Nitrogen-use efficiency of biogas digestate

The digestion of farmyard manure and other organic materials has become increasingly important in recent years. The digestion process produces biogas (methane), and increases the proportion of easily available nitrogen compounds in the digestate produced. To date, there has been little research on the fertiliser value of digested farmyard manure that is of relevance to Swiss conditions, especially with regard to long-term nitrogen availability. We used a numerical model to estimate the nitrogen-use efficiency (NUE) of digestates common in Switzerland. Depending on the duration of the model and the quality of the digestate, NUEs of 64 % to 83 % are achieved within 80 years. The mineralisation of organic nitrogen in subsequent years of application contributes substantially to the high NUE resulting from repeated application.

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