(6) Property, plant and equipment, net

As of March 31, 2025 and December 31, 2024, property, plant and equipment consisted of the following:

As of March 31, 2025 and December 31, 2024, land use rights represented twenty three parcels of state-owned lands located in Xushui District and Wei County of Hebei Province in China, with lease terms of 50 years expiring in 2061 and 2068, respectively.

As of March 31, 2025 and December 31, 2024, certain property, plant and equipment of Dongfang Paper with net values of $nil, have been pledged pursuant to a long-term loan from credit union of Dongfang Paper. Certain property, plant and equipment of Baoding Shengde with net value of $3,028,097 and $3,407,848, repectively, as of March 31, 2025 and December 31, 2024, have been pledged pursuant two short-term loans from credit union of Baoding Shengde. Certain property, plant and equipment of Dongfang Paper with net values of $188,238 was pledged for a short-term loan from Bank of Cangzhou. Certain property, plant and equipment of Dongfang Paper with net values of $308,345 was pledged for another short-term loan from Bank of Cangzhou. See “Short-term bank loans” under Note (8), Loans Payable, for details of the transaction and asset collaterals.

Depreciation and amortization of property, plant and equipment was $3,547,398 and $3,481,788 for the three months ended March 31, 2025 and 2024, respectively.