Impact of Trace Metals on Biogas Production Parameters in Mesophilic and Thermophilic Downflow Anaerobic Bioreactor

ABSTRACT The anaerobic digestion (AD) of molasses, a byproduct of the sugar industry, presents considerable potential for biogas production; nevertheless, its efficiency may be constrained by shortages in micronutrients. This study examined the impact of adding essential micronutrients—ferric chloride (FeCl 3 ), cobalt chloride (CoCl 2 ), nickel chloride (NiCl 2 ), and zinc chloride (ZnCl 2 )—on the anaerobic breakdown of molasses under mesophilic (35°C–37°C) and thermophilic (55°C–60°C) conditions. Batch studies were performed to assess organic matter clearance, biogas yield, and methane generation rates under both temperature conditions. The results indicated that micronutrient supplementation markedly increased the degree of molasses breakdown, particularly under thermophilic circumstances. Methane production rates also increased, indicating greater methanogenic activity. Thermophilic digesters produced up to 15% more methane than mesophilic systems, demonstrating the temperature‐dependent efficiency of micronutrients. These results underline the prominence of micronutrient optimization in AD systems, particularly for high‐organic‐load substrates like molasses. The study reveals that strategically supplementing trace metals might improve biogas production efficiency, particularly under thermophilic conditions, providing valuable insights for industrial‐scale AD operations.