Monday, January 23, 2012

ECHO Asia's Earthbag House: A Potential Seed Bank Approach

Lue and James appear to be sitting in front of a grass hut.  But looks can be deceiving.  The small structure is actually the ECHO Asia Seed Bank's earthbag house that is nearing completion.

Two factors that affect the long term viability of stored seed are humidity and high temperatures.  Modern seed (gene) banks generally make use of climate controlled rooms to keep both humidity and temperature sufficiency low.  ECHO Asia's seed bank employs a simple air conditioning unit that moderates the temperature (and the humidity to some degree).  But for improved control of relative humidity, as well as seed-storage pests such as bruchids, we also store our seeds in vacuum sealed bags.

However, in many places, there is limited access to electricity to enable seeds to be stored in an expensive air-conditioned climate controlled environment.  As ECHO promotes community-based seed sharing and saving, it is also part of our mission to recommend appropriate ways for communities and organizations in the developing world to better store seeds.

Underground structures, such as root cellars, have long been used as an appropriate way to modify temperatures for the long term storage of plant products.  Underground temperatures can be significantly lower (or higher) than the above-ground ambient temperature, making a huge difference towards keeping harvested plant products from perishing.

Along the same lines, it seems logical to use root cellars as seed banks as long as seeds can be stored in containers in which the humidity is modified by using vacuum (or partial vacuum) and/or desiccants such as silica gel or even parched rice.  

Unfortunately, not every location has a hill, favorable soil depth or a low water table for which to dig a root cellar.  Therefore, modified earthbag structures (with walls composed of sacks filled with soil) are an appealing possibility.  

James (ECHO Asia intern) and Lue (Assistant Seed Bank Director) were trained in earthbag house construction by Engineering Ministries International (eMi).  Afterward, they brought their skills to the seed bank and facilitated the construction of a small earthbag house.  To prevent the invasion of surrounding warmer air (the seed bank is located in a tropical/sub-tropical region), a small door with a foam interior and a thick but light ceiling composed of sacks filled with burnt rice husks were installed.  And to keep costs low, almost the entire structure was made from local, cheap materials, including a roof of fan palm thatch.

Data loggers will be installed this week to record the interior temperature and relative humidity.  These will be compared with outside readings over a period of one year.

So we look forward to reporting on the long term results of the modification of temperature by the earthbag house and the potential of such structures for community-based seed storage in the tropics.

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