Anaerobic digestion of crude glycerol from biodiesel manufacturing using a large-scale pilot plant: Methane production and application of digested sludge as fertilizer

This report is the first to consider methane production energy balance from crude glycerol at a practical rather than a laboratory scale. Crude glycerol was added to the plant progressively at between 5 and 75L glycerol/30m³-day for 1.5years, and the energy balance was positive at a loading rate of 30L glycerol/30m³-day (1ml/L-day). At this loading rate over one year, an energy output equivalent to 106% of the energy input was achieved. The surplus energy was equivalent to transport for 1200km, so the proper feedstock-transportation distance was within a 12.5-km radius of the biogas plant. In addition, the digested sludge contained fertilizer components (T-N: 0.11%, P₂O₅: 0.036%, K₂O: 0.19%) that increased grass yield by 1.2 times when applied to grass fields. Thus, crude glycerol is an attractive bioresource that can be used as both a feedstock for methane production and a liquid fertilizer.