Stored Grain Management

Maintaining grain quality while staying safe

This article is excerpted from a webinar on stored grain management and handling in storage held April 22, 2020. The panel was organized by Klein Ileleji, professor and extension engineer in the Department of Agricultural and Biological Engineering at Purdue University, West Lafayette, IN.

The webinar featured a panel of stored grain academic and industry specialists speaking on various issues related to the topic. Panelists included:

  • Dirk Maier, professor and extension agricultural engineer at Iowa State University.
  • Ken Hellevang, professor and extension agricultural engineer at North Dakota State University.
  • Carol Jones, professor in the Buchanan Endowed Chair at Oklahoma State University.
  • Bob Marlow, independent consultant and Grain Journal columnist.
  • Pete Mueller, president and owner of Fumigation Service & Supply Inc.
  • Chuck Schwab, professor and extension safety specialist at Iowa State University.
  • Sammy Sadaka, associate professor and extension engineer at the University of Arkansas.

The webinar also included three moderators:

  • Klein Ileleji.
  • Sam McNeill, extension agricultural engineer at the University of Kentucky.
  • Janie Moore, assistant professor at Texas A&M University.

In preparing this article, Grain Journal included portions of the webinar most relevant to the upcoming fall harvest and winter storage season.

Outdoor Storage Piles

Bob Marlow: Managing outdoor bunkers and piles presents some unique challenges, and almost every facility has some different challenges, as well. First and foremost, I would certainly segregate, trying to do my best to avoid mixing any of the challenged grains, especially on moisture, damage, and so forth with other good grains. I know that it is very difficult, especially when your surface or your base already has some damage. The challenged grain just naturally wants to mix in. I’d suggest the following things:

  • I recommend a good reclaim plan based not only on speed, which is generally very important, but also on quality segregation. Clearly communicate that plan to your employees. In the case of those who might be using contractors, make sure that they understand that, as well.
  • Use a grain dryer, if available. While moisture meters determine averages, perform a close examination of the sample to determine if it contains a large quantity of swollen or sprouted kernels. If so, this type of grain needs to be dried. You can regulate how much heat is used with your dryer, which have tremendous airflow rates. They are a great tool to dry, cool, and condition the grain. Additionally, it can help reduce odors associated so many times with grains reclaimed off piles, bunkers, etc.
  • Be prepared in some circumstances to set aside or possibly discard grain that is heavily damaged or insect-infested. Instead of dealing with this material during reclaim, setting it aside gives you some time. These are tough decisions to make and have financial impacts, but don’t attempt to “blend away” this type of material. You need to take into account blue eye mold, mycotoxins, and the reintroduction of excess moisture into a stable grain mass that could have serious quality and safety impacts down the road.

Insect Pest Risks

Pete Mueller: Keep in mind that insects are actually a symptom of an existing condition. They need time, food, and temperature. I think it goes without saying that the Purdue acronym SLAM is always important – sanitation, loading, aeration, and monitoring.

With sanitation, the grain is never going to get any better than it was when we put it into the bin. Make sure that if you are carrying over grain, do something either to treat it or ensure that the quality is high, and there are no current pest pressure or pest issues.

Site sanitation is important as well. Bob Marlow just spoke about cleaning up ground piles. That dumpster pile on the edge of the property could be the spark that leads to the upcoming year’s infestation. If you were blending foreign material or high-moisture grain with other good grain, there’s a chance that this is going to come back and bug you again later.

Technically, aeration is not for drying grain. It’s for controlling the temperature. Loading at 87 degrees or warmer, not only are we reducing the shelf life of the grain, but we are reducing insect lifecycles. If we get it down to 45 degrees, reproduction will shut down. In 90 days at 87 degrees, you can go from a population of two rice weevils to 32,250 in just three generations. If you think about it economically, a bushel of corn is a little bit over 80,000 kernels, so in a few generations, you start taking a hit.

Carbon Dioxide Monitoring

Dirk Maier: Carbon dioxide (CO2) monitoring does work for any grain type, because it measures biological activity, whether it’s for molds or insects or high-moisture grain respiration. Because it measures a gas that naturally occurs in grain, it can pick up problems more easily than temperature cables. Cables are limited to detecting only those problems near a temperature node, while CO2 monitoring picks up gas that moves within the grain mass itself.

So a key action step, especially during years when there is a lot of grain of marginal quality in storage, is to buy at least a handheld CO2 sensor and determine the quality level of stored grain. Without knowing what the quality is, you can’t make any good management decisions. It costs about $500 for a handheld sensor, which is relatively inexpensive compared to the value of stored grain.

If the CO2 readings are below 600 ppm, you essentially have good-quality grain and more flexibility on how long to store it. Ideally, the good-quality grain is kept cool or cold, and at a minimum, also cored and the peak removed. Ideally, we seal the aeration fans to keep that cored grain cold into the spring.

If you check CO2 on a weekly basis, you essentially have a good management and monitoring strategy. If your readings are between 600 and 1,500 ppm, you need to make some plans for what to do with the grain. Maybe unload and market the grain, until the CO2 level drops back below 600 ppm in the rest of the grain mass. That remaining grain could still be stable and could continue in storage.

