Automatic Methane Potential Test System Research Articles

Metagenomic Analysis during Co-Digestion Buffalo Sludge and Tomato Pomace Post Thermal Stress: A Case Study

The tomato industry and buffalo farming generate waste, including sludge (BS) and tomato pomace (TP), which can significantly impact their economic and environmental sustainability. The case study tracked changes in microflora composition after a thermal shock during anaerobic co-digestion. The inoculum-to-substrate ratio was 0.5 based on volatile solid content under mesophilic conditions. An Automatic Methane Potential Test System was used to monitor the process before and after thermal stress (50°C) occurred for three days. Next-generation sequencing analyzed the bacterial and archaeal communities. The pH decreased, and methane production plateaued due to the high volatile solid content (87 g/L). After thermal stress, the pH returned to neutral, and the batch resumed biogas production. The cumulative CH4 production reached 3,115 Nml. The biogas had a maximum methane peak of 78.5% compared to 58.4% in BS. The taxonomic classification showed that Firmicutes (51.7%) and Bacteroidetes (29.9%) represented 81.6% of the total OTUs among the bacteria. Fonticella, the most abundant Clostridiaceae (average 4.3%), was absent in BS and increased (up to 17.1%) in TP during methane production. Methanocorpusculum was the most abundant in the archaeal community. However, Metanosarcina showed a stronger correlation with methane production. Brief thermal stress significantly altered bacterial and archaeal populations and allowed to resume biogas production.

Study on preliminary economic availability of electric energy use from drying bed sludge by biogas from anaerobic digestion and incineration in Brazil

This study aimed to analyze electrical energy generation derived from anaerobic biogas digestion and the incineration of drying bed sludge (DBS) from an Upflow Anaerobic Sludge Blanket (UASB) reactor using samples from a Wastewater Treatment Plant in Itajubá, Minas Gerais, Brazil. Some data including Automatic Methane Potential Test System (AMPTS II) were obtained from Moni Silva et al. (2021). An experimental apparatus comprised of a biodigester and gasometer was elaborated to conduct quali-quantitative evaluation of DBS biogas generation. Economic analysis was conducted on the Thermal Power Plant (TPP) electrical generation system, powered by biogas with data from i. experimental apparatus, and ii. AMTPS, as well as an incineration power plant. Greenhouse Gas (GHG) emission reductions were assessed. The results demonstrate that TPP from biogas with biodigestion without temperature control (experimental apparatus) was not economically feasible, even when considering ICMS tax exemptions; nonetheless, it would be capable of mitigating GHG emissions. Biodigestion with temperature control enabled TPP projects economic viability with payback in 20 years (178.67 kW, 9% IRR) considering a minimum population of 3,000,000 inhabitants. In all cases, the ICMS taxation reduces project feasibility.

Chemical pre-treatments on oil palm empty fruit bunches: Impacts on characteristics and methane potential

Production of biogas from lignocellulosic biomass by anaerobic digestion (AD) has attracted much interest. Oil palm empty fruit bunches (OPEFB), one of lignocellulosic biomass, is highly abundant in Indonesia and has potential as feedstock for bioenergy production such as biogas or methane. Yet, pre-treatments are needed to improve biogas production due to its complex crystalline structures. Chemical pre-treatments with acid or alkaline solution were reported to increase cellulose or highly reduce the lignin content of OPEFB. This study aimed to evaluate the effect of acid and alkaline pre-treatments on the characteristics of OPEFB and methane potential. The acid pre-treatment experimental design was used factor of H2SO4 concentration (1, 1.3, and 1.6 (%v/v)) and NaOH concentration (1.8, 2.8, and 3.8 (%w/v)). Methane potential evaluation was carried out using the biochemical methane potential (BMP) test with the Automatic Methane Potential Test System (AMPTS) II under mesophilic condition (37°C), operated for 28 days. The results showed that both dilute acid and alkaline pre-treatment positively impact altering the characteristics of OPEFB, hence the specific methane potential. Alkaline pre-treatment with NaOH 3.8 (%w/v) gave the highest average SMP value of 0.161 ± 0.005 m3 CH4/kgVSadded.

