Influence of trace elements on methane formation from a synthetic model substrate for maize silage

Area of Science:

• Biochemistry
• Environmental Science
• Chemical Engineering

Background:

• Anaerobic digestion is a key process for biogas production from organic matter.
• Trace elements are crucial micronutrients for microbial activity in anaerobic digestion.
• Optimizing trace element supply can enhance biogas yield and process stability.

Purpose of the Study:

• To investigate the impact of a defined trace element solution, specifically nickel, cobalt, and molybdenum, on the anaerobic digestion of a synthetic maize silage model substrate.
• To determine the optimal concentrations of these trace elements for maximizing methane production.

Main Methods:

• Batch reactor experiments were conducted at 35°C using a synthetic substrate composed of xylan, starch, and urea.
• Inoculum sludge from a mono-maize biogas plant was used.
• Different concentrations of nickel, cobalt, and molybdenum were added to assess their effects on methane yield and process stability over 30 days.

Main Results:

• Addition of the trace element solution increased methane yield by up to 30%.
• Nickel (10.6 μM) enhanced methane production by 25% and resulted in a final yield of 407 L/kg ODM; its absence decreased yield and stability.
• Cobalt (0.4–2.0 μM) increased methane production by approximately 10%, while molybdenum showed no significant effect.

Conclusions:

• Nickel and cobalt are essential trace elements for efficient anaerobic digestion of maize silage, significantly improving methane yield.
• The absence of nickel negatively impacts both methane production and process stability.
• Molybdenum does not appear to be a limiting factor for this specific substrate and digestion conditions.