(a) Open-Top Silos
Nearly all open-top silos today are made of concrete, either cast-in place (poured) or pre-cast stave. There are several brands of steel open-top silos available but to date these have not gained widespread acceptance in Ontario. Basically all open-top silos use some type of top unloader.
(b) Oxygen-Limiting Silos
Most oxygen limiting silos are constructed of steel or concrete. Of the steel units, the most popular is made of bolted panels of glass-fused-to-steel. As well, there are units available that consist of galvanized steel with some type of interior lining or coating to protect the steel from the corroding effects of silage acids. Oxygen-limiting silos are also constructed of concrete. Until recently these were all cast-in-place units; more recently several companies have started to market oxygen-limiting silos made with pre-cast concrete staves together with some type of interior lining. In addition, several attempts have been made to supply Ontario farmers with silos made from fiberglass, but to date this has not proven economically successful. Nearly all oxygen limiting silos are equipped with some type of bottom unloader; one company uses a top unloader with bottom delivery in its forage units.