Enhancement of Biogas Production via Co-Digestion of Wastewater Treatment Sewage Sludge and Brewery Spent Grain: Physicochemical Characterization and Microbial Community

The present study intends to evaluate a synergy towards enhanced biogas production by co-digesting municipal sewage sludge (SS) with brewery spent grain (BSG). To execute this, physicochemical and metagenomics analysis was conducted on the sewage sludge substrate. The automatic methane potential test system II (AMPTS II) biochemical methane potential (BMP) batch setup was operated at 35 ± 5 °C, pH range of 6.5–7.5 for 30 days’ digestion time on AMPTS II and 150 days on semi-continuous setup, where the organic loading rate (OLR) was guided by pH and the volatile fatty acids to total alkalinity (VFA/TA) ratio. Metagenomics analysis revealed that Proteobacteria was the most abundant phyla, consisting of hydrolytic and fermentative bacteria. The archaea community of hydrogenotrophic methanogen genus was enriched by methanogens. The highest BMP was obtained with co-digestion of SS and BSG, and 9.65 g/kg of VS. This not only increased biogas production by 104% but also accelerated the biodegradation of organic matters. However, a significant reduction in the biogas yield, from 10.23 NL/day to 2.02 NL/day, was observed in a semi-continuous process. As such, it can be concluded that different species in different types of sludge can synergistically enhance the production of biogas. However, the operating conditions should be optimized and monitored at all times. The anaerobic co-digestion of SS and BSG might be considered as a cost-effective solution that could contribute to the energy self-efficiency of wastewater treatment works (WWTWs) and sustainable waste management. It is recommended to upscale co-digestion of the feed for the pilot biogas plant. This will also go a long way in curtailing and minimizing the impacts of sludge disposal in the environment.

Comparison of two gas volume measurement systems by evaluating biochemical methane potential

AbstractThe objective of this study is to compare and analyze the efficiency of an automated measurement system for biogas flow with a control performed by a programmable logic controller (PLC) called the SAMB compared to commercial equipment widely disseminated for this purpose, the automatic methane potential test system (AMPTS II). The objective is to identify the accuracy in gas flow analysis of the two systems. The experiments were conducted in triplicate at a constant temperature of 37°C in anaerobic reactors. Two synthetic substrates and two natural substrates combined with a microbial inoculum were used. Considering the different ways the two systems capture data, the results show that all samples differed statistically between them (p < 0.01) in each system. However, in relation to paired substrates between systems, the samples did not present statistically significant differences (p > 0.05). Thus, with the advancement and globalization of knowledge, it is necessary to develop systems capable of generating standardized, precise, and accurate data. In this context, the systems evaluated here present different forms of methane measurement but the results have no significant statistical differences.

The Performance Evaluation on Co-Digestion of Domestic Sewage Sludge and Food Waste for Methane Yield and Kinetics Analysis

Sewage sludge and food waste; are organic wastes suitable for the anaerobic digestion. However, the digestion of sewage sludge and food waste as solely substrate is having a drawback in term of methane yield. Therefore, many researchers combined these two wastes as a co-substrate and used in co-digestion. This study focused to evaluate the anaerobic co-digestion of domestic sewage sludge (in form of primary and secondary sewage sludge) with food waste under mesophilic temperature in a batch assay. Two series of batch biochemical methane potential (BMP) test were conducted using the Automatic Methane Potential Test System (AMPTS II). Each set are labelled with BMP 1(PSS:FW) and BMP 2 (SSS:FW). The BMP tests were monitored automatically until the methane production is insignificant. Using the data observed in the laboratory, the kinetic paremeters were calculated. Also, the First-order and Modified Gompertz modeling were included to predict the anaerobic digestion performance. Finding showed that BMP 1(PSS:FW) have better performance with respect to the higher ultimate methane yield and methane production rate as compared to BMP 2 (SSS:FW). Besides, the kinetic parameters from laboratory work and modeling were slightly different. In which the kinetic paremetes from modelling is lesser. However, both modelling are well fitted to the experimental data with high correlation coefficient, R2 ranged from 0.993 to 0.997.

