How to Dry Walnuts at Bear River

1. The target, and why it is 8%

We ship at 8% kernel moisture (the board's line is 8.2%). Under about 7% we are giving away weight we are paid for and the kernels get brittle; over 9% ShoEi marks the load wet and mold risk climbs in the bin and in their storage. The green and tan bands on the Bin Map are the window: tan (8 to 9) is ready, red (under 8) is past ready.

Our probes and ShoEi's meter do not agree load to load, and the reason is temperature. Hot nuts straight off the heat read about three quarters of a point higher on our probes than ShoEi later finds; nuts that sat cold overnight read a point or more lower. ShoEi tests after the nuts have cooled to about 80°F. So judge a bin for shipping by its reading at the same time each day, best in the morning after the burner has been off a while, and expect a bin that reads 8.0 hot to come in near 7.3 on their sheet.

2. How fast the dryer actually dries

With the burner on, a bin loses about 0.8 points an hour. Wet nuts come down faster (0.9 to 1.0 an hour above 15%) and the last stretch is slowest (0.6 an hour between 10 and 9, and slower still from 9 to 8). From the fill: a load that starts at 20 to 30% needs about 16 hours, one that starts over 30% about 22 hours. Solano has run 15 hours, Chandler 21, Durham 21, Serr 25.

Plan with those numbers. A bin filled at 10 am from a wet block will not be ready for the morning truck; one filled by noon from nuts in the twenties usually will. The board's finish time uses this season's curves and is usually within a couple of hours once a bin is below 15%.

3. Temperature: what to look for

The two barn sensors are the Lower one by the fan intakes (the air going into the bins) and the Upper one in the exhaust (the air coming out). With the burner on, the exhaust has sat between 90 and 100°F nine hours in ten, and that is the range to keep. Above 100°F the drying rate did not go up, it went down (0.75 an hour against 0.85), and kernel color suffers with long runs over 105. Intake air has run 75 to 95°F with the burner on.

Rules of thumb: exhaust under 90 with the burner on means the barn is losing heat, close doors; exhaust over 102 means turn the burner down or open a door; exhaust rising while the bins read wetter means the heat is not reaching the nuts, check the fan and the burner on that row.

4. Humidity: what the air can and cannot do

Every parcel of air has a moisture it will drive nuts toward and no further; the Environmental page calls it "where the air would take the nuts" and paints it in the Bin Map colors. Air at 60% humidity and 90°F parks nuts near 8%. Air at 85% humidity parks them near 12%, whatever the temperature. That is why heat works: warming air from 60 to 90°F cuts its humidity roughly in half and moves its parking spot from 12% down to 7%.

With the burner on, our intake air has run 47 to 75% humidity, which is why the bins keep moving. Outside air this month is drier than 55% only from about 10 am to 6 pm; by 9 pm it is over 75% and from midnight to 8 am it is 80 to 88%. Pushing that night air through the bins without heat takes water back into the nuts.

5. Barn doors: open at mid-morning, close at sunset

This is the clearest signal in the season's data. Compare the air inside at the intakes with the air outside, hour by hour. From 10 am to 7 pm the outside air is drier than the barn air by 1 to 3.5 points of nut moisture (the barn traps the water the nuts give off, and the sun is on the roof). From 8 pm to 9 am it flips: the barn air is 2 to 5 points drier than the outside air, because the burners have warmed it and the outside has gone to dew.

So: open the big doors around 10 am once the outside humidity has dropped under 60% (the weather box on the Environmental page shows it), and close them at sunset, which is 6:30 pm now and 5 pm by mid-November. On a foggy morning (outside over 85% at 8 am) keep them shut until the fog lifts, usually by 9:30. On a rain day keep them shut all day and let the burners carry it. The Environmental page shows the two lines; when the green outside line sits below the blue intake line, open; when it sits above, close.

6. Burner off means the nuts get wetter

Every hour this season with a row's burner off, the bins on it did not hold, they went back up: a tenth to three tenths of a point an hour at night, and one night hour in six they gained more than that. Fans alone in night air are worse than nothing. If a row has to come off heat overnight, shut the fans and the doors too, and expect to give back half a point by morning.

A burner that quits is the costliest thing that happens in this barn. On October 5 Row C's burner went out while WECO still showed it on; the bins climbed from 21 to 23% in ninety minutes before anyone saw it. The board now texts the crew when most open bins on a row turn wetter for an hour with the burner supposedly on. When that text comes, go look at the flame, not the screen.

7. Night and day

With the burner on, night drying is as good as day drying, 0.8 an hour either way, and the best hours of the whole cycle are 7 pm to 1 am (0.9 to 0.95). The worst are 8 am to noon (0.5 to 0.55): the barn is coldest, the outside is at its wettest, and the morning's fresh fills are pulling heat. Do not judge a slow bin at 9 am; look again at 2 pm.

8. The days are getting shorter and the nights wetter

Daylight at the ranch was 12.5 hours in mid-September, is 11.2 hours now, and will be 10.1 hours by mid-November (sunset 4:50 pm once the clocks change on November 1). The hours per day when outside air could dry nuts to 8% by itself were 10 to 11 in early October and 6 this week, with highs in the 60s and lows in the 40s. Night humidity has gone from the mid-70s to the mid-80s.

What that means for the rest of the season: the burners carry almost all of the drying from here on, so budget propane for it; open-door hours shrink to 10 am to 5 pm; expect a wet Chandler bin to need 24 hours or more rather than 20; and fill early in the day so a bin has the good afternoon air and a full night of heat before the morning truck.

9. Weather

Hot clear day (90s): best drying of the season, open doors by 9:30, and the barn exhaust will push past 100°F by afternoon, so ease the burners back rather than cook the top of the bins. Fog or heavy dew morning: doors shut until it lifts, burners on, and do not read bins for shipping until it clears, the probes read the damp. Rain or a storm front: doors shut all day, burners on, nothing filled from wet windrows if it can wait a day; nuts picked up wet start in the high 30s and take a full extra day. Wind: a dry north wind afternoon is free drying, open everything; a south wind ahead of rain brings the humidity up hours before the rain, watch the outside line climb.

10. A day in the barn

11. Reading the board

Dark blue and blue, 12% and up: wet, leave it alone. Teal, 10 to 12: drying, on schedule. Green, 9 to 10: close, usually tomorrow morning's truck. Tan, 8 to 9: ready. Red, under 8: ship it today, it is losing weight. A small time under a bin is the predicted finish; "holding" means it reached target and is now creeping back up with the heat off, so the number shown is the lowest it got, which is the one ShoEi will see. The Environmental page answers the door question: green line below blue, open; green above blue, close.