US thermal coal exports surged to four-year high 36.17 million mt in 2021, up 47.9% from 2020, according to US Census Bureau data released Feb. 9. December thermal coal exports totaled 3.12 million mt, up 0.7% on the month and 18.7% from December 2020. December coal exports were at a six-month high —the highest monthly volume since 3.25 million mt…