The 2013 Equity and Incentive Plan as amended (the "2013 Plan") authorizes the issuance of up to 7,800,000 shares of the Company's common stock for use in paying incentive compensation awards in the form of stock options or other equity awards such as restricted stock, restricted stock units ("RSUs"), stock appreciation rights ("SARs") or performance share units ("PSUs"). Of the 7,800,000 shares authorized, a maximum of 4,621,000 shares may be issued for awards other than option rights or SARs, as defined in the 2013 Plan. The 2016 Non-Employee Directors' Long-Term Equity Compensation Plan (the "2016 Plan") authorizes the issuance of up to 400,000 shares of the Company's common stock for equity awards. Both plans have been approved by the Company's stockholders. At December 31, 2018, there were 3,695,156 shares available for granting equity awards under the 2013 Plan, of which 2,374,533 shares were available for awards other than option rights or SARs. At December 31, 2018, there were 194,370 shares available for granting equity awards under the 2016 Plan.

The Company's Board approves the granting of performance-based RSUs as the long-term equity component of director, officer and certain key employee compensation. The RSUs require no payment from the recipient and compensation cost is measured based on the market price of the Company's common stock on the grant date and is generally recorded over the vesting period. RSUs granted to officers and certain key employees in 2016, 2017 and 2018 either vest on a pro-rata basis over three years or upon obtainment of specified retirement or years of service criteria. Upon vesting, each RSU is exchanged for an equal number of shares of the Company's common stock. The vesting period for RSUs granted to non-employee directors is one year and each RSU is exchanged for an equal number of shares of the Company's common stock upon vesting for awards issued under the 2016 Plan and following the termination of the participant's service as a director under prior plans. RSUs do not have an option for cash payment.

The following table summarizes RSUs issued and the compensation expense recorded for the years ended December 31, 2018, 2017 and 2016:



	RSUs (a)	Weighted Average Fair Value		Expense
(Dollars in thousands, except per unit)	RSUs (a)	Weighted Average Fair Value		2018		2017		2016
Directors:
2015	59,985	$	15.69	—		—		314
2016	109,998	$	7.00	—		257		513
2017	56,203	$	13.70	179		641		—
2018	43,821	$	20.54	511		—		—
Employees:
2013	170,582	$	20.63	—		—		66
2014	190,832	$	25.21	—		316		669
2015	239,679	$	16.53	230		597		880
2016	536,773	$	7.09	935		1,011		995
2017	286,251	$	13.70	1,019		1,417		—
2018	242,791	$	19.93	1,656		—		—
Total				$	4,530	$	4,239	$	3,437



	Number of Shares		Weighted Average Grant-Date Fair Value
Non-vested at December 31, 2017	801,939		$	11.73
Granted	286,612		20.03
Vested	(478,917	)	12.48
Forfeited	(26,254	)	14.11
Non-vested at December 31, 2018	583,380		15.08

At December 31, 2018, the total unrecognized compensation expense related to non-vested RSUs was $4.9 million, which will be recognized over a weighted-average period of 1.7 years. There was a $1.1 million decrease in excess tax benefits from RSUs recognized in equity in 2016. Upon the adoption of changes issued by the FASB amending the accounting for stock-based compensation, the Company records any excess tax benefits or shortfalls as a component of income tax expense. See Note 2, Recently Adopted and Recently Issued Accounting Standards, for additional information.

The Company's Board approves the granting of SARs to officers and certain key employees under the 2013 Plan. The SARs generally vest on a pro-rata three year basis from the grant date or upon specified retirement or years of service criteria and expire no later than ten years after the grant date. The exercise price of the SARs is equal to the fair value of Harsco common stock on the grant date. Upon exercise, shares of the Company's common stock are issued based on the increase in the fair value of the Company's common stock over the exercise price of the SAR. SARs do not have an option for cash payment.

During 2016, the Company issued SARS covering 554,719 shares in May and 21,686 shares in November under the 2013 Plan. During 2017, the Company issued SARS covering 266,540 shares in March under the 2013 Plan. During 2018, the Company issued SARS covering 221,818 shares in March and 7,622 in July under the 2013 Plan.

