Soil Steaming Treatment Services

In 2018, SoilSteam started a research project with the Norwegian Institute for Bioeconomic Research (NIBIO) to study how steaming soil can combat alien plant species in contaminated soil masses. The study, “BIOIMMIGRANTS” (https://www.nibio.no/prosjekter/bioimmigrants), which ended in November 2022, resulted in two scientific articles on the topic of soil steaming.

The first paper, Stationary soil steaming to combat invasive plant species for soil relocation (https://www.cambridge.org/core/journals/invasive-plant-science-and-management/article/stationary-soil-steaming-to-combat-invasive-plant-species-for-soil-relocation/822BBCF63526306F7110F5C3A4DE22B1)(Bitarafan et al., 2021), looked at the effect of temperature and duration of steaming on five species.

• Bigleaf lupine (Lupinus polyphyllus) 
• Himalayan balsam (Impatiens glandulifera) 
• Common wild oat (Avena fatua) 
• Canada goldenrod (Solidago canadensis) 
• Bohemian knotweed (Faloppia x bohemica)

They concluded that steam is very effective when used to kill the test species and that soil disinfection with steam can prevent the spread of alien species when moving soil.

The second paper, Soil steaming to disinfect barnyardgrass-infested soils (https://www.cambridge.org/core/journals/weed-technology/article/soil-steaming-to-disinfect-barnyardgrassinfested-soil-masses/70CFBC8D3490E42ECD6700C2F8A108A8)(Bitarafan et al., 2021) deals with the different temperatures and exposure time needed to kill barnyardgrass (Echinochloa crus-galli), an extremely harmful species. It concludes that “soil steaming can guarantee excellent control of barnyardgrass seeds in infested soil masses”.

Investigating the effect of steam temperature and exposure time on 15 species

Collaboration with academia and our own research is an integrated part of what we do in SoilSteam. In 2019, SoilSteam received funding from the Research Council of Norway for a project to find the optimal combination of temperature and time needed for steaming to kill various harmful organisms and alien invasive species. The project, which will last until 2025, is called ResourceReturn (https://prosjektbanken.forskningsradet.no/project/FORISS/321616). The project’s partners are NIBIO, the Norwegian University of Environmental and Biosciences (NMBU), Lindum AS, Toten Onionpackery, Larvik Onion, the Norwegian Agricultural Advisory Service, and the National Road Administration.

This project investigates the effect of steam temperature and exposure time on 15 species: 

• Common wild oat
• Barnyard grass
• Giant hogweed
• Persian hogweed
• Himalayan balsam
• Scotch laburnum
• Common laburnum
• Garden lupine
• Japanese rose
• Red elderberry
• Black nightshade
• Canadian goldenrod
• Sycamore maple
• Lady’s mantle
• Dwarf serviceberry

Botanical names: Avena fatua, Echinochloa crus-galli, Heracleum mantegazzianum, Heracleum persicum, Impatiens glandulifera, Laburnum alpinum, Laburnum anagyroides, Lupinus polyphyllus, Rosa rugosa, Sambucus racemosa, Solanum nigrum, Solidago canadensis.

NIBIO will publish several reports on the findings of this project this year. So far, we can conclude that steam treatment kills all root parts and seeds of the alien invasive species tested in the project. It’s just a matter of finding the best temperatures and exposure times. We have already gained good knowledge and certainty about the minimum duration and temperatures necessary to combat the most invasive species.