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PYSTI project tests pyrolysis products for cutting ammonia emissions

The Finnish PYSTI-project assesses possibilities to cut ammonia emissions from animal slurries with pyrolysis products

Slow pyrolysis is a promising thermochemical processing technique for converting various waste biomasses to a range of value-added carbonized products. The process is based on heating the biomass in the absence of oxygen, which decomposes the feedstock into solid char, non-condensable gas and liquid fraction. The aqueous component of pyrolysis liquid that forms in mild temperatures (< 280 °C) contains acetic acid and several other weak organic acids. In a previous small-scale study of the current research group, this bio-based liquid showed potential in replacing synthetic concentrated sulphuric acid in acidification of animal slurry (see Keskinen et al. 2018). This substitution could improve the safety and environmental performance of the acidification treatment aiming at reducing ammonia emissions. Furthermore, achieving a meaningful use for the pyrolysis liquid would enhance the operational preconditions of pyrolysis plants thus supporting circular economy.

The so-called biochar fraction of pyrolysis is considered as a desired soil amendment due to carbon sequestration and possible beneficial effects of the added char on soil chemical and physical properties. Applying biochar as a floating cover for slurry lagoons might offer an alternative way of exploiting pyrolysis products in cutting ammonia emissions. Besides acting as a physical cover preventing diffusion of gases, certain types of biochars may be able to directly absorb ammonia.  In connection with manure spreading, the biochar cover would be distributed on the field and continue serving as a soil conditioner.

The PYSTI project addresses 1) legislative prerequisites associated with utilization of the pyrolysis products in agriculture, 2) performance of pyrolysis liquids and biochars derived from various biomasses in the target treatments and 3) feasibility, agronomic efficiency and safety of the treatments in a field-scale. The first results obtained indicate that process conditions and selection of the feedstock material play a key role in determining the suitability of the products for the intended use.

PYSTI project is implemented conjointly by the Natural Resources Institute Finland (Luke) and Association of ProAgria Centres between late 2018 and end of 2020. Ministry of the Environment of Finland funds the project with 210 000 € from the Programme to promote the recycling of nutrients and improve the ecological status of the Archipelago Sea as one of the Finnish government key projects.


Further information:

Riikka Keskinen,

Kimmo Rasa,

Keskinen, R., Hyväluoma, J., Wikberg, H., Källi, A., Salo, T., Rasa, K. 2018. Possibilities of using liquids from slow pyrolysis and hydrothermal carbonization in acidification of animal slurry. Waste and Biomass Valorization 9: 1429-1433.