Sludge refining through pyrolysis

Purpose and goal

The project goals, to verify EkoBalans´ sludge treatment process in terms of technical function, sustainability, and cost efficiency, have been fulfilled. Cd can be removed to > 90 % while P remains in the biochar. Sludge can be treated reliably in a continuous process. The energy surplus can be used for drying or energy production. The environmental analysis showed that sludge biochar is superior to sludge or artificial fertilizers in terms of energy, climate, and pollution. The cultivation trials showed that biochar should be seen as long term P amendment.

Expected results and effects

The project has shown that the pyrolysis process removes the pollutants that today makes sludge spreading difficult. If residual heat is used at drying the total energy consumption is very low which gives low operational costs. Net carbon capture makes the process interesting as a contribution to climate change reversal. Result effects so far are cooperation with municipalities: Feasibility studies to evaluate pyrolysis as sludge treatment method and work with applications to EU and the Swedish Board for the Environment in cooperation with the municipalities.

Planned approach and implementation

The project work was divided into the subprojects 1. Technical verification, 2. Energy balances, 3. Environmental systems analysis, and 4. Biochar usage. The work was done in cooperation with SP The Swedish Technical Research Institute, Borås University, and Lund University for 1-3, and with Lund University for 4. The combination of lab and pilot trials on-site technology provider was very rewarding. The value of the environmental systems analysis was clarified when focused on sustainable P recycling. Cultivation trials to determine biochar usage should be run at least 5 seasons.