20. Commitments

We have commitments under various operating leases with initial terms greater than one year for property, machinery and facilities. These leases have terms that will expire on various dates through 2025. We expect that in the normal course of business, these leases will be renewed or replaced by other leases. Rent expense for operating leases that provide for periodic rent escalations or rent holidays over the term of the lease is recognized on a straight-line basis. We also have commitments to purchase minimum volumes of refined product from Western under commercial agreements that we entered into with Western at the closing of the Offering. See Note 22, Related Party Transactions, for further discussion of these agreements.

The following table presents our annual minimum rental payments under non-cancelable operating leases that have lease terms of one year or more as of December 31, 2015 (in thousands):



2016	$	7,912
2017	6,040
2018	3,274
2019	1,180
2020	180
2021 and thereafter	479
	$	19,065

Total rental expense was $9.2 million, $8.8 million and $6.4 million for the years ended December 31, 2015, 2014 and 2013, respectively. Contingent rentals and subleases were not significant in any year.