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Sustainable Dismantling and Recycling of Metallic Aerostructures

Final Report Summary - SENTRY (Sustainable Dismantling and Recycling of Metallic Aerostructures)

Executive Summary:
The SENTRY Project comprised the dismantling, recycling and environmental assessment of the End of Life (EoL) phase of the “B2 Demonstrator” panels, a subcomponent of “low weight metallic fuselage section”, which has been manufactured within the Eco-Design for Airframe (EDA) activity in the Clean Sky (CS) programme. The SENTRY Project has assessed the current EoL management practices, based mainly on a size reduction step, where the output is a mix of the alloys included in the panel, a drying step of the metal scraps to remove the moisture and a remelting process to produce secondary raw materials.

The proposed new EoL procedures have been tested with a panel dismantling experiment at AELS facility, an accredited EoL aircraft manager, where parts have been identified, separated, sorted and shredded in order to satisfy input specifications of metal smelters that recycle them. The separated metallic fractions (once decoated and dried) have been processed in a bench scale melting facility and the produced metallic alloys characterised in order to validate their close loop recycling as better alternative than the downgrading practice. During dismantling and recycling activities, materials and energy flows, emissions and waste generation have been inventoried in order to complete the Life Cycle Assessment (LCA) of the EoL of the “B2 Demonstrator” panels that have been compared with the one of a reference panel. The final results have been the definition of the new EoL schemes for the “B2 Demonstrator” panels manufactured by Dassault Aviation (Panel B) and IAI (Panel A). The assessment of the environmental aspects related to the new EoL scenarios has allowed the identification of those activities with a strong environmental impact and the definition of ecodesign solutions to optimize potential reuse/recycling of metallic materials.

Within the SENTRY Project, a new EoL scenario, able to recover high quality aluminium alloys by promoting proper and efficient sorting techniques that avoid the down-cycling, has been defined and demonstrated. Considering the results of the chemical assays completed on the recovered aluminium alloys and the validation from Constellium, as global aluminium products manufacturer, it can be stated that they exhibit a maximum reuse potential since, due to the absence of contamination, they can be considered as first quality materials and therefore directly introduced again in the aeronautic sector.

In particular and focusing in the chemical composition results, it is shown that in all the cases the recovered aluminium alloys fulfil the specifications, containing percentages of the most critical elements below the maximum limits (Si <0.04 wt%, Fe <0.06 wt%, Na <0.001 wt% and Ca <0.002 wt%). Regarding metal losses originated during the bench scale remelting process, and paying special attention to the valuable and volatile elements in the alloys (Ag, Li and Mg) it could be confirmed that the Ag content did not vary. The Li losses were about 7.6-11.2% for those alloys with initial Li contents in the range 0.8-1.8 wt%. The Mg losses were 20-36% for the alloys with initial Mg contents in the range 0.31-0.40 wt% and 0-2.4% for the ones in the ranges 1.37-1.82 wt% and over 4.5 wt%.

From the environmental point of view, when the market value of recyclable scraps relative to primary material was considered in the LCA, determining the product-specific degree of quality loss and the appropriate EoL credit, the impacts derived from the new EoL scenario were, in almost all impact categories, lower than the impacts derived from the current EoL. However, in a holistic approach, overall impacts throughout the entire life cycle of a product must be considered, meaning that impacts arising in the manufacturing, use and EoL phases should be regarded.

Finally, it is essential to add that all collected data from B2 Demonstrator and Reference Panels have been exchanged with the EDA Activity to be incorporated in the EDA LCA database, contributing thus with valuable and detailed LCA data on aeronautic components that can be applicable for the analysis of other parts.
Project Context and Objectives:
The sustainable development, which essentially has associated with a balanced use of resources and energy, is already a demand for any sector or activity and has, as final main consequences, less waste generation and greenhouse gases emissions. In the particular case of aeronautics, enormous efforts are being done in terms of improving engine performance, searching of more durable and light structures or implementing renewable origin materials and energy sources. One specific result is the design of “low weight green fuselage sections” in which light metallic alloys, that save fuels during the use phase, will require to be recycled when reaching the end of life phase. The need of adapting existing end of life aircraft management activities to the presence of new parts and materials was the justification of the SENTRY Project. In this context, the SENTRY Project has been built with the aim of defining dismantling and recycling treatments for new metallic aerostructures with low environmental impact by maximizing the new use of the recovered materials, mainly metals.

The SENTRY Project has been an initiative led by the Technological Centre GAIKER-IK4, as responsible for the environmental assessment and the coordination of the project as a whole. The consortium was completed with the Technological Centres IK4-LORTEK, reference in joining solutions, which has undertaken the selective dismantling of the parts, and IK4-AZTERLAN, expert in the area of aluminium metallurgy, which has taken care of the light alloy recycling. Additionally, the European companies Dassault Aviation (Topic Manager and aircraft manufacturer), AELS (authorised End of Life aircraft manager) and Constellium (global aluminium producer), together with the Israeli IAI (aircraft manufacturer), have participated in the project with their knowledge in the development of parts for the aviation sector and supported the EoL aircraft management, the aluminium metallurgy and the environmental assessment activities.

