Greenhouse gas (GHG) emissions from soils amended with digestate derived from anaerobic treatment of food waste

RATIONALE The application of organic materials to agricultural lands is considered good practice to improve soil organic matter content and recycle nutrients for crop growth. The anaerobic treatment of food waste may have environmental benefits, particularly with regard to greenhouse gases (GHGs) mitigation and enhancement of carbon sequestration. METHODS This work presents the results from a field experiment to evaluate CO2, CH4 and N2O emissions from grassland amended with digestate produced by anaerobic fermentation of food waste. Experimental plots, located close to Rothamsted Research-North Wyke, were established using a randomized block design with three replicates and two treatments, added digestate (DG) and the unamended control (CNT). The digestate was applied on three occasions at an equivalent rate of 80?kg?N ha1. RESULTS The application of digestate led to an increase in CO2 emissions, especially after the 2nd application (74.1?kg CO2-C ha1?day1) compared with the CNT soil (36.4?kg CO2-C ha1?day1), whereas DG treatment did not affect the overall CH4 and N2O emissions. The total grass yield harvested on a dry matter basis was greater in the DG treated plots (0.565?kg?m2) than in the CNT plots (0.282?kg?m2), as was the 15?N content in the harvest collected from the DG plots. CONCLUSIONS The results suggest that the digestate can be applied to agricultural land as a fertilizer to grow crops. Our study was conducted in an exceptionally dry growing season, so conclusions about the effect of digestate on GHG emissions should take this into account, and further field trials conducted under more typical growing seasons are needed. Copyright (c) 2012 John Wiley & Sons, Ltd