Anaerobic digestion in the agricultural sector: an overview of the Italian scenario

Abstract

Anaerobic digestion of livestock effluents, energy crops, and agro-waste is a widespread practice at farm level in Italy. Since high subsidies are granted for the production of renewable energy in this specific sector are granted (280 € per MWh for plants below 1 MW, energy crops are the main (and sometime sole) feedstock for anaerobic digesters. This largely determines the use of land, water and fertilizers, which is not sustainable on a long-term perspective. Moreover, beside carbon (which can be converted to energy), these materials also introduce considerable amounts of nitrogen in the anaerobic digesters. This can limit the agricultural use of the digestate, especially in Nitrate Vulnerable Zones (NVZ). However, the introduction of these considerable subsidies for renewable energy production allows for the application of a number of different technological solutions for nitrogen management. The subsidy system will be changed soon and smaller size will be favored. Also, small plants treating livestock effluents as sole substrates will be economically favoured.