has been attributed to multiple in-flight engine failure and grounding incidents. Supply shortage South Korea , a shortage of DEF in South Korea was continuing and brought havoc to its economy. As most of the urea used is supplied by China, imports have slowed since China introduced mandatory inspections of urea exports in September. Nearly 97% of South Korea's urea imports came from China between January and September. In 2015, South Korea had made it mandatory for diesel cars to use urea solutions to control emissions, a move that now impacts 40% of registered vehicles. Diesel vehicles made since 2015 were required to be fitted with SCR systems. The South Korean government started rationing urea solution, and banned its resale as panic buying by drivers exacerbated an acute shortage that could cause transport and industry to grind to a halt. Australia In early December 2021, the Australian National Road Transport Association also raised concerns about a shortage of DEF in the country due to the shortage of urea in China. China capped exports to protect its domestic supplies and rising DEF prices. By mid-December there was approximately 7 weeks’ supply of AdBlue left in Australia. On 14 December, an Australian company stated that it would build a new plant. References External links ISO 22241-1:2019 Diesel engines — NOx reduction agent AUS 32 — Part 1: Quality requirements Adblue consumption by vehicle type Automotive technology tradenames Diesel engine technology Pollution control technologies Air pollution control systems NOx control Solutions