Complex sentence: In 2006, the total European production of all butyl glycol ethers amounted to 181 kilotons per annum (kt/a), approximately 50% (90 kt/a) of which was 2-butoxyethanol.
Split into simpler sentences: In 2006, the European production of butyl glycol ethers amounted to 181 kilotons. Approximately 50% (90 kt/a) of which was 2-butoxyethanol.