Modelling the energy balance of an anaerobic digester fed with cattle manure and renewable energy crops.

Institute of Water Quality Control, Technische Universität München, Am Coulombwall, 85748 Garching, Germany.
Water Research (Impact Factor: 5.32). 11/2007; 41(18):4085-96. DOI: 10.1016/j.watres.2007.05.061
Source: PubMed

ABSTRACT Knowledge of the net energy production of anaerobic fermenters is important for reliable modelling of the efficiency of anaerobic digestion processes. By using the Anaerobic Digestion Model No. 1 (ADM1) the simulation of biogas production and composition is possible. This paper shows the application and modification of ADM1 to simulate energy production of the digestion of cattle manure and renewable energy crops. The paper additionally presents an energy balance model, which enables the dynamic calculation of the net energy production. The model was applied to a pilot-scale biogas reactor. It was found in a simulation study that a continuous feeding and splitting of the reactor feed into smaller heaps do not generally have a positive effect on the net energy yield. The simulation study showed that the ratio of co-substrate to liquid manure in the inflow determines the net energy production when the inflow load is split into smaller heaps. Mathematical equations are presented to calculate the increase of biogas and methane yield for the digestion of liquid manure and lipids for different feeding intervals. Calculations of different kinds of energy losses for the pilot-scale digester showed high dynamic variations, demonstrating the significance of using a dynamic energy balance model.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Rape oilcake is a by-product formed after the removal of oil from rapeseed. Due to the high content of organic matter rape oilcake seems a good substrate for anaerobic digestion when it cannot be used as fodder. The aim of this work was to optimise the parameters used in a mathematical model of anaerobic digestion for rapeseed oilcake and cattle manure. The composition of these substrates was determined in order to estimate model inputs. Optimised kinetic constants of hydrolysis and decomposition for oilcake (Kdis=0.77, KhydCH=0.55, khydPr=0.57, khydLi=0.30) were estimated based on batch fermentation. The accuracy of the model with improved input parameters was confirmed by continuous fermentation. The average concentration of methane in biogas was about 50%. The biogas production efficiency from organic matter (defined as volatile solids) was 0.42m(3)kg(-1) with an organic substrate loading rate equal to 3.18kgm(-3)d(-1). The fermentation process demonstrated good stability and efficiency. The accuracy of the optimised model seems sufficient for use in modelling of a full scale process.
    Waste Management 10/2014; · 3.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In anaerobic co-digestion plants a mix of organic materials is converted to biogas using the anaerobic digestion process. These organic materials, called substrates, can be crops, sludge, manure, organic wastes and many more. They are fed on a daily basis and significantly affect the biogas production process. In this thesis dynamic real-time optimization of the substrate feed for anaerobic co-digestion plants is developed. In dynamic real-time optimization a dynamic simulation model is used to predict the future performance of the controlled plant. Therefore, a complex simulation model for biogas plants is developed, which uses the famous Anaerobic Digestion Model No. 1 (ADM1). With this model the future economics as well as stability can be calculated resulting in a multi-objective performance criterion. Using multi-objective nonlinear model predictive control (NMPC) the model predictions are used to find the optimal substrate feed for the biogas plant. Therefore, NMPC solves an optimization problem over a moving horizon and applies the optimal substrate feed to the plant for a short while before recalculating the new optimal solution. The multi-objective optimization problem is solved using state-of-the-art methods such as SMS-EMOA and SMS-EGO. The performance of the proposed approach is validated in a detailed simulation study. A very limited amount of printed copies are available upon request.
    1st 09/2014; , ISBN: 978-94-6259-288-9
  • [Show abstract] [Hide abstract]
    ABSTRACT: Purpose of this work was the evaluation of demand driven biogas production. In laboratory-scale experiments it could be demonstrated that with diurnal flexible feeding and specific combination of substrates with different degradation kinetics biogas can be produced highly flexible in CSTR systems. Corresponding to the feedings the diurnal variation leads to alternations of the methane, carbon dioxide and acid concentrations as well as the pH-value. The long-time process stability was not negatively affected by the dynamic feeding regime at high OLRs of up to 6kgVSm(-3)d(-1). It is concluded that the flexible gas production can give the opportunity to minimize the necessary gas storage capacity which can save investments for non-required gas storage at site.
    Bioresource Technology 09/2014; · 5.04 Impact Factor

Full-text (2 Sources)

Available from
May 17, 2014