Quality of digestate from anaerobic digestion of wetland biomass

Abstract

Abstract. Although the biomass from nature conservation management is gaining particular attention as a supplement or even substitute to energy crops, there is still little research on the production of biogas from wetland biomass and the quality of digestate obtained in anaerobic digestion. This study aimed to analyse selected physical and chemical properties of residues from anaerobically digested biomass harvested in a fluviogenous mire in a context of suitability as an agricultural fertilizer. We conducted a biomethane potential assay of five wetland plants: reed canary grass (Phalaris arundinacea), common reed (Phragmites australis), reed sweet-grass (Glyceria maxima), tufted sedge (Carex elata) and woollyfruit sedge (Carex lasiocarpa), cut in three different seasons of the year. Obtained digestates characterized a higher content of organic matter (75.1-82.4 % TS) and electrical conductivity (12.9-18.8 mS·cm -1 ) compared to the residues from a conventional agricultural biogas plant, treating mainly maize silage. They had, however, lower pH (7.4-7.8) and content of total phosphorus (0.7-1.2 % TS), while total nitrogen and potassium contents were similar (2.8-6.2 % TS and 4.3-6.1 % TS, respectively). Significant differences were found between digestates from different species of wetland plants. Although the term of biomass harvest had the impact on the physical and chemical properties of the digestates, each of the analysed AD products was found to be valuable sources of nutrients and organic matter and possessed a high potential as agricultural fertilizers.