| dc.description.abstract | Anaerobic digestion is one of the efficient processes to manage solid waste. With this
technology, waste converts to energy by producing biogas with high content of methane.
Methane is an alternative to fossil fuels, which reduces greenhouse gas emissions.
Therefore, increasing the biogas and methane production efficiency is important. Adding
carbon conductive materials to anaerobic digestion can lead to more methane production
by stimulating the direct electron transfer to methane-producing bacteria. In this master's
thesis project, biochar and activated carbon were used as conductive biocarbon. The
biochar was derived at Lindum AS in collaboration with Scanship AS and activated
carbon is commercially available. To analyse the biocarbon effect, a pressurised
biochemical methane potential (BMP) test was set up in serum bottles under mesophilic
conditions. Then the pressure of the collected gas inside the bottle was measured regularly,
to obtain the gas volume. Also, the effect of biofilm formation on the surface of biocarbon
particles was evaluated by reusing the particles. The biocarbon surface was monitored by
Scanning Electron Microscopy (SEM) to observe microorganisms attached, and their
chemical elements on the surface were analysed by Energy Dispersive X-ray
Spectroscopy (EDX).
The two different biocarbon acted differently in the digestion process. Activated carbon
could improve biogas production by 3.5%, while biochar decreased it, but biochar
increased the methane percentage to more than 85%. pH increasing to more than 8.5 in
addition to biochar, was one of the main inhibitors in biogas production. This pH
development was mainly due to the high ash content of biochar. Thus, to take advantage
of this biochar and similar ones, a lower load should be added to prevent pH development
by presenting a high amount of ash. Although the biochar is less conductive than activated
carbon, it is expected that providing optimum pH for microorganisms, can result in more
biogas and methane production. | |