If readings are above about 1,500 ppm, you need to make plans about what to do with the grain more aggressively. Around August, it can indicate insects becoming more active. I highly recommend the use of CO2 meters for monitoring stored grain quality from the time the bins are filled to unloading them for any grain type.

Insect Control Options

Mueller: There are a number of ways to monitor for insect pressure inside of a bin. The first is sampling during coring. That’s when you pull the center gate and draw down the grain until you have an inverted cone at the peak. Then, you take samples either while you’re pulling truckloads or while you’re moving the grain over to another bin.

The advantage with this is that it gives you a vertical snapshot of both your grain quality and your insect population. The disadvantage is you physically need to move the grain. So if you have no place to go, or it will tie up your equipment doing so, you can incur an additional expense from electricity to move it, as well as some shrink or damage, especially in the corn and soybean areas of the country.

Another way to test is the Cargill probe method. It’s where you use a portable vac system and a tube or probe that goes down about 20 feet or 5.5 meters into the grain. It’s great for when you are working in bunkers, flat storage, or ground piles, where you can’t physically move the grain easily to determine your insect presence. The disadvantages are that you need special equipment and power to move it around.

An old-school method is simply taking a manual truck probe. I’ve seen them covered in dust in the back closet, now that things are getting more and more automated in the scalehouse, but they’re already paid for. The disadvantage is that to do it appropriately, you have to enter the grain bin. And that’s currently not a best practice.

Dr. Maier has done good research with companies like The Andersons and CGB on CO2 monitoring with very interesting results. Insects respire and produce CO2, as well as molds and secondary feeders. It is a cheap method to look for these types of things around vents, hatches, and exhaust fans. And it doesn’t require a confined space permit to actually go into the bin to acquire that information.

Mixing for Moisture

Carol Jones: It’s better just to dry grain. On paper, we have all kinds of equations that show you how to make it look like your composite moisture content is acceptable. What really happens in the real world is that you end up with pockets of high-moisture grain throughout your storage. That leads to mold and insect infestation in those wet areas. When we see spontaneous combustion fires in grain bins, many times they come from those pockets of wet grain.

From a safety standpoint, pockets of 18% moisture grain cause clumping. At best, it doesn’t come out of the reclaim system. At worst, it causes an entrapment or a death in the grain bin from a wall of grain breaking loose or from bridging.

I know it’s more costly, and it takes time, but dry that 18% down a little bit before you integrate it.

Danger Signs

Chuck Schwab: A person who knows the history about the unloading and loading of a bin will have a better understanding as to what would be visible from the top surface. Is the surface peaked, or is it an inverted cone? In other words, have you cored the bin? Are there conditions such as shiny metal or clean sidewalls that should be present when the grain has dropped from unloading? If that grain hasn’t revealed a shiny or clean sidewall, that tells you that the top surface most likely has bridged, creating a potential for entrapment.

Sidedraw Unloading

Marlow: If your central discharge well is plugged, get in contact with your grain bin manufacturer before using any sidedraw or truck loadout spout. Discuss your particular situation, and let them be a part of your guidance.

If the manufacturer has designed the truck loadout spout properly, you should be able to use the spout normally. However, you might want to consider reducing the speed of unloading.

A plugged center sump really is not a normal situation. So you want to continually monitor the process for any shell deformation and foundation movement, and safely monitor what’s going on inside the tank. If you have a large dome of material fall over or collapse, you may have another, bigger problem.

Also, if you choose this route, remember that eventually, you must level the grain again. It’s not a good idea to pull grain off to the side and then refill the bin.

And finally, closely monitor the center sump. Sometimes just pulling the off-center outlets, things shift a little bit on the inside, and suddenly the center sump starts to operate again.

Plug Prevention

Sammy Sadaka: Moving the grain from time to time will help prevent potential plugging issues. However, take into account that more movement of the grain means higher costs for management.

On the other hand, for rough rice and in some other cases, we don’t lean toward movement of rough rice within the storage bin or between bins, because this can negatively affect the quality of the rice.

Crust Removal Before Unloading

Ken Hellevang: Each situation is different. We need to develop a plan as to how we’re going to work on that crust. If we have unloaded some grain, and we don’t see an inverted cone or funnel shape, then we’re likely to have a void underneath that crust. Recommended safety practices become absolutely critical – working in teams, wearing harnesses, and making sure we don’t end up with the crust collapsing and someone falling into that space, getting covered and entrapped.

People can use poles and other methods from outside the bin to break up the grain. There is a danger of creating grain clumps that impede the flow by getting caught in the sump. There is no easy solution. Again, keep safety in mind.

When you start looking at entrapments that lead to fatalities, it’s often individuals who are working by themselves. When we discover we have a problem, we need to shift gears and think about how we are going to safely remove the crust. If we need to go find somebody so we have a team, that needs to be the first priority.

