Integrated waste treatment at the Orvieto plant

The company Acea Ambiente manages a major plant for the treatment, recovery and disposal of waste in Umbria, 3 km from the town of Orvieto. The main plant sections are mechanical biological treatment of solid urban waste, composting and refining of the organic fraction of the separated waste and disposal in landfills. The activities carried out allow the recovery of material (production of quality compost) and energy (use of the biogas produced).
Management is carried out in compliance with certified management systems (see Corporate identity, Management systems) with the aim of achieving maximum recovery from the materials and encouraging both the production of energy from renewable sources and the reduction of waste to be sent to landfill. In 2018 the total waste entering the plant was 91,142 tonnes. 56% (about 51,300 tonnes) was disposed of in landfills and the remainder almost entirely sent to the anaerobic digestion and composting section of the treatment plant. For more details see Environmental Accounts.

As specified above, at the Orvieto site there are two energy production plants powered respectively by the biogas produced by the anaerobic section of the treatment plant and by the biogas produced by the landfill. The electricity generated is broken down as follows:

• at the treatment plant, in 2018, the biogas produced was about 3.1 Mm³ and about 5.6 GWh of electricity was sold to the grid;
• about 7.7 Mm³ of biogas were produced at the landfill and about 11.7 GWh of electricity was sold to the grid.

The drop in biogas and energy produced compared to 2017 (-15%) is due to ongoing works to extend the landfill the unavailability of techniques in the treatment plant because of improvements to the anaerobic digestion section.
The Orvieto hub is also equipped with a photovoltaic plant owned by Acea Produzione, which generated about 450 MWh in 2018, used to cover part of the plant’s consumption of electricity.
Taken as a whole, the biogas treatment line, the plant making efficient use of the biogas from landfill and the photovoltaic plant have allowed a transfer to the electricity grid equal to 3,230 TOE (Tonnes of Oil Equivalent).