Poor solid reduction and longer retention time are the main drawbacks of AD. Thermal hydrolysis (TH) is a potential pretreatment method for solubilization of sewage sludge (SS) solids thereby improving biogas production during AD post-treatment. In this study, the SS sample (total solids = 1.75 wt% and total chemical oxygen demand (COD) = 15,450 mg L-1) was subjected to TH pretreatment (temperature = 140-180°C and reaction time = 60 minutes) in a 0.7-L capacity stainless-steel high-pressure reactor. At a reaction temperature of 180°C, the maximum solid solubilization (total dissolved solids = 4652 mg L-1) and improved dewaterability (time to filter = 4.7 s.L g-1) were observed. The biochemical methane potential test results showed almost doubling of methane generation from 145 to 284 mL gCOD-1 after TH pretreatment at 180°C. The life cycle assessment approach was used to compare various SS treatment and disposal scenarios, two of which included hydrothermal pretreatment. The scenarios involving hydrothermal pretreatments showed the least global warming potential.

Effects of biogas slurry reflux mode and reflux rate on methane production by mixed anaerobic digestion of corn straw and pig manure

Biogas slurry reflux is a promising method to realize biogas slurry reduction and improve biogas production performance of anaerobic digestion. The purpose of this study was to investigate the effects of reflux mode and reflux ratio on mixed anaerobic digestion of corn straw and pig manure to obtain the best biogas slurry reflux process. The influence of reflux mode and reflux ratio on the internal environment during anaerobic digestion were clarified by kinetic analysis. The results showed that compared with the control group, the degree of substrate hydrolysis in the hydrolysis phase reflux (HPR) and two-phase synergistic reflux (TPSR) treatment groups increased, and the initial concentration and peak value of volatile fatty acids (VFAs) increased by 20.35%–85.81% and 24.72%–74.37%, respectively. The modified Gompertz model fitting results that the three biogas slurry reflux modes all significantly shortened the lag period of anaerobic digestion (17.29%–48.32%) and increased the peak gas production (7.54%–88.07%). And the maximum daily gas production (65.82 mL/(g VS∙d)), methane production (422.86 mL/g VS) and biodegradation rate (83.65%) were obtained under the TPSR mode with reflux ratios of 75% and 100%. This study provides a theoretical basis for the development of biogas slurry reflux technology in the mixed anaerobic digestion of corn straw and pig manure, and realizes the reduction and resource utilization of biogas slurry.

Anaerobic Digestion of Agricultural Waste Using Microbial Inocula: Performance and Characterization of Bacterial Communities Using 16S rRNA Sequencing Approach

Anaerobic digestion is considered a beneficial treatment for biogas production (BP). To improve the performance of this bioprocess, the addition of well-selected inocula could be an interesting approach that affects the overall efficiency of the BP. In this study, the reactor performance and energy analysis of liquid-state anaerobic digestion of cattle manure (CM) at high solids concentration (TS%) (94.87%) with six different inocula—two cellulosic (C.I1, C.I2), one lipidic (Li.I), two lactic (La.I1, La.I2), and one saccharidic (Sacc.I)—were investigated. The results showed that inocula improved the biogas production and yield during anaerobic digestion of CM by 109%, 86%, and 52.4%, respectively, when the cellulosic (C.I1), lipidic (Li.I), and lactic (La.I1) inocula were added, compared with the substrate production alone at a substrate/inoculum (S/I) ratio of 5:3 (v/v). The addition of inocula in an appropriate range is useful for the performance of the anaerobic digestion process. In our study, the 16S rRNA sequencing approach was followed to investigate microbial community structure and diversity in the substrate CM and the three inocula that showed a significant improvement in biogas production (C.I1, Li.I, and La.I). The most abundant bacterial populations were found to be Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria, with different abundance percentages. Interestingly, C.I1, which resulted in the highest biogas production, showed the dominance of Cyanobacteria (53.44%) belonging mainly to the class Nostocophycidae. This study highlighted the role of inocula in improving biogas production from cattle manure (CM) thanks to their microbial diversity.

