A revolution rooted in the circular economy: thanks to separate waste collection, organic waste is fed into an anaerobic digestion process to produce biogas.
Biomethane: a clean resource of biological origin
So, what makes this source of methane “bio”? Quite simply, it’s how it is produced: not by drilling into deep underground deposits, but by fermenting organic waste in dedicated facilities. Biomethane can be produced continuously, it is inexhaustible, and production can be increased simply by building more plants. This makes it one of the clearest examples of a circular economy.
In Spilamberto, a biodigester converted into a biomethane plant
An innovative plant for the production of biomethane is in operation in Spilamberto, in the province of Modena. It was developed by the NewCo Biorg, a joint venture between the Hera Group and Inalca (Cremonini Group), through a total investment of around €28 million and the use of the best available technologies.
Starting from separately collected organic waste and agri-food effluents, the plant – the result of converting an old biodigester – produces, at full capacity, 3.7 million cubic metres of biomethane per year, a 100% renewable fuel intended for transport, and around 18,000 tonnes of compost.
A cutting-edge plant for the energy transition and the circular economy
The 100% renewable natural gas is produced through anaerobic digestion of organic waste from separate collection carried out mainly in Modena and the province, along with waste from local agri-food processing and meat production by Inalca. Once refined, it becomes biomethane and can be fed into the gas network.
Significant environmental benefits: around 7,000 tonnes of CO₂ avoided
Thanks to the injection of biomethane into the network and its use in transport, significant environmental benefits are expected. Every year, around 3,000 tonnes of oil equivalent (TOE) in fossil fuels are saved, and approximately 7,000 tonnes of CO₂ emissions are avoided. Absorbing such an amount of CO₂ would require, on average, 280,000 trees.
What happens in our plant in Sant'Agata
Organic waste, collected through separate waste collection, undergoes anaerobic digestion to produce biogas. This is how the process works: the waste is shredded and screened, then remains for about 21 days in four horizontal digesters, where suitable microorganisms carry out the digestion process and produce biogas (composed of methane and carbon dioxide). After this, the biogas undergoes an upgrading, or purification, phase using pressurised water: the carbon dioxide dissolves and separates from the methane. The result is biomethane, a gas with a methane content above 95%, and a completely renewable source of energy. Not only that: at the end of the digestion process, lignocellulosic material is added to the outgoing solid fraction, producing a compact mass that then undergoes composting to create high-quality compost, which can be used as potting soil or agricultural fertiliser.
Biomethane is therefore another revolution rooted in the circular economy, one that we at Hera Group are committed to advancing. We do all this with the goal of creating shared value, as Andrea Ramonda, CEO of Herambiente, emphasises: “The direction we have taken looks towards the industrial sector with an increasing focus to creating shared value and partnerships. We are aware that sustainable waste management, focused on recovery and in full compliance with regulations, is essential in today’s world and generates benefits for the entire community.”
Working together for a circular city
At Hera Group, we have joined forces with Bologna Airport and Tper to launch a circular economy project that contributes to decarbonising urban mobility and improving air quality.
What does this partnership involve? The Airport delivers its organic waste to Hera, which collects it at the Sant'Agata Bolognese plant together with similar waste produced by citizens and transforms it into biomethane that Tper purchases to feed the fuel tanks of a significant part of its bus fleet.
This is an important step forward for our Group and for two major organisations in our area, which, like us, serve hundreds of thousands of people. We share a commitment to improvement and sustainability, in line with the UN 2030 Agenda.
Advanced wastewater management: resilience and reuse for the integrated water service
Wastewater management is undergoing a profound transformation. With increasingly resilient purification systems and technologies that enable reuse, the integrated water service is evolving towards a circular model.
Wastewater is the water that results from domestic, agricultural and industrial use. Before it is returned to the environment, it must undergo purification treatments to remove pollutants, including the solid fraction commonly known as sludge.
Within the integrated water service, the sewerage and purification system plays a central role in safeguarding environmental quality and public health. Its resilience — the ability to adapt and operate effectively even under critical conditions — is now essential to meet the challenges posed by climate change and the growing pressure on water resources.
