6. Property, plant and equipment, net

Property, plant and equipment, net, consisted of the following (in thousands):

Property, plant and equipment depreciation expense was $221,000 and $218,000 for the three months ended March 31, 2025 and three months ended March 31, 2024, respectively. Equipment under construction is comprised of our lithium-ion battery recycling commercial equipment along with various components being manufactured or installed by the Company.

In April 2025, the Company’s Board of Directors approved a plan to sell a facility located at TRIC that was under construction and intended for our Li AquaRefining recycling campus. The decision was driven by a change in the Company's strategic priorities and capital allocation plans. The facility includes the building structure, the underlying land, and various permanent improvements, and was previously classified as construction-in-progress within property, plant, and equipment on the Company’s consolidated balance sheet as of March 31, 2025. In accordance with ASC 360-10-45-13, the Company determined that the assets met the criteria to be classified as held for sale in April 2025. As a result, the assets will be reclassified to assets held for sale in the second quarter of 2025. The total carrying value of the assets group was approximately $9,345,000 as of March 31, 2025, net of depreciation. An impairment charge of $5,247,000 was recognized during the three months ended March 31, 2025. The fair value of the asset group was determined to be $4,100,000 which is a level 3 measurement. The fair value was determined based on a market analysis of comparable properties recently sold. The Company anticipates the sale will be completed during the second quarter of 2025.