Environmental Microbiology

Organic residues in circulation

Organic residues from society contain valuable plant nutrients that ought to be recycled to the soil ecosystem.

To secure sustainable food production, while at the same time protect our environment we have to capture the plant nutrients bound in plant and food residues. The organic residues must be handled and composted or converted to biogas, and sewage must be treated to yield a clean product. Our overall goal is to increase the knowledge on how the soil ecosystem reacts on organic fertilizers and from such response suggests measures for improvements in the treatment chain.

Microorganisms living in close contact with soil particles are ideal probes for reading changes in the soil ecosystem. After fertilization we measure how carbon compounds are degraded (soil respiration), how microorganisms release nitrogen (nitrogen mineralization), how they covert ammonium to nitrite (nitrification), and their capacity to respire nitrate (denitrification). Integrated response can be used for interpreting the quality of the organic residue.

Fertilization with organic residues increases the risk for production of greenhouse gases (GHG), mostly nitrous oxide. The nitrous oxide molecule is several hundred times stronger GHG than carbon dioxide and arable land is a great source of the global production of this gas. We know that soil moisture and temperature as well as how we fertilize controls the amount of nitrous oxide emitted. In our work we compare different fertilizing strategies to find a way to mitigate the emissions.

Pollutant Degradation - John Stenström

The Swedish EPA estimate that there are 1 400 contaminated sites in Sweden that can pose a large risk for the environment or for human health. We study how microorganisms, especially actinobacteria and white-rot fungi, can be used to clean up such contaminated sites from organic contaminants.

We also study the environmental fate of pesticides and develop bioprophylactic methods and techniques to prevent pesticide contamination of the environment. A special topic has for a long time been studies of weed control and microbial degradation of herbicides in railway embankments where we have an on-going collaboration with the Swedish Traffic Administration.

Using bioprophylactic approaches we aim to prevent contamination, both from point sources (for example from spills occurring at the filling of the spray tank) and diffuse sources (for example from leaching and surface transport after spraying in the field). One efficient and simple method for reduction of point source contamination is the use of biobeds. For reduction of diffuse contamination we study the possibility to add pesticide-degrading microorganisms or enzymes concurrent with the pesticide application. We also study the possibility to reduce pesticide transport in the environment by using biochar as an adsorbent.