Farm­ers need to take pre­cau­tions when stor­ing wet grain

The Southwest Booster - - FRONT PAGE - PAMI

Given the re­cent and wide­spread rain, snow, and cool tem­per­a­tures ex­pe­ri­enced across the grain belt, Prairie Agri­cul­tural Ma­chin­ery In­sti­tute (PAMI) is re­mind­ing pro­duc­ers of a num­ber of rec­om­men­da­tions to help them min­i­mize the risk of spoilage of wet grain stored in bins.

“We know pro­duc­ers are very con­cerned about the mois­ture con­tent of their crops go­ing into the bin,” said Dr. Joy Agnew, project man­ager of Agri­cul­tural Re­search Ser­vices at PAMI. “This has been an area of much re­search at PAMI and although some of our mul­ti­year projects are still on­go­ing, the data we have al­ready col­lected on the use of heat in grain dry­ing can be used by pro­duc­ers to min­i­mize losses in wet years like this.”

Adding sup­ple­men­tal heat to nat­u­ral air dry­ing in­volves two ba­sic steps, she said. The first is to use the heat to draw mois­ture out of the grain and into the air that is in the pock­ets be­tween ker­nels, and then use mod­er­ate air­flow rates to move that moist air out of the bin.

“A lot of our re­search has cen­tered on wheat and canola but the physics ap­ply across the board to any crop,” said Agnew. “For every 10° C you can in­crease the tem­per­a­ture of the air go­ing into the bin, you cut the rel­a­tive hu­mid­ity in half. That means you can turn a cold, mis­er­able, driz­zly day into per­fect dry­ing weather.”

The fol­low­ing are some ba­sic rec­om­men­da­tions for im­prov­ing re­sults and re­duc­ing risk when stor­ing wet grain.

1. The air mov­ing through the bin needs to be at least 10-15° C for op­ti­mal dry­ing po­ten­tial and should not ex­ceed 20-30° C to avoid high grain tem­per­a­tures that can ini­ti­ate spoilage.

2. Use a fan with an air­flow rate of at least 0.75 cu­bic feet per minute (CFM) per bushel. Any­thing lower could re­sult in heat­ing of the grain, which can ini­ti­ate spoilage. And, the higher the tem­per­a­ture in­crease of the air go­ing into the bin, the more CFMS are re­quired. With sup­ple­men­tal heat­ing, hot­ter air is not nec­es­sar­ily bet­ter as you need to match your tar­get tem­per­a­ture with your fan ca­pac­ity. If you don’t know your fan ca­pac­ity (CFM per bushel), go to pami.ca/stor­age to learn how to mea­sure or es­ti­mate your air­flow.

3. En­sure there is ad­e­quate ven­ti­la­tion at the top of the bin to al­low moist air to es­cape. That means one square foot of ven­ti­la­tion space per 1,000 CFM. Some bin and fan man­u­fac­tur­ers are pro­duc­ing fans specif­i­cally de­signed to move air out of the tops of bins.

4. Ro­tate the bin con­tents fre­quently (every few days) by re­mov­ing at least one-third from the bot­tom and au­gur­ing it back in the top.

5. Mon­i­tor the con­di­tions in the bin. Ide­ally, the mois­ture con­tent should be mon­i­tored but, at a min­i­mum, mon­i­tor the tem­per­a­ture in the bin. When us­ing sup­ple­men­tal heat, the dry­ing rate is con­sid­er­ably faster than with no heat, so keep a close eye on grain con­di­tions to pre­vent over-dry­ing.

6. The size of the heater should be based on the de­sired tem­per­a­ture in­crease (which de­pends on the am­bi­ent tem­per­a­ture and the tar­get tem­per­a­ture) and the air­flow rate from the fan, keep­ing in mind the min­i­mum air flow rate of 0.75 CFM per bushel.

7. Con­sider in­vest­ing in ther­mo­static con­trols for heaters. The more con­sis­tent the air tem­per­a­ture go­ing into the bin, the more ef­fec­tive the dry­ing will be.

8. Heat trans­fer ef­fi­ciency is im­por­tant. Prop­erly de­signed sys­tems that are ap­pro­pri­ate for the bins and fans are best, and set­ting up the sys­tem prop­erly is key to ef­fi­ciency and ef­fec­tive­ness.

9. The tar­get tem­per­a­tures men­tioned above are valid for the fall sea­son but when the out­side tem­per­a­ture drops below about -5° C, the tem­per­a­ture of air go­ing into the bin should be re­duced to pre­vent damp grain from freez­ing to the sides of the steel bin.

10. When the grain is al­most dry, turn off the heat and cool the grain to below 15° C. Cool­ing the grain will re­sult in some ad­di­tional mois­ture re­moval (rang­ing from ap­prox­i­mately 0.5% to 2%).

Agnew cau­tioned pro­duc­ers to use care hook­ing up heat­ing and elec­tri­cal sys­tems to grain bins as they pose po­ten­tial safety risks. She also noted that the main dif­fer­ence among the heat­ing op­tions (propane, nat­u­ral gas, in­di­rect hy­dronic, etc.) is op­er­at­ing cost and ease of use. Di­rect fired heat­ing sys­tems do add mois­ture to the air en­ter­ing the bin, but the amount of wa­ter added is neg­li­gi­ble com­pared to the wa­ter be­ing re­moved from the bin.

PAMI’S on-go­ing re­search on this topic will bet­ter de­fine the min­i­mum air­flow rates for use with sup­ple­men­tal heat­ing, the dry­ing rates with dif­fer­ent tar­get tem­per­a­tures, and the en­ergy ef­fi­ciency and op­er­at­ing costs of dif­fer­ent sup­ple­men­tal heat­ing sys­tems. In­terim re­sults will be avail­able in 2019 and the study wraps up in 2020. This re­search is funded by Saskwheat and Saskcanola.

More in­for­ma­tion on crop stor­age can be found at pami. ca/stor­age

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