Anaerobic fermentation is increasingly used in the waste sector to treat biomass and to produce biogas (energy). Nutrients such as nitrogen and phosphorous can be recycled when the residual biomass, i.e. digestate, are used as fertilizer and soil amendment in agriculture. Unfortunately, pollutants present in the waste biomass may also be recycled to the soil, such as persistent organic pollutants (POPs), polycyclic aromatic hydrocarbons (PAHs) [1], trace metals [2], and pharmaceuticals [3,4].

Organic pollutants which are not or only partly degraded through thermal pre-treatment and the subsequent digestion, express a resilience towards high temperatures and (at some production plants) pressure, as well as both aerobic and anaerobic conditions. Spread of chemical pollutants which resist degradation to the environment, by applying digestate from biogas production on farmland, may pose a health risk to wildlife and humans. Hence, we developed a multi-method for the detection of several classes of antibiotics and steroid hormones. The aim of the present study was to determine whether biogas digestates contained pharmaceutical residues.

All over the detection levels and frequencies were low, despite MDLs in the ng – μg kg^-1 range. However, a few antibiotics and one glucocorticoid were found at concentrations above 400 μg kg^-1 dw. These elevated levels may promote antibiotic resistance and cause harm towards soil microorganisms when the digestate is applied as fertilizer. Most concerning was the detection of ciprofloxacin at 430 μg kg^-1 dw, considering the stability of this antibiotic in soil. Further, the penicillin amoxicillin was found at 460 μg kg^-1 dw in a digestate produced solely from food waste. The levels and implication of our findings are discussed in detail in the planned presentation.

[1] K. Suominen, M. Verta, S. Marttinen, Science of the Total Environement, 2014, 491, 192-199
[2] Ivan Dragicevic, Susanne Eich-Greatorex, Trine A. Sogn, Svein J. Horn, Journal of Environmental Management, 2018, 217, 12-22
[3] Aasim Ali, Astrid S. Nesse, Susanne Eich-Greatorex, Trine A. Sogn, Stine G. Aanrud, John A. Aasen Bunæs, Jan L. Lyche, Roland Kallenborn, Environmental Science: Processes & Impacts, 2019, 9, 1498-1508
[4] Astrid Spielmeyer, Jenny Ahlborn, Gerd Hamscher, Analytical and Bioanalytical Chemistry, 2014, 406, 2513-2524