Enhancing hydrolysis and syntropy simultaneously in solid state anaerobic digestion: Digester performance and...

Area of Science:

• Biotechnology
• Environmental Science
• Chemical Engineering

Background:

• Anaerobic digestion is crucial for biogas production from lignocellulosic biomass.
• Pearl millet straw (PMS) presents challenges in hydrolysis and syntropy for efficient methane generation.
• Optimizing process parameters is key to maximizing methane yield and economic viability.

Purpose of the Study:

• To investigate the combined effect of alkali and biochar on PMS hydrolysis and syntropy.
• To optimize dosing of alkali and biochar for enhanced methane yield in solid-state anaerobic digestion (SS-AD).
• To evaluate the techno-economic feasibility of the optimized process.

Main Methods:

• A Taguchi-based design of experiments was employed for optimization.
• Grey relation analysis was used for multi-output optimization of hydrolysis and syntropy.
• Confirmation tests were conducted to validate optimized parameters.

Main Results:

• Optimized dosing was determined as 0.5 g alkali/100 g PMS and 10 g/L biochar.
• Biochar (48%) and alkali (21%) significantly contributed to multiple output optimization.
• Optimized conditions showed a hydrolysis rate constant (k) of 0.0521 d⁻¹ and TVFA/Alkalinity ratio of 0.36.

Conclusions:

• Alkali and biochar addition effectively enhances hydrolysis and syntropy for higher methane yield from PMS in SS-AD.
• The optimized process demonstrates techno-economic viability with a positive net present value and internal rate of return.
• Further sensitivity analysis indicates capital expenditure and methane yield are critical factors influencing economic outcomes.