Towards a standardization of biomethane potential tests

8 PáginasProduction of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.The workshop in Leysin, Switzerland, has been financed by the Swiss Federal Office for Energy, and co-sponsored by Bioprocess Control Sweden AB, Lund, Sweden. The authors thank Alexandra Maria Murray for editing the English

An overview on techniques and regulations of mechanical-biological pre-treatment of municipal solid waste

Landfilling of municipal solidwaste (MSW) causes significant problems from the production of landfill gas (LFG) and highly polluted leachate over long periods of time. These emissions have to be controlled, treated and sustainable reduced during the aftercare phase, incurring significant costs. Therefore, the overall wastemanagement strategy in Europe is towards reducing landfilling and promoting energy recovery fromMSW. However, as thermal treatment capacities are currently limited and incineration plants rely on largewaste input quantities (>150,000 t * a-1),mechanicalbiological pre-treatment (MBP) of waste was implemented as an alternative in different EU countries. By means of a combination ofmechanical pre-treatment and subsequent biological treatment, the emissions potential of the residual MSW can be significantly reduced under controlled conditions. As a result, MBP can be seen as an integral part of modern waste management concepts, including the mandatory separation of the high caloric fraction to be used as a fuel and for the production of biologically stabilised waste for landfilling. In order to improve the overall energy balance, modern MBP plants often include anaerobic treatment as the biological process component, hence increasing the efficiency of energy recovery from MSW

Potential emissions from two mechanically-biologically pretreated (MBT) wastes.

The interaction of parameters determining the potential emissions of two different mechanically-biologically pretreated municipal solid wastes (MBT wastes) is elucidated in this work. The origins of the wastes are Germany and Sweden. By means of lab-scale experiments, increased stabilisation through composting is preferably determined by a decrease in respiration activity. Concurrently, the stabilisation is verified for the leachates by a decrease in COD, DOC, and BOD(5). Total organic carbon content reflects stabilisation less accurately. FT-IR and thermal analytical methods add valuable information about the state of degradation, especially when several distinct thermal parameters are taken into account. Mobility of Cr, Ni, Pb, and Zn produced by a batch leaching test with deionized water is reduced by the pretreatment of both materials. Mobility of copper unambiguously increased. A principle component analysis (PCA) of membrane fractionated leachates indicates an affinity of Cu to mobile humic acids or dissolved organic carbon. High Cr, Zn, and Ni contents in the solid co-occur with high contents of solid humic acids. To a lesser extent, this is also true for solid Cd, Cu, and Pb contents. Due to differences in required landfilling conditions, actual emissions and after-care phase length will depend on whether each waste is landfilled in Germany or Sweden

Development of a method to produce standardised and storable inocula for biomethane potential tests \u2013 Preliminary steps

In biomethane potential (BMP) tests, different sources and origins of inocula might cause significant variations in the tests\u2019 results, preventing from acquiring a harmonised and standardised evaluation of the different substrates. In this study, a method to produce standardised and storable inocula was elaborated. For the development of the different investigation steps a control sludge originated from a wastewater treatment plant was utilised. Freeze-drying was applied in the framework of this study as a long-term conservation method for the anaerobic inocula. In order to ensure a closed system with anaerobic conditions at all times, a test system was developed to allow accurate and representative mass-balance experiments. The test results demonstrated that inocula conservation and re-suspension in BMP tests is possible; the limit value of the expected methane yield of a positive and lyophilised reference-control, was reached. However, a lag phase of 7\u201310 days was obtained, possibly due to the damage of microorganisms as a consequence of the conservation process. Further investigations need to be carried out to optimise the conservation process of the produced inocula or an initial preparation phase should be considered to reduce the lag phase

Investigation of standardised and adapted inocula for biomethane potential tests

In biomethane potential (BMP) tests, different sources and origins of inocula might cause significant variations in the tests’ results, preventing from acquiring a harmonised and standardised evaluation of the different substrates. In this study, a method to produce standardised and storable inocula was elaborated. In anaerobic bioreactors, inoculum based on Dried Destined Grain Substrates (DDGS) pellets was initially produced as substrate under defined conditions. Freeze-drying was applied in the framework of this study as a long-term conservation method for the anaerobic inocula. In order to ensure a closed system with anaerobic conditions at all times, a test system was developed allowing accurate and representative mass-balance experiments. The test results demonstrated that inocula preservation and re-suspension in BMP tests is possible; the limit value of the expected methane yield of the positive and lyophilised DDGS-substrate- control, was reached. However, the lyophilized inoculum with DDGS as substrate showed a significant lower specific biogas production compared to the postive control. After the repeated addition of DDGS after 68 days of incubation, no lag phase was observed in biogas production in the lyophilized batch. In this case, a lower substrate degradation compared to the first step was observed. Therefore, further investigations are necessary to reduce the lag phase and to develop a two-stage BMP test in which the standardised and storable inoculum can be added at defined concentrations in capsule or tablet form

Degradation of thermoplastic cellulose acetate-based bioplastics by full-scale experimentation of industrial anaerobic digestion and composting

The ability of full-scale industrial plants to degrade bioplastics waste must be verified to exclude any negative effects on the quality of the process outputs. This study aims to assess the degradation of two thermoplastic cellulose acetate-based bioplastics, in pure and composite forms in both Anaerobic Digestion (AD) and Composting (C) industrial conditions. The main degradation occurred during AD, where a disintegration of about 36% and 50% was achieved from pure and composite thermoplastic cellulose acetate, respectively. The disintegration during C did not exceed 20% for both samples. The combined process resulted in a slightly higher degradation (58–40%) than that obtained in AD, revealing how the main alteration of samples occurred in an anaerobic environment. Despite this macroscopic degradation, the samples showed only minor superficial degradation as highlighted from SEM analysis. FT-IR spectroscopy, TGA andDSC analyses showed that the biodegradation mechanism involved mainly the plasticizer loss and deacetylation of the cellulose matrix, with only partial degradation of cellulose backbone However, both deacetylation and degradation were favored in AD and AD + C processes and from the presence of filler in anaerobic conditions. These results demonstrated how the degradation obtained on an industrial scale can differ significantly from those obtained in the laboratory scale, especially for pure thermoplastic cellulose acetate. Furthermore, current industrial AD and C process resulted not optimized for the treatment of thermoplastic cellulose acetate-based bioplastics. Hence, this works could help waste facilities managers to process emerging materials such as bioplastics in a more sustainable way. © 2023 Elsevier B.V