Cutting through the clutter on bin aeration

What equipment you need and when to aerate are just two of 
many questions when it comes to protecting grain in the bin

With hot and dry conditions throughout much of this year’s growing season, proper aeration of grain has become more important than ever in order to prevent overheated grain or spoilage.

At the same time, there’s a never-ending parade of new aeration solutions on the market, creating a lot of confusion among growers looking for better efficiency from their systems.

The first step is to know the basics and then work from there, says a project manager with a Saskatchewan-based applied research organization. That way, producers can be more informed when they attempt to buy aeration equipment.

“The salesperson may tell them to use this ducting system or this size fan for this size bin but without background knowledge or understanding of what is happening they’re only taking their word for it,” said Joy Agnew with the Prairie Agricultural Machinery Institute (PAMI).

“It’s a big investment when you’re talking about a 10,000-bushel bin with canola that’s worth $100,000.”

What is aeration?

Although the terms aeration and natural air drying are often used interchangeably, grain aeration focuses on cooling and conditioning grain to a uniform temperature throughout the bin. Natural air drying removes moisture.

The key difference between the two is airflow rate, with natural air drying requiring a much higher airflow rate than aeration.

“Aeration is just one of the tools producers can use to help manage their stored grain,” said Agnew. “The equipment that’s needed is pretty basic and widely available: Ducting or air distribution at the bottom of the bin and a fan attached to the bin to blow air through the grain. Depending on the size of the bin, added ventilation may be required. But for smaller bins of less than 5,000 bushels, the bin cap is usually sufficient.”

The need to aerate depends on the grain’s condition, temperature, and moisture content.

“For grains like canola, we recommend aeration as soon as it goes in the bin. You have to cool the grain and reduce moisture content due to the potential for respiration for roughly six weeks after harvest. Others — like wheat, peas and barley — do not necessarily need to be aerated unless they’re harvested on a hot day or they go into the bin warm and/or tough.”

Temperature must be uniform

Uniformity is key to any successful aeration system.

“If the airflow through the grain isn’t uniform there will be pockets of grain in the bin that don’t get any airflow. What provides that uniformity is the air distribution system or ducting system.”

There are new types of ducting systems coming on the market all the time, said Agnew. However, there has been little third-party testing on the effectiveness of most of these systems. “The gold standard aeration ducting is full floor aeration for flat bottom bins and the ‘rocket-style’ system for hopper bottom bins, which helps situate the air in the centre of the bin and pushes air out through the side and the top.”

Temperature sensors are a crucial part of any aeration system.

Installation of a temperature cable in a small hopper bin.

Installation of a temperature cable in a small hopper bin.
photo: Prairie Agricultural Machinery Institute

Installed in the bin prior to grain placement, these sensors are mounted on cables suspended from the ceiling of the bin and run through the depth of the structure. These cables are equipped with three or four sensors that allow producers to read the bin temperature with either a hand-held reader or, in some cases, a cellphone. Smaller bins usually only require a single cable, but larger bins may require more.

“These are popular and affordable and can almost be considered insurance on the grain stored in the bin,” said Agnew. “There’s no way to know what’s going on in the bin without those sensors inside.”

Some temperature sensors are also able to read the moisture content of the grain.

“In-bin moisture sensors are ideal for monitoring the progress of natural air drying. Monitoring temperature alone isn’t always a good indicator of drying rates,” she said.

The safe store zone

The optimal temperature for grain is 15 C.

“That’s pretty much universal for the grain types,” said Agnew. “You want to get the grain to 15 C or lower to get it in the safe storage zone.”

However, a cooler benchmark may be required depending on whether the grain falls within moisture content limitations for safe storage.

“For most cereals the target moisture content is around 14 to 14.5 per cent. With oilseeds you want a lower moisture content than that, around nine or 10 per cent.”

Night or day?

The best time of day to aerate is one of the most common questions Agnew gets from producers. “The conventional wisdom for the past 30 years said daytime air is best for drying,” she said. “However, a few years ago some researchers from Saskatchewan concluded that nighttime air is best. That debate raged back and forth for about a year or two and there are still questions of when producers should run their fans for drying.”

Agnew maintains that daytime air has the greatest drying capacity. However, nighttime aeration may be sufficient to reach moisture benchmarks depending on the condition of the grain.

“Cool nighttime air is relatively dry. It doesn’t hold a lot of moisture to begin with so when cool outside air is passed through the warm grain the air is going to warm up and expand its capacity to hold moisture,” she said.

“That results in taking off a maximum of two per cent moisture content. So if you have just barely tough grain and you only need to take out one per cent, then running your fans only at night will dry it enough that it’s at a safe to store condition.

“But if it’s tough grain and you need to take off three or four per cent to get it into that safe storage zone, daytime air is the best to remove moisture until you’re about one per cent above the safe to store moisture content. Then nighttime air can be used to finish drying and cool the grain for safer storage.”

Top down or bottom up?

Aeration can be achieved either by blowing the air from the bottom of the bin or pulling air from the top. In Western Canada, the preferred choice by far is bottom up, while the reverse is common in Eastern Canada, particularly Quebec. Agnew said the bottom-up choice largely comes down to bin capacity. “When you have the air ducting at the top you have to wait until the bin is full before you can actually engage it. A lot of producers in Western Canada prefer to use their aeration system whether it’s full, half-full or even a quarter-full. The top-down system is not ideal for that.”

Safety considerations

As with all farm activities, personal safety is paramount when dealing with grain bins and aeration equipment.

“Basically never enter the bin — no matter what — when there’s grain in there,” said Agnew. “The biggest hazard is people climbing into bins to either probe it for temperature or to fix a sensor. Make sure you’re only doing those kinds of modifications or repairs when the bin is empty.”

Also, when using aeration equipment to dry grain, producers should not use rigged-up systems to add supplemental heat.

“Some farmers have been talking about rigging up their own systems with a propane torch of some sort. Those kinds of systems are not CSA certified and they can cause massive issues and pose great safety hazards. Always install and use properly certified equipment and follow the manufacturer’s recommendations when installing it to ensure safety.”

There are a lot of specifics involved in aeration. PAMI has fact sheets and studies that can help producers make the right decisions regarding airflow rates for specific grains, fan sizes and a host of other factors. Further information can be found at pami.ca.

“Farmers need to educate themselves on airflow rate and the things that affect airflow rate because those will have a huge impact on the effectiveness of aeration or natural air drying,” said Agnew.

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