The main objective of SENTRY project has been to define dismantling and recycling treatments for the new metallic aerostructures with the minimum environmental impact, in order to maximize the recycling of the recovered materials, mainly light aluminium alloys. For this purpose, the SENTRY Project set the following partial objectives:

- To define the limitations and barriers of the current recycling processes to achieve high quality aluminium alloys from aircraft parts and define an optimized EoL procedure for the B2 Demonstrators Panel A and Panel B
- To perform a live demonstration of the proposed dismantling and recycling schemes with the aim of validating the separation of Al-Li alloys parts and the recycling of Al-Li alloys to produce ingots which fulfil the requirements for aeronautics uses
- To carry out a comparative Life Cycle Assessment of the proposed EoL practices associated with the low weight green metallic fuselage panels (B2 Demonstrators) and the current and proposed EoL practices of the Reference Panel
- To identify the steps or operations, with a strong environmental impact, involved in the EoL practices proposed for the B2 Demonstrators, focusing mainly on impacts linked to energy consumption
- To define any limitations to maximize new light aluminium alloys valorisation and consider eco-design solutions to optimize the environmental performance of fuselage panel at their EoL phase
Project Results:
The SENTRY Project has been divided into three technical work packages, the activity and results achieved in each work package are detailed below.

The WP1 has been led by GAIKER-IK4, whereas IK4-LORTEK and IK4-AZTERLAN has been participants. The WP1 was initiated on 01/04/2014 and, after the amendment, finished on 30/09/2015. The WP1 comprises three main tasks: Task 1.1 “Primary data collection” (M2 to M18), Task 1.2 “Life Cycle Impact Assessment” (M1 to M15) and Task 1.3 “Results analysis and interpretation” (M13 to M18). The general objective of the WP1 has been to carry out a comparative LCA of the new EoL strategy defined for the three panels (Reference Panel, B2 Demonstrator - Panel A and B2 Demonstrator - Panel B) and the current EoL practice for the Reference Panel. The environmental assessment of the EoL phase have allowed the identification of those activities with the strongest impacts, focusing mainly on impacts linked to energy consumption, and the definition of eco-design solutions to optimize potential reuse/recycling of metallic materials.

The completed activities within Task 1.1 Task 1.2 and Task 1.3 have been focused on:
- The definition of the LCA framework and the setting of the boundaries of the new dismantling/recycling operations for Reference Panel, B2 Demonstrator-Panel A and B2 Demonstrator-Panel B
- The assessment of the environmental impacts related to the dismantling/recycling operations, proposed and verified within the project, for the Reference Panel, B2 Demonstrator-Panel A and B2 Demonstrator-Panel B
- The comparison of the LCIA results obtained for the four EoL scenarios
- The identification of the unit operations of the B2 Demonstrator panels EoL practices with a strong environmental impact, focusing mainly on impacts linked to energy consumption
- The definition of eco-design solutions with the aim of optimizing the environmental performance of fuselage panel at EoL phase

Life Cycle Assessment (LCA) is an internationally standardized technique for assessing the environmental aspects associated with products (goods/processes/services) over its life cycle and their effects on the environment and human health. LCA captures the full life cycle of the system being analysed: from the extraction of resources, through production, use and recycling, up to the disposal of remaining waste.

Taking into consideration the LCA methodology and the EoL scenarios defined and implemented within SENTRY project, the following activities have been completed:

1. Definition of the goal and scope of the LCA study
Life Cycle Scope and Goal Definition includes the clear statement of the purpose of the study, the description of the panels (Reference Panel, B2 Demonstrator-Panel A and B2 Demonstrator-Panel B) and the EoL scenarios to be assessed, the system boundaries, allocation procedures, cut-off criteria, data quality requirements, LCIA methodology, impact categories and environmental indicators. Additionally, a literature review has been achieved to check and analyse:
- Different methodological approaches of modelling EoL stages in LCA and, in particular, aluminium EoL stage
- Recommendations of Aluminium Associations
- Dismantling and recycling process in the aircraft sector

2. Life Cycle Inventory (LCI)
LCI is the straight-forward accounting of everything involved in the “system” of interest. It consists of detailed tracking of all the flows in and out of the product system, including raw resources or materials, energy by type, water, and emissions to air, water and land by specific substance. Regarding the current LCA study, the aim of LCI is to gather all the necessary information about consumptions and outputs related to the current EoL of Reference Panel defined in the project and the new EoL of Reference Panel, B2 Demonstrator-Panel A and B2 Demonstrator-Panel B, implemented within the project. Data gathering has been as follows:
1.- Partners in charge of production of Reference Panel, B2 Demonstrator-Panel A and B2 Demonstrator-Panel B have provided data about the composition, alloys and coatings.
2.- Partners in charge of definition of dismantling and recycling steps have supplied data about process modelling.
3.- Partners in charge of dismantling / decoating / recycling live demonstrations have supplied data about equipments or tools used, operation times, consumptions, input and output materials and waste generated.
4.- GAIKER-IK4 has gathered EoL inventories from consortium partners and literature. Generic industry data, available in LCI databases, are used for upstream processes, when needed. Data have been used to built flowcharts for every step (part dismantling, part sorting, shredding, decoating, drying, remeting, recycling) in the current and new EoL scenarios.

3. Life Cycle Impact Assessment (LCIA)
Data collected in LCI have been modelled using the software package GaBi 6 (compilation and following two different allocation methods: the Avoided Burden Approach and the Value Corrected Substitution. A selected set of impact categories have been assessed, translating data into a set of numerical indicators which represent the impact categories defined previously, and outlining thus the environmental profile of the EoL scenarios.

