Evaluation of orange peel waste and its biochar on greenhouse gas emissions and soil biochemical properties within a loess soil.

The environmentally safe disposal of the large quantity of orange peels waste produced each day causes economic and environmental problems, which after conversion into biochar via pyrolysis technique might be used as an effective soil amendment. In this study, a 90-day incubation experiment was conducted to investigate the effects of orange peel waste and waste-derived biochar amendments on greenhouse gas emissions (GHG), soil biochemical properties, and soil enzyme activities. There were five treatments with different amendment levels: control without an amendment (Control), orange waste 1% (W1), orange waste 2% (W2), orange waste biochar 1% (B1), and orange waste biochar 2% (B2). The results showed that, compared with control, the amendments decreased cumulative N2O emissions by 59.2% (B2), 45.2% (B1), 20.6% (W2) and 10.2% (W1), respectively; and increased cumulative CH4 emissions by 81.7% (W1), 84.4% (W2), 75.8% (B1) and 74.9% (B2), respectively. Cumulative CO2 emissions decreased for the B1 (29.3%) and B2 (43.5%) over the waste treatments. While soil pH, SOC, nitrate nitrogen (NO3--N) and enzyme activities (urease and catalase) were significantly increased with the passage of time from the biochar amendments, ammonium nitrogen (NH4+-N) and invertase activities did not show this trend with time. Our study suggests that orange peel waste conversion to biochar should be a viable alternate method of disposal since land application resulted in reduced GHG and improvements in soil fertility.