ALUMINIUM, CARBON & THE ENVIRONMENT

EPD’S Explained

Based on years of research, scientists organised together with UN have de-veloped a number of standards and methods that estimate the amount of carbon footprint (and other environmental factors) for different stages of a building’s (or product) life. This is called a Life Cycle Assessment (LCA).[22]. Each stage of a product is documented, and the amount of power, fuel and resources used are measured. Where there is unreliable or unverified data, a 15% extra addition can be added to the amount of carbon. [23]. Substances that have a larger effect on the climate are modelled in carbon dioxide equivalents (CO2eq). Methane, for example, has a global warming potential (GWP) around 28 times that of CO2 over 100 years, so 1 ton of methane can be measured or described as 28 tons CO2eq. Similarly, 1 ton of nitrous oxide (N2O) is equivalent to 310 tons CO2eq over 100 years. These figures need to be taken into account when calculating a carbon footprint.[24] GUIDANCE FIGURES Most countries and specialist groups have developed lists of carbon fig-ures to use for materials and activities. NZ Government recommends al-lowing for approximately 0.03kg of carbon per km per kg of material on sea freight. This draws from the United Kingdom Government’s data, which in turn comes research done by the International Maritime Organisation in 2009. [25] [26] [27]. Typically, any figure not taken from actual real local data, or any considered unreliable, is penalised (e.g., recycled plastic con-tent may be taken as fresh virgin material if no data is found from a verified source). source).

MATERIAL & PROCESS IMPACTS The use of coal and other fossil fuels during manufacture has a large impact on the amount of embodied carbon of a product. Aluminium is energy in-tensive to produce from raw mined deposit due to the refining processes. The amount of electricity used to refine is more than steel, and how the electricity is produced has a big impact. For example, virgin aluminium bil- let can contribute more than 16 kgCO2eq/kg when produced via coal pow-er, or less than 2 kgCO2eq/kg (cradle to gate for billet before extrusion) when produced in NZ with hydropower [5][6][28].

RECYCLING Aluminium is one of the most recycled metals in the world, with almost 75% of the aluminium produced still in circulation.[29] Recycling aluminium uses less energy than recycling steel, and can be undertaken in NZ too.[30] The amount of recycled material also has a large impact, and subtracts from the total carbon footprint figure. For example, a significant proportion of our XBEAM platform is recyclable, so in effect it has a footprint of -5.33 kgCO2 per kg of platform for its life cycle.

ALUMINIUM Mined overseas and able to be refined, recycled and extruded in NZ using renewable electric power. Can have a high carbon footprint/climate impact if not manufactured using renewable energy. It is highly recyclable, and one of the most recycled metals in the world. Can be used in coastal environments without protective coatings and maintenance. WOOD Wood is a carbon sink (absorbs carbon) while growing, so are generally re-garded as ‘carbon negative’ (i.e., they remove carbon from the atmosphere). Larger structures can be manufactured with wood, although this typically re-quires chemicals such as chromated copper arsenate (CCA) which limit the ability to use the product for other purposes at the end of life. Treated wood is normally sent to landfill at end of life, creating positive carbon input (nega-tive for the environment).[6][31] Wood structures require coating and main-tenance in external environments to prevent decay. CONCRETE Concrete is heavy, and the main component cement has a high carbon con-tent. Both of these aspects increase its carbon footprint. Cement is most-ly produced locally and has traditionally used coal as a heat source, though some manufacturers are including more sustainable heat sources. Concrete can be recycled and included (as a percentage) in new batches. There are new products and initiatives to reduce the amount of traditional cement and other materials and replacing it with products such as blast furnace slag. STEEL Mined both in NZ and overseas, sheet/plate steel and rods are refined and manufactured in NZ, however all structural sections are currently imported. The manufacture of steel typically requires coal to refine. Most steel is export-ed for recycling or dumped with less than 5% of the total recycled in NZ.[1][32] Steel also requires maintenance and coatings for external structures to prevent corrosion.

Green Star is a brand of certification for buildings administered by the NZ Green Building Council. It is similar but not fully aligned to the Australian Green Star program. Green Star uses a set of rules that a building must meet – includ-ing a reduction in carbon emissions – to obtain a ‘Green Star’ rating. The certification of Green Star involves a third-party verified LCA of the design, and the as-built building, for its expected life (e.g., over 50 years). The end-of-life process is also modelled, and the environmental impacts calculated for the whole building to be demolished and recycled or disposed of, depending on the types of material. The cost of certification can be expensive, and some property owners use the principles without having their building certified. Three levels of Green Star criteria reflect carbon content reductions (when compared with conventional construction). As well as carbon content reduc-tions, each level places more expectations on reduced operational or life cycle carbon. (Although quite similar, there can be different values for upfront and embodied carbon depending on measurement criteria and definitions.)

