Greenhouse gas emission assessment of bio-coke from wood for application as bioanode in aluminium production

In aluminium reduction cells, carbon anodes are used for electrolysis. Petroleum coke is the primary source of material used in the manufacture of these anodes. There is a trend of falling quality of petroleum coke and the level of impurities is also increasing. This is particularly concerning to the aluminium industry because this reduces the anode performance, contributes to corrosive gases in the exhaust stream, and contaminates the aluminium metal product. These supply issues, combined with an increased awareness and preparedness to reduce greenhouse gas (GHG) emissions, opens the aluminium industry to the possibility of replacing fossil-based carbon anodes with low ash, renewable carbon based biocoke. The biocoke is to be used for making anodes known as 'bio-anodes' (de Vries et al., 2009). Our research has highlighted that viable anode grade petroleum coke requires a density of 800 kg/m3. This is possible using a CSIRO patented technology of bio-coke making. This process requires high temperature pyrolysis of wood under mechanical compressive force