Special Issue "Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Wastewater Treatment and Reuse".

Deadline for manuscript submissions: closed (31 July 2020).

Special Issue Editors

Prof. Dr. Konrad Koch
Website
Guest Editor
Chair of Urban Water Systems Engineering, Technical University of Munich, Garching, Germany
Interests: improvement of anaerobic digestion; process control and modelling; development and evaluation of measurement methods; critical assessment and enhancement of guidelines
Prof. Dr. Sasha D. Hafner
Website
Guest Editor
Department of Engineering, Aarhus University, Aarhus, Denmark
Interests: modeling environmental processes; data analysis; laboratory methods; biological treatment; biogas; ammonia and greenhouse gas emission
Prof. Dr. Christof Holliger
Website
Guest Editor
Laboratory for Environmental Biotechnology, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
Interests: biological wastewater treatment; enhanced biological phosphorous removal; microbial ecology of aerobic granular sludge; standardization of biomethane potential tests

Special Issue Information

Dear Colleagues,

Biochemical methane potential (BMP) tests are routinely conducted as part of anaerobic digestion research and practice in order to quantify the maximum methane yield that a substrate can provide. The first BMP method was described 40 years ago, and many variations have since been proposed. Despite its widespread use and importance to both research labs and plant operators, BMP measurement suffers from high variability among laboratories, significantly limiting its value in both areas. How can BMP measurement be improved? Can we get more out of BMP trials? Standardization of methods may help in reducing both systematic and random error. Development of validation criteria could help technicians to reject flawed results and identify sources of error. Examination of kinetic data from BMP tests might help further to evaluate data quality with little additional effort.

This Special Issue of Water will focus on recent developments in BMP measurement and application of BMP tests in research and practice. We are primarily interested in contributions on these topics:

  • Critical review of the current state-of-the-art;
  • Improvement of existing BMP guidelines;
  • Comparison of BMP methods and identification of problems;
  • New methods for the determination of BMP;
  • Inter-laboratory studies;
  • Use and limitations of BMP tests;
  • Kinetics from BMP tests;
  • Case studies/application of BMP tests in research and practice.

The open-access journal Water provides an ideal forum for papers on this topic that are relevant to all biogas research groups and treatment plant operators. We are looking forward to receiving high-quality manuscripts from the global biogas community. Please contact us with any questions.

Prof. Dr. Konrad Koch
Prof. Dr. Sasha D. Hafner
Prof. Dr. Christof Holliger
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Anaerobic digestion
  • Biogas technology
  • Biochemical methane potential (BMP) tests
  • Laboratory methods
  • Standardization of BMP tests
  • Modeling of kinetics

Published Papers (6 papers)

