Abstract
Short rotation plantations of willow genotypes, harvested in vegetative growth phases, were tested as an alternative biomass for methane production. The substrate characteristics, maximal methane yields (K) and highest methane production rates (µmax) were determined. Leaves and stems from diploid Energo (EN) and tetraploid (PP) plants, harvested in June were superior methane sources to woody tissue. This could be related to the lower lignin contents in green willow. Fermentation of pooled biomasses from tetraploid genotypes harvested in June-August was more efficient than methane production from diploid tissues. Microbial community analyses by 16S rRNA genes showed a dominance of the order Clostridiales. In field study, based on Energo plantation, the maximum in green biomass accumulation was in early month 9 of the vegetation period. A theoretical calculation showed similar or better energy potential per unit area for willow than in the case of maize silage. This study encourages the use of green willow biomass as feedstock in biomethanation processes due to its relatively low production costs and uncomplicated agricultural practice.
Highlights
Concerns over climate change and energy security urge the increase of biomass use for sustainable heat and biofuel production
The biogas industry is growing dynamically worldwide accompanied with increasing concern about supplying the anaerobic digestion (AD) reactors with first generation biomasses, i.e. energy plants cultivated on agricultural land (Kalamaras and Kotso poulos, 2014), such as maize silage (Purdy et al, 2017; Wagner et al, 2018)
An early harvest in May was used for biomass productivity estimation only
Summary
Concerns over climate change and energy security urge the increase of biomass use for sustainable heat and biofuel production. The biogas industry is growing dynamically worldwide accompanied with increasing concern about supplying the anaerobic digestion (AD) reactors with first generation biomasses, i.e. energy plants cultivated on agricultural land (Kalamaras and Kotso poulos, 2014), such as maize silage (Purdy et al, 2017; Wagner et al, 2018). The cultivation cost of maize silage and similar crops is relatively high, and the fertile agricultural lands should be used for food and feed production. Intensive search is in progress to switch biogas production towards second-generation, alternative substrates that do not come into conflict with crops that could serve human or animal nutritional pur poses (food vs energy debate) (Brethauer and Studer, 2015; CliftonBrown et al, 2019). Valuable insights can be drawn by analyzing this community via highthroughput 16S rRNA gene amplicon sequencing, linking the bacterial and archaeal structures of AD microbial communities to feed substrates and process parameters (Kougias et al, 2018)
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