Just like nature

 By Luca Longo

At the Eni’s Renewable Energies and Environment Laboratory in Novara, nature is being studied. Through the study of the anaerobic decomposition of the early living organisms, researchers at Novara have been able to develop a process that transforms the wet fraction of solid urban waste into bio-oil. A bio-oil to be used directly as fuel or to be sent to a subsequent refining stage to obtain biofuels for our cars…

Obtaining energy from waste is a goal that is being pursued across the world. By the end of this year, Amager Bakke, a futuristic waste disposal and energy recovery facility will be come into operation in Copenhagen, achieving new records for the treatment of urban waste, energy production and environmental protection.
Despite its stunning declared performance, Amager Bakke is the latest evolution of a process as old as human beings: that of burning waste to eliminate it and recovering some of the energy that still trapped in it.

Already in the Palaeolithic era, some ecological pioneers must have realised that – instead of burning just wood – they could also burn the scraps produced by their family both to warm themselves and cook food. Besides, it was also more convenient: it was no longer necessary to gather dried branches and bring them to the cave, and at the same, the was no need to take out the rubbish. Brillian, and very green! For the Copenhagen incinerator the basic principle is exactly the same, unchanged over time: energy is obtained by spending more energy. How? It is enough to heat urban waste (spending energy) that by nature is rich in water (up to 70%), until the water is eliminated and the particles that remain pass into a gaseous state. In this way they can finally burn and release their energy. It is at this point that waste can heat not just caves and shacks, but homes and skyscrapers.

A model of how the Amager Bakke plant will be, once finished

For more than a century and a half we have known that it is more effective and eco-friendly to collect waste and burn it in large dedicated plants, rather than in the garden behind the house or outside the cave. From the first incinerators, built born in Nottingham in 1874 and in Manhattan in 1885, collecting waste from the city, concentrating it in one place and burning it all together offered efficiencies and while also making combustion more controllable.
The futuristic Amager Bakke plant is a traditional grate incinerator, but with enormously enhanced energy efficiency compared with previous generations, but still limited to just 28% as it has to treat waste at high temperatures and evaporate all the water that it contains in order for it to be used. Moreover, it has to cool and adequately handle all the gases and fumes produced in order to limit environmental pollution.

At the Eni Research Centre for Renewable Energy and the Environment, they have taken a big step forward by looking back to our Palaeolithic friend, and studying a much larger and older natural event with a life of several hundred millions of years.
This process, based on the anaerobic decomposition of the first living organisms, led to the creation and accumulation of the oil and natural gas we know so well in the belly of the earth. In this case it took nature millions of years and enormous pressure that developed very high temperatures. But at Eni they have learned to replicate the whole process in two or three hours at temperatures of just 250-310° C. And without even having to eliminate the water.

A journey inside the pilot plant for waste treatment at the Novara Research Centre

The process is called thermo-liquefaction and makes it possible to transform the humid fraction of urban solid waste into the bio-oil (in other words, using the humid waste that often improperly call “organic” waste).
The bio-oil produced can be used directly as a fuel oil or it can be further refined, for example at the Eni refinery of Sannazzaro, for the production of biofuels for use in our cars.

In other, less technical and simplified, terms, the main advantages of the process developed in the Eni Research Centre for Renewable Energies and the Environment in Novara are many. First and foremost (and no small thing) waste – for which a collection chain already exists is used as a raw material, while at the same time offering an alternative and virtuous solution to urban waste/sludge management; this wet biomass is used as it is, i.e. avoiding the cost of drying costs typical of standard incinerators (including Amager Bakke!); it operates in blander conditions than other conversion processes such as gasification (800-1000°C) or pyrolysis (400-500°C). In addition, bio-oil is produced with a high carbon content and a high calorific value (about 35 MJ/Kg) and with an energy yield of over 80%… significantly higher than the enhancement of biogas waste (50-60%) and incinerators (10-30%).

After the first pilot plant, built in Novara and capable of handling half a ton of waste at a time, the construction of a much larger demonstration plant is underway.
This revolutionary class of humid waste management facility can make a decisive contribution for our country in its efforts to meet the goals set by the European Directive on Renewable Energy Resources (RES), while also allowing us to obtain advanced biofuel from waste materials… And to repeat the now-famous phrase used by our colleagues involved in this research: Just like nature does it, only faster!

SEE MORE: Road to bioplastic by Michelle Leslie

about the author
Luca Longo