The potential and usability of municipal and industrial residues or waste materials as substrates for biogas generation were identified, compared and assessed. The TZW activities focused on the investigation and assessment of fermentation residues from the perspective of water conservation with regard to possible pollutant levels.
Strict requirements on the pollutant levels must be defined when introducing fermentation residues to drinking water conservation and catchment areas. The first step in the project was therefore to determine and evaluate the composition of random fermentation residues originating from waste materials.
Random samples of fermentation residues from several residual substance and waste facilities were investigated for various pollutants and micropollutants of particular importance to water conservation. Conclusions could then be made on the potential to apply fermentation residues in water protection areas or if the fermentation residues have to be treated.
Random testing of fermentation residues from biogas plants that ferment residual materials and biowaste indicated contamination of some fermentation residues, for example with active pharmaceutical ingredients, plasticisers, PAHs and mineral oils.
It is generally assumed that some residual materials and waste are not suitable substrates for biogas plants because of the pollutant level in the event of planned agricultural utilisation of the fermentation residues. In principle, only substrates with a low pollutant content, clear origin and composition should be used and continuous monitoring of the pollutant content if the created fermentation residues are to be used in agriculture. Nevertheless, to reuse fermentation residues contaminated with pollutants on land used for agriculture for the purposes of a circular economy and not to dispose of them necessitates additional requirements on treatment to achieve a substantial reduction in the pollutant levels.
Publications:
Kiefer, J.: Anforderungen an eine Gewässer schützende Biogasproduktion – Aktuelle Ergebnisse von DVGW-Vorhaben [Requirements on biogas production that conserves water – latest results of the DVGW project]. DVGW energie|wasser-praxis 9/2012, 116 (2012)
