Optimizing the selection of organic waste for biomethanization

Area of Science:

• Biotechnology and Bioengineering
• Environmental Science
• Sustainable Energy

Background:

• Optimizing anaerobic digestion (AD) feeding strategies is crucial for maximizing biogas production.
• Nutrient balancing is a key factor influencing the efficiency of AD processes.
• Understanding nutrient ratios is essential for effective waste stream valorization.

Purpose of the Study:

• To assess the feasibility of using simultaneous mass balances of different nutrients for optimizing AD feeding composition.
• To evaluate various nutrient ratios, including total chemical oxygen demand/total Kjeldahl nitrogen (TCOD/TKN) and soluble chemical oxygen demand/TCOD (SCOD/TCOD).
• To validate theoretical optimal values derived from mass balances against experimental AD co-digestion results.

Main Methods:

• Application of mass balance calculations to 50 random mixtures of diverse organic wastes.
• Assessment of key nutrient ratios (TCOD/TKN, SCOD/TCOD, TCOD/TVS, P/N) across various waste streams.
• Experimental co-digestion of selected waste mixtures to compare with mass balance predictions.

Main Results:

• A linear relationship was observed between phosphorus and nitrogen (0.06 kg P/kg TKN) for most waste types.
• Mass balance predictions were validated through experimental anaerobic co-digestion.
• The co-digestion of glycerol, strawberry extrudate, and fish waste (41:54:4 in VS) yielded a maximum methane production of 0.308 m³ CH₄/kg TVSadded.

Conclusions:

• Simultaneous nutrient mass balances are a feasible tool for optimizing AD feeding strategies.
• Specific waste mixture compositions, guided by mass balances, can significantly enhance methane yields.
• This approach offers a predictive method for improving biogas production efficiency from complex organic waste streams.