- The impact categories selected are:
- Global Warming Potential (GWP 100 years) (kg CO2-eq.)
- Acidification Potential (AP) (kg SO2-eq.)
- Eutrophication Potential (EP) (kg phosphate-eq.)
- Photochem. Ozone Creation Potential (POCP) (kg ethene-eq.)
- Abiotic Depletion (ADP elements) (kg Sb-eq.)
- Abiotic Depletion (ADP fossil) (MJ)
- Freshwater eutrophication (FE) (kg P-eq.)
- Marine eutrophication (ME) (kg N-eq.)
- Photochemical oxidant formation (POF) (kg NMVOC)
- CO2 (kg)
- NOx (calculated as NO2) (kg)

4. Interpretation of results
The results of the LCIA achieved for the four EoL scenarios have been analysed in order to identify the environmental benefits and drawbacks of the new EoL scenario developed within the project and the influence of the panel design & structure in the new EoL stages. For that, the following assessments have been carried out:
- Comparative assessment of current and new EoL of Reference Panel
- Comparative Life Cycle Assessment of new EoL scenarios
- Sensitivity check: Assessment of alloys
- LCIA of the manufacturing of alloys
- Evaluation of alloy prices

As a result of these assessments, the following conclusions have been drawn:

Allocation approach
The employment of accurate allocation methods is critical when different EoL are compared for a same product or system and when the quality and value of the recovered streams are different for each EoL. Focusing on current and new EoL for Reference Panel, this turns into a penalization of the down-cycling recycling operations and a promotion of proper and efficient sorting techniques to recover high quality aluminium alloys.

Comparative Assessment of current and new EoL for Reference Panel
Considering Avoided Burden Approach, the impacts derived from the new EoL of Reference Panel show the highest scores in almost all categories with an average difference in the scores of a 25%. On the other hand, following Value Corrected Substitution, the current EoL of Reference Panel contributes to most categories with the highest scores, increasing in this case the average difference in the scores from a 25% to a 70%.

Comparative Assessment of new EoL scenarios
Bearing in mind that the three panels are totally different if the weight and composition are considered, the impacts derived from the size reduction and remelting steps are similar for the three panels. The effect of a different structure can be observed when the dismantling step is checked, since the reduced number of rivets included in B2 Demonstrator-Panel A drives to lower operation time and therefore to a more friendly environmental profile.

Concerning the decoating routes, it should be necessary to remark that the impacts derived from both routes would probably be significantly reduced at industrial scale and that some alternative decoating process may also be used industrially.

Regarding the replacement of lost material following both allocation approaches, the new EoL for B2 Demonstrator-Panel B shows the most negative environmental performances, followed by for B2 Demonstrator-Panel A. In both cases, the lower remelting yield and the loss of valuable components in the alloys are the cause of the high amount of material to be replaced.

Assessment of alloys
The impacts derived from the manufacturing of alloy AlMgLi show the highest scores in seven of the eleven categories while the impacts in the other four categories correspond to the manufacturing of alloy 2050. Focusing on the main metals used in panel alloys, the manufacturing of 1 kg of silver shows the worst environmental profile in almost all categories followed by lithium.

Eco-design solutions
In view of the conclusions detailed previously, it can be concluded that the environmental profile of the panels is highly influenced by:

- The employment of electricity as energy source during all EoL steps
- The yield of the EoL operations
- The final value of the alloys
- The environmental impact of the alloy manufacturing.

Considering these parameters and with the aim of optimizing the environmental performance of the three panels at EoL phase, the following eco-design solutions can be proposed:

- The use of other energy sources such as natural gas, heavy fuel oil or hard coal shows lower impacts and can drive to a more environmental friendly profile, as it was assessed in Deliverable 1.1.
- To improve the remelting step to minimize the losses of alloying elements prone to oxidation and keep the maximum value of alloys. Industrial scale optimized processes would bring better yields.
- To use alloys with low impact potential. The evaluation of the environmental profile of the aluminium alloys examined at the EoL stages shows that the contents of silver, lithium and other alloy metals account for a major share of the total score in some impact categories and can explain that, focusing exclusively on the End-of-Life stage, those alloys appear as less environmentally favoured.

However, in a holistic approach, overall impacts throughout the entire life cycle of a product must be considered. That means that impacts arising in the manufacturing, use and end-of-life phases should be regarded. Thus, in the case of alloy AlMgLi, alloy 2050, alloy 2198 and alloy 2099, it should be appraised whether the benefits achieved in the service life of the aircraft thanks to the properties (lightness, corrosion resistance or good strength and toughness combination) obtained by the presence of silver, lithium, magnesium would outweigh the worse environmental performance attributable to those high-impacting materials in manufacturing and EoL phases.

According to recent data from Lufthansa Group, 1 kg of weight saving equals a reduction of kerosene consumption of 30 tonnes per year in every aircraft of a whole fleet, which consist of 627 aircrafts. That makes 47.84 kg of kerosene savings per aircraft on average of the fleet. Assuming 40 years service life in an aircraft, the contribution of lighter fuselage panels to energy savings and emissions reduction, due to differences in fuel consumption linked to aircraft weight reduction, might be remarkable.

This WP was lead by IK4-LORTEK, GAIKER-IK4 and IK4-AZTERLAN were participants. The WP2 was initiated on 01/04/2014 and finished on 30/09/2014. The WP2 comprised two main tasks: Task 2.1 “Definition of dismantling methods and processes” (M1 to M6) and Task 2.2 “Definition of recycling methods and processes (M1 to M6). The general objectives of the WP2 have been the assessment of current dismantling and recycling methods and processes applied or applicable to panels at their EoL phase and the selection and definition of the new dismantling and recycling specifications to apply to the Reference Panel, B2 Demonstrator - Panel A and B2 Demonstrator - Panel B.

Task 2.1 Definition of dismantling methods and processes
The completed activities within Task 2.1 have been focused on:

1. Current airframe design
In order to define a specific dismantling procedure, an insight into the structural components that constitute the fuselage, and the way they are joined and assembled have been considered and reviewed.

The airframe panel consists of a series of frames at intervals along the skin, which give the fuselage its cross-sectional shape, connected by stringers which run the length of the fuselage and bear the skin cabin pressure and shear loads. Stringers or longerons are really stiffeners to prevent the skin buckling, and carry longitudinal tensile and compressive loads, whereas circumferential frames maintain the fuselage shape and redistribute loads into the skin. This form of construction is called semi-monocoque. Depending on the specific design, the number of riveted joins can vary significantly.

