What Becomes of Old Shoes, a question asked and answered in the Feb. 1870 issue of Manufacturer and Builder.
The old shoes were cut up in small pieces, and were put for a couple of days in chloride of sulphur, which made the leather very hard and brittle. Afterwards the material was washed with water, dried, ground to powder, and mixed with shellac or some sort of glue.
It was then pressed into molds and shaped into combs, buttons, knife handles and other articles.
A later article added the following...
"Waste leather is an excellent fertilizer, and in some parts of the world, chiefly in England, is cut up in small pieces and used in manuring the land. The same is done with woolen rags, which are highly valuable for this purpose — a fact which should be better known among farmers and Southern planters, who are in general very wasteful in regard to utilizing many substances highly valuable as fertilizers."
According to the article, leather contains gelatin, and treating the leather with an alkili will release the gelatin.
"By proper treatment, the gelatine from old leather may be made palatable, and one of the curious feats of modern chemistry, sometimes performed by Professor Van der Weyde before his class in the Cooper Union, NewYork, is the making of a palatable pudding from a pair of old used-up boots, sweetened with sugar made from linen fibre, that is to say, from an old shirt."
Old and scrap leather was also used in the manufacture of paints.