Anaerobic Co-Digestion of Common Reed and Plant-Based Biowaste from Households

Abstract

Organic wastes from households, private gardens, the maintenance of urban greenery, and active nature conservation measures are often difficult to manage. This lignocellulosic biomass may be suitable for anaerobic digestion (AD). However, the mono-digestion of plant material, such as waste from active conservation measures for wetlands, results in a low methane (CH4) yield. The aim of this study was to assess the feasibility of using common reed silage for co-digestion with plant-based biowaste from households. The specific methane yield (SMY) was determined in biochemical methane potential (BMP) tests performed on biowaste, reed silage, and combinations of reed silage with 10%, 30%, 50%, 70%, and 90% of biowaste on a fresh weight basis. The lowest SMY was observed for the mono-digestion of reed silage (160.40 ± 4.09 NL kgVS−1), while biowaste had the highest CH4 yield (284.03 ± 7.03 NL kgVS−1). The subsequent addition of biowaste enhanced CH4 production from 158.57 ± 7.88 NL kgVS−1 (10% of biowaste) to 233.28 ± 11.91 NL kgVS−1 (90% of biowaste). A key advantage of biogas production is its role in reducing CO2 emissions into the atmosphere, which result from the use of conventional fuels for energy generation. The avoided CO2 emissions generated in electricity and heat production range between 378.62 kgCO2 tTS−1 and 676.36 kgCO2 tTS−1 depending on the reed silage-to-biowaste ratio used for biogas production. This study reveals that reed silage is not an optimal feedstock for biogas production, and its share in co-digestion with biowaste should not exceed 10% of the total input to the biogas plant.