Quantification of leakage in batch biogas assays

Hafner, Sasha D.; Rennuit, Charlotte; Olsen, Palle J.; Pedersen, Johanna

doi:10.2166/wpt.2018.012

Cited by 6 publications

(6 citation statements)

References 8 publications

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“…In contrast to some earlier literature [34,35], differences among measurement methods should not be accepted as unavoidable or indicative of effects on microbial activity. Differences in fact more likely show biases in one or more methods, and it is possible to eliminate these biases, as shown in the results of this study and in other studies [36,40].…”

Section: Bmp Measurement Methodssupporting

confidence: 51%

“…Assessment can take different forms, including, very simply, the use of a positive control in every BMP trial, or informal inter-lab comparisons using cellulose in addition to more complex substrates. In the case of manual volumetric or manometric methods (which, while clearly able to provide accurate results, are apparently not always reliable), gravimetric measurements can easily be used to check accuracy [12,40]. In contrast to some earlier literature [34,35], differences among measurement methods should not be accepted as unavoidable or indicative of effects on microbial activity.…”

Section: Bmp Measurement Methodsmentioning

confidence: 99%

“…Surprisingly large differences (up to 2-fold) have been found between different volumetric methods as well [37]. All BMP methods except the gravimetric approach [12,39] could be affected by leakage [36,40], which is rarely quantified. Data processing, i.e., calculation of BMP from raw measurements, may be another source of variation.…”

Section: Introductionmentioning

confidence: 99%

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Improving Inter-Laboratory Reproducibility in Measurement of Biochemical Methane Potential (BMP)

Hafner

Laclos

Koch

et al. 2020

Water

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Biochemical methane potential (BMP) tests used to determine the ultimate methane yield of organic substrates are not sufficiently standardized to ensure reproducibility among laboratories. In this contribution, a standardized BMP protocol was tested in a large inter-laboratory project, and results were used to quantify sources of variability and to refine validation criteria designed to improve BMP reproducibility. Three sets of BMP tests were carried out by more than thirty laboratories from fourteen countries, using multiple measurement methods, resulting in more than 400 BMP values. Four complex but homogenous substrates were tested, and additionally, microcrystalline cellulose was used as a positive control. Inter-laboratory variability in reported BMP values was moderate. Relative standard deviation among laboratories (RSDR) was 7.5 to 24%, but relative range (RR) was 31 to 130%. Systematic biases were associated with both laboratories and tests within laboratories. Substrate volatile solids (VS) measurement and inoculum origin did not make major contributions to variability, but errors in data processing or data entry were important. There was evidence of negative biases in manual manometric and manual volumetric measurement methods. Still, much of the observed variation in BMP values was not clearly related to any of these factors and is probably the result of particular practices that vary among laboratories or even technicians. Based on analysis of calculated BMP values, a set of recommendations was developed, considering measurement, data processing, validation, and reporting. Recommended validation criteria are: (i) test duration at least 1% net 3 d, (ii) relative standard deviation for cellulose BMP not higher than 6%, and (iii) mean cellulose BMP between 340 and 395 NmLCH4 gVS−1. Evidence from this large dataset shows that following the recommendations—in particular, application of validation criteria—can substantially improve reproducibility, with RSDR < 8% and RR < 25% for all substrates. The cellulose BMP criterion was particularly important. Results show that is possible to measure very similar BMP values with different measurement methods, but to meet the recommended validation criteria, some laboratories must make changes to their BMP methods. To help improve the practice of BMP measurement, a new website with detailed, up-to-date guidance on BMP measurement and data processing was established.

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Section: Bmp Measurement Methodssupporting

confidence: 51%

Section: Bmp Measurement Methodsmentioning

confidence: 99%

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Improving Inter-Laboratory Reproducibility in Measurement of Biochemical Methane Potential (BMP)

Hafner

Laclos

Koch

et al. 2020

Water

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“…Leakage in the individual bottles was identified and accounted for when cumulative mass loss exceeded the total detection limit estimated from water-only bottles [17]. Total detection limits were set to interval detection limits multiplied by the square root of the number of intervals, where the interval detection limit was five times the standard deviation of the mass of water-only controls [18].…”

Section: Data Processingmentioning

confidence: 99%

Development and Validation of a Low-Cost Gas Density Method for Measuring Biochemical Methane Potential (BMP)

Justesen

Astals

Mortensen

et al. 2019

Water

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Accurate determination of biochemical methane potential (BMP) is important for both biogas research and practice. However, access to laboratory equipment limits the capacity of small laboratories or biogas plants to conduct reliable BMP assays, especially in low- and middle-income countries. This paper describes the development and validation of a new gas density-based method for measuring BMP (GD-BMP). In the GD-BMP method, biogas composition is determined from biogas density. Biogas density is based on bottle mass loss and biogas volume, and these can be accurately measured using only a standard laboratory scale, inexpensive syringes, and a simple manometer. Results from four experiments carried out in three different laboratories showed that the GD-BMP method is both accurate (no significant bias compared to gravimetric or volumetric methods with biogas analysis by gas chromatography) and precise (<3% relative standard deviation is possible). BMP values from the GD-BMP method were also comparable to those measured for the same substrates with an industry standard automated system (AMPTS II) in two independent laboratories (maximum difference 10%). Additionally, the GD-BMP method was shown to be accurate even in the presence of leakage by excluding leakage from mass loss measurements. The proposed GD-BMP method represents a significant breakthrough for both biogas research and the industry. With it, accurate BMP measurement is possible with only a minimal investment in supplies and equipment.

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“…Prior to incubation of the experiments, bottle mass, inoculum mass and substrate mass were noted for each individual bottle. Mass loss during incubation was used to detect leaks [11].…”

Section: Batch Anaerobic Digestion Bottle Setupmentioning

confidence: 99%

Determination of Nitrogen and Sulphur Mineralization in Batch and Semi-Continuous Anaerobic Digestion Using an Artificial Fiber Bag Technique

et al. 2021

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In the biogas industry, feedstock plans are used to estimate methane production and nutrient content in the digestate, however, these predictions do not consider the mineralized nitrogen fraction of the feedstock, which is useful when determining the quality of the digestate. In this study, the artificial fiber bag technique, which is commonly used to study feedstock degradation in ruminants, was implemented in anaerobic digestion to quantify mineralization of N and S. The artificial fiber bags were used to enclose substrates but with access to inoculum because of small pores in the bags, thereby enabling digestion. The content of the bags was analyzed before and after digestion to quantify residual mass as well as N and S concentration in the substrate. The method was validated through batch anaerobic digestion of a single substrate with and without bags, where the bags showed little influence on methane production and degradation. Semi-continuous anaerobic digestion experiments showed higher substrate degradation and higher N and S release at thermophilic conditions using four different types of feedstocks and proved useful for solid feedstocks but less so for semi-solid feedstock. For N, most of the mineralization occurred during the first 15 days over a trial of 30 days.

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Quantification of leakage in batch biogas assays

Cited by 6 publications

References 8 publications

Improving Inter-Laboratory Reproducibility in Measurement of Biochemical Methane Potential (BMP)

Improving Inter-Laboratory Reproducibility in Measurement of Biochemical Methane Potential (BMP)

Development and Validation of a Low-Cost Gas Density Method for Measuring Biochemical Methane Potential (BMP)

Determination of Nitrogen and Sulphur Mineralization in Batch and Semi-Continuous Anaerobic Digestion Using an Artificial Fiber Bag Technique

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