World Grain - February 2017 - 83

GRAIN OPERATIONS

only samples the top of the pile and also raises safety concerns because workers would have to walk onto the pile to
extract samples. Tarps have slick surfaces to shed rain and
snow, which makes these inclined surfaces slippery and
GLI¿FXOWWRZDONRQHYHQZKHQKRRNHGWRDIDOOSURWHFWLRQ
system. Workers have been blown off tarps that got loose
DQG VWDUWHG WR ÀDS GXULQJ KLJK ZLQGV 6WHHO FDEOHV ZLWK
temperature and relative humidity sensors can be installed
before a pile is covered, albeit with much effort. A number
of commercial systems are available. Traditionally, cables
only included temperature sensors, but more recently cables with both temperature and relative humidity sensors
have become available commercially. Given the changing
temperatures and associated variation in relative humidity
of the air moving through the grain pile due to continuous
aeration, installing cables to monitor both grain temperature and moisture content is the more comprehensive approach for successful quality monitoring of grain stored in
outdoor piles.
CO2 sensors are a complement or even an alternative to
cables for monitoring the quality of stored grain in outdoor
piles. Given that aeration fans draw air out of the grain
pile at ground level, a manager can hold a CO2 sensor at
the outlet of each fan and determine whether CO2 content
in the exhaust air is stable (e.g., 400 to 600 ppm, normal
values) or is increasing from week to week. Increases in
CO2 readings often are picked up in a certain section or
slice of an outdoor pile. This will allow a manager to detect
the onset of limited spoilage earlier than temperature and
"moisture" cables.
How to utilize CO2 sensors and interpret observed CO2
readings has been described in a previous article, which is
accessible on-line in the July 2016 issue of World Grain
(www.World-Grain.com).

A hand-held CO2 sensor placed at the outlet of an aeration fan in a downdraft aeration system of an outdoor pile is used for the early detection of
the onset of grain spoilage. Photo by Dirk Maier.

gated from the rest of the piled grain as it is brought into
permanent storage or shipping bins.
As grain is reclaimed, grain with higher levels of damage typically from the grain surface, locations where water penetrated through holes or seams in the tarp, or from
locations where grain with high levels of broken corn and
¿QHVDFFXPXODWHGVKRXOGEHVHJUHJDWHGIRUDGGLWLRQDOFRQditioning such as cleaning, drying and blending.
Grain with objectionable odor also should be segregated
from the rest of the grain. It could be treated with ozone
to remove the objectionable odor, a practice that has been
utilized successfully by a number of grain companies.
Grain samples should be taken from all loads and analyzed for moisture content and grade factors (especially
GDPDJH 6RPH JUDLQ HVSHFLDOO\ DORQJ WKH EDVH DQG HGJH
RIDSLOHPD\EHVXI¿FLHQWO\VSRLOHGWKDWLWVKRXOGEHOHIW
GRAIN RECLAIM
on the ground after the rest of the pile has been removed.
Outdoor piles should be picked up as soon as permanent It often contains non-grain materials such as gravel (if not
VWRUDJH VSDFH EHFRPHV DYDLODEOH 7KH FRVWV DQG EHQH¿WV paved) from the bottom surface of the pile and needs to
of partial reclaim should be weighed against penalties as- discarded.
sociated with quality deterioration that accrue when waitOverall weight and quality loss should be assessed,
ing until space becomes available for the entire pile. Once and costs for storing grain in outdoor piles for the season
it has been decided that grain will be reclaimed from an should be determined. Consideration should be given to
outdoor pile, the tarp has to be at least partially removed improvements for the next season such as paving the surtogether with the inlet aeration ducts placed on the surface face, improving the aeration system and tarping a pile that
of the grain.
will be regularly used, or adding more permanent storage
Although generally not possible, if a section or slice of structures to avoid weight and quality losses from tempoan outdoor pile previously was identified to have higher rary storage in outdoor piles.
CO 2 readings, it would be preferable to start unloading the
Dirk Maier and Sam Cook are post-harvest engineers with the Iowa
pile at or near that location. Grain from that area likely
Grain Quality Initiative at Iowa State University. They may be
will have higher damage levels. Rectangular piles posireached at dmaier@iastate.edu and scook@iastate.edu.
tioned with the long axis pointing from east to west may
contain grain with greater quality deterioration along one
We want to hear from you - Send comments and inquiries to
face of the pile. Grain from these areas should be segre- worldgrain@sosland.com. For reprints of WG articles, e-mail reprints@sosland.com.
www.World-Grain.com / World Grain / February 2017

http://www.World-Grain.com http://www.World-Grain.com

World Grain - February 2017

Table of Contents for the Digital Edition of World Grain - February 2017