Investigation of the effect of equal and unequal feeding time intervals on process stability and methane yield during anaerobic digestion grass silage

Journal article


Egwu, U., Onyelowe, Kennedy, Tabraiz, S., Johnson, Emmanuel and Mutshow, A. 2022. Investigation of the effect of equal and unequal feeding time intervals on process stability and methane yield during anaerobic digestion grass silage. Renewable and Sustainable Energy Reviews. 158, p. 112092. https://doi.org/10.1016/j.rser.2022.112092
AuthorsEgwu, U., Onyelowe, Kennedy, Tabraiz, S., Johnson, Emmanuel and Mutshow, A.
AbstractThe effects of equal and unequal feeding intervals, organic loading rates (OLR) and operating temperatures on specific methane production (SMP) during the anaerobic digestion (AD) process were investigated using three pairs of continuously stirred tank reactors (CSTRs). The Pair 1, 2 and 3 CSTRs were operated at psychrophilic (25 ± 2 °C), mesophilic (40 ± 3 °C) and thermophilic (60 ± 2.5 °C) conditions, respectively. After acclimatization, the reactors were fed at an OLR of 1.0 and 1.5gVS/L.d at selected intervals, while maintaining their pH 6.8–7.2 with NH4HCO3 solution. The results showed that during uneven feeding regime (day 8–93), the mean SMP from Pair 1, 2 and 3 reactors were 294.5, 433.5 and 370.2 N mLCH4/gVS fed, respectively. At failing state (day 60–93), the mean concentrations of free ammonia nitrogen (FAN) in the psychrophilic, mesophilic and thermophilic CSTRs were 19.1, 33.7 and 127.2 mg/L; VFAs of 6940.1, 6852.3 and 4694.9 mg HAc/L; which reduced their SMPs to 140, 273.8 and 231.1 N mLCH4/gVS, respectively. Therefore, uneven feeding, trace elements (TEs) deficiency, VFAs accumulation and FAN (for thermophilic) led to CSTRs failure. An even (24-hourly) feeding regime with daily biomass ash-extracts supplement enhanced the recovery of the failed CSTRs. Although, uneven daily feeding conditions led to AD process instability, it favoured SMP in mesophilic CSTRs compared to psychrophilic and thermophilic. These results strongly indicate that the soluble TEs and alkalinity contained in ash-extracts facilitated the recovery of the failed AD reactors and therefore can be used to revive failed AD processes.
KeywordsAnaerobic digestion; Feeding time intervals; Operating temperature; Perennial ryegrass; Specific methane production; Supplements
Year2022
JournalRenewable and Sustainable Energy Reviews
Journal citation158, p. 112092
PublisherElsevier
ISSN13640321
Digital Object Identifier (DOI)https://doi.org/10.1016/j.rser.2022.112092
Official URLhttps://doi.org/10.1016/j.rser.2022.112092
FunderTertiary Education Trust Fund
Publication dates
Online13 Jan 2022
Publication process dates
Accepted09 Jan 2022
Deposited17 Jan 2022
Output statusPublished
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https://repository.canterbury.ac.uk/item/901y1/investigation-of-the-effect-of-equal-and-unequal-feeding-time-intervals-on-process-stability-and-methane-yield-during-anaerobic-digestion-grass-silage

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