At June 30, 2021 and December 31, 2020, property and equipment, net, and other assets consisted of the following:

	June 30,		December 31,
	2021		2020
	(Unaudited)
Property and equipment, net of accumulated depreciation of $2,420,796 and $2,195,198 as of June 30, 2021 and December 31, 2020, respectively	$	1,916,145	$	1,987,006
Right-of-use operating lease asset		802,821		1,103,761
Security deposits and other assets		300,270		293,288
Property and equipment, net, and other assets	$	3,019,236	$	3,384,055

We compute depreciation using the straight-line method over the estimated useful lives of the property and equipment. Depreciation expense for the three months ended June 30, 2021 was $115,463, including $72,416 of depreciation expense reflected within “Cost of revenue” in our condensed consolidated statements of operations as it related to assets used in directly servicing customer contracts and was $225,598 for the six months ended June 30, 2021, including $140,792 of depreciation expense reflected within “Cost of revenue.” Depreciation expense for the three months ended June 30, 2020 was $50,846, including $14,455 of depreciation expense reflected within “Cost of revenue,” and was $101,067 for the six months ended June 30, 2020, including $28,273 reflected within “Cost of revenue.”

We recorded right-of-use operating lease assets related to our corporate office lease and the office lease space in Burlington, NC in accordance with ASC 842. Refer to Note 8, Leases for additional information.

On February 20, 2018 (the “Closing Date”), we entered into an Asset Purchase Agreement with Earth Media Partners, LLC to sell certain assets of our wholly owned subsidiary, Earth911, Inc., in exchange for a 19% interest in Earth Media Partners, LLC, which was recorded as an investment in the amount of $246,585 as of the Closing Date, and a potential future earn-out amount of approximately $350,000. The net assets sold related to the Earth911.com website business and consisted primarily of the website and its content and customers, deferred revenue, and accounts receivable as of the Closing Date. Earth911, Inc. was subsequently renamed Quest Sustainability Services, Inc. The carrying amount of our investment in Earth Media Partners, LLC is included in “Security deposits and other assets” and we have an accrued receivable in the amount of $310,363 and $259,017 related to the earn-out included in “Accounts receivable” as of June 30, 2021 and December 31, 2020, respectively.