Genome-centric investigation of anaerobic digestion using sustainable second and third generation substrates

Roland Wirth,Bernadett Pap,Dénes Dudits,Balázs Kakuk,Zoltán Bagi,Prateek Shetty,Kornél L Kovács,Gergely Maróti

doi:10.1016/j.jbiotec.2021.08.002

Abstract

Biogas production through co-digestion of second and third generation substrates is an environmentally sustainable approach. Green willow biomass, chicken manure waste and microalgae biomass substrates were combined in the anaerobic digestion experiments. Biochemical methane potential test showed that biogas yields of co-digestions were significantly higher compared to the yield when energy willow was the sole substrate. To scale up the experiment continuous stirred-tank reactors (CSRTs) are employed, digestion parameters are monitored. Furthermore, genome-centric metagenomics approach was employed to gain functional insight into the complex anaerobic decomposing process. This revealed the importance of Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes phyla as major bacterial participants, while Methanomicrobia and Methanobacteria represented the archaeal constituents of the communities. The bacterial phyla were shown to perform the carbohydrate hydrolysis. Among the representatives of long-chain carbohydrate hydrolysing microbes Bin_61: Clostridia is newly identified metagenome assembled genome (MAG) and Bin_13: DTU010 sp900018335 is common and abundant in all CSTRs. Methanogenesis was linked to the slow-growing members of the community, where hydrogenotrophic methanogen species Methanoculleus (Bin_10) and Methanobacterium (Bin_4) predominate. A sensitive balance between H2 producers and consumers was shown to be critical for stable biomethane production and efficient waste biodegradation.

Highlights

The global demand for clean energy has led to an increased attention on the sustainability of energy supplies
We examined and compared different codigestion mixtures of green willow biomass (GWB), microalgalbacterial biomass grown on wastewater (MABA) and pre-treated chicken manure (TCM)
The key factor was the high “soluble” content. Both TCM and Microalgal-bacterial biomass (MABA) had a low C/N ratio compared to GWB, but contains high amount of additional nutrients (Table 1)

Summary

Introduction

The global demand for clean energy has led to an increased attention on the sustainability of energy supplies. Using edible biomass competes with food crops, requires significant amount of fertilizer, pesticides and water, large areas of cropland (Kakuk et al, 2021; Rulli et al, 2016). Second generation biogas sources are more renewable al ternatives by utilizing inedible lignocellulosic materials such as crop wastes, sawdust, low-priced woods (Neshat et al, 2017). This generation overcomes the drawbacks of the first generation, like the net emitted/consumed carbon is neutral or even negative and can be pro duced in non-cultivable lands. Microalgae have a higher biomass productivity than that of terrestrial crops and can be cultivated all year around (Klassen et al, 2016)

Methods

Results

Conclusion