Recycling | EPFL Graph Search

Recycling is the process of converting waste materials into new materials and objects. This concept often includes the recovery of energy from waste materials. The recyclability of a material depends on its ability to reacquire the properties it had in its original state. It is an alternative to "conventional" waste disposal that can save material and help lower greenhouse gas emissions. It can also prevent the waste of potentially useful materials and reduce the consumption of fresh raw materials, reducing energy use, air pollution (from incineration) and water pollution (from landfilling). Recycling is a key component of modern waste reduction and is the third component of the "Reduce, Reuse, and Recycle" waste hierarchy. It promotes environmental sustainability by removing raw material input and redirecting waste output in the economic system. There are some ISO standards related to recycling, such as ISO 15270:2008 for plastics waste and ISO 14001:2015 for environmental manageme

Porto Marghera. A new productive Lanscape

Nicola Zanin

Fusina is a particular area of Porto Marghera, Venice mainland industrial area, different from any other areas inside the industrial compound. It's situated in the southern border, the most close to the Veneto coun- tryside. This area was one of the last to turned from rural to agricultural at the beginning of the 60's, with more reprises in the following years. The rural landscape characterized by woods, countryside and isolated vernacular buildings turned into an industrial landscape characterized by infrastructures, factories, vapor and ash. ; The heavy industrialization deeply compromised the fragile lagoon ecosystem and lead to a diffuse problem of soil and water pollution. The project aim to transform Fusina in a big machine for the de-pollution where can be tested experimental techniques, fast and slow method of cleaning of the soil. The masterplan try to improve the industrial grid of roads and factory, defining distinct parcels and trying to preserve most important recycling and energy factories still active in the area and reconverting some of them into a research centre or laboratories. The program of my project is a thermal desorption for the cleaning of the soil and a thermal plant for the production of energy through biomass.

2016

Nature-inspired Circular-economy Recycling (NaCRe) for Proteins

Simone Giaveri

Since a few decades our planet has been loaded with billion tons of synthetic polymer-based materials, commonly named plastics. The large scale of plastic production, associated with its limited recyclability, are the driving force for the accumulation of such materials into the environment. Garbage patches, i.e. islands of plastics in the ocean, are striking evidences of this issue. A sustainable handling, that is production and disposal, of synthetic polymer-based materials is one of the greatest challenges that humanity has to face.Proteins and nucleic acids are natural polymers. Arguably, Nature produces an amount of such polymers that is higher with respect to man-made polymers. However, these materials do not accumulate into the environment, that is the approach used by Nature to handle these polymers is sustainable. The secret for its sustainaibility lies on the circularity in the materialsâ use. Indeed, proteins and nucleic acids are sequence-defined polymers that undergo depolymerization to monomers, and recycling into new materials by reassembling the so obtained monomers into arbitrarily different sequences. Organisms digest proteins into amino acids. These monomers are in turn polymerized to produce the protein of need, at the time of the protein synthesis.In this thesis we show that this process is achievable outside living organisms. Indeed, we depolymerized structurally different short peptides, and peptides mixtures into their constitutive amino acids, and recycled such monomers into biotechnologically relevant proteins (green, and red fluorescent proteins), by using an amino acid-free cell-free transcription-translation system. We further applied our methodology to recycle proteins with high relevance in materials engineering such as Î²-lactoglobulin films, used for water filtration, or silk fibroin solutions into green fluorescent protein. We were also successful in recycling mixtures composed of short peptides, and technologically relevant proteins into fluorescent proteins, as well as into bioactive enzymes (catechol 2,3-dioxygenase). Finally, we achieved multiple cycles of recycling (two cycles), and we demonstrated that the strategy can be expanded beyond the set of the twenty proteinogenic amino acids.Presented herein is a nature-inspired approach to recycling of soft materials, where unknown mixtures of polymers are recycled into the polymer of need, by the local community, at the time of recycling. The materials are costantly transformed into different ones, without any external feed, and there is no way to distinguish a new polymer from a recycled one. The strength of this method lies in its compatibility with the principles of circular economy.

