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Item type:Publication, Access status: without files , Improving Methane Yields of Semi-continuous Anaerobic Digestion of Deinking Sludge from Wastepaper Recycling(2020-09-01); ; Purpose: The purpose of the study was to investigate the role of trace elements (TEs) supplementation in connection with the organic load rate (OLR) and the hydraulic retention time (HRT) on methane (CH4) yields in semi-continuous anaerobic digestion of deinking sludge (DS) in order to judge the possibility to use DS as alternative energy source in wastepaper recycling companies. Methods: After substrate characterization, a semi-continuous anaerobic digestion was performed for 74 days using 2-L stirred tank reactors at a mesophilic (37 °C) condition, whereas one of them was supplemented with a mixture of TEs (cobalt, nickel, molybdenum and selenium). The feeding periods had a duration of 4, 7 or 8 days. Results: The highest cumulative CH4 yield after a feeding period was found to be 151 NmL/g oDM after TE supplementation. The TEs-supplementation has resulted in 42% increase in CH4 yield compared to the non-supplemented variant. The increase took place at the end of the experiment. Earlier feeding periods with similar conditions regarding HRT and OLR, did not show an increase. This can be explained by the fact that TEs supplementation requires a longer adaption time for the microorganism. Conclusions: TEs addition has shown a strongly positive impact on CH4 yields. Our results showed that it is possible to receive the same yields in semi-continuous, more practice-close operation, compared to previous potential determination experiments under batch conditions. A further optimization potential is seen by optimizing TEs supplementation in connection with VOA level in the reactor, optimizing C/N ratio and lowering the duration of the feeding intervals. Graphic Abstract: [Figure not available: see fulltext.]Publicationtype: Journal Article29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Anaerobic treatment of deinking sludge: Methane production and organic matter degradation(2019-02-15); ; Deinking sludge (DS) is a residue from the waste paper recycling industry. It is a by-product originating from the deinking process which is designed to remove inks and other impurities from waste papers to recover usable fibers. The aim of this study was to investigate the possibility of anaerobic digestion (AD) of DS in order to produce methane (CH4) by degrading organic matter. DS differs clearly from common AD substrates due to its specific composition. The focus was laid on comparing various inocula in order to find appropriate microbial consortia. Three inocula from different origins were investigated. After sludge and inocula characterization, batch AD at a mesophilic (37 °C) condition was performed for 21 days to determine biogas and CH4 potentials as well as sludge biodegradability in comparison to cellulose. The highest average CH4 yield achieved in the 21 days of the batch experiment was 167 NmL/g organic dry matter (oDM). However, the CH4 potentials from all experiments did not have a wide range (average 160 NmL/g oDM; standard deviation ±5.0 NmL/g oDM). The highest organic matter degradation achieved was 31%. It can be stated that conventional AD inocula are usable to degrade DS, but that a significant part of the oDM was anaerobically not degradable. The overall CH4 yields were lower compared to top AD substrates such as energy crops, but in a similar range like residue-based AD substrates such as manure. Since actual DS management is cost-intensive and affecting the profitability of waste paper industry significantly, AD as a management option with an energetically valuable output is a very promising option.Publicationtype: Journal Article316