The rate of consumption in the last few decades has gradually taken its toll on our planet’s resources, posing new challenges to energy supply. The rising needs of industry and private individuals are obliging countries to produce or import ever greater quantities of energy. The repercussions are many. Putting aside questions of geopolitics and society, the damage to the environment is top of the list of priorities to address. That’s why research into alternative energy sources is essential if we are to turn back the tide of global warming. Wind, solar, geothermal and marine have all led to an ever greater share of renewable energy production on the market.

Alternative sources to hydrocarbons are becoming more and more popular, and biomass, biogas and biodiesel have carved out a place in the last few years.  

There are a range of techniques for producing these kinds of energy. The simplest is based on an age-old principle, an intuitive process, dating back to Palaeolithic times, when families would warm their cramped caves and shelters by burning their own rubbish. It stopped them having to wander out into a world full of danger, in search of wood and dry leaves, every time they needed fire. At the same time, they did away with the litter their small communities left behind. Now, hundreds of thousands of years later, we have methods like waste-to-energy, which are alike in a way to their primitive forebear. If you heat up rubbish (which takes energy) and make around 70% of the water it naturally holds evaporate, you get combustion, which produces more heat, which can then be used to produce energy. The advantage of this process is getting rid of rubbish and doing controlled combustion into the bargain. So far, though, the most modern plants today have an energy efficiency of around 30–35%. They have to treat waste at high temperatures and are forced to make all its water evaporate to get any worth out of it. And to limit environmental pollution, all the gas and smoke they produce has to be handled properly. Hence why, in recent years, they’ve gone down other roads, without renouncing the basic principles of keeping energy dispersion to a minimum and putting a lid on pollution.

One method to come out of Eni’s Renewable Energy and Environmental Research Centre is thermo-liquefaction, which is at the heart of its waste-to-fuel technology. The process turns organic rubbish into bio-oil, taking inspiration from nature, specifically the lengthy formation of hydrocarbons, in which biomass becomes an energy source. Anaerobic digestion in living organisms, under certain pressure and temperature conditions, over millions of years, has formed in the earth’s bowels the petrol and the gas that we use today. So, waste-to-fuel uses waste material as raw material (in line with circular economy principles) and there is an established chain for collecting it. Biomass, in its usual state, can be processed without being dried, as in incinerators. This doesn’t demand such high temperatures as gasification (800–1,000 °C) or pyrolysis (400–500 °C). Last but by no means least, its energy yield is 80%. Another advantage is that it recovers the water inside organic rubbish, which, if properly treated, can be used for irrigation. The energy it produces helps reduce waste and live up to international agreements on the climate made at COP 25, as well as EU directives on renewable sources in transport. The technique could be of huge benefit to society. The finished product could even be used as fuel oil for ships or further processed to become a biofuel, for example for cars.

Interest in energy production systems like these is growing generally. The Italian government recently approved a decree to set up a national system for certifying the sustainability of biofuels and bioliquids. This legislation is in line with EU directives to get delivery chains for biofuels and bioliquids certified. It ensures sustainability is respected and systems of incentives can be enjoyed. The end goal is to have a stronger handle on the mechanics and transparency of the chains, which is why it’s compulsory for so-called advanced biofuels to comply with the national system. Italy is a pioneering researcher and user of biofuels.  

The enthusiasm of the country’s institutions is evident in an agreement between Eni Rewind (Eni’s environmental company) and the multi-use company covering the metropolitan city of Venice to make an industrial prototype. The partnership was endorsed by the city’s mayor, Luigi Brugnaro, and signed by Vincenzo Maria Larocca, CEO of Eni Rewind and Andrea Razzini, General Manager of Veritas, the multi-utility that has been picking up and processing rubbish in Venice since last spring. The bio-oil produced at the new Venetian plant will be ready for use as sulphur-less fuel on boats or sent to another refinery to produce biofuel for transport.

Eni is leading the way on this strategic path of applying the principles of the circular economy to business. There’s clear evidence of this at another of its plants in Venice, the world’s first example of a traditional refinery converted into a bio-refinery, where the Ecofining^TM process takes place. “Venice has made the circular economy one of its strong points and it’s no mistake that the city and its people are top in Italy for the amount of rubbish they sort in a year,” says Brugnaro . “We’ve got all the pieces in play to set a good example of how to generate new energy sources. We don’t throw anything away and we turn waste into wealth. What seems a cost and a problem today becomes an advantage tomorrow, just as the strategic plan for the city, which we approved unanimously last December, states. Venice wants to be an example to the world of how you can be a big city with thousands of residents and millions of visitors but at the same time have a scientifically and technologically innovative system, with an ever more environmentally sustainable mindset, creating revenues and jobs.”

In partnership with SNDP, the Tunisian national petrol company, Eni has embarked on a project of semi-industrial cultivation of castor oil plants, not for food but for generating sustainable biofuels. The first project of its kind in a semi-desert area, its aim is to produce vegetable oil with a low environmental impact to gradually replace palm oil, which the EU will ban in 2030. The caster oil plant is native to Tunisia and very resistant to the hot, dry climate of the site. It is an opportunity for local development, for creating a sustainable chain of farming and energy.

Over the water in Barcelona, the car maker Seat has launched a project, “Life Metamorphosis”, to turn organic rubbish into biomethane. If it’s true, as the statistic says, that the city’s average resident churns out 1.5 kg of rubbish a day, then the figure for the whole place is a hefty 2.5 million kg a day. Regrettably, only 40% of this tidal wave of trash gets recycled. So, at Ecoparc 2 in the Catalan capital, they are picking out the contents of organic bins and anything that could be of use from other bins. Once all that organic filth is together in one facility, the transformation can begin. They put it into anaerobic digestors (which run without oxygen) more than 20 metres high, unleashing a process of decomposition and gas generation. After 30 days, out belches a biogas, about 65% of which is methane. Before moving on to the next step, they send the solid organic residue off for fertiliser; again, the circular economy is the guiding light in the experiment. Now the methane is purified of the carbon dioxide it’s mixed with, to make high-quality biomethane, good for powering cars. Finally that gas is compressed and stored. The experiment is currently limited to producing gas for cars signed up to the pilot project, but the chances for further development are huge and they’re already talking about doing it on a large scale.

So, systematically produced biofuels could be a very big resource with a two-pronged solution, on the one hand satisfying growing energy needs without investing more in extracting raw materials, on the other pulling off the feat of closing the agri-food production chain by giving an outlet to all that rubbish that’s otherwise left to pile up in bins and tips, where it does nothing and, what’s more, damages the environment. Cultural and social pressure today is forcing us to take stock of our priorities and turn our focus to the circular economy, which encourages us to reuse raw materials in whatever way we can. It’s within all of our grasp. We just need to reach out to it.