Resource utilization of biomass waste has attracted considerable attention as an important method to reduce greenhouse gas emissions and also to alleviate the current dependence on fossil fuels. Herein, wheat straw, an abundant agriculture waste, was employed as a green reducing agent for direct reduction of CuO into metallic Cu under mild hydrothermal temperatures. Meanwhile, wheat straw was converted to value-added organic acid such as lactic acid and acetic acid. More than 90% yield of Cu with 40-80 mmol/L lactic acid was obtained at 220-250 degrees C for 1-3 h. This study provides a promising low-carbon and energy saving approach for Cu smelting and an alternative route for the chemical production from renewable resources. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.