Property, Plant, and Equipment

Property, plant, and equipment consisted of the following at December 31:



(dollars in thousands)	2017			2016
Buildings	$	59,314		$	59,314
Machinery and equipment	52,383			49,079
Computer software	17,635			14,849
Computer equipment	4,855			4,599
Furniture and fixtures	1,876			1,772
Leasehold improvements	1,590			1,477
Land improvements	493			493
Land	395			401
Buildings improvements	613			189
Construction in progress	219,234			53,891
	358,388			186,064
Accumulated depreciation and amortization	(31,984		)	(23,832		)
Total	$	326,404		$	162,232

Depreciation and amortization expense was approximately $10.5 million, $9.2 million, and $8.2 million for the years ended December 31, 2017, 2016, and 2015, respectively.

During 2013, Heartland and Jasper County, Missouri ("Jasper") entered into an agreement pursuant to which Jasper agreed to issue up to an aggregate principal amount of $55.0 million of industrial revenue bonds ("Bonds") to be purchased by Heartland. As noted below, Jasper issued the bonds and used the proceeds from the Bonds to purchase manufacturing equipment from Heartland, which was then leased back to Heartland. As Heartland will become the owner of the equipment at the end of the lease term, the lease meets the requirements of a capital lease and the equipment is being recorded as property, plant, and equipment. The Company has the right and intends to set-off any obligation to make payments under the lease agreements with the proceeds due from the Bonds. As of December 31, 2017 and 2016 Jasper had issued, and Heartland had purchased, $55.0 million, of industrial revenue bonds and Jasper had purchased from, and leased back to, Heartland certain manufacturing equipment for a corresponding amount.

In August 2016, Heartland and the City of Joplin, Missouri, or Joplin, entered into agreements by which Joplin agreed to issue up to an aggregate principal amount of approximately $83.3 million of industrial revenue bonds to purchase from Heartland the land on which the current Joplin Dry Food Facility resides and the land on which the Jopin Treats Facility would come to reside, and the associated buildings, structures, and fixtures, including the additional manufacturing equipment included in the Joplin Treats Facility (collectively, the “Property”), which will then be leased back to Heartland. As Heartland will become the owner of the Property at the end of the lease term, the lease meets the requirements of a capital lease and the equipment and land are recorded as property, plant and equipment our balance sheet. The Company has the right and intends to set-off any obligation to make payments under the lease agreement with the amounts due under the industrial revenue bonds. As of December 31, 2017 and 2016, Joplin had issued and Heartland had purchased approximately $31.9 million and $10.8 million, respectively, of industrial revenue bonds and Joplin had purchased from, and leased back to, Heartland certain Property for a corresponding amount.