NENIM: N2O reducing bacteria in digestates (NFR project number 266888) .
Anaerobic digestion (AD) is about to become the standard way of treating sewage sludge, urban organic wastes and animal manure, both in Norway and China, and the digestates are increasingly used to fertilize farmland. One important motivation for these huge investments in AD-technology is to reduce climate forcing by eliminating methane emission from storage and to replace fossil fuel with biogas.
Here we propose to add a new dimension to the climate performance of AD: by growing aggressively N2O-reducing bacteria (ANB) in the digestates, we can reduce the N2O emission which is otherwise induced by the fertilization with the digestate. We will search for biodigestate-competent ANB that also grow/survive in soil, thus securing a more long lasting reduction of the N2O emission from farmland.
We have recently identified several types of bacteria that can potentially act as strong N2O sinks, either because their only denitrification gene is the one coding for N2O reductase (nosZ), or because they express nosZ more than the other denitrification genes.
A primary challenge will be to enrich such organisms in the digestates. We will use either digestates or soils as initial inoculum and select for ANB by providing a suitable electron acceptor. Metagenomics and proteomics will be used to track and identify the dominating organisms in the enrichment, and to guide attempts to isolate ANBs. Microcosms will be used to test the effects of ANB on N2O kinetics in soils, and to test the effects of nitrification inhibitors. Upscaling to field experiments will be done by cultivation in pilot plants, and possible implementations in existing AD systems will be explored in collaboration with AD industries that are associated with the project.
University partners: China Agricultural University, Beijing, Jiao Tong University Shanghai
Industrial partners: CAMBI (Norway), Golden State (China)