The impact of crude glycerol from biodiesel production and its trace element content on biomethane production in a batch experiment: modelling as a step towards impartial routine comparison of results

In this study, crude glycerol from the biodiesel industry was tested as a co-substrate in biogas production. To investigate the influence of crude glycerol and the underlying trace element (TE) content on the efficiency of biomethane production, a batch experiment using Automatic Methane Potential Test System (AMPTS II) was carried out. The single addition of crude glycerol significantly contributed only to the total content of K (14.4%), Si (17.3%), and P (11.6%), whereas the contributions of other metals were within the range of other substrates. The addition of crude glycerol increased biomethane production, however, its utilization beyond 1% of total volume resulted in prolonged lag phase and final cessation of biomethane production. The negative effects of inorganic salts present in crude glycerol were reflected in progressively diminishing parts of glycerol and methanol being utilized in its anaerobic digestion, posing serious problems for daily routine use. A nonlinear least square regression analysis was performed to fit the Gompertz, Logistic, Transfer, and Richards models to biomethane production. The most suitable model was the Richards model, exhibiting the best fit to the experimental curves for complex substrates. Glycerol fractions remaining after biodiesel production have to be pre-tested for their negative effects on the content of TEs and inorganic salts, lag phase in biogas production, before they are used as co-substrates in biogas production phase.

Kinetics Modelling of Batch Anaerobic Co-digestion of Domestic Primary Sewage Sludge and Food Waste in a Stirred Reactor

Anaerobic digestion was conventionally applied for treating sewage sludge. However, the accumulation of solid waste particularly food waste has reach the critical levels worldwide. In practice, the food waste was dumped into the landfill for ultimate disposal. However, the greenhouse gases produced in the landfill makes this is no longer a preferable option. Anaerobic digestion was seen as an alternative for managing the food waste in a sustainable way. Methane, a renewable energy is potentially in replacing fossil fuel. However, the methane yield from the digestion of food waste inefficient. Therefore, a study of the co-digestion of sewage sludge and food waste was conducted to investigate the improvement of the methane yield. This study was conducted by using a mixture of domestic primary sewage sludge and food waste as a co-substrate for the anaerobic digester. The kinetics modified Gompertz modelling was applied to describe the anaerobic digestion process. A series of batch biochemical methane potential (BMP) assay was prepared using Automatic Methane Potential Test System (AMPTS II) to investigate the anaerobic digestibility of the mixture of domestic primary sewage sludge and food waste. The BMP assay showed that the co-digestion improved the ultimate methane yield by 32.6% higher than domestic primary sewage sludge alone, indicated that the co-substrate characteristics influencing the methane yield. Besides that, the greater VS/TS ratio of the substrate also resulted in the greater methane yield. The kinetics parameter from the modelling analysis were slightly lower as compared to the laboratory data.

Effect of Particulate Disintegration on Biomethane Potential of Particle-Rich Substrates in Batch Anaerobic Reactor

An investigation of particle disintegration was carried out using batch anaerobic reactors and a particle-rich substrate from pig manure supernatant. Two types of samples were applied, one high in suspended particles (raw feed) and another low in suspended particle content (centrifuged feed). Both feeds were digested with and without cellulase enzyme addition to obtain a better understanding of particle degradation mechanisms. An automatic methane potential test system (AMPTS) was used to carry out batch reactions at 35 °C. The raw feed with high-suspended solids had higher biomethane potential than the centrifuged feed but the conversion rate and methane yield was lower. The addition of cellulase increased biomethane production rates in both high- and low-particle content samples enhancing yield by 54% and 40%, respectively and converting 69% and 87% of feed chemical oxygen demand (COD), respectively. This implies that the feed particles have high contents of cellulose. This is also the case for the smaller particles remaining after centrifugation. Comparisons of anaerobic digestion model no. 1 (ADM1) simulations with experimental data reveal that classifying substrate particles into a fast and a slow degrading fraction with separate disintegration kinetics fit the experimental data better than lumping all particles into one parameter.

