Inventories

12 Months Ended

Dec. 31, 2017

Inventory Disclosure [Abstract]

Inventories

Inventories

The major components of inventories were as follows:

	December 31,
	2017		2016
Petroleum products	$	8,731	$	11,550
Crude oil	29,873		73,133
Caustic soda	5,755		4,593
NaHS	8,277		9,304
Raw materials - Alkali Operations	4,550		—
Work-in-process - Alkali Operations	7,355		—
Finished goods, net - Alkali Operations	14,075		—
Materials and supplies, net - Alkali Operations	10,030		—
Other	7		7
Total	$	88,653	$	98,587

Inventories are valued at the lower of cost or net realizable value. The net realizable value of inventories were not recorded below cost as of December 31, 2017 and December 31, 2016.

Materials and supplies include chemicals, maintenance supplies, and spare parts which will be consumed in the mining of trona ore and production of soda ash processes.