| Affiliation: | 1. Department of Agricultural Sciences, University of Bologna, Viale Fanìn 44, 40127 Bologna, Italy;2. Department of Civil, Environmental, and Materials Engineering, University of Bologna, Via Terracini 28, 40131 Bologna, Italy;1. Department of Mechanical Engineering, University of Brawijaya, Veteran Street, Malang, East Java 65145, Indonesia;2. Department of Mechanical Engineering, Yamaguchi University, Ube, Yamaguchi 755-8611, Japan;1. Key Laboratory of New Materials and Facilities for Rural Renewable Energy of Ministry of Agriculture and Rural Affairs of China, Henan Agricultural University, Zhengzhou 450002, PR China;2. Changzhou University, Changzhou 213164, PR China;1. Guangzhou Institute of Energy Conversion, CAS Key Laboratory of Renewable Energy, Chinese Academy of Sciences, Guangzhou 510640, China;2. Key Laboratory of Environmental and Applied Microbiology, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China;1. Department of Chemistry, “La Sapienza” University of Rome, P.le Aldo Moro 5, 00185, Rome, Italy;2. Department of Environmental Science, Informatics and Statistics, Via Torino 155, 30170, Venezia Mestre, Italy;3. Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134, Verona, Italy |
| Abstract: | Organic acids are envisaged as alternative catalysts to strong mineral acids, in pre-treatment of ligno-cellulosic biomass for anaerobic digestion (AD). To evaluate this hypothesis, an untreated control and four pre-treatments (25 °C for 24 h) involving two levels of maleic acid (34.8 and 69.6 kg m−3), alone and combined with sulphuric acid (4 kg m−3), were studied in three agricultural substrates: Arundo (aka giant reed), Barley straw and B133 fibre sorghum. Methane production was assessed in a batch AD assay (35 °C for 51 days) with 4 g L−1 of volatile solid (VS) load. Fibre composition and structure were investigated through chemical analysis and Fourier transform infrared (FTIR) spectrometry. Arundo and B133 that were the most and least recalcitrant substrate, respectively, staged the highest and lowest increase in methane with high maleic acid: +62% over 218 cm3 g−1 of VS in untreated Arundo; +36% over 284 cm3 g−1 of VS in untreated B133. Barley straw showed an intermediate behaviour (+41% over 269 cm3 g−1 of VS). H2SO4 addition to maleic acid did not improve CH4 output. The large increase in methane yield determined by pre-treatments was reflected in the concurrent decrease of fibre (between 14 and 39% depending on fibrous component). Based on FTIR spectra, bands assigned to hemicellulose and cellulose displayed lower absorbance after pre-treatment, supporting the hypothesis of solubilisation of structural carbohydrates and change in fibre structure. Hence, maleic acid was shown a suitable catalyst to improve biodegradability of ligno-cellulosic biomass, especially in recalcitrant substrates as Arundo. |