Process Improvement of Biogas Production from Sewage Sludge Applying Iron Oxides-Based Additives

Iron additives are effective in the anaerobic sewage sludge digestion process, but the composition and dosage of these additives are not precisely defined. This research investigates the effects of three iron oxides-based additives on the destruction of volatile solids, the production and quality of biogas, as well as the quality of the supernatant. Additive No 1 contained >41.5% of FeO and >41.5% of Fe2O3, additive No 2 contained ≥86% of Fe3O4, and additive No 3 contained ≥98% of Fe3O4. The best results were obtained by applying an iron oxides-based additive with a higher content of divalent iron oxide. The increase in efficiency of the VSs destruction was not significant and on average 2.2%. The increase in biogas production was on average 20% while the average increase in the content of methane in the biogas was 6.3%. Applying the additive, the reduction in the concentration of ammonium nitrogen in the supernatant was up to 28%, as well as a reduction in the concentration of phosphate phosphorus in the supernatant by up to 3.1 times could be expected compared to the case when the additive was not applied. The dose of additive No 1 was between 7.5 g/kg of dry solids and 15 g/kg of dry solids in the lab-scale test. The dose was specified in the full-scale test, and the recommended dose of the additive was 10 g/kg of dry solids to improve biogas production.

Anaerobic digestion of agro‐industrial waste enriched with bovine bone meal for improved biogas production and biofertilization

AbstractThe increase in animal and agro‐industrial production must be accompanied by the development of appropriate waste and by‐product management strategies. Anaerobic digestion is a promising approach to recycle these wastes and reintegrate them into the economic production cycle of biogas and biofertilizer. In order to improve the performance of the anaerobic mesophilic digestion of abundant agro‐industrial wastes constituted by potato peel (PP), and poultry waste (PW) and study the contribution of bovine bone meal (BB) as additive rich in phosphorus, which can help to neutralize the acidity of the substrate. The 10‐point simplex‐centroid design and the isoresponse surfaces strategy were used. This study demonstrated that in mesophilic bio‐digestion, the using bovine bones in admixture with agroindustrial residue provided for the proper balance of chemical components required for proliferation of microbiological agent of bioconversion, which also resulted in an increase in biogas production capacity. The best formula was so composed by 66.67% bovine bone, 16.67% potatoes peel, and 16.67% poultry waste. The stability was achieved here after only 12 days. The digestate generated from it was fulfilled with the microbiological and chemical requirements for safety defined by the NF U44‐551 standard. Germination test revealed that this optimal produced digestate, did not hinder growth, in fact, almost 85% of seed was germinated. Finally, fertilization experiments prove that this digestate can boost the growth of bell pepper (Capsicum annuum).

Two-step anaerobic digestion of rice straw with nanobubble water

Lignocellulose usually requires pretreatment to improve biogas production. To enhance lignocellulose biodegradability and improve anaerobic digestion (AD) efficiency, different types (N2, CO2, and O2) of nanobubble water (NW) were applied in this study as soaking agent and AD accelerant to increase the biogas yield of rice straw. The results showed that the cumulative methane yields of treating with NW in two-step AD increased by 11.0%–21.4% compared with untreated straw. The maximum cumulative methane yield was 313.9±1.7 mL/gVS in straw treated with CO2-NW as soaking agent and AD accelerant (PCO2-MCO2). The application of CO2-NW and O2-NW as AD accelerants increased bacterial diversity and relative abundance of Methanosaeta. This study suggested that using NW could enhance soaking pretreatment and methane production of rice straw in two-step AD; however, combined treatment with inoculum and NW or microbubble water in the pretreatment needs to compare in future.

