Expert story
The flagship
Sesto San Giovanni project
Antonio, you were on the front line of the project in Sesto San Giovanni. How did the plant come into being?
Antonio: The short answer is that the Sesto San Giovanni plant fulfilled a long-felt need. For the longer answer, we need to unravel the history of sewage sludge treatment in Italy. The country has a long history of using most of its sewage sludge in agriculture, as a fertiliser. By way of comparison, although people in Switzerland are familiar with this practice, it has been prohibited since 2006. In Italy, however, it has remained prevalent. The agricultural sector in Lombardy is by far the largest user of sludge. Every year, hundreds of thousands of tonnes are transported from the local area and from all over Italy to this fertile region.
Let’s jump back to 2016, when the people of Pavia, a region in the southwest of Lombardy, lodged a complaint. The stink of the sludge had become a real issue. Official studies showed that the sewage sludge that was being used also contained prohibited pollutants. In 2017, stricter legal regulations were introduced: sewage sludge is now categorised according to different levels of quality, with only the highest level being permitted as fertiliser. But that wasn’t all. It wasn’t just the smell or composition of the sewage sludge that was a problem, but the sheer quantity of it.
Why was the quantity an issue? After all, incinerators already existed in Italy before Sesto San Giovanni.
Antonio: Of course, but the situation changed after the law was amended. Just imagine it: approximately 450,000 tonnes of civilian sewage sludge are produced every year from wastewater treatment. Up until recently, about 80% of this was then used in agriculture. When the law was tightened up in 2017, only a fraction of the sludge was allowed to be used in agriculture. Some of the rest could be incinerated in the existing waste incineration plants, but they did not have sufficient capacity to dispose of the whole amount, meaning that a lot of the sludge had to be delivered to incinerators abroad at very high cost. Understandably, operators of wastewater treatment plants were looking for solutions that would make them self-sufficient and financially independent.
Lucas, what’s new about this facility? Why are people describing this as a flagship project?
Lucas: The sewage sludge incinerator itself is a modern facility that is nowadays standard technology. In Italy, however, this facility is the first of its kind. It involves the conversion of an existing waste incineration plant that was slated for decommissioning due to its age. The facility’s existing chimney was replaced with a new one that has less of an impact on local residents. There is also a newfound synergy with the adjacent sewage treatment plant, as the sewage sludge digesters there have been converted into fermentation units. Biogas is first generated from kitchen waste and then converted into biomethane after treatment.
This project is pioneering by virtue of the holistic thinking that it demonstrates.
In other words, Sesto San Giovanni is a plant with a difference. Paolo, what do you think of it?
Paolo: The Sesto plant is truly groundbreaking. The announcement of the project in 2019 marked a push for modernisation. More and more plants have followed this example and been converted. We’re talking about a wave of sewage sludge incineration!
How do you mean?
Paolo: The conditions are different now. There’s new legislation and new systems that make it possible for sludge to be disposed of independently, while eliminating any regional surplus of sewage sludge. When you scale these regional developments at plant level onto a wider national scale, it’s clear to see how the entire system of sewage sludge treatment is changing in Italy.
Thomas, you’ve been handling projects in Italy for many years now. What do you think made this turnaround possible? And what was our part in that?
Thomas: As I see it, all the minor developments, happening one after the other, were what got the ball rolling. We won the Sesto San Giovanni public tender, so we were able to support that transformation. We’ve been active in Italy for 30 years now and have been able to immerse ourselves in Italian culture. We don’t go to work in another country and expect processes to be exactly the same as in Switzerland – but that’s what makes working in other countries, as we do in Germany, France and elsewhere, so exciting. This requires a sure instinct, good references and a wealth of experience.
Ultimately, our work in Italy, like in Switzerland, is about enabling, about moving forward. We think about how we can offer simple, effective solutions – which requires close cooperation with our customers. This aligns with how we see ourselves: as a visionary company keen to innovate in conjunction with its customers. And that’s how these flagship projects come about.