Added sludge biochar for thermophilic digestion – does it do any good?

On June 3, Aashutosh Kumar Thakus presented his degree project "Investigating the Impact of Sewage Sludge Biochar on Biogas Production in Thermophilic Anaerobic Digestion" at Chalmers University of Technology.

Previous research has indicated that the addition of biochar and other conductive materials can improve the anaerobic digestion process. In his thesis, Aashutosh compared biogas production from digested sludge under thermophilic conditions (55 °C) in lab-scale reactors with and without addition of sludge biochar. Since the pilot within Testbed Ellinge could not be commissioned in the spring, the thesis had to be carried out with sludge biochar from a Danish wastewater treatment plant.

The experiment was conducted in two stages. In the first stage cellulose was used as substrate and in the second stage acetate was used. The results showed no major influence of the sludge biochar on biogas production from cellulose. However, a significant positive effect of sludge biochar was demonstrated when acetate was used as substrate. This indicates that the sludge biochar had an impact on the microorganisms that convert acetate to methane, but not on the fermenting microorganisms that break down cellulose.

Aashutosh thinks the results are interesting and that further studies clarifying exactly how the addition of biochar affects the microbiota in the digestion process are needed.

You can find the entire thesis here.