An Investigation of Some Critical Physico-chemical Parameters Influencing the Operational Rotary In-vessel Composting of Food Waste by a Small-to-Medium Sized Enterprise

Autor: M. Fuller, D. Orthodoxou, N. Knight, Stephen R. Smith, M. Newton, T.R. Pettitt
Rok vydání: 2015
Předmět:
Zdroj: Waste and Biomass Valorization. 6:293-302
ISSN: 1877-265X
1877-2641
DOI: 10.1007/s12649-014-9332-5
Popis: Decentralised treatment of food waste (FW) by in-vessel composting by small-to-medium sized enterprises supports the proximity principle of waste management and recycling, but the process is susceptible to instability from acidogenic reactions and low process temperatures due to the high degradability and moisture content (MC) of the feedstock. Physical and chemical parameters within an operational in-vessel FW composting reactor were monitored to determine the critical management factors controlling process acidification and activity. The process was monitored for 8 weeks during an initial period of sub-optimal operation due to severe acidogenesis, and after management interventions to re-establish normal composting activity. Interstitial gas analysis demonstrated that acidogenesis coincided with adequate O2 concentrations, therefore, the development of anaerobic conditions in the reactor, whilst a possible contributory mechanism, was not considered to be the main reason for process failure. The key factors influencing the pH value of the compost mixture and inhibiting the temperature rise to thermophilic conditions were identified as the FW MC and acidity. The influence of MC on composting temperature was probably initiated through its effect on the process thermodynamics by increasing thermal conductivity and losses and the specific heat of the composting mixture. This potentially restricted the temperature rise and the metabolism of organic acids reducing the pH value, which initiated a pH mediated feedback mechanism leading to further acidogenesis, aerobic microbial inhibition and temperature reduction. The upper critical MC determined for in-vessel shredded FW composting was 40 %. Monitoring of CO2 evolution and O2 utilisation gave a good indication of the progress of the composting process.
Databáze: OpenAIRE
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