United States SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ______________________________________ FORM 10-K ______________________________________ x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2018 or ¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission File Number: 001-37822 Advanced Emissions Solutions, Inc. (Name of registrant as specified in its charter) Delaware ...