In this context, wastewater management is evolving to consolidate a sustainable model based on reducing consumption, reusing treated water and improving the energy efficiency of processes. It is an approach that turns discharges into opportunities, creating value at every stage of the water cycle.
Reusing purified wastewater
The Hera Group is making investments to strengthen the resilience of the sewerage and purification system, also in response to extreme weather events.
The multi-utility takes concrete action to reduce water consumption, providing customers with self-monitoring tools and acting directly on the management of its own operations. Hera promotes agricultural and industrial reuse through agreements with public bodies and local companies, backed by rigorous testing protocols to ensure quality. As for sludge management, the focus is on reducing landfill disposal and recovering value through innovative reuse solutions.
Around three million cubic metres of drinking water are saved every year by reusing purified water.
Algae and biostimulants: a new frontier for agriculture
In San Cesario sul Panaro, in the province of Modena, Hera has built a pilot plant to cultivate algae and turn them into biomass for the agronomy sector. The project allows to reduce nitrogen and phosphorus concentrations at different stages of purification, as required by regulations, and reuses these elements to support algal growth. The resulting biomass can be processed and turned into a natural biostimulant, a concrete example of circular economy in action. The initiative was developed in collaboration with the University of Bologna through a PhD funded by Hera with NRRP funds, and with the contribution of European experts in biostimulants. The pilot plant is a pioneering technology for urban wastewater treatment plants.
Technology applied at the San Cesario wastewater treatment plant
The pilot plant consists of a 90-square-metre greenhouse built inside the San Cesario wastewater treatment plant, which has an annual capacity of 600,000 cubic metres and enough space to accommodate the new technology.
Inside the greenhouse, located near the wastewater inflow, there is advanced equipment and machinery: a unit for storage and culture preparation, a tank and a vertical photobioreactor for algal cultivation, a centrifugal separator to collect the biomass, and a field laboratory. Here, staff from Biosyntex — a company based in Imola specialising in algal strain selection and pilot plant construction — will isolate from wastewater samples the strains suitable for small-scale algal growth, whose subsequent processing will produce the biostimulant to be used in the agronomy sector.
Prototypes for irrigation and fertilisation
Another example of wastewater reuse in agriculture is the project developed in collaboration with ENEA, the University of Bologna and Irritec: a technologically advanced prototype that allows wastewater to be purified and then used for the irrigation and fertilisation of cultivated fields (https://www.gruppohera.it/-/irrigare-e-fertilizzare-i-campi-con-acque-reflue-depurate-arriva-il-prototipo). The project, which is an example of circular economy, not only enables water reuse but also allows to reduce the use of chemical fertilisers, making the treatment chain even more sustainable.
Beyond giving wastewater a second life, can we also make the sludge life cycle circular by reducing the amount of waste to be disposed of?
Yes, thanks to ultrasonic hydrolysis, a system already installed at the Forlì treatment plant (https://www.gruppohera.it/-/le-acque-reflue-si-fanno-belle-con-un-trattamento-a-ultrasuoni ).
Major steps to protect the environment in smaller urban centres
The Group is carrying out several projects to upgrade and adapt treatment plants, including: the expansion of the Ca’ Nordio (Padua) plant, which will strengthen Padua’s entire sewerage and treatment system even under adverse weather conditions and optimise treatment capacity; the upgrade of the anaerobic digester at the Gramicia plant in Ferrara (Ferrara) to improve sludge management; and the enhancement of the Calcinelli (Pesaro-Urbino) plant.
Many projects have already been completed or are underway in the province of Ferrara to ensure the compliance of discharges in small villages which are not yet connected to treatment plants. Some examples include the upgrade of Cona’s wastewater discharges, with two new pumping stations and a new sewer system about 900 metres long, and the project in Quartiere, where combined flows now reach the Portomaggiore wastewater treatment plant through a new sewer system more than two kilometres long and are then returned to the environment after purification.