Determination of the dewatered digestate amounts and methane yields from the co-digestion of biowaste as a basis for a cost-benefit analysis.

Marco Wehner, Thomas Lichtmannegger, Sabine Robra, Alice do Carmo Precci Lopes, Christian Ebner, Anke Bockreis

Waste management (New York, N.Y.) 2021 May 01

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Co-digestion is the simultaneous digestion of two or more substrates and a common practice at wastewater treatment plants (WWTPs). The amounts of methane and digested sludge produced are key parameters for evaluating the economic efficiency of co-digestion. However, the share of dewatered digestate produced from co-substrates is not known. Synergistic effects in co-digestion, i.e. a better biodegradability compared to the mono-digestion of each substrate, might reduce the amounts of digested sludge and increase methane yields. However, these effects might also influence the calculation of methane and digestate quantities from co-substrates. The main objective of this work was to provide a basis for the cost-benefit analysis of biowaste (BW) co-digestion at WWTPs for this data. Therefore, continuous and batch experiments with sewage sludge (SS) and BW co-digestion were conducted and evaluated for methane and digestate production, and possible synergistic effects. BW co-digestion led to an additional production of 0.35 t total solids (TS) of dewatered sludge per ton TSadded in continuous and 0.23 t TS of dewatered sludge per ton of TSadded in batch experiments. The methane yield from BW was 441 L/kg TSadded in continuous experiments and 482 L/kg TSadded batch test. No synergistic effects were observed in both batch and continuous co-digestion experiments. Batch tests were found to be suitable for a rough estimation of the co-digestion economic efficiency key parameters. Continuous experiments are recommended to obtain more robust data. A cost-benefit analysis found that electricity production from co-digestion can generate savings of 88-170 €/t TSadded compared to grid purchase. Copyright © 2021 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Citation

Marco Wehner, Thomas Lichtmannegger, Sabine Robra, Alice do Carmo Precci Lopes, Christian Ebner, Anke Bockreis. Determination of the dewatered digestate amounts and methane yields from the co-digestion of biowaste as a basis for a cost-benefit analysis. Waste management (New York, N.Y.). 2021 May 01;126:632-642