Biofuels from waste through Waste to Fuel
The in-depth study by Luca Longo
Take nature as an example, but do it better. This is the goal set by the researchers of the Eni Research Center for Renewable Energy and the Environment of Novara.
Here in 2012 the first process was born that allows the organic fraction of solid urban waste to be transformed into bio-oil. It is called Waste to Fuel ( W2F ).
And in 2019 the first continuous pilot plant based on this technology started in Gela.
From urban waste, therefore, a hydrocarbon is born that can be used directly as a fuel or sent to a subsequent refining stage to obtain biofuels for our cars …
Eliminating waste or – better yet – finding ways to use it and extracting the energy it still contains is a goal that is being sought around the world. But the first invention and the first complete industrial realization was born in Italy.
In reality it is not exactly a completely original invention … it is the latest high-tech evolution of a process as old as human beings: it is about burning waste to eliminate it and to recover part of the energy that is still trapped there.
Already in the Paleolithic, in fact, some pioneers of ecology must have thought that – instead of burning only the wood – they could also burn the scraps produced by their family to warm up and cook food. Besides, it was even more convenient: he didn't have to go to collect dead branches and carry them to the cave and, vice versa, he didn't have to go and throw the rubbish somewhere. Brilliant and very green!
From caves to metropolises, the process has always remained the same: energy is obtained by consuming more energy. Such as? Just heat the urban waste (by spending energy) which by their nature is rich in water (they contain up to 70% of it), until all the humidity is eliminated and the particles that compose them pass into a gaseous state. This way they can finally burn releasing their energy. It is at this point that the waste can heat caves, stilts, houses and skyscrapers.
For a century and a half we have learned that it is more effective and ecological to collect waste and burn it in large dedicated plants rather than in the courtyard behind the house or behind the cave. From the first incinerators born in Nottingham in 1874 and Manhattan in 1885, collecting all the city's waste, concentrating it in one place and burning it all together has advantages in terms of efficiency and also allows combustion to take place in a more controlled way. The futuristic Amager Bakke plant – which manages waste in the city of Copenhagen – is one of the most advanced in the sector. It is part of the class of grate incinerators, has an enormous energy efficiency compared to previous generations, but still limited to only 28% precisely because it has to treat waste at high temperatures and evaporate all the water it contains in order to enhance it. Furthermore, it must cool and adequately manage all gases and fumes produced to limit environmental pollution.
At the Eni Research Center for Renewable Energy and the Environment they decided to take a big step forward by looking even further back than our Palaeolithic friend, thinking well of studying a much larger and more ancient natural event lasting several hundred. of millions of years. This process, based on the anaerobic decomposition of the first living organisms, made it possible to create and accumulate in the bowels of the earth the oil and natural gas that we know well. That time it took nature millions of years and enormous pressures that developed extremely high temperatures. But at Eni they learned to replicate the whole process in two or three hours at temperatures of only 250-310 ° C. And to top it off without having to remove the water first!
The process takes the name of thermoliquefaction and allows the wet fraction of municipal solid waste to be transformed into bio-oil (in other words: the contents of the waste bin, which we often improperly call “organic”). The bio-oil produced can be used directly as fuel oil or it can be sent to a subsequent refining stage in the new Biorefinery in Gela, thus obtaining biofuels for use in our cars.
In other words, less technical and for the sake of simplification my colleagues will forgive me, the main advantages of the process developed in Novara are many. First of all (and this is not trivial) a waste material is used as a raw material for which a collection chain already exists, at the same time offering an alternative and virtuous solution to the management of waste / sludge in urban areas; wet biomass is treated as it is, avoiding the costs for drying typical of all incinerators (even the most sophisticated, such as Amager Bakke); milder conditions are sufficient compared to other thermal conversion processes such as gasification (800-1000 ° C) or pyrolysis (400-500 ° C). Furthermore, a bio-oil is produced with a high carbon content and high calorific value (about 35 MJ / Kg) and the energy yield is over 80% … In short, much higher than the valorisation 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, a much larger demonstration plant was inaugurated this year.
In Gela, next to the new Biorefinery, the first W2F plant in the world that processes waste continuously is now in operation.
The plant – designed and built under the supervision of Eni researchers in Novara – is able to treat 700 kg of organic waste per day supplied by the Company for the regulation of the Ragusa waste management service. These are transformed into 70 liters of bio-oil.
But the plant is fully integrated and provides for an enhancement for all products, as well as the bio-oil. The waters are used for the production of biogas / biomethane and then purified so that they can be used in agriculture. The solid residue is instead rendered inert by recovering the residual energy within the process itself.
Finally, all energy recoveries are “carbon neutral”. In other words, carbon dioxide is produced equal to the carbon present in the starting biomass without the need to add more from fossil fuels.
But the research does not stop: now in Novara and Gela we are working for the optimization of the plant and for the intensive development of the entire process in view of ever larger plants able to make organic waste disappear from entire cities. producing biofuels, water and building materials without increasing carbon dioxide in the atmosphere.
This revolutionary class of plants for the management of wet waste can give our country a decisive contribution to achieving the objectives set by the European Directive on renewable sources in transport (RES), allowing to obtain an advanced biofuel from waste raw materials … AND taking up the now famous phrase used by colleagues engaged in this research: How nature creates, but much faster!
(Extended version of an article published on eni.com)
This is a machine translation from Italian language of a post published on Start Magazine at the URL https://www.startmag.it/energia/biocarburanti-dai-rifiuti-attraverso-il-waste-to-fuel/ on Sat, 10 Oct 2020 05:06:59 +0000.