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Composites and the carbon label

News International-French

22 Feb 2011

Where does the composites industry stand with respect to carbon inventory issues? Is it useful for the manufacturers concerned to know their carbon impact in order either to use it in promoting their development, if it is favourable, or else to find ways of improving it if it is unfavourable? The answers to these questions are vital for anticipating the future and addressing the latest regulations, as well as for keeping one step ahead of the competition.



According to most scientists, greenhouse gas (GHG) emissions are the direct cause of global warming. With this in mind, and in the framework of the Kyoto protocol, the latest Copenhagen conference and, in France, the Grenelle Environment Round Table, significant research has gone into studying the impact of GHGs and the possibilities of keeping the formation of these gases to a minimum.


Since all human activity generates, either directly or indirectly, greenhouse gas emissions, it is incumbent on every manufacturer to take an interest in their own contribution to these emissions and in the resulting economic consequences. Accounting for greenhouse gas emissions may take the form of an inventory which can be used in making decisions with a view to reducing these emissions. In France, the "Bilan Carbone®" is the standardised carbon inventory method developed by ADEME, the French Environment and Energy Management Agency, for this type of accounting. It is based on the ISO 14064 standard, which defines the life cycle analysis principle. Furthermore, any process of eco-design, which is now becoming the rule (see standard ISO 14062), has to involve analysis of these emissions in order to select as far as possible the "low-emission" processes, while at the same time using products with a lowcarbon label.


There are several types of greenhouse gases, with differing contributions to global warming (methane, for example, is 25 times more harmful than CO2). A simple unit allowing products to be compared has therefore been defined: the carbon equivalent.


The carbon inventory is a standardised aid in the calculation of greenhouse gas emissions. This method is one of the tools needed for establishing life cycle analyses, the scope of which extends beyond greenhouse gas emissions alone. Due to the many uncertainties attached to the values used for making the calculation, this method nonetheless remains purely indicative. It helps you to pinpoint the critical emission items and to identify solutions for reducing them.


The carbon label

The carbon label for a product reflects the greenhouse gas emissions generated throughout the product’s manufacturing, marketing and end-oflife process. The label depends on several parameters, the main ones being the source of the raw materials, the production process, the mode of transportation and the marketing method.


These emission factors, therefore, depend on the mode and place of production. For example, for the manufacturing of aluminium, the carbon labels may vary widely according to whether this involves recycled material or else material produced from metal ore, and according to the production location.


The values for France, the USA and Australia (kg CO2 / kg product) are as follows:


Tab. 1: Carbon label for aluminium according
to its geographical origin
Aluminium from ore recycled
France 2.89 0.67
USA 3.90 0.70
Australia 6.30  

The power production method involved in the manufacture of aluminium – nuclear power in France or coal in Australia – is taken into account.


Raw materials

When a product is manufactured, raw materials or semi-processed materials are used. The following table presents various materials and their carbon label. In the case of France, the orders of magnitude are as in table 2 (ADEME V5 emission factors guide).


Tab. 2: Carbon label for various raw materials in France
Raw material Kg carbon
(equivalent per kg)
Kg carbon
(equivalent per
m²/mm thickness)
Steel from ore 0.87 7,800 6.79
Aluminium from ore 2.89 2,700 7.80
Glass 0.28 2,500 0.70
Virgin plastic 0.64 1,000 0.64
0.46 1,500 0.69
0 600 0
Other forestry wood 0.5 600 0.30


This table illustrates the intrinsic influence of the raw material. The last column demonstrates the direct and favourable influence of a low product density. Note the case of wood which, in a sustainablymanaged forest, has a carbon label of zero since, during its growth, it absorbs the CO2 that it will emit at the end of its life cycle.


Production processes

The manufacturing process may use energy from various sources. The following table illustrates the CO2 emissions produced per kWh according to the fuel source used.


Tab. 3: Carbon label for fuels
Fuels g CO2/kWh
Gasoline 264
Heavy fuel oil 271
Kerosene 267
Coal 343
Gas 206
LPG 231
Household waste 149
Electricity, France ~ 15


Note the case of electricity in France, for which the carbon label value is very low on account of it being produced from nuclear energy; the same does not apply if it is produced from fossil fuel power plants.


During the manufacturing phase, other emissions are taken into account, such as personnel movements, buildings, etc.


Mode of transportation

The last link in the manufacturing chain is the transportation of the product to its destination, with the emissions depending on the mode of transport. For example:


Tab. 4: Carbon label for transports
Mode of
Kg C equ. / T
/ km
Truck (20 t) 0.0710
Train 0.0062
Boat 0.0010
Plane 0.6000


Even if maritime transport produces relatively low levels of greenhouse gases, manufacturing products close to their place of use is once again becoming a favourable criterion.


