Investigation of greenhouse gases in Swedish fiberbanks

Historically, large amounts of cellulose, wood fibers and environmental toxins were released into the sea and lakes during the production of paper and pulp. This led to the formation of so-called fiberbanks on the seabed. When microbes in these oxygen-free sediments break down the wood fibers, greenhouse gases such as carbon dioxide and methane are formed. The FIB-GHG project investigates how, where and in what quantities these gases are formed in different types of fiberbanks.

The rate of decomposition of the organic material depends on both environmental factors (such as oxygen levels, temperature and nutrients) and the balance between different microbial communities, where methanogens are responsible for the final degradation step that leads to methane formation. As the temperature in our waters is expected to rise due to climate change, greenhouse gas emissions from fiberbanks are also expected to increase, with the risk of increased spread of environmental toxins as a result. To better assess fiberbanks as a source of greenhouse gases, more knowledge is needed to understand which factors affect the formation of greenhouse gases in this unique type of sediment and how gas production differs in different aquatic environments in Sweden. This information is important for the authorities to be able to prioritize which fiberbanks require remediation.

The research project FIB-GHG will investigate fiberbanks in both marine, brackish and limnic environments. We will study how methane production varies within fiberbanks with different fiber composition and investigate how production is linked to the distribution and composition of different microbes in the fiberbanks. The measurements will include advanced DNA sequencing for the identification and quantification of microbes, as well as analysis of greenhouse gas concentrations using gas chromatography (GC) and their isotopic compositions using gas chromatography–isotope ratio mass spectrometry (GC-IRMS). The aim is to understand the spatial variation of greenhouse gas emissions and to investigate the dominant microbial degradation pathways.

In addition to the project members, the project has a broad reference group consisting of various authorities working with contaminated sediments to promote dissemination of the results.