The table below reconciles the change in the carrying amount of goodwill for the period from January 1, 2023 to September 30, 2023:

	GRE		Genie Renewables		Total
	(in thousands)
Balance at January 1, 2023	$	9,998	$	—	$	9,998
Additions/deductions during the period		—		—		—
Balance at September 30, 2023	$	9,998	$	—	$	9,998

The table below presents information on the Company’s other intangible assets:

	Weighted Average Amortization Period		Gross Carrying Amount		Accumulated Amortization			Net Balance
	(in thousands)
September 30, 2023
Patents and trademarks		18.1 years	$	3,510	$	(1,325	)	$	2,185
Customer relationships		9.0 years		1,100		(744	)		356
Licenses		10.0 years		479		(186	)		293
Total			$	5,089	$	(2,255	)	$	2,834
December 31, 2022
Patent and trademark		18.1 years	$	3,510	$	(1,154	)	$	2,356
Customer relationships		9.0 years		1,100		(652	)		448
Licenses		10.0 years		479		(150	)		329
Total			$	5,089	$	(1,956	)	$	3,133

Amortization expense of intangible assets was $0.1 million and $0.3 million in the three and nine months ended September 30, 2023, respectively. Amortization expense of intangible assets was $0.1 million and $0.3 million in the three and nine months ended September 30, 2022, respectively. The Company estimates that amortization expense of intangible assets will be $0.1 million, $0.4 million, $0.4 million, $0.3 million, $0.3 million and $1.4 million for the remainder of 2023, and for 2024, 2025, 2026, 2027 and thereafter, respectively.