2. Current practices for dismantling
Aircraft dismantling activities are not conducted in the same way around the world. This is caused by the absence of global environmental legislation or guidance for aircraft dismantling. Additional logistic issues also arise from aircraft dismantling, since withdrawn components will not be reinstalled. A good traceability is crucial based on an accurate mapping of the parts and materials which are going to be disassembled. The process usually takes place in a specially-designed area consisting of a concrete slab on impermeable geo-membranes synthetic liners.

Currently available most typical practices and tools for dismantling are:
- Engine dismantling practices and tools: plasma cutter, blow torch, thermal lance, etc.
- Fuselage scrapping practices and tools: pneumatic or hydraulic scissors mounted on excavator, high pressure water jet, etc.
- Practices for rivet removal: the industry standard is to drill out the rivet. Extraction of rivets is typically performed using an electrical or pneumatic drill
- Metal sheet cutting practices: circular cutting saw, reciprocating saw, nibblers

Additionally, there are some tasks to consider prior to recycling like paint stripping (currently there does not exist legal requirements to remove the paint and coatings in commercial aircraft during dismantling and recycling operations) and shredding, once aircraft fuselage has been chopped using big hydraulic scissors mounted on excavators, metal scrap is reduced to handling dimensions. Taking into account this, the current dismantling scenario has been defined, where Reference Panel is understood as an individual product of the whole fuselage scrapping step. The dismantling operations are based mainly on a size reduction, being the output a mix of the alloys included in the panel. This mix of metal scraps will be treated in the current recycling scenario, described in the following tasks.

3. Safety considerations and procedures
It is necessary to take into account that dismantling an aircraft exposes a person to potentially hazardous conditions, depending on the chemicals, petroleum products, tools and heavy machinery that are present. Therefore, appropriate materials, tools, equipment and assembly or fabrication jigs, where applicable, have been selected and prepared for the particular dismantling requirements. A “Best Management Practice” guide published and updated by AFRA is available on AFRA’s website, where recommended aspects related to both dismantling and recycling procedures can be consulted [AFRA 2013].

4. Methodology for demonstrator panels dismantling
The main objective within SENTRY Project is to define dismantling and recycling procedures for new metallic structure aircrafts with the minimum environmental impact, so that to maximise potential reuse of the recovered material (primarily Al alloys). The airframe parts (skin, stringers, frames, other) are all joined with rivets, and with exception of the Reference Panel, all the aluminium alloys are third generation Al-Li alloys.

The dismantling strategies and procedures have been defined for the three panels involved in the project. Therefore, for each specific panel (Reference Panel, B2 Demonstrator - Panel A and B2 Demonstrator - Panel B), material groups and subgroups have been defined, according to components descriptions.

A new dismantling scenario for Reference Panel, B2 Demonstrator - Panel A and B2 Demonstrator - Panel B, has been defined. In this new dismantling scenario, both Reference Panel and B2 Demonstrator Panel-A and B2 Demonstrator Panel-B are dismantled according to the specific procedure defined for each panel. For that, firstly the panel rivets are drilled out, then, the different parts are sorted according to material groups and finally, each part is cut to reduce the size prior to the recycling step.

Task 2.2 Definition of recycling method processes
The completed activities within Task 2.2 have been focused on:

1. Analysis of current recycling operations
Conventional separations of aircraft scrap are based on physical properties and these systems are, in general, limited to the separation metals from no metals although some techniques are able to get a more exhaustive separation by metal types. Currently, EoL aircraft aluminium alloys recycling solution consists on dilution with other primary alloys that results on a down-cycling, where the material is converted into lower value products. Considering this and the output of the current dismantling scenario, in the current recycling scenario the mix of metal scraps is treated in a drying step to remove the moisture, parameter that must be avoided in any remelting process. Finally, the mix of alloys is remelted to obtain a secondary raw material.

2. Definition of recycling method and processes
In the SENTRY Project, a satisfactory separation of alloys by main alloying elements is achieved during dismantling steps. The key actions for a successful close loop recycling of alloys are to minimize the presence of improper materials, the removal of coatings and to control remelting. Considering this, the recycling strategy includes the decoating of the recovered alloys by means of impact method (pressure blast system) and the remelting of each material group. All materials are weighed before and after melting to measure the losses. The melt quality is characterized by chemical and metallographic analysis to check the presence of undesired phases and inclusions/oxides. The main alloying element content, in special Li, Mg and Ag are compared with the nominal chemical composition measured over the aluminium parts dismantled from Reference Panel and B2 Demonstrator Panels.

a. Decoating
During the remelting process, the presence of inorganic elements from the coats could have harmful influence on the final composition. For this reason, the decoating seems a key process in the loss of metal, impurity pickup and product quality.

- Summary of the types of coatings in the industry has been carried out
- Summary of the components, coating and base material for each panel has been described
- Coating classification groups and their codification have been defined
- Coating removal techniques have been listed

b. Cleaning and drying
The decoated alloys are cleaned to assure the absence of any waste coming from the decoating process. Previous the remelting process, a drying is performed to remove moisture or any solvent used before.

c. Remelting technology of single alloy or compatible alloys
The remelting process is the last step of the recycling procedure proposed in SENTRY project. The aim of remelting technologies is to remove the undesired elements or inclusions from the melt, while maintaining as maximum possible the alloying content. In the SENTRY project, weight, chemical composition, compatibility studies of the aluminium alloys have been defined for each panel.
- Reference Panel: Alloy 2024 and Alloy 7050
- B2 Demonstrator Panel-A: Alloy 2198, Alloy 2050 and Alloy 2099
- B2 Demonstrator Panel-B: Alloy 2050 and Alloy AlMgLi

3. Environmental recording
Life Cycle Assessment (LCA) of the End of Life phase of the panels is required. Life Cycle Assessment of the end of life phase” is focused on the complete environmental assessment, and thus it will be detailed in the Deliverables D1.1 “Life Cycle Assessment Preliminary” and D1.2 “Life Cycle Assessment”. The WP2 has included the task “Environmental recording”, with the aim of listing and gathering all data induced by the dismantling and recycling processes and required in the life cycle inventory.