Marketing method

In the marketing process, the travel of sales reps, the manufacturing of brochures, participation in trade fairs, etc., are all parameters of varying magnitude that are taken into account in order to produce a comprehensive analysis. In conclusion, all these values – which remain purely indicative since they depend on numerous parameters that are difficult to quantify with precision – are nonetheless significant. They make it possible to bring to light the stand-out items, with a view to attempting to minimise them. This method makes it possible to allocate to a product its contribution to greenhouse gas emissions. This in turn allows the user of the manufactured product to know just how the products that he or she uses are contributing to CO2 emissions. This may therefore encourage the user to prefer one solution over another.



When carrying out a Bilan Carbone® carbon inventory for a company, you start by defining the scope of the study, then you take into account everything that will contribute to greenhouse gas emissions. Once this accounting is set up, you seek to identify the most important items that need to be addressed in order to make the company eco-responsible. In an example taken from the November 2005 brochure of ADEME dealing with the Bilan Carbone®, the following GHG emission items are given for Company "X":


Power 1,000 T
Emissions excluding power 200 T
Freight 4,000 T
Movement of persons 500 T
Packaging materials 1,600 T
Other raw materials 2,000 T
Waste products and waste water 100 T
End-of-life packaging 700 T
Amortization of buildings and equipment 300 T


Raw materials are the second-largest emissions item after freight. Therefore, one way of reducing your carbon inventory would either be to use less of the raw materials, or to use raw materials with a low-value carbon label or to use lighter products. Cutting down on the raw materials and reducing the weight would then have a beneficial impact on the freight item. This is where the composites industry may have a particular role to play, with several scenarios at its disposal. Cutting down on the raw materials Table 2 presents several examples of carbon labels for various raw materials. It shows that the release of CO2 is in part linked to the type of raw materials and in part directly proportional to the weight. To reduce this carbon inventory item, you may: 1) choose a raw material with a low-carbon label or 2) reduce the weight of the chosen raw materials.


1) Choosing the raw material with the lowest GHG emissions Raw materials can be divided into four main families: metals, plastics, woods, minerals. The choice of raw material may be made either within a family or by switching from one family to another, once feasibility is checked.


  • Metals: among the common materials, steel and aluminium can substitute for one another. In this case, the weight needs to be taken into account, along with the stiffness and impact resistance. Table 2 then becomes:


    Tab. 5: Compared carbon label for steel and aluminium at iso property
    Kg C equ.
    per kg
    Kg C equ.
    per m²/mm
    Kg C equ.
    @ iso-stiffness*
    Kg C equ.
    @ iso-impact*
    from ore
    0.87 7,800 6.79 4.74 2.0
    from ore
    2.89 2,700 7.80 7.8 7.8
    *modulus of steel three times greater than that of aluminium, but stiffness integrating thickness 1.43 times greater

    ** steel impact strength 3.5 times greater than that of aluminium


    Taking account of the useful mechanical characteristics only, steel may release 1.6 to 3.9 times less GHGs than aluminium.


  • Metals versus composites: certain parts can be made either out of metal or out of composites. The following table compares the two possibilities in terms of the carbon inventory (table 6).


    Tab. 6: Carbon label for steel vs composites
    Kg C equ.
    per kg
    Kg C equ.
    per m²/mm
    Kg C equ.
    @ iso-stiffness*
    Kg C equ.
    @ iso-impact*
    from ore
    0.87 7,800 6.79 4.74 2.0
    from ore
    2.89 2,700 7.80 7.8 7.8
    *modulus of steel 20 times greater than that of the composite material, but stiffness integrating thickness 2.70 times greater

    ** steel impact strength 5 times greater than that of the composite


    Tab. 7: Carbon label for recycled steel vs composites
    Kg C equ.
    per kg
    Kg C equ.
    per m²/mm
    Kg C equ.
    @ iso-stiffness*
    Kg C equ.
    @ iso-impact*
    0.67 7,800 5.23 1.93 1.0
    0.46 1,500 0.69 0.69 0.69


Despite its very high stiffness, steel is at a disadvantage compared to composites on account of its weight. The same calculation based on recycled steel gives the following results (table 7).


These two examples, without being exhaustive and while only taking into account stiffness or impact strength, nevertheless show that the choice of raw material is never neutral in terms of GHG emissions. Composites, on account of their light weight, always come out well.


2) Reducing the weight of the manufactured product – the structural sandwich panel

The other solution which preserves the main properties of the manufactured product in terms of strength, functionality, aspect, aesthetics and durability is, if the part so allows, the structural sandwich panel solution.


