Strategies to Optimize the Energetic and Material Utilization of the Organic Fraction of Municipal Solid Waste by Considering the Entire Value Chain

The organic fraction of municipal solid waste (OFMSW) is a valuable and globally debated resource for a bioeconomy and its current treatment based on the combination of anaerobic digestion (AD) and composting is the best existing state-of-the-art utilization that already represents a circular approach. The existing OFMSW value chain, however, needs to be optimized for a best-possible bioeconomy, especially with regard to collected waste volumes, achieved energy yields or product qualities. Furthermore, alternative technologies to supplement the existing AD and composting concepts have to be discussed. Several strategies to optimize the energetic and material utilization of OFMSW can be addressed through knowledge on OFMSW material properties or by considering the entire value chain from waste production and collection to utilization and recycling. The following aspects are therefore included and discussed within this doctoral thesis:

1) OFMSW production: a comprehensive physico-chemical characterization of German OFMSW samples originating from a consistent collection area depending on season and settlement structure.
2) OFMSW collection and logistics: monitoring of storage processes to determine their influence on material properties of OFMSW depending on storage temperature and condition.
3a) OFMSW utilization in AD: energy potentials of OFMSW in co-digestion with digested sewage sludge (DSS) depending on defined process temperatures in AD.
3b) OFMSW utilization in AD: energy potentials of OFMSW in co-digestion with DSS and wood ashes depending on different mixing ratios for nutrient supply.

Knowledge on waste characteristics, storage processes, co-digestion possibilities, adjusted process parameters and alternative business models in the AD of OFMSW should be considered for the design of more efficient OFMSW treatment concepts. The future utilization of OFMSW could be a combination of bio-chemical, thermo-chemical and bio-technological approaches to fully utilize the energetic and material potential of OFMSW that contains a variety of different biogenic substances. But until further treatment methods can supplement the state-of-the-art treatment, the optimization of the current value chain needs to be a priority. This thesis mainly presents suggestions for improvements of the current OFMSW value chain but also discusses future treatment concepts in the context of OFMSW and other biogenic residues. In addition, raw data of the laboratory experiments are included in this thesis. They can be accessed and used for further evaluations or for the design of other experiments. All aspects of this doctoral thesis are of relevance for both research and practice.