[ Duplex ]
[ Duplex ]
Cradle to gate
Cradle to grave
Materials Construction Use End of life Recycling
Figure 1 . The main stages of a product life cycle .
emission data . The methodology for the calculations is based on predefined rules for a certain product type ( PCR ) using LCA systematic according to either EN 15804 or ISO 21930 . Typically , the boundary condition for assessing a material is limited to a so-called cradleto-gate scenario , meaning emissions from raw material supply , transport and manufacturing , and potentially information about waste processing and recyclability are included ( Figure 1 ). However , the construction and use phases are normally excluded from the LCA scope .
Product Carbon Footprints ( PCF , ISO 14067 ) Product Carbon Footprint ( PCF ), CO2e , is estimated based on partial LCA similar to EPD but using slightly different rules , covered by ISO 14067 . A third party can also verify a PCF according to ISO 14064 . The methodology behind a PCF encourages the use of primary emission data directly provided by the raw material suppliers . While EPD only allows industry average emission data for raw materials taken from verified databases ( so-called secondary data ). The objective of the stricter rules behind an EPD is to ensure comparability between different EPDs . On the other hand , when a company is at the forefront of implementing decarbonisation measures , e . g ., using selected suppliers , a PCF calculated according to ISO 14067 is often less conservative than an EPD . Moreover , under such changing conditions , an EPD report is soon out of date unless it is verified and republished . Can a PCF value be compared with a CO2e value from an EPD ? Basically not . They are calculated based on different methodologies and rules . Nevertheless , I argue differently . For stainless steels , we prefer to use PCF as they more accurately describe our products . The PCF represents a specific product rather than a group of products , which often is the case of the EPD for practical reasons . The calculation is based on a 12-month rolling average . The latest third-party validated PCF can , in this case , be obtained from the supplier . The PDF is communicated on the material test report ( certificate ) along with all other material-specific test data . The EPD is a published report valid for up to 5 years and is either obtained directly from the supplier or databases at official EPD program operators .
Carbon footprint comparisons Stainless steels ( from PCFs ) - In Figure 2 , PCF values are shown for type 316L , duplexes , high-alloy austenitics and nickel alloy 825 . All grades are produced by electric arc furnace ( EAF ) and delivered in hot rolled condition from the same mill 1 . Typically , PCF increases with increasing alloying content . The PCFs for duplex grades are generally slightly higher than type 316L but lower than high-alloy austenitics and nickel alloy 825 . Thus , the more advanced grades require a higher share of virgin raw materials , e . g ., chromium , nickel and molybdenum . The emissions generated by recycled raw materials are limited to scrap handling and transport , while virgin raw materials have the greatest impact on the carbon footprint . Therefore , it is crucial to choose the right raw material suppliers to minimise the PCF . The target for the ‘ low-CO2 ’ versions of both 316L and LDX 2101 depicted in green in Figure 2 is to reduce the emission level by 50 % compared to the regular versions , to below 1 kg CO2e per kg . This reduction is obtained by maximising the recycled content , using biofuel , focusing on the best possible heat and production efficiency through the mill , and minimising all transports needed for the manufacturing . Stainless Steels ( from EPDs ) - Figure 2 shows the total CO2e values declared
in recently published EPDs from us and other stainless steel suppliers . The complete list of references is at the end of the article , listed in the order of appearance left to right from ‘ lowest ’ green , ‘ low ’ blue to ‘ high ’ grey emission levels in Figure 2 . Note that the CO2e value from the EPD for type 316 conforms well with the PCF , 1.5 vs 1.3 kg CO2e kg , mainly due to low additions of virgin metals 2 , and the other manufacturers are slightly higher 3 , 4 . The duplexes from the EPD ( average of many grades ) have significantly higher CO2e values than the PCFs , as indicated in green ‘ lowest ’ value 5 . In addition , one manufacturer from East Asia representing an undefined mix of austenitic and duplex grades is depicted in blue 6 , and one European manufacturer in grey 7 . Note , none of the EPDs represent the same duplex grade mix . How do stainless steel CO2 values compare to other materials ? Let ’ s start with carbon steels . Carbon steels ( from EPDs ) - There is a clear market trend towards more high scrap ( near 100 %) electric arc furnace ( EAF ) produced carbon steel . A recently published EPD was declared to be as low as 0.5 kg CO2e per kg of steel 8 ( Figure 2 ). Otherwise , the best-in-class currently hovers around 0.8 kg CO2e per kg from steel production in either North America or Europe 9 , 10 . An average value of 1.7 kg CO2e kg representing several steel mills in the USA is provided by AISC 11 . For blast furnace steel production ( BOF ) out of iron ore , the declared CO2e emission in identified EPDs are about 2.7 – 3.0 kg CO2 per kg for hot rolled plates 12 , 13 . Aluminum , nickel and titanium alloys ( from EPDs ) - Many EPDs are available for aluminum alloys , mainly from Europe , North America , and a few from Asia . A selection is presented in Figure 2 14-16 . The declared CO2e values vary greatly depending on how much scrap is used for their production ( near 100 %, 80 % and unknown , respectively ).
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