The WP3 has been led by IK4-AZTERLAN, GAIKER-IK4 and IK4-LORTEK have been participants. The WP3 was initiated on 01/09/2014 and, after the amendment, finished on 30/09/2015. The WP3 comprised three main tasks: Task 3.1 “Set up of the sorting, disposal and dismantling process” (M6-M12), Task 3.2 “Set up of the elements valorisation and traceability” (M10-M18) and Task 3.3 “Live demonstration” (M10-M18). The main objective of the WP3 was to put in practice the new EoL strategy theoretically, defined at WP2, for the three panels (Reference Panel, B2 Demonstrator - Panel A and B2 Demonstrator - Panel B) and complete the dismantling, sorting and recycling methods to get the recycled aluminium alloys able to meet aeronautic grade requirements. The completed activities within Task 3.1 Task 3.2 and Task 3.3 have been focused on:

- Setting up of the sorting disposal and dismantling process
- Setting up of the elements valorisation and traceability
- Performing an in live demonstration with the aim of validating the proposed dismantling and recycling methods and processes, separating from the recycling stream the parts in materials different to Al-Li and recycling aeronautic grade aluminium All-Li alloys which meet aeronautic requirements

To reach these objectives the work package is split into three tasks where the three participants contributed although the leading role is played by IK4-AZTERLAN.

Task 3.1 Set up of the sorting, disposal and dismantling process
The activities in this task have comprised the necessary actions for putting in practice the new dismantling and sorting protocol defined theoretically in WP2 for every metallic fuselage panel during their live dismantling demonstration. After the analysis of parts, materials and coatings in panels, all panels were studied theoretically and reference panel was studied also physically at IK4-LORTEK, detailed instructions were given to the Dutch aircraft disassembler and dismantler, AELS, on the requirements to fulfil during the demo. Additional discussions were held with AELS in order to select the necessary tools and ancillary equipment to complete the dismantling. Special debate was associated the decision of considering or not the de-coating operation during dismantling but finally, supported on preliminary recycling test it was agreed to skip it. The final decisions made were to focus on the removal of rivets and the classification of parts by type of material and, optionally, by type of coating.

As result of these actions three differentiated “Dismantling and Sorting Protocols” and three “Operation Record Sheets”, one per each panel, were developed in order to have a defined sequence of operations for the dismantling and organise the recording of all relevant technical and environmental data.

Task 3.2 Set up of the elements valorisation and traceability
Dassault Aviation and IAI have provided some samples with the similar base material and coatings of the original panels to be recycled at IK4-AZTERLAN facilities. These tasks started in M10, some preliminary tests have been performance with these samples to adjust methodologies for processing the future dismantling materials.

1. Identification and classification of materials
The analytical method to control the chemical composition has been set up and optimised. The results obtained of the base alloys agree with the ones provided by the suppliers. The final chemical composition and metallographic inspections have been carried out on the demonstrator panels when they arrived after dismantling procedure.

2. Pre-melt processing
De-coating operation has been proposed in the SENTRY Project. Each panel has been decomposed in all the components in a theoretical work taking into the account the information supplied by Dassault Aviation and IAI about the composition, weight of materials and coatings. Three theoretical possibilities have been checked:
- Compounds being able to decompose into elements that could be incorporated to the metal as inorganic element
- Compounds that can be eliminated as volatile compounds
- Compounds to be incorporated to the slag

As a result of this theoretical study, the most important part of the coatings would be in the volatile fraction and the slag products. This theoretical study was checked with the actual re-melting process. The definitions of “volatiles”, “slags” and “inorganics” categories are as follow:

- Volatiles: organic compounds and zinc oxide (ZnO) since it is an inorganic substance with a low sublimation temperature that usually is collected in furnace aspiration stream
- Slags: inorganic oxides that cannot reduce themselves and cannot incorporate to the melted metal
- Inorganics: inorganic compounds (except oxides) that could dissociate with temperature and incorporate as metallic element to the melted metal

In order to select the possible methodologies to decoate, different properties (such as costs, effectiveness, toxicity, wastes or safety for operators) has been checked in each methodology. After the study of the different removing technologies, the best methods have been:
- Chemical striper
- Pyrolysis
- Impact
- Laser

Besides, an assessment of the existing advantages and disadvantages of the different decoating methods has been carried out. The decoating method selected taking into account the evaluation score of the classification of the methods and the ratio of advantages/disadvantages was the “Impact method”.

3. Set up of the melt process
The B2 Demonstrator Panels studied in SENTRY project are mainly made of new green Al-Li alloys which require a specific recycling strategy due to the particular properties of Lithium. Lithium tends to a quick oxidation at high temperature in presence of oxygen. Consequently, the remelting of this kind of Al-Li alloy requires a protective atmosphere. The same process was used in the case of the alloys without Li in order to compare the results after applying exactly the same process. The remelting phase is divided into two test scales (laboratory and bench scale) at IK4-AZTERLAN facilities in Durango (Spain).

Remelting Tests at Laboratory scale

The Lifumat Vac 3.3 is an induction laboratory furnace with a controlled protective Argon atmosphere. The maximum capacity is approximately 35 g of Aluminium and the maximum power is 3.3 kW (HF). This kind of equipment is commonly used in metallurgical research to be compared with conventional techniques. It provides an excellent reproducibility, minimal elemental losses, sample throughput and reliability.

