Anaerobic co-digestion as a strategy for treating coffee Pulp: Insights into process performance.

Area of Science:

• Environmental Science
• Biotechnology
• Waste Management

Background:

• Coffee pulp (CP) is an abundant agro-industrial waste with high energy potential.
• Anaerobic digestion (AD) of CP can be unstable due to inhibitory compounds.
• Cattle manure (CM) is a common co-substrate in AD systems.

Purpose of the Study:

• To evaluate the performance and microbial dynamics of CP mono-digestion and co-digestion with CM.
• To investigate the impact of increasing organic loading rates (OLRs) on digester stability and methane yield.
• To understand the shifts in methanogenic communities under different OLRs and retention times.

Main Methods:

• Experimental setup comparing CP mono-digestion, CM mono-digestion, and CP:CM co-digestion (4:1 VS basis).
• Application of increasing OLRs (1.0 and 1.5 g VS L⁻¹ d⁻¹).
• Analysis of methane yields, digester stability, and microbial community structure (methanogens) using molecular techniques.

Main Results:

• CP mono-digestion achieved higher methane yields than CM mono-digestion and co-digestion at 1.0 g VS L⁻¹ d⁻¹ under stable conditions.
• Methane yields significantly decreased in CP-rich systems at 1.5 g VS L⁻¹ d⁻¹, indicating feedstock-related inhibition.
• Extended retention time (30 days) resulted in similar methane yields and a shift towards hydrogenotrophic methanogens in CP-based systems.

Conclusions:

• Coffee pulp has substantial energy potential for anaerobic digestion but is sensitive to high organic loading rates.
• Feedstock-related inhibition at elevated OLRs favors hydrogenotrophic methanogenesis over acetoclastic pathways.
• Strategies to mitigate inhibitors are crucial for stable and efficient methane production from coffee pulp.