Assessing the Effects of Substrate Disintegration on Methane Yield

Hofmann, Josephine; Müller, Liane; Weinrich, Sören; Debeer, Lies; Schumacher, Britt; Velghe, Filip; Liebetrau, Jan

doi:10.1002/ceat.201900393

Cited by 6 publications

(2 citation statements)

References 11 publications

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“…in four AD feedstock formulations at 37 °C in a small scale laboratory system. Although previously shown to be a useful study tool [ 12 ], laboratory-scale batch systems may not be representative of full-scale continuous commercial bioreactors due to differences in inoculation methods, rheology and hydrodynamic factors [ 27 ]. Moreover, as our feedstock mixtures were formulated on a volumetric basis, it is possible that the organic load could have been different between the various formulations.…”

Section: Discussionmentioning

confidence: 99%

A Small Study of Bacterial Contamination of Anaerobic Digestion Materials and Survival in Different Feed Stocks

et al. 2020

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If pathogens are present in feedstock materials and survive in anaerobic digestion (AD) formulations at 37 °C, they may also survive the AD process to be disseminated in digestate spread on farmland as a fertilizer. The aim of this study was to investigate the prevalence of Salmonella spp., Escherichia coli O157, Listeria monocytogenes, Enterococcus faecalis and Clostridium spp. in AD feed and output materials and survival/growth in four formulations based on food waste, bovine slurry and/or grease-trap waste using International Organization for Standardization (ISO) or equivalent methods. The latter was undertaken in 100 mL Ramboldi tubes, incubated at 37 °C for 10 d with surviving cells enumerated periodically and the T90 values (time to achieve a 1 log reduction) calculated. The prevalence rates for Salmonella spp., Escherichia coli O157, Listeria monocytogenes, Enterococcus faecalis and Clostridium spp. were 3, 0, 5, 11 and 10/13 in food waste, 0, 0, 2, 3 and 2/3 in bovine slurry, 1, 0, 8, 7 and 8/8 in the mixing tank, 5, 1, 17, 18 and 17 /19 in raw digestate and 0, 0, 0, 2 and 2/2 in dried digestate, respectively. Depending on the formulation, T90 values ranged from 1.5 to 2.8 d, 1.6 to 2.8 d, 3.1 to 23.5 d, 2.2 to 6.6 d and 2.4 to 9.1 d for Salmonella Newport, Escherichia coli O157, Listeria monocytogenes, Enterococcus faecalis and Clostridium sporogenes, respectively. It was concluded that AD feed materials may be contaminated with a range of bacterial pathogens and L. monocytogenes may survive for extended periods in the test formulations incubated at 37 °C.

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Section: Discussionmentioning

confidence: 99%

A Small Study of Bacterial Contamination of Anaerobic Digestion Materials and Survival in Different Feed Stocks

et al. 2020

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“…Since the pretreatment process is an energy-intensive operation, a reduction in energy demand would positively affect the economics of the entire process [31]. In addition, substrate pretreatment can also have a positive effect on the mixing and pumpability of the digester contents and the prevention of floating layers, which can lead to a reduction in stirring and pumping efforts and thus savings in operating costs [25,96]. However, these side effects are very difficult to prove in laboratory experiments and would need to be tested in field trials.…”

Section: Energy Balance Of the Pretreatment And Consideration Of Prof...mentioning

confidence: 99%

Comparison of Different Mechanical Pretreatment Methods for the Anaerobic Digestion of Landscape Management Grass

Heller,

Brandhorst,

Hülsemann

et al. 2023

Energies

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The aim of this study was to use landscape grass from species-rich orchards for biogas production, thus preserving these very valuable areas for future generations. Since these grass clippings have high lignocellulose content, the substrate has to be pretreated before being fed into the biogas digester. In this study, three different mechanical treatment processes (cross-flow grinder, ball mill and a mounted mower) were investigated and compared with untreated grass clippings. Chemical composition, specific methane yield, degradation kinetics and microscopic images were analyzed. In order to derive recommendations, the harvesting and pretreatment processes were examined in terms of energy demand, additional methane yield, and suitability of the substrate for use in biogas plants, taking into account conservation aspects. Within the pretreatment process, ball milling leads to the highest significant increase in specific methane yield of up to 5.8% and the fastest gas formation kinetics (lag time λBM: 0.01 ± 0.0 d; duration to reach half of total gas production ½M(x)BM: 5.4 ± 0.2 d) compared to the untreated variant (λUT: 1.02 ± 0.2 d; ½M(x)UT: 6.5 ± 0.2 d). A comparison of the energy required for the mechanical disintegration of the substrates with the increased yield of methane during the digestion process shows that the mechanical processing of these substrates appears to be useful. A positive energy balance was achieved for the cross-flow grinder (12.3 kWh tVS−1) and the ball mill (21.4 kWh tVS−1), while the Amazone Grasshopper left a negative balance (−18.3 kWh tVS−1), requiring more energy for substrate pretreatment than was generated as methane surplus. In summary, the pretreatment of landscape management grass is a suitable approach for utilizing agricultural residues efficiently in a biogas plant and thus contributing to sustainable energy production.

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Effects of Pretreatment with a Ball Mill on Methane Yield of Horse Manure

Heller

Roth

Hülsemann

et al. 2023

Waste Biomass Valor

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Lignocellulosic biomass is an abundant organic material, which can be utilised in biogas plants for sustainable production of biogas. Since these substrates usually have high lignin contents and consist of rather elongated particles, a special pretreatment is required for an economical and process-stable utilisation in the biogas plant. The mechanical pretreatment of horse manure was carried out with the prototype of a ball mill at different speeds. The aim of ball milling is to comminute the substrate and disintegrate the lignocellulosic bond. Mechanical pretreatment in the ball mill resulted in a significant increase in specific methane yield of more than 37% in anaerobic batch digestion (up to 243 LCH4 kgVS−1) of horse manure. The kinetics of the methane gas formation process was analysed by a modified Gompertz model fitting and showed a higher methane production potential and maximum daily methane production rate as well as a lower duration of the lag phase after pretreatment at 6 rpm. This was further confirmed by sieve analyses, which showed a significant reduction of particle size compared to the untreated variant. Thus, the use of the ball mill increases the specific methane yield and improves the fermentation of lignocellulosic substrates such as horse manure. Graphical Abstract

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Assessing the Effects of Substrate Disintegration on Methane Yield

Cited by 6 publications

References 11 publications

A Small Study of Bacterial Contamination of Anaerobic Digestion Materials and Survival in Different Feed Stocks

A Small Study of Bacterial Contamination of Anaerobic Digestion Materials and Survival in Different Feed Stocks

Comparison of Different Mechanical Pretreatment Methods for the Anaerobic Digestion of Landscape Management Grass

Effects of Pretreatment with a Ball Mill on Methane Yield of Horse Manure

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