Anaerobic digestion of animal manure, organic waste and crop biomass is used for biogas production as a sustainable alternative to fossil fuel. The sludge or digestate, the semi-solid leftover after anaerobic digestion, has several advantages as crop fertilizer compared to animal slurry; e.g., a lower C/N ratio, higher concentrations of K, P and N, and a better availability of the latter, as NH4.

The ingredients for biogas production, namely manure, organic wastes and crop biomass, can be contaminated with weed seeds and, if these survive the process of anaerobic digestion, the use of contaminated sludge as a crop fertilizer could contribute to their spread. This can be particularly troublesome in the case of, for example, invasive weeds or herbicide resistant weeds. Even if digestate is only used as an on-farm fertilizer, there is a risk that repeated exposure to anaerobic digestion may select for seeds that are more resistant to conditions as encountered in biogas plants.

The risk that crop biomass is contaminated with weed seeds can be separated into two components, namely 1) the probability that seeds enter the biogas production chain, and 2) the probability that they survive the various processes along the biogas chain (ensiling or ingestion, anaerobic digestion). Factors influencing the first probability are completely unknown; little is known about the second probability.

Seeds are the most likely plant structure to survive anaerobic digestion, because they tend to be well-protected by seed coat and other protective structures, they usually have a low metabolic rate and dormancy mechanisms that prevent germination, and they are known to be able to endure and survive adverse environmental conditions. Weed species differ considerably in seed characteristics, and are, therefore, expected to differ in survival probability during anaerobic digestion. However, systematic research on the likelihood of weeds from different taxonomic or functional groups to enter or survive the biogas production chain is still in its infancy.

General objectives of our research include;

    - identifying high-risk species based on morphological, physiological or taxonomic characteristics
    - quantifying the probability that weed seeds enter the biogas production chain
    - quantifying the probability that the seeds of different plant species survive the biogas production chain including ensiling, anaerobic digestion, and storage of digestate
 

Bärbel Gerowitt
Juliane Hahn
Rosa Minderlen

Ophélie Rollin 2015 - Wildpflanzen und Silage
Fabian Hildebrandt
Torsten Heidenreich
Christine Kurtz

BSc and MSc students
Anja Tanke MSc 2019 - Überleben von Riesenbärenklausamen in Biogasanlagen
Julia Schulz MSc 2019 - Temperatur induzierte Inaktivierung von Samen der Poaceae-Familie unter Beziehung von herbizidresistenten Biotypen
Johanna Modrozinski BSc 2019 - Modelluntersuchungen zur Abschätzung des Überlebens der Samen von Hirsearten in Biogasanlagen
David Parzych MSc 2016 - Der Einfluss der Temperatur auf das Überleben von Wildpflanzen-Samen
Christoph Lück MSc 2012 - Überlebensfähigkeit von Gräsersamen in der Biogasprozesskette
Pilar Xamaní Montserrat 

Investigation into the phyto-sanitary risk of anaerobic fermentation of plant biomass in biogas plants; Risks posed by weeds 

Fate of wild-flowering mixtures in the Biogas chain – Risk of contamination and survival dependent on process Parameters