The procedure of remelting consists of 5 steps listed below:

1.- Preparing the material. The material is cut into pieces small enough to fit into the crucible
2.- The weight of the material must be in concordance with the capacity of the permanent mould
3.- Remelting the sample in the furnace following the usual procedure
4.- After the pouring, the permanent mould is cooled into water
5.- Sample from the permanent mould

A drawback of the furnace is that the heating occurs very fast, barely two minutes, and the temperature distribution is heterogeneous so some melted points reach elevated temperatures whereas other points remain still solid. This might influence the loss of some elements sensitive to high temperatures.

4. Characterization of the recycled material
In the laboratory scale, the recycled material have been characterised by chemical analysis whereas, in the bench scale, the melt were cast into ingots which were characterised by chemical and metallographic analysis. The aim of the metallographic inspection was to check for the presence of undesired phases and inclusions/oxides which may have affected of the final product.

Task 3.3 Live demonstrations

Live dismantling demonstration
This activity took place at AELS facilities in Zoetermeer (The Netherlands) on M12, with the aim of validating the proposed new EoL dismantling methods and processes. IK4-LORTEK, GAIKER-IK4, DASSAULT and AELS attended the live demo.

According to the defined Dismantling and Sorting Protocols, selective dismantling and sorting of the three fuselage panels, including reference panel (DASSAULT), panel A (IAI) and panel B (DASSAULT), was carried out successfully.
The Operation Record Sheets were filled with the relevant process details, such as operation times, expended consumables and energy, weight of the dismantled parts, and a collection of pictures of the different stages in the process. The gathered data has been used in the LCI, as it is described in WP1, as input for the study of the LCA. The summary of new EoL process steps related to the dismantling activity are:

1. Panel positioning
The panels were held onto pallets to allow rivet removal and component separation.

2. Rivets removal
A total of 3910 rivets were removed by hand using electric drills. Due to particular conditions in the riveted joints, two approaches were followed. On one hand, for Reference Panel and B2 Demonstrator-Panel B it was necessary to flatten the rivet head in advance, using a disc sander mounted on the drill. Secondly, in the case of B2 Demonstrator-Panel A, due to the sealant being strong, a two pass drilling was necessary in which the first pass consisted in removal of the rivet shanks and the second one, by means of a coarser drill bit, in the complete removal of the rivet head.

The waste from the rivet removal operation accumulated in the form of a mixture of metal, coating and sealant chips. This waste was not recovered, and therefore, the metal fractions of the rivets were not recycled.

The effective time needed for all the rivet removal operations was about 4 h and 30 min each for Reference Panel and B2 Demonstrator-Panel B, and 1 h and 5 min for B2 Demonstrator-Panel A. This is approximately a relation of 2.5 times and the main reason laying on:

1.- The total number of rivets to be removed: 1705 each for Reference Panel and B2 Demonstrator-Panel B in one pass, and 500 for B2 Demonstrator-Panel A in two passes.
2.- The type of rivet used: the process involved an additional operation of rivet head flattening in the case of Reference Panel and B2 Demonstrator-Panel B, as these were round headed. In B2 Demonstrator-Panel A, all the rivet heads were flat.

3. Separation and sorting of the components
Once all the rivets were removed, the different components in the fuselage panels (skin, stringers, frames, junctions and shear ties-cleats) were separated, labelled and sorted according to their related alloy group, in order to have a tracking record of the different component parts.

Additionally, each component was weighed using an industrial scale and, occasionally, for smaller parts such as shear ties-cleats, a small scale with higher precision was used. The measurements were referred to as the mass of the panel after dismantling.

4. Cutting into smaller pieces
Cutting to smaller pieces of approximately 25 x 25 cm2 was carried out using a circular electric saw. The aim of this step, on one hand, was to emulate the metal scrap coming out from an aircraft shredding operation, and on the other hand, to accommodate the size of the metal parts to the recycling furnace feeder in IK4-AZTERLAN facilities.

The effective cutting time was about 30 min per panel. All parts were again weighed, this time using the small and higher resolution scale. The values are referred to as the mass of the panel after size reduction.

5. Disposal of the final parts
Finally, all the panel fuselage parts were collected and disposed according to the alloys classification defined in the sorting protocols, into separate labelled boxes and shipped back to IK4-AZTERLAN for the decoating and recycling activities following the dismantling operations.

Live decoating demonstration
Impact methods
Impact methods are classified by the hardness of the projected particles. According to this property, three different tests were performed with three different families of particles:

- Plastic media
- Sand media
- Other inorganic products

Different tests carried out with this media shows that impact with plastic is not able to remove the coatings of the parts. Also, sand blasting process carried out allows knowing the inefficiency of this process to remove the coatings of the parts.

New tests were conducted using more aggressive inorganic media as glass microspheres and white corundum. The tests carried out allow removing the coatings in some cases but needing other additional operations, as a previous heat treatment or other mechanical processes, in other cases.
Parts from B2 Demonstrator-Panel A were decoated using a pyrolysis step followed by an impact process with glass microspheres. This experience led to try to eliminate the pyrolysis step as it is an additional operation and avoidable energy consumption. So that, parts from B2 Demonstrator-Panel B and Reference Panel were decoated using exclusively an impact process. White corundum was used.

After the impact process a blow cleaning was used to remove the small particles which are deposited on the surface. The used process was able to remove completely the coat from the surface. The metal surface was clean, without any traces of coating and any pollution caused by the impact of the projected particles.

Live recycling demonstration at bench scale
The aluminium alloys recovered from the remelting tests were characterized to calculate the losses of the most valuable elements: Li and Ag. Mg is also evaluated because it is prone to oxidation and tends to increase the amount of slag thus reducing metal yield.

