Each year, approximately 14,000 tons of bagged calcium hydroxide are used in controlled
atmosphere (CA) warehouse facilities throughout Washington to keep stored fruit from ripening
prior to shipment to domestic and overseas markets. Through adsorption of carbon dioxide, the
calcium hydroxide converts to calcium carbonate (lime) while still in the bag. At present, only a
small portion of the calcium carbonate by-product is reused, with the balance either disposed at
the county landfill, stockpiled long-term, or illicitly dumped on vacant land. Disposal of the lime
is considered a significant problem by the Washington State Department of Ecology and
numerous local regulators and municipalities.
The most desirable solution to this significantly excess by-product is to reprocess the spent CA
lime into high-value lime products for use as a filler material in numerous industrial and
agricultural applications. Processing would be conducted to mill the calcium carbonate to an
average particle size range of 2 to 3 microns, to meet various industrial specifications. These
processes could be accomplished economically, in an enclosed light industrial setting with dust
controls throughout the processing area.
This project describes an outstanding opportunity to implement full recycling and beneficial reuse
of an existing industrial by-product in Central Washington. It is particularly appealing
because the by-products are contained in kraft bags and stored on pallets, and as such are free of
contaminants. Nearly all of the material, including the bag, can be reprocessed into products of
equal or greater value than the original raw material.