Atividade Metanogênica Específica: Metodologias simplificada e automatizada para lodos de reatores anaeróbios

O teste da atividade metanogênica específica (AME) permite conhecimento sobre o potencial de lodos anaeróbios em digestão de material orgânico, no entanto, ainda não possui protocolo prático para o seu desenvolvimento mais disseminado nas Estações de Tratamento. O presente trabalho avaliou dois métodos de AME, um simplificado e outro automatizado. Em ambos métodos houve inoculação de lodo de reator anaeróbio, diluição com solução nutritiva e adição de substrato (acetato de sódio), em concentrações adequadas. Para o método simplificado foram utilizados frascos de antibiótico com medição manual da produção de biogás, por meio de seringa esmerilhada, e análise de metano via cromatografia. No método automatizado foi utilizado o equipamento AMPTS (Automatic Methane Potential Test System), o qual fornecia os resultados por meio de interface com software específico. Os resultados obtidos com o método simplificado foram mais coerentes ao esperado (valores em torno da faixa de 0,2 a 0,3 gDQOCH4/gSV.d), confiáveis e de custo inferior, considerando todos os recursos materiais envolvidos, quando comparados com os obtidos com método automatizado (valores em torno de 0,1 gDQOCH4/gSV.d). Além disso, verificou-se que novas praticidades podem ser implementadas.

Batch biodegradability study of fresh and aged food waste: performance and kinetic

Peninsular Malaysia generates 17000 tonnes of municipal solid waste (MSW) per day in 2002 and it is estimated to increase to 31,000 tonnes per day on 2020, unfortunately food waste (FW) is the largest component of MSW. The high amount of FW generated related to landfill’s main issues such as foul odour, toxic leachate, emission of greenhouse gases and vermin infestation. FW is highly potential in producing methane because it is rich in volatile solid. Therefore, the research trend on anaerobic digestion of FW has shifted for methane production because methane can be transformed to electrical energy production. The objective of this research is to evaluate the methane potential and kinetics of methane production from the anaerobic digestion of fresh and aged food waste taken from fast food restaurant. The methane production under mesophilic condition was monitored by using Automatic Methane Potential Test System II (AMPTS II). Triplicate sample reactors were prepared for each substrate (fresh and aged FW) at IS ratio of 2.0 on VS basis. Besides that, duplicate blank reactors were prepared concurrently, contained only inoculum. The fresh FW resulted in higher ultimate methane yield (Mo) and methane production rate (Rm). Comparing to results from fresh FW, the Mo and Rm observed from digestion of aged FW were decreased by 17% and 27% respectively. Kinetic analysis using Modified Gompertz modelling showed that Mo for fresh and aged FW were increased, as well as for lag phase (λ). Meanwhile the decreased Rm was observed for fresh and aged FW.

Methane Potential from the Digestion of Food Waste in a Batch Reactor

The anaerobic digestibility of a targeted substrate, measured as methane yield is conducted via biochemical methane potential (BMP). In this study, the batch BMP test was conducted using Automatic Methane Potential Test System (AMPTS II) for 25 days and focused on the methane production from the digestion of food waste (FW, in the form of raw and diluted) at inoculum to substrate ratio (I/S) ratio of 2:0 and under mesophilic temperature. The results showed that solids (TS and VS) concentration reduced significantly due to the dilution. The ultimate methane yields from the digestion of raw FW and diluted FW were 1891.91ml CH4/gVS and 1983.96 ml CH4/gVS respectively. This showed that the dilution significantly improved the methane yield. In addition, the lag phase of the methane yield curve for both BMP tests was less than one (1) day, showing the good biodegradability of FW. The kinetic methane production from laboratory data and Modified Gompertz modelling fitted well. However, the kinetic equation parameters such as Mo, Rm and l from the model were slightly lower based on the observation of the laboratory data.

Bioaugmentation of anaerobic digesters treating lignocellulosic feedstock by enriched microbial consortia.