Although there was a discrepancy in some of the weight losses between the bench tests and laboratory tests, similar conclusions could be extracted. It is considered that bench scale losses are more reliable than the laboratory scale losses because:

- The amount of metal remelted is larger
- The aluminium content in the slag was estimated following the procedure of Annex VI, thus the metal yield increases

Conclusions of decoating and remelting Live demo
The main conclusions of the recycling phase of the new EoL scenario implemented in the SENTRY project are listed below. The main conclusions refer to bench tests, although similar conclusions were obtained from laboratory scale.

- No contamination of other elements than those present in the bare material before remelting is observed in all the recycled aluminium alloys of the SENTRY project when the new EoL scenario is implemented for the following alloys: 2024, 7050, 2050, 2198, 2099 and Al-Mg-Li
- The weight yield of aluminium alloy without lithium in the Live Demo bench test is 99.8 and 99.9 for the aluminium alloys without lithium, 7050 and 2024 respectively. While the weight yield of the aluminium alloy containing lithium is between 92.4-96.4 %. That means in a range between 3.5-7.5 % lower weight yield than the alloys without lithium remelted in exactly the same conditions
- The weight yield of aluminium alloy after the remelting trial with coatings (reference panel-2024) is much lower than the trial without coatings. While the metal yield without coating is almost 100 %, for the trial with coating the metal yield obtained is 90.7 %
- Regarding the elements losses due to remelting:
- No variation in the chemical composition of the Ag are observed
- Li is lost about 7.6-11.2 % in the bench tests for 2050, 2198, 2099 and Al-Mg-Li alloys with a lithium content varying between 0.8 – 1.8 wt. %.
- Mg lost percentage depends on the Mg content:
- Low Mg content alloys 2198, 2050 and 2199 with between 0.31-0.40 wt.% have losses between 20-36 %, the maximum amount total lost being of 0.13 wt. %
- Intermediate Mg content alloys 2024 and 7050 with 1.37-1.82 wt. % have losses between 0 and 2.4 %, the maximum amount total loss of 0.07 wt.%
- High Mg content in the Al-Mg-Li alloy with 4.5 wt. % of Mg loss is 0.3 wt. % at bench test (that is surprising in view of the metal yield compared to Al-Cu-Li alloys)
- Si and Fe fulfil the requirements for the Al-Li alloys. Si<0.04 wt.% and Fe<0.06 wt.%
- Regarding the recommended values of Na and Ca for Aluminium - Lithium alloys (Na<0.001 wt.%) and (Ca<0.002 wt.%), all the bench remelting tests fulfil both requirements. In a few trials higher values are observed. However, as there is at least other trial performed with the same alloy with low Na or Ca requirement. These high values are considered as incidental contamination

Note 1: There are some elements (especially Cu) which present a slight higher value than the bare material before remelting. It has to be taking into account the following two factors;

- The values are percentage values and remelted samples have a metal yield between 92.4 - 99.9 %. Aluminium loss in slag is higher than the loss of elements such as Cu but also Zr and Ag. Thus, the percentage of those elements in the remelted products tends to increase
- All the chemical analysis values have their own uncertainty limit

Note 2: The value of aluminium alloys recycled in the present project depends mainly on the Li and Ag content. Mg losses are also evaluated because it an element which present an easy fading. It is prone to oxidation and tends to increase the amount of slag thus reducing metal yield.

Based on the results detailed before, the following overall conclusions were extracted:

Definition and implementation of new EoL scenario
- A new EoL scenario has been designed for B2 Demonstrators Panels and Reference Panel based on dismantling and recycling. The dismantling operations have included the removal of panel rivets, the separation and sorting of the different alloys and the size reduction of parts. The recycling operations have considered the decoating of the surfaces by means of sandblasting and the separate remelting of each material group.
- A protocol for the dismantling operations has been developed, based on the panel structures and compositions and focused on recovering the main groups of alloys. The performance of the dismantling operations has fulfilled this protocol and the results have been the expected.
- Several decoating methods have been assessed, selecting the decoating by means of a pressure blasting system. The implementation of this decoating method has lead to the complete removal of panel coatings.
- A protocol for the remelting operations has been defined, focused on minimizing the losses of the most valuable and volatile components of the alloys. The implementation of the remelting operations at both laboratory and bench scales have fulfilled this protocol achieving similar results. The main element losses during the remelting tests have been lithium and magnesium ones. These losses have not been critical since, though the final composition of the recovered alloys has been slightly altered, they can be considered as first quality alloys.

Environmental assessment of EoL scenarios
- The use of accurate allocation methods is critical when different EoL are compared for a same product or system and when the quality and value of the recovered streams are different for each EoL. In the case of current and new EoL for Reference Panel, this turns into a penalization of the down-cycling recycling operations and a promotion of proper and efficient sorting techniques to recover high quality aluminium alloys.
- The environmental profile of the panels is highly influenced by the energy source employed during the EoL steps, by the yield of the EoL operations, the final value of the recovered alloys and the environmental impact of the alloy manufacturing.
- All the results are related to the panels and to the EoL operations assessed within the SENTRY Project, and therefore, they must be analysed and understood in SENTRY Project framework. Additionally, in a holistic approach, overall impacts throughout the entire life cycle of a product must be considered. That means that impacts arising in the manufacturing, use and end-of-life phases should be regarded.

