The influence of biochar position in a leach bed system anaerobically digesting chicken litter

Ben A Collins; Cristian H Birzer; Stephen P Kidd; Tony Hall; Paul R Medwell

doi:10.1016/j.jenvman.2023.118404

The influence of biochar position in a leach bed system anaerobically digesting chicken litter

J Environ Manage. 2023 Oct 15:344:118404. doi: 10.1016/j.jenvman.2023.118404. Epub 2023 Jun 20.

Authors

Ben A Collins¹, Cristian H Birzer², Stephen P Kidd³, Tony Hall⁴, Paul R Medwell²

Affiliations

¹ School of Electrical and Mechanical Engineering, The University of Adelaide, South Australia, 5005, Australia; Humanitarian and Development Solutions Initiative, The University of Adelaide, South Australia, 5005, Australia. Electronic address: ben.collins@adelaide.edu.au.
² School of Electrical and Mechanical Engineering, The University of Adelaide, South Australia, 5005, Australia; Humanitarian and Development Solutions Initiative, The University of Adelaide, South Australia, 5005, Australia.
³ Australian Centre for Antimicrobial Resistance Ecology (ACARE), School of Biological Sciences, The University of Adelaide, South Australia, 5005, Australia; Humanitarian and Development Solutions Initiative, The University of Adelaide, South Australia, 5005, Australia.
⁴ Faculty of Sciences, The University of Adelaide, SA 5005, Australia.

PMID: 37348304
DOI: 10.1016/j.jenvman.2023.118404

Abstract

As a consequence of the rapidly growing poultry industry, chicken litter is becoming an abundant and problematic waste. Anaerobic digestion of chicken litter can mitigate environmental issues while producing valuable by-products. Recent studies have shown that leach bed reactor (LBR) systems are suitable for processing chicken litter and that anaerobic digestion can be enhanced using biochar. This study investigates the influence of biochar position within an LBR system on anaerobic digestion of chicken litter. Compared to a system without biochar, application of biochar in both the LBR (mixed in with the feedstock or as a layer below the feedstock) and coupled leachate tank (LT) increased methane yield by 6 to 8% at 51 days and accelerated VFA degradation and methane production. More significant differences in methane yield were observed at shorter solid retention times. Biochar mixed in feedstock in addition to a filter in the LT performed best in terms of both methane and hydrogen sulfide production, with a 77% reduction in hydrogen sulfide yield and hydrogen sulfide contents maintained below 500 ppm. The enhanced rates of VFA degradation and methane production when applying biochar in both reactors corresponds with observed differences in the methanogen population. Biochar application in both reactors increased the abundance of Methanobacteriales in digestate and Methanosarcinaceae in leachate compared to the control. Microbial attachment and activity on biochar also increased when mixed in feedstock. Increased diversity of the methanogen population throughout the system, as well as increased activity on biochar, may have facilitated the syntrophic relationship between acetogenic bacteria and methanogens, thus accelerating VFA degradation and methane production. These results suggest mixing biochar in feedstock, in addition to a biochar filter in the LT, to enhance anaerobic digestion of chicken litter in this system.

Keywords: Anaerobic digestion; Biochar; Biogas; Chicken litter; Hydrogen sulfide; Leach bed reactor.

MeSH terms

Anaerobiosis
Animals
Bioreactors / microbiology
Chickens*
Hydrogen Sulfide*
Methane

Substances

biochar
Hydrogen Sulfide
Methane