The effects of warm weather on fermentation
As summer temperatures soar across the U.S., ethanol plants are looking for ways to optimize production. But while the problem may be obvious, the solution is anything but.
Every ethanol plant is different—from processes to equipment and even a plant’s physical location, any number of factors can play a role in the steps necessary to keep production optimized. Add to that the myriad of potential environmental stressors, and a fermentation problem can quickly become a nightmare to troubleshoot.
In those types of situations, the last thing you want is to play a guessing game. That’s why it’s so important to understand how environmental conditions can affect the fermentation process.
Last year, we showed you 7 ways to prepare your plant for warmer temperatures. Now, as summer temperatures soar across much of the U.S., the time to be proactive has, for the most part, passed. But that doesn’t mean there’s nothing you can do to keep your plant running like the well-oiled machine it should be.
Higher temperatures: a stressor for yeast
Frank Moore, a biofuels process specialist at Novozymes, spent 35 years in the processing and business development segments of the ethanol industry. He said the problem is simple.
“Once temperatures go up just a few degrees in the summer, there just isn’t enough heat exchange capacity,” Moore said.
Yeasts—the microorganisms that convert sugars into ethanol—are routinely exposed to a variety of environmental stressors, and these can include changes in temperature outside of optimal conditions. In fact, inability to precisely control fermentation temperature is possibly the biggest and most common factor affecting ethanol yield.
And, while it may not be a new problem, it’s not going away. Because of faster fermentation and enhanced ethanol production, more heat is released in the fermentation process today than it was in the past. As a result, heat removal has become a bottleneck area in most plants regardless of location and weather.
“One important thing to remember also is that stress is cumulative,” Moore added. “So when you remove one stressor, you’re able to deal with temperatures better.”
Everyone has a plan, until…
Of course, as a proactive measure, your plant design should incorporate enough cooling capacity to avoid causing heat-induced stress, and additional capacity should be planned for peak summer rates of production at the highest sugar levels possible. You should also be performing regular inspections of often-overlooked portions of your facility like the cooling tower, so that it doesn’t become your operation’s limiting factor.
But what if your cooling system isn’t working at 100%? Or what if you planned for heat, but just not this much?
The easiest way to reduce fermentor temperature once it starts rising is to reduce the sugar level going into the fermentor; this will reduce yeast growth and activity. Another way to deal with higher temperatures is to incorporate temperature staging. In this method, the temperature is gradually reduced to lower levels than typical later in fermentation to remove the temperature stress and avoid premature yeast death.
“The other option is to extend the fermentation time,” Moore suggested. “You can work with our technical service staff to slow it down a bit during extremely hot weather.”
Staying a few steps ahead of the weather
Lower ethanol yield is one effect of higher temperatures and stressed yeast, as can be the inadvertent production of unwanted components such as fusels. And in fact, the issues can cascade through the production line all the way to distillers grains, which can become sticky and hard to handle due to higher sugar content and/or the high humidity associated with hot summer days.
As mentioned, no two plants are the same, and you likely know yours better than anyone else. But the most useful piece of advice, Moore said, is universal: Take a few minutes every day to tune into your local forecast.
“Fermentation can be two to three days long,” said Moore. “Watch the weather, and be aware of when the heat waves are coming.”