Title: Thermophilic anaerobic digestion of source separated institutional food waste and kitchen waste
Abstract: Food wastage in Europe is increasing, and measures for the reduction and for the utilization of wastes should be taken in order to reduce economic and environmental impacts. Food waste is an attractive feedstock for anaerobic digestion as it has high methane potential, due to its composition with lipids and proteins. Present thesis work assesses thermophilic digestion (55 °C) of food wastes and kitchen wastes collected from University of Jyvaskyla restaurant Ylisto. The produced waste quantities from the restaurant were estimated. The composition and the chemical characteristics of the wastes was analyzed, and the substrate performance was studied in batch and reactor (CSTR) experiments. Overall ca. 2780 kg of kitchen waste and ca. 9450 kg of food waste are estimated to be produced annually. Food waste had average total solids (TS) and volatile solids (VS) content of 28-32% and 27-30% and kitchen waste 16-23% and 15-22%, respectively. Methane yields for food waste and kitchen waste in batch assays performed at 55 °C were 174 and 186 mL gVS -1 , respectively. Digesters receiving wastes was monitored over period of 210 days, in order to identify the process performance, applicable organic loading rates (OLR) and methane yields in thermophilic process. The highest specific methane yield of food waste in reactor experiments with OLR 6 gVS L -1 d -1 and retention time (HRT) 30 d was 399 mL gVS -1 . At same OLR and HRT, highest specific methane yield for kitchen waste was 433 mL gVS -1 . Increased volatile fatty acid (VFA) concentrations and ammonia inhibition related to mono-digestion, elevated process temperature and the composition of feedstock occurred at OLR above 3 gVS L -1 d -1 . With determined institution specific waste production ratio of 4.5:1 food to kitchen waste, present study had highest specific methane yield of 354 mL gVS -1 at OLR 6 gVS L -1 d -1 and least signs of inhibition. Nevertheless, the maximum OLR that could sustainably be used in longer time period in order to maintain stable methane production under thermophilic process is around 3 gVS L -1 d -1 that in codigestion of food waste and kitchen waste with HRT 30 d yields methane 150 mL gVS -1 . JYVASKYLAN YLIOPISTO, Matemaattis-luonnontieteellinen tiedekunta Bioja ymparistotieteiden laitos Ymparistotiede ja -teknologia Koponen Jari: Ruokaja keittiojatteiden kasittely termofiilisessa anaerobiprosessissa Pro Gradu: 50 s. Tyon ohjaajat: FT Prasad Kaparaju & FT Leena Sivula Tarkastajat: Prof. Jussi Kukkonen & FT Prasad Kaparaju Joulukuu 2013 Hakusanat: Termofiilinen anaerobinen kasittelyprosessi, ruokajate, keittiojate, OLR, ammoniakki-inhibitio, VFA.
Publication Year: 2013
Publication Date: 2013-01-01
Language: en
Type: article
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