Applicability of the results and value of the knowledge brought by the project
- An efficient recycling of high quality aluminium alloys need to include a selective separation step to avoid the mixture with other materials which would decrease the final value
- A decoating step is recommended when high quality aluminium alloys are recycled. Although no contamination is observed in the chemical composition of the recovered products, the remelting tests of coated samples at laboratory and bench scales show lower metal yield, higher Li losses and high amount of fumes. At industrial scale, rotary furnace recycling could be an option, however the slags associated with this process should be treated later to recover the metal included in this mixture of fluxes and slags.
- A remelting process with protective atmosphere is critical to avoid Li losses. At industrial scale, equivalent conditions should be applied to achieve comparable results.
- Attending to the previous conclusions, it can be confirmed that the SENTRY Project has demonstrated the technical and environmental feasibility of dismantling, sorting, decoating and remelting operations applied to different high grade aluminium alloys in the “B2 Demonstrator” fuselage panels. Bearing in mind an implementation of the achieved results in a real-life scenario, the economic aspects should be considered in order to make industrially profitable the end of life proposed. For that, the price per mass of the resulting material should be significantly higher than current practices to make it possible. Topics such as a selective shredding instead a manual dismantling, an automatic material sorting and an industrial pretreatment and remelting of the separated aluminium alloys to produce the recycled materials should be solved.
Potential Impact:
The execution of the SENTRY Project has achieved two main final results. On one hand, the implementation of an efficient and value-preserving new EoL scenario has been completed which avoids the down-cycling recycling operations and drives to the recovery of high grade aluminium alloys. On the other hand, the comparative LCA which once completed has concluded that the environmental profile of the panels is highly influenced by the energy source employed during the EoL steps, by the yield of the EoL operations, the final value of the recovered alloys and the environmental impact of the alloy manufacturing. Additionally, considering these factors and with the aim of optimizing the environmental performance of the three panels at EoL phase, several eco-design solutions have been proposed such as the use of natural gas as energy source or the improvement of the remelting step to minimize the losses of alloying elements.

Despite the fact that the technical and environmental feasibility of the new EoL has been demonstrated, the expected socio-economic impacts will be associated with the industrial implementation of the new EoL in a profitable way. An initial revision pointed out that costs associated with labour for, either dismantling parts by drilling and cutting, or sorting fractions by classifying compatible materials, or conditioning particles by shredding and decoating, should be reduced. Attending to this, some of the next actions or steps should be considered:

- To carry out Life Cycle Cost (LCC) of the new EoL scenario implemented in SENTRY Project
- To assess the new EoL scenario applied to other alloys or sections of an aircraft
- To develop selective shredding processes and mainly automatic material sorting and identification methods focused on light aluminium alloys

To conclude, the true impacts of the SENTRY Project will be associated directly with the implementation of the proposed solutions by EoL aircraft managers and material recyclers. These actions will have effect on companies devoted to the manufacturing of dismantling and recycling equipment and will retrofit the aircraft manufacturers and decision makers. Besides, the implementation of selective aircraft dismantling and recycling practices, technically, economically and environmentally feasible, would contribute to raw materials and energy preservation, supporting the close loop recycling alternative instead dilution and downgrading. The amount of aeronautic grade aluminium scraps from post-consumer origin to be recycled was estimated in 60,000 t/year after considering the number of airplanes currently in service, a life span for them in the range 20-25 years and the implementation of the EoL management practices defined within the SENTRY Project. Calculations based on global aeronautic grade aluminium alloy consumptions determined that another 60,000 t/year of post industrial scraps could be generated during aircrafts manufacturing. The market value of these high grade alloys could range 1,600-1,800 €/t, double or triple than the conventional aluminium alloys.The main dissemination activities carried out within the project are:

- Sustainable Dismantling and Recycling of Metallic Aerostructures, 12/03/2015,
- Recycling aircraft more efficiently / Reciclar aviones de forma más eficiente / Hegazkinak eraginkorkiago birziklatzea, 16/03/2015,
- Recycling aircraft more efficiently, 17/03/2015,
- The SENTRY Project at ETB1 - EITB (Euskal Irrati Telebista /Basque Radio Television), 17/03/2015, min. 17:40
- The SENTRY Project at ETB2 - EITB (Euskal Irrati Telebista /Basque Radio Television), 17/03/2015, min 18:25
- The SENTRY Project, 01/04/2015, Radio Euskadi/Euskadi Irratia
- The SENTRY Project, 26/05/2015, Sustainability Report of CONSTELLIUM
- The SENTRY Project, 18/06/2015, Cadena SER
- Otra vía para el reciclaje del fuselaje aeronaútico / Another route for the recycling of aeronautic fuselage, 01/05/2015, EMPRESA XXI, Mayo / May 2015
- Periodic Report Summary 1 - SENTRY (Sustainable Dismantling and Recycling of Metallic Aerostructures), 19/08/2015,
- Un reciclado de aviones aún más eficiente, verificado y listo para despegar / A more efficient aircraft recycling verified and ready to take off, 22/06/2015, RETEMA (Revista Técnica del Medio Ambiente / Environment Technical Journal) 82 (July 2015) 92-96
- The SENTRY Project, 25/06/2015, Presentation of SENTRY for Eco-Design Airframe ITD
- The SENTRY Project – - Environmental assessment of the EoL phase of the B2 Demonstrators -Low weight green metallic fuselage panels- including dismantling and recycling, 24/09/2015, EARS 2016 (3rd European Aircraft Recycling Symposium), Stuttgart (Germany), 16-17 March 2016
List of Websites:

The SENTRY project does not have an own public website.
At CORDIS site ( general information, news and results related to SENTRY project can be searched
At CLEAN SKY site ( SENTRY project synopsis can be found and downloaded

Relevant contacts

Project Coordinator:
Dr. Sixto ARNAIZ
GAIKER Technology Centre
Parque Tecnológico, 202
48170 Zamudio (Spain)
Tel.: +34 94 600 2323

Topic Manager:
Dassault Aviation
78, quai Marcel Dassault - Cedex 300
92552 Saint-Cloud Cedex France
Tel.: +33 (0) 1 47 11 54 52