Rising temperature and humidity in the summer months leads to reduced cooling capacity at ethanol plants. When temperatures reach levels inhibitory to yeast, fermentation kinetics slow down, allowing native bacteria to get a head start over the yeast cells. This results in increased levels of lactic acid above 0.2% w/v and eventually yield loss.
Cleaning is key!
A cleaner plant:
saves money due to fewer shutdowns caused by infection, has less maintenance downtime due to cleaner plumbing, optimizes CIP chemical costs and operates more efficiently and consistently.
A 100 MGY plant that experiences 5 days of infected fermentations at 3 infected fermentations per day can expect a loss of up to $1.4 million.
However, ethanol plants face many challenges when it comes to industrial cleaning practices. Here are 5 tips to keep it clean:
Review CIP procedures
Effective clean in place (CIP) procedures will depend on your plant’s specific layout and operating conditions. Here are some general guidelines to consider:
Use a caustic strength of 3-5% and temperature ≥180°F
Confirm the pipe flow rate during CIP is approximately 5 ft/s to create desired turbulence
Rinse with evaporator condensate or process condensate
CIP after every propagation and fermentation
Visually check that spray balls are working properly, and the bottom of propagation and fermentation tanks are empty. Tank drain samples could be used to take pH and sodium levels to ensure proper cleaning.
Do a plumbing audit, checking for deadlegs and remove them.
Use regular microbial plating
Take samples from infection-prone sections of the plant or suspected areas to rule out the presence of bacteria. Typical sources of infection include heat exchangers and fermentation fill headers. Adjust antibiotics to 1 ppm and rotate regularly. Use an emergency dose of ~10 ppm if infection is severe.
Choose your yeast wisely
Innova yeast strains have demonstrated tolerance to organic acid levels as high as 0.6% w/v lactic acid with no change in fermentation performance or ethanol yield. For more information please contact your Novozymes Account Manager.
For more information on the guidelines above please reach out to a Novozymes Specialist to make the most of your strategy.