Three different bioaugmentation cultures enriched from natural and engineered cellulolytic environments (cow and goat rumen, a biogas reactor digesting sorghum biomass) were compared for their enhancement potential on the anaerobic digestion of wheat straw. Methane yields were determined in batch tests using the Automatic Methane Potential Test System operated for 30 days under mesophilic conditions. All cultures had positive effects on substrate degradation, and higher methane yields were observed in the bioaugmented reactors compared to control reactors set up with standard inoculum. However, the level of enhancement differed according to the type of the enrichment culture. Methane yield in batch reactors augmented with 2% cow rumen derived enrichment culture was increased by only 6%. In contrast, reactors amended with 2% goat rumen derived enrichment culture or with the bioaugmentation culture obtained from the biogas reactor digesting sorghum biomass produced 27 and 20% more methane, respectively. The highest methane yield was recorded in reactors amended with 6% goat rumen derived enrichment culture, which represented an increase by 36%. The microbial communities were quite similar at the end of the batch tests independently of the bioaugmentation sources, indicating that the introduced microbial communities of the enrichment cultures did not dominate the reactors.

Early assessment of a rapid alternative method for the estimation of the biomethane potential of sewage sludge

This short communication briefly presents a rapid method using a fluorescent redox indicator, similar to resazurin, in order to estimate the biodegradability of sewage sludge during anaerobic digestion (AD). The biodegradability and by extension the Biochemical Methane Potential (BMP) of nineteen municipal sludge samples (primary, biological and tertiary) were investigated and estimated in only 48h. Results showed the relevance to follow the metabolic activity of anaerobic sludge by the kinetic of probe reduction. The extended lag phase of inoculum indicated an impact of pre-treatments on enzyme activity. The comparison with Automatic Methane Potential Test System II (AMPTS) confirmed the estimated values of BMP according to an uncertainty limit of 25%. These first results highlight the interest of this rapid assay as a preliminary tool of the biodegradability of sewage sludge in anaerobic digestion.

Mitigation of Humic Acid Inhibition in Anaerobic Digestion of Cellulose by Addition of Various Salts.

Humic compounds are inhibitory to the anaerobic hydrolysis of cellulosic biomass. In this study, the impact of salt addition to mitigate the inhibitory effects of humic compounds was investigated. The experiment was conducted using batch tests to monitor the anaerobic hydrolysis of cellulose in the presence of humic acid. Sodium, potassium, calcium, magnesium and iron salts were tested separately for their efficiency to mitigate humic acid inhibition. All experiments were done under mesophilic conditions (30 °C) and at pH 7. Methane production was monitored online, using the Automatic Methane Potential Test System. Methane production, soluble chemical oxygen demand and volatile fatty acid content of the samples were measured to calculate the hydrolysis efficiencies. Addition of magnesium, calcium and iron salts clearly mitigated the inhibitory effects of humic acid and hydrolysis efficiencies reached up to 75%, 65% and 72%, respectively, which were similar to control experiments. Conversely, potassium and sodium salts addition did not mitigate the inhibition and hydrolysis efficiencies were found to be less than 40%. Mitigation of humic acid inhibition via salt addition was also validated by inductively coupled plasma atomic emission spectroscopy analyses, which showed the binding capacity of different cations to humic acid.

Determination of methane yield of cellulose using different experimental setups.

In this work, biochemical methane potential (BMP) tests with cellulose as a model substrate were performed with the aid of three manually operated or conventional experimental setups (based on manometer, water column and gas bag) and one automated apparatus specially designed for analysis of BMP. The methane yields were 340 ± 18, 354 ± 13, 345 ± 15 and 366 ± 5 ml CH4/g VS obtained from experimental setups with manometer, water column, gas bag, and automatic methane potential test system, which corresponded to a biodegradability of 82, 85, 83 and 88% respectively. The results demonstrated that the methane yields of cellulose obtained from conventional and automatic experimental setups were comparable; however, the methane yield obtained from the automated apparatus showed greater precision. Moreover, conventional setups for the BMP test were more time- and labour-intensive compared with the automated apparatus.