The fair value of each SAR grant was estimated on the grant date using a Black-Scholes pricing model with the following assumptions:



	Risk-free Interest rate		Dividend Yield		Expected Life (Years)	Volatility		SAR Grant Price	Fair Value of SAR
May 2016 Grant	1.39	%	—	%	6.0	42.1	%	7.00	2.93
November 2016 Grant	1.74	%	—	%	6.0	43.8	%	12.25	5.38
March 2017 Grant	2.17	%	—	%	6.0	43.9	%	13.70	6.13
March 2018 Grant	2.69	%	—	%	6.0	44.6	%	19.80	9.16
July 2018 Grant	2.87	%	—	%	6.0	44.7	%	24.65	11.48



	Number of Shares		Weighted Average Exercise Price		Aggregate Intrinsic Value (in millions) (b)
Outstanding, December 31, 2017	1,679,276		$	15.40	$	7.9
Granted	229,440		19.99
Exercised	(150,013	)	17.88
Forfeited/Expired	(13,256	)	24.53
Outstanding, December 31, 2018	1,745,447		15.73		8.9

The following table summarizes information concerning outstanding and exercisable SARs at December 31, 2018:



	SARs Outstanding					SARs Exercisable
Range of exercisable prices	Vested	Non-vested	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Life in Years	Number Exercisable	Weighted-Average Exercise Price per Share
$7.00 - $13.70	484,331	242,513	$	9.41	7.65	484,331	$	9.24
$16.53 - $22.70	532,700	217,343	18.58		6.78	532,700	18.08
$23.03 - $26.92	260,938	7,622	24.84		5.45	260,938	24.84
	1,277,969	467,478	15.73		6.94	1,277,969	16.11

Total compensation expense related to SARs was $1.9 million, $2.0 million and $1.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. Vested and currently exercisable SARs have a weighted-average remaining contractual life of 6.94 years and an intrinsic value of 8.9 million at December 31, 2018 and total unrecognized compensation expense related to non-vested SARs was $2.2 million, which will be recognized over a weighted average period of 1.8 years.

Weighted-average grant date fair value of non-vested SARs for the year ended December 31, 2018 was as follows:



	Number of Shares		Weighted-Average Grant Date Fair Value
Non-vested shares, December 31, 2017	877,417		$	4.42
Granted	229,440		9.17
Vested	(626,123	)	4.63
Forfeited	(13,256	)	7.51
Non-vested shares, December 31, 2018	467,478		6.65

The Company's Board approves the granting of PSUs to officers and certain key employees that may be earned based on the Company's total shareholder return over the three-year performance period. PSUs are paid out at the end of each performance period based on the Company’s performance, which is measured by determining the percentile rank of the total shareholder return of the Company's common stock in relation to the total shareholder return of a specific peer group of companies. For PSUs issued in 2016, 2017 and 2018, the peer group of companies utilized is the S&P 600 Industrial Index. The payment of PSUs following the performance period will be based in accordance with the scale set forth in the PSU agreements, and may range from 0% to 200% of the initial grant. PSUs do not have an option for cash payment.

During the year ended December 31, 2016, the Company granted 527,249 shares in May and 9,524 shares in November under the 2013 plan. During the year ended December 31, 2017, the Company granted 286,251 shares in March under the 2013 Plan.

During the year ended December 31, 2018, the Company granted 233,266 shares in March and 6,742 shares in July under the 2013 Plan. The fair value of PSUs granted was estimated on the grant date using a Monte Carlo pricing model with the following assumptions:



	Risk-free Interest rate		Dividend Yield		Expected Life (Years)	Volatility		Fair Value of PSU
May 2016 Grant	0.84	%	—	%	2.65	33.3	%	$	7.19
November 2016 Grant	0.96	%	—	%	2.14	35.2	%	17.84
March 2017 Grant	1.54	%	—	%	2.83	34.2	%	17.05
March 2018 Grant	2.36	%	—	%	2.83	34.7	%	29.56
July 2018 Grant	2.69	%	—	%	2.42	33.1	%	39.06

December 31, 2018, 2017 and 2016, respectively. At December 31, 2018, total unrecognized compensation expense related to non-vested PSUs was $5.9 million, which will be recognized over a weighted average period of 1.8 years.



	Number of Shares		Weighted-Average Grant Date Fair Value
Non-vested shares, December 31, 2017	743,583		$	10.91
Granted	240,008		29.83
Forfeited	(34,426	)	13.33
Vested, not issued (c)	(454,283	)	7.41
Non-vested shares, December 31, 2018	494,882		23.13

(c) The measurement period for PSUs issued in 2016 ended on December 31, 2018 and these shares vested but will not be issued until the Board of Directors certifies the measurement period results in early 2019. A total of 908,566 shares are expected to be issued and have been included in the Company's calculation of diluted weighted average shares at the end of December 31, 2018.