LAUSR

Biosolids are a by-product of wastewater treatment, and their nutritional composition makes them ideal for fertilizing crops. However, pre-treatments, such as conditioning and/or (vermi)composting, are often required to stabilize the product and remove pathogens. Biosolids, cow manure, and a 50–50% mixture were conditioned for 21 days, composted or vermicomposted with Eisenia fetida (Savigny 1826) for 28 days, and applied to soil cultivated with wheat (Triticum sp. L.), while emissions of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) were monitored. Emissions of CH4 were large from the biosolid and N2O from the cow manure during conditioning. Emissions of CH4 remained high during (vermi)composting of the biosolids, while the emissions of N2O from the cow manure dropped. The addition of E. fetida did not affect the emissions of greenhouse gases during (vermi)composting. The emission of N2O was higher when (vermi)composted biosolid was applied to soil cultivated with wheat than when (vermi)composted cow manure was applied. The global warming potential (GWP) of the sum of the emitted greenhouse gases (GHG) during conditioning, (vermi)composting, and when the final product was applied to soil was 3 times larger from the cow manure than from the biosolid, but mixing biosolid with cow manure eliminated that difference. It was concluded that mixing biosolid with cow manure might be a simple way to reduce the GWP of the emitted GHG during storage, (vermi)composting, and when applied to soil.