
	Useful Lives (Years)	December 31,
		2022		2021
Land	—	$	172,464	$	117,703
Land improvements	10 – 30	201,284		112,374
Buildings and improvements	10 – 50	492,509		383,879
Machinery and equipment(a)	2 – 45	4,446,315		3,619,712
Mineral rights and reserves	7 – 60	1,795,668		1,783,691

Construction in progress	—	2,246,090		2,057,387
Total		$	9,354,330	$	8,074,746

(a)Consists primarily of (1) short-lived production equipment components, office and building equipment and other equipment with estimated lives ranging 2 – 7 years, (2) production process equipment (intermediate components) with estimated lives ranging 8 – 19 years, (3) production process equipment (major unit components) with estimated lives ranging 20 – 29 years, and (4) production process equipment (infrastructure and other) with estimated lives ranging 30 – 45 years.

The cost of property, plant and equipment is depreciated generally by the straight-line method. Depletion of mineral rights is based on the units-of-production method. Depreciation expense, including depletion, amounted to $273.0 million, $225.6 million and $203.6 million during the years ended December 31, 2022, 2021 and 2020, respectively. Interest capitalized on significant capital projects in 2022, 2021 and 2020 was $31.1 million, $50.0 million and $30.4 million, respectively.

In October 2022, the Company announced it has been awarded a nearly $150 million grant from the U.S. Department of Energy to expand domestic manufacturing of batteries for EVs and the electric grid and for materials and components currently imported from other countries. The grant funding is intended to support a portion of the anticipated cost to construct a new, commercial-scale U.S.-based lithium concentrator facility at our Kings Mountain, North Carolina location. The grant will be received over the life of the construction period for the new facility (projected as 2023 to 2026) as reimbursement for capital expenditures. As funds are received the Company will reduce the cost of the assets by the amount of the grant, and income will be recognized by the lower depreciation expense over the useful life of the assets.