Bioconversion of mixed solids waste to ethanol.

Area of Science:

• Biomass Conversion
• Renewable Energy
• Waste Valorization

Background:

• Mixed solid waste (MSW) presents a significant disposal challenge.
• Lignocellulosic biomass is a potential feedstock for biofuel production.
• Efficient conversion of MSW to ethanol requires effective pretreatment and hydrolysis methods.

Purpose of the Study:

• To convert a mixed solid waste feedstock into ethanol.
• To optimize enzymatic hydrolysis and fermentation processes.
• To evaluate the potential of enzyme recycling and residue combustion.

Main Methods:

• MSW feedstock composed of construction lumber, almond prunings, wheat straw, office paper, and newsprint.
• Dilute sulfuric acid pretreatment (0.4% w/w) at 210°C for 3 min via steam explosion.
• Water washing to recover solubilized hemicellulose.
• Batch and enzyme-recycle bioreactor enzymatic hydrolysis.
• Fed-batch fermentation using adapted Saccharomyces cerevisiae.
• Furnace experiments to assess solid residue slagging and fouling characteristics.

Main Results:

• 90% cellulose digestibility achieved in batch enzymatic hydrolysis.
• Greater than 90% cellulose hydrolysis obtained with enzyme recycling at 10 FPU/g cellulose.
• Hexose sugars were readily fermented by adapted yeast.
• Solid residue exhibited low to moderate slagging and fouling potential.

Conclusions:

• Enzyme recycling via membrane filtration and fed-batch fermentation is a cost-effective strategy for cellulose hydrolysis.
• MSW can be successfully converted to ethanol.
• The solid residue from the process has potential for combustion applications.