• Able to resist climate change events sea level rise, storms etc. • The amount of waste it produces while operating. • The amount of fossil fuels and energy used per year less than typical reference building. • Certain substances such as solvents in paints and adhesives (VOCs) may either be minimized or not be allowed to be used in or during its construction.[33]

• Increasing access to ecological transport, Providing return back to the community, or social Return on investment • Innovative methods of construction or building systems • Reuse of a building • Sourcing of materials from certified responsible manufacturers (can also be a requirement)

There are also other building certifications and labelling systems such as ‘living building challenge’, which is international and emphasises place, equity, beauty, materials and so forth. Many projects use some or all of these same principles without getting the getting certification, auditing and documentation that is required for a full Green Star project.

AN EPD IS A STANDARDISED & PEER REVIEWED LIFE CYCLE ANALYSIS OF A PRODUCT. The EPD provides the carbon footprint and other impacts of a product per weight of the product. The data from an EPD can be used to input into a whole building LCA. EPDs for building and construction are typically produced to some or all of the standards EN 15804, EN 15978-4 and ISO 2193.[34] Most of these are third-party verified and reviewed to ISO 14025, although there are also self-declared EPD’s that use the ISO 14021 standard.[35] UNDERSTANDING VARIATIONS: Despite standardisation, there can still be large variation between EPD’s, and this can relate to the scope or the number of processes included in the analysis. Things such the number of steps analysed to end of life of the product (cradle to grave) or from manufacture to dispatch (cradle to gate) can have a large impact. When using cradle-to-gate EPDs, it is important to check where the location of the ‘gate’ given in the EPD is in the whole product life cycle. There are also variations such as exclusion of installation and use, but inclusion of the end-of-life disposal/recycling stage. Other variations can relate to the way the units are measured and the values used for these for instance products can be measured in weight, surface area or volume and the respective environ-mental impacts in tons or kg.

To achieve a comprehensive understanding, it is essential to conduct a full cra-dle-to-grave analysis, accounting for the diverse processes involved in materi-als. Notably, all Green Star-rated buildings undergo a complete life cycle analy-sis (from fabrication to disposal or building demolition), and the same holds for government-mandated buildings exceeding $5 million in value. Interpreting EPDs often follows the cradle-to-gate approach, which hinges on identifying the specific ‘gate’ point. For instance, in the case of structural steel, the EPD encompasses the manufacturing processes, which could take place in various locations like China, Korea, or Eastern Europe, but the ‘gate’ is the point where the steel is ready for use. In the construction of a structure, various activities such as cutting, welding, coating (in the case of steel), transportation, assembly, and erection typically occur after the ‘gate’ of the EPD, and should also be taken into account. Further, most EPDs don’t include considerations for transportation to NZ or wholesale distribution. A cradle-to-gate EPD may incorporate end-of-life considerations, but these additional stages are typically absent. By contrast, NZ manufactured aluminium from Monkeytoe can show a lower im-pact – not only because of local manufacture (which reduces transport costs, as well as the aforementioned reduced environmental impact of local aluminium), but also because our solutions are readily assembled on site with no hot works etc.

The data used for the reporting and the end result of an EPD can vary depend-ing on the the software used and assumptions made even though is produced to the correct standard [37]. For example, the recycled content or ease of dis-assembly were not taken into account in the EPD produced for the XBEAM. The power supply content of hydro power was also changed. (Some of this is to do with the need for accurate information, time spent, and use of datasets that are standard rather than specific for the product.) When the stages that include maintenance and end-of-life are included, this can become even more variable, depending on the person conducting the LCA. For best results using the same experienced LCA professional and actual on-site experience and knowledge of each constriction type, material and method is preferred for accurate compar-isons. Architects and specifiers may also use a measured amount of “high carbon” product to ensure the building lasts with little maintenance. Life cycle analyses have also increased the focus on whether each part of the building will last as long as the ‘whole life’ (often 50 years). This is of special interest when manu-facturers’ products are rated to much shorter time frames, such as roofing sys-tems, which are rated to just 15 years. For this reason, easy-to-install products from Monkeytoe score highly at the disposal stage when modelled correctly. As a final note for interpreting EPDs, be aware of the units: figures might be per kg or per ton, and scientific format numbers might be easy to misinterpret (e.g., 4.43E+03 is 4430 not 4.43.)

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