Comparative study between mono-digestion and co-digestion of Terrestrial weed (Lantana camara)

Abstract: Lantana camara is widely recognised as one of the twenty most invasive terrestrial weeds due to its rapid growth and high reproductive capacity. It can spread quickly and dominate forest ecosystems within a short period. Control and eradication of this species are difficult because of its strong regenerative ability. However, its abundant availability makes it a potential lignocellulosic feedstock for renewable energy generation through anaerobic digestion. In mono-digestion, methane production occurs but at relatively lower yields due to the accumulation of inhibitory compounds. Therefore, co-digestion is often employed to improve nutrient balance and reduce the impact of toxic inhibitors. In biochemical methane potential (BMP) assays, an F/M ratio of 1.5 was identified as optimal for the anaerobic digestion of Lantana camara, producing 191 mL CH₄ g⁻¹ VS on day 26. In co-digestion BMP assays, the same ratio resulted in a higher methane yield of 211 mL CH₄ g⁻¹ VS by day 14, indicating improved degradation kinetics. Additionally, the hydrolysis phase was shorter in co-digestion compared with mono-digestion. Scale-up experiments were conducted in a 20 L batch reactor with a 15 L working volume to validate the optimal F/M ratios obtained from BMP assays. The results demonstrated improved biogas production performance. Batch reactor studies further suggested an optimum hydraulic retention time (HRT) of 13 days for achieving peak methane production during anaerobic co-digestion of Lantana camara. Subsequently, a continuous anaerobic digester was operated for 60 days using the optimal F/M ratio determined from the BMP experiments.