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In Europe, the agricultural biogas sector is currently undergoing fast developments, and cattle manure constitutes an important feedstock. Batch dry digester processes with leachate recirculation prove to be particularly interesting for small-scale plants. However, their startup being relatively slow, the process could be facilitated by co-digestion with energy crops. In this study, Miscanthus x was chosen for its high biomass yields and low input requirements. The carbohydrate accessibility of this lignocellulosic biomass is limited but may be improved with alkali pretreatment. The efficiency of lime (CaO) pretreatment with low water addition on the biochemical methane potential (BMP) of miscanthus was investigated through two experimental designs (CaO concentrations ranged between 2.5 and 17.5% and pretreatment lasted 1, 3, or 5 days). The pretreated miscanthus was then co-digested with cattle manure in dry leach bed reactors. CaO pretreatments led to a 14⁻37% improvement of miscanthus BMP, and a 67⁻227% increase in the first-order kinetics constant; a high contact time was shown to favor methane production. According to these results and to industrial requirements, miscanthus was pretreated with 5 and 10% CaO for 5 days, then co-digested with manure in dry leach bed reactors. Nevertheless, the promising results of the BMP tests were not validated. This could be related to the high water absorption capacity of miscanthus.giganteus was chosen for its high biomass yields and low input requirements. The carbohydrate accessibility of this lignocellulosic biomass is limited but may be improved with alkali pretreatment. The efficiency of lime (CaO) pretreatment with low water addition on the biochemical methane potential (BMP) of miscanthus was investigated through two experimental designs (CaO concentrations ranged between 2.5 and 17.5% and pretreatment lasted 1, 3, or 5 days). The pretreated miscanthus was then co-digested with cattle manure in dry leach bed reactors. CaO pretreatments led to a 14⁻37% improvement of miscanthus BMP, and a 67⁻227% increase in the first-order kinetics constant; a high contact time was shown to favor methane production. According to these results and to industrial requirements, miscanthus was pretreated with 5 and 10% CaO for 5 days, then co-digested with manure in dry leach bed reactors. Nevertheless, the promising results of the BMP tests were not validated. This could be related to the high water absorption capacity of miscanthus.

In the context of increasing needs of lignocellulosic biomass for emerging biorefinery, miscanthus is expected to represent a resource for energy production. Regarding biogas production, its potential may be improved either by genotype selection or pretreatment. Eight different miscanthus genotypes belonging to Miscanthus × giganteus (FLO, GID and H8), M. sacchariflorus (GOL, MAL, AUG, H6) and M. sinensis (H5) species were first compared for biomass composition and potential methane. In a second time, alkali pretreatments (NaOH 10 g 100 gTS−1, CaO 10 g 100 gTS−1) were applied at ambient temperature and high solid content, in different conditions of duration and particle size on the genotype FLO presenting the lowest methane potential. The methane potential varied between miscanthus genotypes with values ranging from 166 ± 10 to 202 ± 7 NmLCH4 gVS−1. All of the studied pretreatments increased the methane production up to 55% and reduced Klason lignin and holocellulose contents up to 37%. From this study, NaOH was more efficient than CaO with an increase of the methane production between 24 and 55% and between 19 and 30%, respectively. [ABSTRACT FROM AUTHOR]