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Research

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Open AccessArticle
How Different Are Manometric, Gravimetric, and Automated Volumetric BMP Results?
Water 2020, 12(6), 1839; https://doi.org/10.3390/w12061839 - 26 Jun 2020
Cited by 1
Abstract
The objectives of this study were to: (1) quantify differences in biochemical methane potential (BMP) measured using three measurement methods, including two popular methods (a commercial automated system (AMPTS II) and manual manometric) and one newer method (gravimetric), and (2) assess the importance [...] Read more.
The objectives of this study were to: (1) quantify differences in biochemical methane potential (BMP) measured using three measurement methods, including two popular methods (a commercial automated system (AMPTS II) and manual manometric) and one newer method (gravimetric), and (2) assess the importance of the mixing position in the measurement sequence. Powdered microcrystalline cellulose was used as the substrate in simultaneous tests. All methods gave similar results (<8% difference in the mean BMP) and were reasonably accurate (recovery of 80–86% of the theoretical maximum BMP). Manometric BMP values were consistently lower than gravimetric by 4–5%. Precision was lower for the automated method (relative standard deviation (RSD) of about 7%) than for the manual methods (RSD about 1–3%). Mixing after biogas measurement resulted in 3% higher BMP for both manual methods than mixing before, due to the lower measured CH4 production from blanks. This effect may be linked to a fraction of CH4 that remains dissolved or even as attached bubbles, and suggests that mixing before measurement is preferable. The automated volumetric and gravimetric methods (mode 2) gave very similar mean BMP values (1% different). However, kinetic analysis showed that methane production was faster with the automated volumetric method. This could come from an error in the estimation of the CH4 production rate for the automated method, or an increase in the degradation rate due to better mixing. Both automatic volumetric and manual gravimetric measurements met current validation criteria for mean cellulose BMP, but the RSD from the automated system exceeded the limit. Full article
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Open AccessFeature PaperArticle
Improving Inter-Laboratory Reproducibility in Measurement of Biochemical Methane Potential (BMP)
Water 2020, 12(6), 1752; https://doi.org/10.3390/w12061752 - 19 Jun 2020
Cited by 1
Abstract
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 [...] Read more.
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. Full article
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Open AccessArticle
Impact of Storage Conditions on the Methanogenic Activity of Anaerobic Digestion Inocula
Water 2020, 12(5), 1321; https://doi.org/10.3390/w12051321 - 07 May 2020
Cited by 1
Abstract
The impact of storage temperature (4, 22 and 37 °C) and storage time (7, 14 and 21 days) on anaerobic digestion inocula was investigated through specific methanogenic activity assays. Experimental results showed that methanogenic activity decreased over time with storage, regardless of storage [...] Read more.
The impact of storage temperature (4, 22 and 37 °C) and storage time (7, 14 and 21 days) on anaerobic digestion inocula was investigated through specific methanogenic activity assays. Experimental results showed that methanogenic activity decreased over time with storage, regardless of storage temperature. However, the rate at which the methanogenic activity decreased was two and five times slower at 4 °C than at 22 and 37 °C, respectively. The inoculum stored at 4 °C and room temperature (22 °C) maintained methanogenic activity close to that of fresh inoculum for 14 days (<10% difference). However, a storage temperature of 4 °C is preferred because of the slower decrease in activity with lengthier storage time. From this research, it was concluded that inoculum storage time should generally be kept to a minimum, but that storage at 4 °C could help maintain methanogenic activity for longer. Full article
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Open AccessFeature PaperArticle
Evaluation of Common Supermarket Products as Positive Controls in Biochemical Methane Potential (BMP) Tests
Water 2020, 12(5), 1223; https://doi.org/10.3390/w12051223 - 25 Apr 2020
Cited by 1
Abstract
Biochemical methane potential (BMP) tests are commonly applied to evaluate the recoverable amount of methane from a substrate. Standardized protocols require inclusion of a positive control with a known BMP to check the experimental setup and execution, as well as the performance of [...] Read more.
Biochemical methane potential (BMP) tests are commonly applied to evaluate the recoverable amount of methane from a substrate. Standardized protocols require inclusion of a positive control with a known BMP to check the experimental setup and execution, as well as the performance of the inoculum. Only if the BMP of the positive control is within the expected range is the entire test validated. Besides ignorance of this requirement, limited availability of the standard positive control microcrystalline cellulose might be the main reason for neglecting a positive control. To address this limitation, eight widely available grocery store products have been tested as alternative positive controls (APC) to demonstrate their suitability. Among them, Tic Tacs and gummi bears were very promising, although they are dominated by easily degradable sugars and so do not test for hydrolytic performance. Coffee filters exhibited a similar performance to microcrystalline cellulose, while whole milk might be chosen when a more balanced carbohydrate:protein:lipid ratio is important. Overall, the approach of predicting the BMP of a substrate based on the nutritional composition provided on the product packaging worked surprisingly well: BMP of the eight tested products was 81–91% of theoretical maximum BMP based on nutritional information and generic chemical formulas for carbohydrates, proteins, and lipids. Full article
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Open AccessFeature PaperArticle
Development and Validation of a Low-Cost Gas Density Method for Measuring Biochemical Methane Potential (BMP)
Water 2019, 11(12), 2431; https://doi.org/10.3390/w11122431 - 20 Nov 2019
Cited by 3
Abstract
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 [...] Read more.
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. Full article
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Review

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Open AccessReview
Existing Empirical Kinetic Models in Biochemical Methane Potential (BMP) Testing, Their Selection and Numerical Solution
Water 2020, 12(6), 1831; https://doi.org/10.3390/w12061831 - 26 Jun 2020
Abstract
Biochemical Methane Potential (BMP) tests are a crucial part of feasibility studies to estimate energy recovery opportunities from organic wastes and wastewater. Despite the large number of publications dedicated to BMP testing and numerous attempts to standardize procedures, there is no “one size [...] Read more.
Biochemical Methane Potential (BMP) tests are a crucial part of feasibility studies to estimate energy recovery opportunities from organic wastes and wastewater. Despite the large number of publications dedicated to BMP testing and numerous attempts to standardize procedures, there is no “one size fits all” mathematical model to describe biomethane formation kinetic precisely. Importantly, the kinetics models are utilized for treatability estimation and modeling processes for the purpose of scale-up. A numerical computation approach is a widely used method to determine model coefficients, as a replacement for the previously used linearization approach. However, it requires more information for each model and some range of coefficients to iterate through. This study considers existing empirical models used to describe biomethane formation process in BMP testing, clarifies model nomenclature, presents equations usable for numerical computation of kinetic parameters as piece-wise defined functions, defines the limits for model coefficients, and collects and analyzes criteria to evaluate and compare model goodness of fit. Full article
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