Yesterday I heard a short lecture about a fascinating subject: the European genizah. The European genizah is not a genizah in the original sense of the word. The Hebrew word genizah means something like 'hiding place', or 'storage room', and denotes a place where old, worn out, usually Hebrew language manuscripts were stored, before they were buried in a Jewish cemetary.  A famous example is the Cairo genizah, a forgotten room in a synagogue in Fostat (Old Cairo) where some 210.000 Jewish manuscript fragments were found, most of them dating to the 9th till 15hth century.
In Europe, like in the Middle East, old and worn out Hebrew manuscripts were buried. However, the humidity of the earth caused them to decay and an European genizah in the sense of the Cairo genizah has not been found. What then is the European genizah that has been found in the last 30 years? As opposed to the regular genizah, where Hebrew manuscripts were kept 'safe' (albeit to be buried), something completely different happened in Europe, not only with Hebrew manuscripts but with all the different language medieval  parchment manuscripts. They were recycled. 
Since parchment is a very enduring and quite expensive material, old and discarded manuscripts were dismantled and used, one folio or one bifolio at a time, as binding for another manuscript. Or a book. Or even an archival file. 
Especially in Italy, thousands of folia and bifolia of Hebrew manuscripts have been found, used as bindings for the city archives.
Even incunabula were not exempt from this practice.
From the introduction to "the Italian Geniza" by Mauro Perani:
"In fact I found in the Archives of Nonantola and Cento some bifolia of the first edition of the Bible, printed in Bologna in the year 1482, such as of the Torah with various commentaries printed in 1490 in the spanish town of Iijar."