Unravelling (maize silage) digestate features throughout a full-scale plant: A spectroscopic and thermal approach. (20th August 2018)

• Record Type: Journal Article
• Authors: Provenzano, Maria Rosaria; Cavallo, Ornella; Malerba, Anna Daniela; Fabbri, Claudio; Zaccone, Claudio
• Is Part Of: Journal of cleaner production. Volume 193(2018)
• Page Start: 372
• Page End: 378
• Publication Date: 2018-08-20
• Subjects: Anaerobic digestion -- EEM -- FTIR -- Molecular fluorescence -- T50 -- TGA; AD anaerobic digestion -- D1 and D2 digestates from the two primary digesters -- DTG differential thermogravimetric -- EEM excitation emission matrix -- EEWP excitation/emission wavelengths pair -- FI fluorescence intensity -- FTIR Fourier Transform Infrared -- MAF moisture and ash free -- OM organic matter -- PD digestate from the post-digester -- ST digestate from the storage tank -- TGA thermogravimetric analysis -- TG-T50 temperature at which 50% of the mass loss occurs -- TG-T75 temperature at which 75% of the mass loss occurs -- TKN total Kjeldahl nitrogen -- TOC total organic carbon -- TS total solids -- VS volatile solids -- WL weight loss; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2018.05.081
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: A safe and functional application of digestate in agriculture requires an in-depth scientific knowledge of its nature in order to speculate about possible impacts on the soil-plant system, as well as on the surrounding environment. As all soil amendments, digestate should consist of stabilized organic matter (OM) in order to avoid phenomena including phytotoxicity, greenhouse gases and odorous emissions, and nutrient losses. To date, the stability of digestate has been assessed using several (often state-of-the-art) techniques and approaches, although most of the studies have been generally carried out on the final product of the anaerobic digestion (AD) and/or in batch experiments. Here, we collected digestate samples from the two primary digesters, the post-digester and the storage tank of a real, full-scale AD plant processing maize silage. Digestates were characterized from the chemical, spectroscopic and thermal points of view in order to assess the evolution of OM at plant scale. Spectroscopic and thermogravimetric data clearly show that changes in OM features mainly occurred in the two primary digesters, resulting in a more recalcitrant ( i.e., richer in ligno-cellulosic compounds) and thermally stable OM. On the opposite, no relevant differences were observed in the post-digester and in the storage tank. Moreover, Fourier transform Infrared (FTIR) and fluorescence spectroscopies underlined how, at plant scale, the OM degradation may evolve differently in the two primary digesters, thus suggesting that stochastic microbial community assembly are potentially able to affect the AD process; this phenomenon resulted in digestates having different proportion of aromatic vs. polysaccharide compounds. In conclusion, this study demonstrated that FTIR, molecular fluorescence and thermogravimetric analysis could be used as simple and potentially routine techniques to monitor the digestate during the whole AD process, and that, in full-scale plants like that under investigation, such a monitoring could be limited to the primary digesters. Graphical abstract: Image Highlights: Digestates were collected from a real, full scale anaerobic digestion plant. Digestates were analysed using FTIR and fluorescence spectroscopies as well as TGA. Changes in digestate quality mainly occurred in the two primary digesters. At plant scale, digestates from the two primary digesters show different features. Thermal parameters are more informative when expressed as moisture and ash free.