Assets are classified as held for sale when, among other factors, they are identified and marketed for sale in their present condition, management is committed to their disposal, and the sale of the asset is probable within one year. Management believes these assets are no longer necessary for the Company's future operating plans. As of   December 31, 2022 and 2021, Aqua Metals had assets with a book value of $47,000 and $2.6 million classified as assets held for sale, respectively.

At December 31, 2022 and 2021, the Company compared the carrying value of the assets held for sale against current fair market values. We determined the carrying value needed to be reduced to align with current fair market values. During the years ended December 31, 2022 and 2021 we recognized a $0.6 million and $0.5 million impairment of assets held for sale, respectively.