Optimizing agricultural wastes storage before anaerobic digestion: impact of ensiling on methane potential of lignocellulosic biomass
Résumé
Storage requirements for anaerobic digestion feedstock are boosting ensiling research for biogas production purposes. However, so far, studies have been mainly focused on good management practices of easily biodegradable biomass. In this article, effect of ensiling, open-air storage and feedstock moisture on methane potential of an agricultural crop were investigated during six months. Open-air storage presented linear losses of organic matter and energy content along storage, culminating in more than 70% and 90% losses after six months, respectively. For ensiling, lack of accessible sources of carbohydrates hindered acidification, allowing undesired secondary fermentation, which led to non-negligible organic matter losses. Wilting was an ineffective technique for this type of crop, since increased organic matter losses from around 10% to 20% after six months, leading to energy losses. Despite the use of a poorly ensilable biomass, fresh raw material at lower moisture content conserved its methane potential along 6 months of ensiling. Water-soluble phase of methane potential will increase with the ensiling duration. Although this may favor methane production kinetics, higher losses of energy content may occur in case of liquid seepage along storage. Storage optimization of this agricultural waste will be achieved by ensiling raw material without need for wilting and collecting the probable liquid effluent production.
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