A Scoping Review of Options for Increasing Biogas Production from Sewage Sludge: Challenges and Opportunities for Enhancing Energy Self-Sufficiency in Wastewater Treatment Plants

Treating municipal wastewater is a complex and costly process. With rising energy costs and sustainability targets, wastewater treatment plants (WWTPs) are looking for alternatives to reduce operating costs and carbon dependence. Anaerobic digestion is the most common and established technology used in WWTPs to treat sludge since it can potentially improve energy recovery and reduce sewage treatment costs, mainly due to the generation of biogas. Biogas is a renewable energy resource and can be used in several applications, including heating and producing electricity. By exploring the biogas potential, WWTPs can reduce their operating costs and energy demands. The objective of this paper is to conduct a scoping literature review in order to provide the key concepts underpinning alternatives to improve biogas production and utilisation in WWTPs. In addition, this study aims to provide an overview of the current state-of-the-art that may serve as a quick reference for the research community, WWTP operators, and engineers, including definitions and a general overview of the current state of biogas technologies around the world. Methods to increase biogas production, including co-digestion, pre-treatment, and biological hydrogen methanation, are reviewed, and the alternatives to using biogas are also summarised. This review has identified that co-digestion was the most efficient technique to improve biogas production and methane yield, while pre-treatment of sludge improved sludge biodegradability and reduced sludge treatment costs but also enhanced biogas production. Although many studies have explored different methods to improve biogas production in WWTPs, there is still a need for further investigation, especially regarding the techno-economic feasibility of these methods in full-scale facilities. The current challenges are mainly related to the need for extra investment and increased operating costs to integrate the new techniques into the current system. There is a great interest in alternatives to improve energy efficiency and self-sufficiency in WWTPs. This work provides an important review of the increasing number of recently published research papers that focus on improving biogas generation from sewage sludge in WWTPs.

Effects of Magnetic Biochar Addition on Mesophilic Anaerobic Digestion of Sewage Sludge.

As a low-cost additive to anaerobic digestion (AD), magnetic biochar (MBC) can act as an electron conductor to promote electron transfer to enhance biogas production performance in the AD process of sewage sludge and has thus attracted much attention in research and industrial applications. In the present work, Camellia oleifera shell (COS) was used to produce MBC as an additive for mesophilic AD of sewage sludge, in order to explore the effect of MBC on the mesophilic AD process and its enhancement mechanism. Analysis by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectrometry (FTIR), and X-ray diffraction (XRD) further confirmed that biochar was successfully magnetized. The yield of biogas from sewage sludge was enhanced by 14.68-39.24% with the addition of MBC, and the removal efficiency of total solid (TS), volatile solids (VS), and soluble chemical oxygen demand (sCOD) were 28.99-46.13%, 32.22-48.62%, and 84.18-86.71%, respectively. According to the Modified Gompertz Model and Cone Model, the optimum dosage of MBC was 20 mg/g TS. The maximum methane production rate (Rm) was 15.58% higher than that of the control reactor, while the lag-phase (λ) was 43.78% shorter than the control group. The concentration of soluble Fe2+ and Fe3+ were also detected in this study to analyze the function of MBC for improving biogas production performance from sewage sludge. The biogas production was increased when soluble Fe3+ was reduced to soluble Fe2+. Overall, the MBC was beneficial to the resource utilization of COS and showed a good prospect for improving mesophilic AD performance.

Plant seed–based bio-coagulant development and application for fecal sludge treatment and biogas production improvement

Plant seed–based bio-coagulant development and application are promising for fecal sludge treatment and biogas production improvement. However, improving methane yield in anaerobic digestion processes is an important research direction. This work addresses the development and application of Cucumeropsis mannii and Luffa acutangula seed proteins as novel bio-coagulants for fecal sludge concentration to increase the biogas yield. Their seeds’ protein content was determined and extracted using 1 M (NaCl), then isolated and precipitated by ammonium sulfate [(NH4)2 SO4], and purified using a dialysis process. Their coagulation/flocculation was compared to Moringa oleifera and Cucurbita pepo seeds as the primary treatment for the fecal sludge concentration. Optimal coagulant dosages of 20 mg/L at pH 7.25 increased the total solids from 0.4 to 2.8% and obtained 180 to 340 mL/L of fecal sludge volume per liter. Their bio-coagulant effect on the supernatant water reduced 76.48 to 96.88% of turbidity, 71.20 to 88.76% of COD, and 81.33 to 95.30% of ammonia–nitrogen. The biomethane potential result has shown that plant seed–based bio-coagulants are effective and produce substrates potentially favorable to increased methane yield in anaerobic digestion with 350.5 to 465.3 NmL CH4/gVS, by a ratio 2:1 on VS, compared to the FS without bio-coagulant treatment with a specific methane yield of 192.8 NmL CH4/gVS.