EPFL2021

Anode dusting during the electrolytic production of aluminium

Timea Tordai

The disintegration of the carbon anodes during the electrolysis of alumina produces dust particles contaminating the electrolytic bath. This phenomenon, called dusting, is one of the most deleterious Al electrolysis failures, as it leads to a significant deterioration of the current efficiency, which causes severe economical losses for Al smelters. The mechanisms at work, related to carbon oxidations leading to the selective burning of the binder matrix that is responsible of the anode dusting, were reviewed through a detailed study of the literature. In the same manner, an overview of the "state of the art" knowledge, but also of the existing controversies in the field of raw material and anode manufacturing processes that affects the dusting, was delivered. The open questions concerning the root causes of dusting, as well as the ways to alleviate this phenomenon during the anode production, were considered. The process peculiarities of anodes made in China, as well as the atypical properties and behaviour of some anodes exported to the western world, were largely integrated into the frame of the experimental sections. Of particular interest was the fact that rather dense and highly calcined coke was used in the dry aggregate that does not contain recycled materials (baked scrap and butts). This situation results from the usage of a unique calcining process made in shaft (vertical) kilns, where the residence time exceeds those experienced in western rotary kiln/hearth type calcining plants by one order of magnitude. The effects of coke calcining and anode baking heat treatment temperature combinations were studied in a pilot scale simulating shaft and rotary kiln conditions. Representative types of green coke with different levels of volatiles and impurities (as S, V and Ca mainly) were selected for this study. The addition of Na contamination, in form of cryolite used as the main bath component was also examined in order to cover the aspects of the catalytic impact of contaminants present in the binder matrix on oxidation. As expected, the effects of baking were found to be of chief importance. However, the new element brought by this work is that not only the coke's sulphur content is important for its sensitivity to the negative impact of Na, but also its degree of calcination. Coke with a low calcining degree, measured by its real density/crystallite size, is showing a much better resistance to the catalytic effect of Na during the anode oxidation, and this especially when underbaking is a process issue. Recommendations on the optimum calcining heat treatment for western and Chinese calcining technologies are given as a conclusion of this part; this was done considering different scenarios of butts Na contaminations and baking issues in the anode production. The effects of desulphurization during calcining and especially during baking on the anode's physical, electrical and thermal properties were also addressed, so as to give a complete picture including the anode's density but also the butts' weight after usage of anodes during their cycle time in the pots. Optical light microscopy examinations of the porosity created on soft butts, related to permeable low density anodes, as well as on pilot anode cores oxidized in isobar laboratory conditions allowed laying emphasis on the prime importance of anode permeability in the dusting mechanisms. Some Chinese carbon plants are still using batch mixers with low temperatures and mixing intensity potential. As relatively low densification severity vibrators are also used, it felt adequate to study the role of porosity in the dusting propensity in an anode bench scale plant. For this purpose, a multi-factorial design of experiments was set up using two levels of pitching, mixing and forming intensities, and this at two levels of Na contamination and two baking temperatures. The levels of pitching, mixing (sigma blade versus high speed impeller mixers) and forming were selected in such a way that the difference in terms of apparent density reached a significant level (about 0.05 kg/dm3). Their individual impacts on the air and CO2 reactivity dust measured after laboratory oxidation tests were comparable to about 500 ppm Na contamination or 100 °C baking temperature differences, which is quite substantial for the anode behaviour in the pots. As the effect of the porosity differences on gas permeability exceeds one order of magnitude, it is obvious that the level of apparent density and therefore the pitching, mixing and forming conditions are of utmost importance for the anode dusting. The implications for equipment suppliers and plant designers are obvious: for the production of paste, efficient preheaters and intensive kneader mixers as well as controlled paste coolers need to be selected. Efficient forming machines working with vacuum conditions should be preferred and further developed in terms of densification severity and control efficiency. A parallel study on an ultra high intensive laboratory mixer, working with a mixture of fines and pitch only, i.e. producing after forming binder matrix electrodes, demonstrated the enormous potential left for porosity reduction of baked specimens. Substantial shrinkage of the dense green anodes during the baking step was observed on specimens produced under intensive mixing conditions. Concerning the dry aggregate recipe, bench scale trials with extreme ranges of fines content and fineness confirmed that, as long as the level of fineness is compensated by the fines content, optimum anode properties can be achieved with unchanged optimum pitch content. For a laboratory intensive impeller mixer, a range of fineness between 2500 and 5000 Blaine with a corresponding content between 42 % and 21 % provided anodes showing practically the same properties relevant for dusting. The conclusions drawn from the studies performed in the frame of this thesis allow a much better understanding on the traps of manufacturing world class quality anodes with zero dusting in a very different technological environment (as in China). In addition to this, the axis of development for western technology and equipment suppliers could be formulated based on the numerous quantitative pilot information gathered during this thesis work.

EPFL2007