Addressing case specific biogas plant tasks: Industry oriented methane yields derived from 5L Automatic Methane Potential Test Systems in batch or semi-continuous tests using realistic inocula, substrate particle sizes and organic loading

The primary aim of the study was to develop and validate an in-house upscale of Automatic Methane Potential Test System II for studying real-time inocula and real-scale substrates in batch, codigestion and enzyme enhanced hydrolysis experiments, in addition to semi-continuous operation of the developed equipment and experiments testing inoculum functional quality. The successful upscale to 5L enabled comparison of different process configurations in shorter preparation times with acceptable accuracy and high-through put intended for industrial decision making. The adoption of the same scales, equipment and methodologies in batch and semi-continuous tests mirroring those at full scale biogas plants resulted in matching methane yields between the two laboratory tests and full-scale, confirming thus the increased decision making value of the approach for industrial operations.

Pre-treatments for enhanced biochemical methane potential of bamboo waste

Various pre-treatments (acid, alkaline, enzyme and alkaline aided enzyme also termed combined) were evaluated on different fractions of bamboo waste from a chopstick production factory. Chemical oxygen demand (COD) solubilisation, monomeric/dimeric sugar yield, methane yield enhancement and methane production rate were assessed. The biochemical methane potential was determined in batch assays under mesophilic conditions (37±1°C) using the Automatic Methane Potential Test System (AMPTS-II).Pre-treatments led to enhanced COD solubilisation as compared to raw sample. Alkaline aided enzymatic pre-treatment led to the highest sugar yield, comparable to the theoretical yield. However, high sugar yield did not translate to high methane yield. The best pre-treatment in terms of methane yield was alkaline pre-treatment which resulted in a surplus of up to 88% methane yield. There was a positive correlation between dissolved COD and methane yield. Methane yield and methane production rate also increased with decreasing particle sizes. In all investigated scenarios, pre-treatment led to an improved methane production rate as compared to the raw samples.These results demonstrated that alkaline pre-treatment at ambient temperature was an efficient treatment option to improve methane yield of bamboo waste.

Kinetics Modeling of Anaerobic Fermentative Production of Methane from Kitchen Waste Solid Residual

A series of batch mesophilic anaerobic digesntion were conducted using an automatic methane potential test system (AMPTS) and the kinetics of methane production was also discussed using modified Gompertz equation, Logistic function, First-order kinetics model and Transference function, respectively. The results showed that the kitchen waste solid residual was of high biomethane potential, and the maximum specific methane yield was obtained 585 NmL/g TS at inoculums substrate ratio (ISR) 2:1. All of the four models could appropriately fit the accumulative methane production in steady state (R2>0.95), where the 1st-ordre model and Transference function were relatively much better (R2>0.99) than the other two models. The maximum methane production and maximum methane production rate obtained from the Transference function were 569.32 NmL/g TS and 150.22 NmL/g TS day; the maximum kinetics constant obtained from the 1st-order model was 0.272/day; the lag time (λ) was basically negligible in all the cases. These parameters were quite close to the experimental results.

Use of an Automatic Methane Potential Test System for evaluating the biomethane potential of sugarcane bagasse after different treatments

A multi-channel analyzer was used to evaluate biogas potential of sugarcane bagasse (SCB). The Automatic Methane Potential Test System contained fifteen parallel reactors and the same number of gas flow meters attached to the acquisition system. The set of reactors – gas flow meters gave reproducible results during anaerobic digestion of chemically defined carbon source and the units were used to evaluate the biomethane potential of SCB after different pretreatments, such as treatment with water, acid, acid followed by enzymatic treatment and acid followed by treatment with inactive enzymes. Combined pretreatment with 2% sulphuric acid and enzymatic hydrolysis (3.5% enzymes) resulted in conversion of 79% to monomeric sugars present in SCB. SCB treated with acid followed by enzymatic hydrolysis achieved the methane yield of 200NL per kg VSadded. Enzymatic saccharification of acid pretreated SCB resulted in increase of methane yield by 16±5% compared to that from acid treated SCB.