Sustainable valorisation pathways mitigating environmental pollution from brewers' spent grains

Area of Science:

• Biotechnology and Bioengineering
• Sustainable Energy
• Waste Valorisation

Background:

• Brewers' spent grains (BSG) represent a significant lignocellulosic byproduct of the brewing industry.
• Effective valorisation of BSG is crucial for developing sustainable biorefinery concepts and reducing waste.
• Existing methods for BSG conversion require optimization for efficient biofuel production.

Purpose of the Study:

• To investigate and optimize pathways for brewers' spent grains (BSG) valorisation into biofuels.
• To evaluate the production of used oil, bioethanol, and biogas from BSG using experimental data.
• To establish and assess biorefinery scenarios for comprehensive BSG utilization.

Main Methods:

• Solid-liquid extraction with hexane for oil recovery, achieving up to 70% efficiency.
• Acid pretreatment, enzymatic hydrolysis (CellicCTec2), and fermentation (S. Cerevisiae) for optimal bioethanol yield (45%).
• Biogas potential assessment of raw BSG, defatted BSG, and stillage (379±19, 235±21, 168±39 mL biogas/g, respectively).

Main Results:

• Optimized oil extraction reached 70% efficiency.
• Achieved a 45% bioethanol yield through a multi-step process.
• Quantified biogas yields from different BSG fractions, highlighting their potential.

Conclusions:

• BSG can be effectively valorised into multiple biofuels (biodiesel, bioethanol, biogas) within a biorefinery framework.
• Optimized processes demonstrate high efficiency for oil extraction and bioethanol production.
• Full valorisation of European BSG could contribute significantly to renewable energy targets, producing 4.5-7.0 million MJ/y.