Using sugarcane leaves and tops for exploiting higher methane yields: An assessment study

Sugarcane leaves and tops are lignocellulosic agricultural by-products which are considered a significant input for biogas production. Their potential pretreatment by sodium hydroxide prior to co-digestion with cow manure helps increase the methane (CH₄) content, biodegradation efficiency of the lignocellulosic materials and CH₄ yield. The untreated and pretreated sugarcane leaves and tops to cow manure and water of different ratios were digested and co-digested in the 5 L reactors by semi-continuous operation with hydraulic retention time of 40 days. The pretreated sugarcane leaves and tops to cow manure at the initial prepared ratio of 100 g:100 g, in 800 mL water which was corresponding to the organic loading rate (OLR) of 0.61 kg COD/m³·day was recommended. At this ratio, the chemical oxygen demand and total volatile solids degradation efficiency was 68.80 and 72.52%, respectively, the CH₄ content was 44.52% and the CH₄ yield was 331 L/kg COD degraded. According to the results, there is an average of 3.7% deviation between the practical model based on the thermodynamic balance equations carried out using the Aspen Plus and the experimental study. The highest exergy destruction rate is found at 21 kW where the sugarcane leaves and tops, and cow manure ratio is 100 g:100 g, in 800 mL water. The highest energy and exergy efficiencies of the overall system are calculated as 45.53% and 46.02%, respectively.