Both edible and industrial grade have similar thickening and gelling effects and their main component is all protein. Their major difference lies in three aspects derived from raw materials.

Source: edible gelatin is derived from animal skins and bones, while the industrial grade is mainly tanned from leather.
Price: the cost of the latter is much lower due to the lower cost of the leather.
Purity: the latter has poorer quality and more impurities. It is strictly forbidden to use industrial grade in medicine and food.
Uses: industrial grade is mostly used in furniture and printing but forbidden to be used in food as it comes from leather which has a high content of the heavy metal residues- chromium and other harmful chemicals.
Industrial grade almost cannot be distinguished by sensory such as color and taste, but most probably can be tested by the chromium content brought from the leather tanning process.

http://www.chinafooding.com/Gelatin