Promoting anaerobic digestion by algae-based hydrochars in a continuous reactor

Area of Science:

• Biotechnology
• Environmental Science
• Renewable Energy

Background:

• Hydrothermal carbonization (HTC) of algae produces hydrochar, primarily explored for biofuels.
• The application of algae-based hydrochar in anaerobic digestion (AD) remains underexplored.

Purpose of the Study:

• To investigate the effects of microalgae Chlorella-based hydrochar (HC-C) and macroalgae Laminaria-based hydrochar (HC-L) on continuous anaerobic digestion (AD).
• To evaluate the impact of these hydrochars on AD stability and methane yield under varying organic loading rates (OLR).

Main Methods:

• Continuous anaerobic digestion (AD) reactors were operated with and without hydrochar supplementation.
• Different organic loading rates (OLR) were applied, ranging from 2.6 to 6.5 g COD/L/d.
• Sludge granulation, microbial community structure (Methanothrix abundance), enzyme activities, and direct interspecies electron transfer (DIET) were analyzed.

Main Results:

• Both HC-C and HC-L maintained AD process stability under increased OLR.
• Daily methane yield was significantly enhanced by 36.0% with HC-C and 31.4% with HC-L.
• Mechanisms included increased sludge granulation, promoted Methanothrix abundance and key enzyme activities, and facilitated DIET.

Conclusions:

• Algae-based hydrochars show potential for enhancing anaerobic digestion performance.
• These materials can improve wastewater treatment efficiency and energy recovery.
• Further research into algae-based hydrochars could optimize biogas production and waste valorization.