Improving the Energetic Efficiency of Biogas Plants Using Enzymatic Additives to Anaerobic Digestion

This study was carried out to estimate the relevance of biological supplementation in improving the economic efficiency of anaerobic digestion (AD). Three kinds of silages—maize, grass, and igniscum—were initially inoculated with digestate and then supplemented with one of four vaccines containing different bacteria species (APD®, PPT®, JENOR®) or a yeast and mold mixture (HAP®). In addition, each plant silage was fermented without any additives (control A—maize silage, B—grass silage, and C—igniscum silage). The biodegradability process was performed in batch tests at a mesophilic temperature (38 °C). To compare the energetic efficiency of AD, the process kinetics, biogas, and methane production were analyzed. We found that the applied supplementation measures improved biogas production in the case of maize and igniscum (7–62% higher than controls), but decreased the yield of AD when grass silage was fermented (2–34% lower than controls). The greatest increase in methane production (by 79%) was observed when maize silage was digested with the PPT® pretreatment, with 427 Nm3∙Mg−1 VS (volatile solids).

Advancement of nanotechnologies in biogas production and contaminant removal: A review

The challenges of managing fossil fuels, the continued emission of greenhouse gases into the atmosphere, and the global water crisis are increasingly drawing researchers’ attention toward alternative ways to increase the efficiency of biogas production and wastewater treatment. To the best of our knowledge, no previous study has yet summarized the performance of nanomaterials in biogas production and the removal of waste contaminants from wastewater. Thus, this current review aims to describe the performance of nanomaterials in biogas production, wastewater treatment, and the removal of contaminants. Based on the identified research, the performance of nanoparticles (NPs) depends significantly on the dosage and feedstock used, the biodegradability of the feedstock, pH, and the type of nanoparticles. For the removal of contaminants, NPs have proved effective at removing CO2 and H2S from biogas, as well as reducing the chemical oxygen demand (COD) and biological oxygen demand (BOD) of wastewater. Based on the evidence, NPs can improve biogas production and reduce contaminants in biogas and wastewater. The use of nanomaterials is recently an advance method over conventional approach for biogas production. The novelty of this study highlights that metal NPs, metal nutrient NPs, and iron oxide NPs are more suitable to increase biogas and CH4 production as compared to metal oxide NPs (e.g., CuO, Mn2O3, Al2O3, and ZnO). More research is needed to investigate the carbon footprint reductions in biogas production and wastewater treatment while accounting for various other parameters, including nanoparticle size and water temperature.

Improving Biogas Production in Tapioca Industry by Using Onggok as Co-substrate

Improving Biogas Production in Tapioca Industry by Using Onggok as Co-substrate

Influence of pH and the Insulation of Reactor on The Biogas Production of Livestock Waste by Batch Anaerobic Reactor

This study presents the improved biogas production by determining the optimum pH and insulation reactor from cow, sheep, and poultry manure (which are the most available in our location). The experiment was carried out in 2000 mL digester put in the water bath at 37 ˚C. The mixing ratio of animal manure and water used was 1:1 in 12 days of Hydraulic Retention Time (HRT). Produced gas was measured by the volumetric water replacement method. The optimum pH will be chosen in the experimental test with different pH ranges in the first phase. Three set-ups were prepared with different pHs (6.5, 7, 7.5).The results showed that the pH had significant effects on biogas yield, where pH7 had the highest biogas production and pH 6.5 is the lowest. The second phase, investigated the effect of the insulation of the reactor on the biogas yield. The biogas was produced from an insulated reactor higher than the photoreactor because of the growth of algae which produces oxygen in the photoreactor. Therefore, it is given that the study which gave a maximum yield of biogas from the batch digestion process might be met the future energy demand.

