Waste to Energy (WtE) Site Visit

For the third site visit, we visited the largest waste to energy (WtE) plant in Sardinia. In addition to WtE, the site has composting, wastewater treatment (WWT) and hazardous waste treatment facilities. The process engineer in charge of composting plant gave us a tour. 


 According to him, the site strictly follows EU directives given its proximity to the surrounding lagoons, a protected area.

The plant was built on an elevated zone surrounded by a plastic membrane below to intercept, collect and treat any liquid that could potentially leave the site. The organic fraction goes from the receiving area to active composting to refinement to a maturing phase. There are two streams: one for food waste and another for yard. The organic fraction is debagged, mixed in the right proportion and the brought by conveyor belt to begin the active stage. The composting facility has 15 cells: 4m wide, 2.5 m tall and 100 m long with the capacity to contain 250 tons of mixture. Raw compost is used as a landfill cover, and the remainder is analyzed, refined and sold to local farmers for site restoration. The compost is rich in nitrogen, so farmers, of olives, artichokes and wine in particular, use it once a year to replenish their soil.


Next, we toured the Waste to Energy area. We came during a period of routine maintenance: every 2 years, the plant closes for a month to replace broken parts. Due to the site’s proximity to the lagoons, the strong winds carry salt to the grounds, which corrodes the machinery. The plant has 4 combustion chambers: 3 for residual waste and 1 for the destruction of hazardous/hospital waste. Energy is recovered, enough to satisfy the demand for the complex and sell 9.6 MW to the grid. The plant burns 650 tons of waste/day, which requires 200 trucks per day to haul in the waste. The WtE runs nonstop to serve a community of 700,000 people. According to the site engineer, there is synergy between the WtE and WWT facilities: the WTE plant dries WWT plant sludge that is burned to fuel plant processes. The facility processes 80 tons of wet sludge per month, which becomes 8 tons of dry. Wet sludge is harsh on the machinery, which contributes to the needs for maintenance.


While touring the site, we were able to see the 64-meter tall chimneys, the release point for emissions into the atmosphere. At 40 meters, each chimney has a sampling point for emissions. 5 machines constantly monitor 38 parameters. There are five machines, despite only having 4 release points, in case one is down to ensure 24/7 monitoring of emissions.

The last part of the plant we visited, West Recycling, receives E-waste. There were different areas designated to the processing of refrigerators, air conditioners, washers and small appliances. 

(The refrigerator area of the facility)

(The small appliances area of the facility)


(The washer area of the facility)

This facility receives 80% of Sardinian E-waste from collection centers present in every town in the area. West Recycling treats 36 tons of E-waste per day.


(Interesting seeing a localized waste stream: a good portion of the refrigerators were for gelato/ice cream!)

For refrigerators, the first step is to remove easily extractable materials. Then, the refrigerators are placed on a conveyor belt.

 We observed a worker install a clamp to extract oils, volatile hydrocarbons and fluorocarbons. 


Once empty, the same worker cut off wires and the compressor.




The refrigerators are then broken into recoverable metals and plastics. 

(Approximately 60% of the fridge is made of plastic, which is converted into a polyurethane form)



The mixture of oil & gas is warmed to separate the oil from the refrigerants. The oil is sent to a plant in Milan and the refrigerants are sent to Torino to be destroyed. According to a Montreal convention, the oil and refrigerants need to be processed in a certain facility. 

According to Extended Producer Responsibility principles, the producers of E-waste are responsible for the cradle to grave of their product. Therefore, these producers pay for the resource recovery stage as well.

(Seeing the pile of laptops made me think of the life cycle of my own electronics.)


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