A new study reveals a promising method for industries eager to convert tonnes of palm oil waste into clean, renewable biomethane, addressing a significant environmental and economic challenge for the industry. The research demonstrates that by improving key conditions in syringe bioreactors for anaerobic digestion, a process deemed inefficient biomethanising woody biomass, can achieve encouraging levels of biofuel production, offering a viable waste-to-energy solution.
For example, the palm oil industry in Malaysia generates 20 million tonnes of oil palm empty fruit bunches (OPEFB) each year. With traditional incineration methods causing air pollution, the sector is in urgent need of alternative applications for the waste. While anaerobic digestion into biomethane is a promising alternative, its performance has historically been hampered by the tough, woody nature of the lignocellulosic fibres that make up OPEFB. Previous studies on the individual components—cellulose (CE), hemicellulose (XY), and lignin (LI)—have shown very low conversion rates, falling well short of international standards for efficiency.
This new study, published in Fuel sought to overcome these limitations by investigating the effect of specific operational conditions, including the use of an inoculum-to-substrate ratio, a buffered test medium and an adapted inoculum. The findings were a significant progress. Adding a Vitamin B-complex or sodium bicarbonate to the medium reduced the lag phase of digestion by up to 16.2%, but the most dramatic result came from the use of an adapted inoculum. This technique reduced the lag phase for cellulose digestion by a remarkable 80%, allowing it to achieve a degree of methanation of over 90% when combined with the sodium bicarbonate buffer. This far exceeds the performance of earlier studies and the recommended standards of the industry.