Improvement of biogas production and quality by addition of struvite precipitates derived from liquid anaerobic digestion effluents of palm oil wastes

When biogas is produced, the liquid anaerobic digestion effluents (LADE) still contain pollutants. Struvite precipitation is a technique for reducing pollutants as well as recovering useful elements such as nitrogen, phosphorus, and magnesium. This study aims to precipitate struvite from LADE and use it as an additive to palm oil mill effluent (POME) feedstocks in subsequent biogas production systems (batch and continuous operational modes). Struvite precipitation was simply performed using NaOH at a pH range of 8–10 without external sources of magnesium and phosphorus. The result showed that the optimum pH for struvite precipitation was 9, giving the highest yield and purity of struvite. The addition of 5% struvite to POME feedstock improved the performance of biogas production in the continuous stirred tank reactor (CSTR) in terms of stability, high COD removal efficiencies, increased methane yields, and decreased H2S concentrations. The greatest methane yield of 509.8 mL/g-VS and the methane concentration of 65.10% were obtained in the CSTR. The significant decrease in H2S concentration in biogas can increase the energy content of biogas, save on the cost of H2S removal, reduce corrosion, and extend the operating time of gas turbines used for electricity production. The results of this study emphasize the role of integrating struvite precipitation with continuous biogas production in improving the process sustainability and economy. Struvite precipitation from LADE diminishes the polluted wastewater, decreases the long-term process problems of fouling and clogging caused by struvite, and improves the performance of the biogas production.

Upgrading Anaerobic Sludge Digestion by Using an Oil Refinery By-Product

Carbon-based conductive additives have been studied for their positive effects on anaerobic digestion (AD) using synthetic substrates, but their importance in wastewater sludge digestion has not been sufficiently explored. This research investigated and compared the effects of two conductive materials (graphene and petroleum coke) with and without trace metal supplementation. The results indicated that supplementing reactors with graphene and petroleum coke could significantly improve biogas production. The supplementation of 1 g/L petroleum coke and 2 g/L graphene, without trace metal addition, led to an increase in the biogas production by 19.10 ± 1.04% and 16.97 ± 5.00%, respectively. Thus, it can be concluded that petroleum coke, which is an oil refinery by-product, can be used to enhance biogas production in a similar way to other carbon-based conductive materials that are currently available on the market. Moreover, using petroleum coke and graphene, the average chemical oxygen demand (COD) removal was 42.84 ± 1.23% and 42.80 ± 0.45%, respectively, without the addition of trace metals. On the other hand, supplementation of the reactors with trace elements resulted in a COD removal of 34.65 ± 0.43% and 34.05 ± 0.45% using petroleum coke and graphene, respectively.

Improvement of biogas production and nitrogen recovery in anaerobic digestion of purple phototrophic bacteria by thermal hydrolysis

Purple phototrophic bacteria (PPB) are a novel driver to recover organics and nutrients from wastewater by assimilative growth. Depending on the source, assimilated resources from the PPB biomass can still be recovered after a releasing step. Anaerobic digestion (AD) releases carbonand nutrients, but the release is incomplete. Thermal hydrolysis (TH) as a pretreatment before AD improves the digestibility, release, and subsequent recovery potentials. This work determines the effects of TH in batch and continuous modes regarding methane potential, nutrients' release efficiencies, volatile solids destruction, degradability, and hydrolysis rates. Continuous runs over 165 days (d) confirmed enhanced recovery potentials, achieving up to 380 LCH4/kgVS (83 % solids destruction) and 73 % N release, respectively. The TH pretreatment is energy-intensive, but with appropriate heat recovery and increased methane production in the AD of the pretreated biomass, a combined configuration is energy positive.