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12 pages, 1058 KiB

Open AccessArticle

Agro-Waste, a Solution for Rural Electrification? Assessing Biomethane Potential of Agro-Waste in Inhambane Province, Southern Mozambique

by Fastudo Mabecua, Sebastian Schwede, Carlos Lucas and Patrik Klintenberg

Water 2021, 13(7), 939; https://doi.org/10.3390/w13070939 - 30 Mar 2021

Cited by 3 | Viewed by 2459

Abstract

In this study, we investigated the biomethane potential of cassava peels from the four most common varieties of cassava grown in Inhambane Province in Mozambique, Chinhembue, Cussi, Cizangara and Nhassumbi. Agro-wastes from coconut wood and jambolan wood processing were also analyzed to give [...] Read more.

In this study, we investigated the biomethane potential of cassava peels from the four most common varieties of cassava grown in Inhambane Province in Mozambique, Chinhembue, Cussi, Cizangara and Nhassumbi. Agro-wastes from coconut wood and jambolan wood processing were also analyzed to give a complete analysis of the most significant sources of agro-waste in the province. The macromolecular composition (carbohydrates, lipids and proteins) was determined and used to calculate the theoretical maximum biochemical methane potential (BMP). The results show that cassava fiber and cassava peel, which are considered to be waste, are viable resources for biomethane production. Further, the results show that cassava fiber and cassava peel have a higher biomethane potential compared with sawdust, and are therefore more suitable for biomethane production. A study to investigate the effect of toxic cyanogenic glycosides and lignin on cassava peels, using pre-treatment techniques to enhance biogas yield, should be carried out. An estimate of how much electricity can be generated based on the availability of agro-waste (cassava residues) and the amount of biomethane produced in our laboratory experiment was carried out. The amount of electricity that can be produced is enough to provide a valuable contribution to the production process in small and medium sized enterprises (SMEs) and in the cassava industry, or some other use in the rural setting. Full article

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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33 pages, 3951 KiB

Open AccessArticle

Measurement of Biochemical Methane Potential of Heterogeneous Solid Substrates: Results of a Two-Phase French Inter-Laboratory Study

by Thierry Ribeiro, Romain Cresson, Sébastien Pommier, Sébastien Preys, Laura André, Fabrice Béline, Théodore Bouchez, Claire Bougrier, Pierre Buffière, Jesús Cacho, Patricia Camacho, Laurent Mazéas, André Pauss, Philippe Pouech, Maxime Rouez and Michel Torrijos

Water 2020, 12(10), 2814; https://doi.org/10.3390/w12102814 - 10 Oct 2020

Cited by 11 | Viewed by 3610

Abstract

Biochemical methane potential (BMP) is essential to determine the production of methane for various substrates; literature shows important discrepancies for the same substrates. In this paper, a harmonized BMP protocol was developed and tested with two phases of BMP tests carried out by [...] Read more.

Biochemical methane potential (BMP) is essential to determine the production of methane for various substrates; literature shows important discrepancies for the same substrates. In this paper, a harmonized BMP protocol was developed and tested with two phases of BMP tests carried out by eleven French laboratories. Surprisingly, for the three same solid tested substrates (straw; raw mix and dried-shredded mix of potatoes, maize, beef meat and straw; and mayonnaise), the standard deviations of the repeatability and reproducibility inter-laboratory were not enhanced by the harmonized protocol (average of about 25% depending on the substrate), as compared to a previous step where all laboratories used their own protocols. Moreover, statistical analyses of all the results, after removal of the outliers (about 15% of all observations), did not highlight significant effect of the operational effect on BMP (stirring, automatic or manual gas quantification, use of trace metal, uses a bicarbonate buffer, inoculum to substrate ratio) at least for the tested ranges. On the other hand, the average intra-laboratory repeatability was low, about 7%, whatever the protocol, the substrate and the laboratory. It also appears that drying the SA substrate, which contained proteins, carbohydrates, lipids and fibers, does not impact its BMP. Full article

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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15 pages, 2439 KiB

Open AccessArticle

How Different Are Manometric, Gravimetric, and Automated Volumetric BMP Results?

by Corrado Amodeo, Sasha D. Hafner, Rúben Teixeira Franco, Hassen Benbelkacem, Paul Moretti, Rémy Bayard and Pierre Buffière

Water 2020, 12(6), 1839; https://doi.org/10.3390/w12061839 - 26 Jun 2020

Cited by 13 | Viewed by 4603

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

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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31 pages, 3862 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

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

by Sasha D. Hafner, Hélène Fruteau de Laclos, Konrad Koch and Christof Holliger

Water 2020, 12(6), 1752; https://doi.org/10.3390/w12061752 - 19 Jun 2020

Cited by 53 | Viewed by 7209

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 (RSD_R) 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 NmL_CH4 g_VS⁻¹. Evidence from this large dataset shows that following the recommendations—in particular, application of validation criteria—can substantially improve reproducibility, with RSD_R < 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

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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12 pages, 498 KiB

Open AccessArticle

Impact of Storage Conditions on the Methanogenic Activity of Anaerobic Digestion Inocula

by Sergi Astals, Konrad Koch, Sören Weinrich, Sasha D. Hafner, Stephan Tait and Miriam Peces

Water 2020, 12(5), 1321; https://doi.org/10.3390/w12051321 - 7 May 2020

Cited by 23 | Viewed by 4562

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

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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13 pages, 2686 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Evaluation of Common Supermarket Products as Positive Controls in Biochemical Methane Potential (BMP) Tests

by Konrad Koch, Sasha D. Hafner, Sergi Astals and Sören Weinrich

Water 2020, 12(5), 1223; https://doi.org/10.3390/w12051223 - 25 Apr 2020

Cited by 13 | Viewed by 4615

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

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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17 pages, 2248 KiB

Open AccessFeature PaperArticle

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

by Camilla G. Justesen, Sergi Astals, Jacob R. Mortensen, Rasmus Thorsen, Konrad Koch, Sören Weinrich, Jin Mi Triolo and Sasha D. Hafner

Water 2019, 11(12), 2431; https://doi.org/10.3390/w11122431 - 20 Nov 2019

Cited by 25 | Viewed by 6296

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

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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Review

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17 pages, 317 KiB

Open AccessReview

Existing Empirical Kinetic Models in Biochemical Methane Potential (BMP) Testing, Their Selection and Numerical Solution

by Yehor Pererva, Charles D. Miller and Ronald C. Sims

Water 2020, 12(6), 1831; https://doi.org/10.3390/w12061831 - 26 Jun 2020

Cited by 35 | Viewed by 4806

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

(This article belongs to the Special Issue Biomethane Potential Tests—A Key Tool for Anaerobic Digestion Research and Practice)

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