CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net loss	$ (304,201)	$ (75,433)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	30,707	34,605
Amortization of debt issuance costs and original issue discount	1,536	685
Provision for doubtful accounts	746	561
Deferred income taxes	(1,127)	884
Lower of cost or net realizable value inventory adjustments	4,268	0
Loss (gain) on disposal or impairment of assets	224,896	(1,089)
Noncash lease expense	(851)
Stock compensation expense	2,855	3,565
Repayment of PIK accrual on notes payable, related parties	(2,040)
Change in fair value of derivative instruments		(2,537)
Changes in operating assets and liabilities:
Trade accounts and other receivables	21,556	1,451
Inventories	12,214	14,156
Prepaid expenses, other current assets, and right of use assets	2,264	717
Accounts payable	(4,747)	(8,759)
Accrued expenses	1,239	3,710
Income tax receivable, net	(809)	69
Other, net	11	3,162
Net cash used in operating activities	(11,483)	(21,598)
Investing activities
Capital expenditures	(2,192)	(2,039)
Payment of Millen sale post-closing matters	(1,516)
Net proceeds from asset sales	1,070	27,526
Net cash (used in) provided by investing activities	(4,252)	25,487
Financing activities
Repayments on long-term debt	(14,533)
Proceeds from long-term debt	14,533
Repayments on notes payable	(2,670)	(1,385)
Repayments on notes payable, related parties	(25,000)
Payment of debt issuance costs	(218)
Purchase of common stock	(279)	(421)
Net cash (used in) provided by financing activities	(23,561)	1,043
Net (decrease) increase in cash and cash equivalents and restricted cash	(39,296)	4,932
Cash and cash equivalents and restricted cash at beginning of year	83,317	78,385
Cash and cash equivalents and restricted cash at end of year	44,021	83,317
Supplemental cash flow information
Interest paid	6,826	7,700
Pic Onyx Inc
Investing activities
Investment in PicOnyx	(1,114)
Issuance of Note from PicOnyx	(500)
Millen, Georgia Facility
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Loss on sale of business		2,305
Russian Proppant
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Loss on sale of business		350
ATM Program
Financing activities
Proceeds from issuance of common stock under ATM program	$ 4,606	$ 2,849