A multi criteria approach for enhancing the energy efficiency of treatment facilities for organic residues

Client: Federal Ministry for the Environment, Nature Conservation and Nuclear Safety

Schedule: 2009-2012

Head of project: Prof. Dr.-Ing. Klaus Fricke

Coordinator: Dipl.-Ing. Christof Heußner, Dr.-Ing. Tobias Bahr

artner: Bauhaus Universität Weimar, ATZ Entwicklungszentrum,

Location: Braunschweig, Lower Saxony, Germany, Weimar, Thuringia, Germany and Munich, Bavaria, Germany


In Terms of climate protection targets and economic viability, it is necessary to evaluate optimization potentials in energy consumption of waste management measures. Along with the recovery and reutilization of paper, metals and synthetic materials, the biological treatment of organic residues holds appreciable capabilities in reducing carbon emissions and substituting fossil resources. There have been several research projects where energetic optimization potentials of treatment facilities for waste and organic residues were determined mainly by theoretical assessments of generalised efficiency factors. In most cases economical needs as well as the compilation of factors relevant to facility installations have not been taken into account adequately. A relative classification of single facilities with reference to similar existing plants has not been made. Therefore a lack of realistic optimisation potentials and practical implementation approaches can be identified.

To provide specific optimisation measures on existing and intended facilities it is compelling to identify realisable courses of action. In connection with a research project promoted by the German ministry of the environment, the department of Waste and Resource Management at the Leichtweiss-Institute of the Technical University of Braunschweig is carrying out a survey of facility operators in order to procure a comparative background needed to afford an alignment of different technical solutions and procedures increasing the energy and resource efficiency. In terms of a comprehensive analysis the substitution of mineral fertilizer obtained from fossil resources and the consequential energy savings are objects of the examination. Besides the acquisition of technical data such as treatment capacity, energy consumption and turnout, a SWOT analysis is conducted. Being adopted for technical and energy optimisation of waste treatment facilities, this strategic planning method evaluates suitable solutions to improve the facility's efficiency.

In connection with the survey a computer based calculation tool is developed to organize and evaluate the collected technical data. Gathering the specific energy consumption of different treatment facilities (aerobic, anaerobic and thermal) benchmarks will be defined for different treatment steps, allowing an energy efficiency based classification of single treatment facilities or facility sections in comparison to the best available technique. Due to a system similar to LCA (Life Cycle Assessment) or Eco-indicators it is possible to compare different types of plants (e.g. bio waste fermentation, composting and thermal treatment) by these indices. Depending on the complexity of the analysis, energy- and mass-balances of complete process steps can be determined in detail to several units. The so far unequalled itemisation will be achieved, enabling to identify optimisation potentials for specific units.