Schwab: For commercial operations, it’s important to follow the standard operating procedure for confined space entry and lockout/tagout. Part of the standard operating procedure beyond that might be notifying the local emergency rescue or firefighter group to let them know there is a potential for a problem. Regardless of the location, when you are in a non-flowing grain situation, it’s paramount for everyone to reset their priority from getting the grain out of the bin to keeping everyone safe.

Look at the ability to communicate with anyone who has to go inside storage. Can you retrieve that person once he or she is in the bin? There are so many moving parts.

Grain Bin Fires

Sammy Sadaka: For combustion to happen in a grain bin, we need three critical requirements:

  • Fuel, which in this case could be the grain or the fines.
  • Oxydizer, which comes from the air.
  • Ignition source, which could be hot spots from grain respiration or other practical issues such as heat from friction.

The minimum ignition temperature of grain varies. The minimum ignition temperature for wheat flour, corn starch, and grain dust is in the range of 750 to 930 degrees F (400 to 500 degrees C). When corn burns, the temperature could reach 1,472 degrees F.

We have two ways to monitor temperature inside of grain bins – manually monitoring the grain temperature or grain temperature monitoring cables.

If hot spots develop close to one of the cables, it automatically would be detected by the temperature sensors. If it happens far away from the cables, it will not be detected easily.

So we need to turn on the aeration fan once every two weeks for maybe a couple of hours, especially when the ambient temperature is above freezing. That will move the hot air through the grain, and then the cables potentially could easily detect the high temperatures.

In addition, we can measure the CO2 concentration in the airstream from the negative draft aeration duct. You can use a handheld CO2 monitor or install a wall-mounted CO2 sensor to measure the CO2 concentration, which is a measure of hot spots in the grain bin. Then we need to take the appropriate action, such as aeration.

Once the hot spots reach ignition temperature, however, we need to shut off the fans to avoid adding more oxygen that will increase the potential for fire.

One action we need to take is unloading the grain bin, starting from the top to the bottom. We need to take it to ground and move all of the high-temperature or burning grain away from the bin.

We have to be careful not to unload the grain from just one side of the bin, not to solve one problem by creating another with the collapse of the bin due to the pressure differential.

Target Stored Grain Temperature

Hellevang: Keeping that grain at temperatures below roughly 50 degrees F will greatly minimize the potential for insect infestation. In the northern United States, that target could be 40 degrees F. Insects become more active the warmer the temperature. The closer we get to that 70- or 80-degree F temperature range, the more potential for insect problems to occur.

The same thing is true for mold growth. Roughly every 10 degrees F that the grain temperature warms cuts the expected allowable storage time in half. So the goal is to keep it as cool as we can.

Moisture in the Headspace

Carol Jones: Ventilating the headspace is the best answer. Turning on your aeration fans may not be the best plan when it’s humid or if you want to keep the temperature below 40 degrees F. If you can ventilate your headspace, that’s really the answer. That’s when exhaust fans come in handy. Their job is to remove the moisture from the headspace, not to aerate the grain.

It’s unusual to have sweating in a concrete tank, but it does happen. If you can open a manhole at the top, maybe even set an exhaust fan on top of the open manhole, then you can move some of that moisture out of the headspace.

Organic Acid Preservatives

Hellevang: Typically, to be effective, preservatives require handling the grain. You’re trying to get the appropriate amount on the grain. My feeling is that it’s actually easier to run the grain through a dryer than it is to apply the preservative appropriately.

Jones: The grain dryer also is a more economical choice. A larger natural aeration system may work depending on where you are located.

Mycotoxin Testing

Maier: There is no requirement that every load be tested. That’s a function of the quality protocol a facility may choose to implement, whether it’s a grain elevator, feed mill, or processor. The key thing is that most mycotoxin problems in the Midwest already occur in the field. They are then carried into storage.

Generally speaking, relatively less of a mycotoxin develops during storage itself. So knowing the disease load during the growing season is what we typically pay attention to. Then we try to identify areas of the state, the Corn Belt, or the country that is having issues with mycotoxins. That’s typically a more targeted effort.

Mycotoxin testing is relatively easy to do and relatively inexpensive. It’s available at state labs, such as the Iowa Grain Quality Initiative. Many elevators and feed mills are equipped with that testing capability. Getting a representative sample off of the grain mass is key to get a result that is meaningful.

Fumigants

Mueller: The only fumigant that is widely accepted for grain export is phosphine. We have limited tools in the grain industry, so we need to do our best to preserve them.

If grain is fumigated during transit, and it comes to you, the best advice would be to sample. We talked about being the gatekeeper and monitoring with SLAM. A little bit of training goes a long way with your staff to help identify what is a stored grain product pest. Are they alive, or are they dead? Dead insects don’t breed resistance, but we have to ensure the concentration was high enough to kill any insects that come through.

If you do find live insects, you can test for resistance and fumigate it at a higher level to knock out those genetics. You don’t incur any tolerance or resistance in an effort to maintain the integrity of phosphine fumigants.

Reprinted from Grain Journal July/August 2020 Issue