A structural sandwich panel should provide stiffness while reducing structural weight. Compared to traditional monolithic materials, such panels are stiffer and at the same time provide, depending on the cores used, new characteristics such as thermal and acoustic insulation, impact and stress resistance, and all for no extra cost and no additional material. Since they are lightweight, they are also easier to transport and install.


Case of a 2x1 m metallic part supporting a distributed load of 150 kg/m²; influence of raw materials alone (excluding means of production):


Traditional solution:  
1.5-mm steel skin, steel  
reinforcements every 60 cm  
Skin weight 23.6 kg
Reinforcement weight 3.7 kg
Carbon equivalent 27.3 kg


Sandwich solution:  
0.6-mm steel skin, 80 kg/m3  
20-mm polypropylene core  
Skin weight 9.36 kg
Core weight 3.2 kg
Carbon equivalent 10.2 kg


On account of the weight being reduced by a factor of 2.6, the carbon equivalent is reduced by practically two thirds.


For a composite part, this calculation would equate to cost savings approximately proportional to the observed weight savings.


3) Other savings

A structural sandwich panel also incorporates other characteristics, such as thermal or acoustic insulation, that would need to be added and accounted for in the case of a monolithic solution.


Transport savings

Savings linked to transportation may be made:


  • when transporting the manufactured product to its final place of use,
  • throughout its life cycle if the product is used in a mode of transport.


According to the mode of transport, the weight saving has a greater or lesser influence on the GHG emission. For example, a 300-kg weight reduction on a 20-tonne truck that covers 150,000 km/year equates to 4 metric tons of C.


The composites industry

The aforementioned examples broadly demonstrate that the composites industry is well-equipped to win this battle of the carbon inventory through the trump card of weight reduction. Recycling, until recently the sticking point for thermosetting plastics, has evolved so that today there exist industrially viable solutions.


Many manufacturers are addressing these issues. For example:


  • Telene S.A.S., a company specialising in high-performance formulations based on ultra-pure DCPD, has produced in collaboration with the consultancy, Spirit of Innovation, and the French engineering school, ENSAM Chambéry, a comparative study taking in various pairs of materials/processes used in the moulding of large-scale bodywork components. This study takes account of the energy consumption (cost of the energy required for moulding 1 kg of the finished part), the life cycle analysis (from the production of the raw materials to the recycling/revalution process) and the generation of greenhouse gases throughout the life cycle. All this data are related to the case study of a real component. Several end-of-life scenarios are studied (2008 and 2015 baselines). The study is available from Telene (+33 3 21 08 83 20 or
  • The Laboratoire Central des Ponts et Chaussées (Central Laboratory for Bridges and Roadways) in Bouguenais has compared the carbon inventory for bridges made of composites, steel and concrete. “Composite decks and sustainable development, a case study”, a study conducted by Monssef Drissi-Habti,, Xavier Chapeleau and Sébastien Cournée, is now available.
  • Strongly committed to the promotion of structural sandwich panels in industries other than hi-tech sectors such as aerospace, the author has developed, on the basis of the MAGICS finite element analysis software, a decision-making support software for the pre-dimensioning of structural sandwich panels: ASKMAGICS. This software is designed to help the manufacturers concerned to rapidly assess the feasibility and competitiveness of a sandwich solution compared to the traditional monolithic solution.
  • The Belgian company, Elytra, manufactures lightweight structural sandwich panels with polypropylene honeycomb cores and steel skins. These panels, due to steel's very high modulus and the use of very thin skins (3/10 mm), offer a very high level of stiffness for a low weight (approx. 6 kg/m²). This low weight contributes to the panels’ low-carbon label.


With their products on show at JEC Paris, there are more and more manufacturers proposing new resistant and economic cores for the manufacturing of light structural sandwich panels.



ADEME’s Bilan Carbone® is a standardised method for evaluating the CO2 emissions generated by local authorities, companies or manufacturers. Once its carbon inventory has been drawn up, a manufacturer can allocate to the products that it manufactures a carbon label that will allow users to make an enlightened eco-responsible choice.


A carbon tax is due to be introduced in the near future for fuels used in road transportation. This tax evaluates the cost of the CO2 kg at €15/kg. A trading market has been in place for some years now centred on the costs of the right to emit CO2



All these measures go to show that, despite the current transient difficulties, in particular due to the ongoing economic crisis, the carbon label will become a means of influencing socially responsible choices.


The composites industry, one of the selling points of which is the lightness of its products, should reap the benefits of this if it is able to grasp the opportunity and promote itself accordingly.