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Earthbag structure for moderation of temperature when storing seeds

At the ECHO Asia and ECHO Florida locations, earthbag structures were recently built for use as low-input seed storage facilities. The hope is that these structures would help decrease the daily fluctuations in temperature that stored seeds experience. Temperature control is important in the successful storage of seeds. For more information see EDN 86 and/or BPN 5.

We placed a HOBO® temperature datalogger inside of the earthbag structure at ECHO Florida. After logging data for 59 days, the information was downloaded from the device. Outside temperature data were collected with a RainWise® weather station. Maximum and minimum temperatures per day were calculated for both data sets then overlaid on top of each other (Figure 1).


Figure 1. Temperature fluctuations (max and min) per day for inside (red) and outside (green) the earthbag structure at ECHO Florida.

The earthbag structure significantly decreased the fluctuation in temperature from an average of 27.6°F per day to an average of 3.8°F per day (Figure 1; p-value<0.01). The earthbag structure also significantly decreased average temperature from 79°F to 75°F (p-value <0.01). The overall cooling effect of an earthbag house is desirable for extending the life of stored seeds.

Table 1 shows weekly averages of the same temperature variables shown in Figure 1. It is shown as an example of how the data could be displayed if tracking environmental data over a long period of time.

These data were taken with no insulation between the roof and ceiling of the structure. Once that insulation is added, we plan to collect another round of data. Our hope is that roof insulation will block the transfer of heat from the roof (the portion of the structure most exposed to direct sunlight) to the interior of the structure, thereby further reducing maximum temperatures and daily temperature fluctuations inside the earthbag house.

Do you have experience using earthbag structures for seed storage? What have you learned?

Do you have questions about using earthbag structures for seed storage?

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For anyone interested, here is a link to some recent research we did at the ECHO Asia Impact Center. We compared vacuum sealed seeds and unsealed seeds stored in earthbag structures. The article was published in Asia Note #38. Results showed that the combination of vacuum sealing seeds with a cheap modified bicycle pump, inside of an earthbag structure, was an excellent method for storing seeds over a 1 year period.

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