Sustainability Frequently Asked Questions

Specifying a high recycled content can be beneficial for some products however that is not the case for metals that are already highly recycled. Indeed, specifying steel with a high recycled content can have adverse consequences within the broader sustainability context.

In our daily lives we are all encouraged to recycle more. Recycling is good for the planet because it reduces waste and conserves (or substitutes) primary resources, furthermore recycling generally saves energy and carbon emissions.

But how should we measure and incentivise recycling? The answer to this is more complicated than the simple ‘recycling is good’ and ‘recycle more’ messages and needs to be understood by specifiers of construction products if unsustainable and unintended consequences are to be avoided.

There are two main ways of measuring recycling, recycled content and end-of-life recycling rate:

Recycled content is defined in ISO 14021 [1] and is a measure of how much recycled content (pre- and post-consumer) is used in the production of a new product

End-of-life recycling rate is a measure that compares the actual amount of materials recycled with the amount of metals theoretically available at the end of the life of a product. In the context of construction, this is the proportion of demolition arisings that are recycled

Specifying a high recycled content is a good driver for products where the aim is to encourage and establish a market for recycled materials that are otherwise limited, uneconomic or immature.

For example, the recycled content approach may be a useful metric/driver for a material that would otherwise be incinerated or landfilled as waste. Specifying a recycled content for products incorporating these materials, can divert them from incineration and landfill to recycling and reuse. Importantly, this is not the case for metals - as discussed below, metal recycling is economical and the metals recycling market is extensive and mature.

The application of the recycled content approach may create market distortions and environmental inefficiencies. If a designer specifies high recycled content in a well-meaning effort to reduce environmental impacts, it may stimulate the market to direct recycled feedstock towards designated products and away from production where recycling is most economical. For metals, where there is a limited supply of recycled feedstocks, market stimulation is ineffective and may result in inefficient processing and unnecessary transportation. See the declaration on recycling principles by the metals industry [2].

1.1 Global steel production

Global consumption of steel products continues to rise, mainly as a consequence of industrialisation in developing economies and particularly, in recent years, growth in China. For example, the World average per capita consumption of crude steel in 2019 was 229 kg. By comparison, the EU-28 average consumption is 310 kg/capita, UK consumption was 151 kg/capita and average consumption in Africa was just 28 kg/capita [3].

Fig. 1. Growth in global steel production 1950-2019, worldsteel [3]

Fig. 2. Anticipated global demand for steel to 2050 [4]

Anticipated global demand for steel to 2050 Fig. 2. Anticipated global demand for steel to 2050 [4] Global demand for new steel exceeds the supply of scrap steel by a factor of around two and therefore, to meet this increasing demand, new steel has to be produced from primary sources by the BF/BOS production route. Supplies of ferrous scrap are finite and exclusively specifying 100% recycled steel, will result in an increased demand for scrap that is not only unsustainable but may also drive up scrap prices.

Within the global context, there is no point specifying 100% recycled steel (in preference to BF/BOS steel) as all this will mean is that BF/BOS steel will be required to substitute EAF production to meet the excess global demand elsewhere. In addition, specifying imported 100% recycled steel in the UK, adds further transportation impacts.

The corollary of this is that on a global scale and while global demand for new steel exceeds the global supply of scrap, it is the end-of-life recycling rates achieved (not the recycled content) that is important for sustainable development.

This is not just the view of the metals industries. The following are extracts from other, independent sources.

WRAP undertook a number of studies promoting the use and specification of recycled content for construction products. However, for metals, WRAP concluded [5]: For recycled content within the metals industry, where recycling is already optimised (where over 90% of waste arising is recycled or reused), an industry average for each product type, e.g. aluminium sheet or steel sections, should be declared, rather than on a site-by-site or company-by-company basis. If, for example, steel sections available globally to the UK market have 60% recycled content on average, then the steel industry could all use that figure as the recycled content of sections.

In her article [6] Kirsten Henson states: Rather than insisting on high recycled content in structural steel, which ultimately drives no positive climate impact on a global scale (due to the fact that the majority of steel is already captured at end-of-life and recycled) and potentially contributes to the further decline of the UK steel industry, architects and building owners must seek innovative ways of re-using existing structures and engineers must use ingenuity to deliver the most materially efficient design solutions.

The ICE database V2.0 [7] includes an excellent, detailed treatise on how to account for the recycling of metals in embodied carbon assessments. The ICE authors share the views of the metals industry about market possible distortions that can result from specifying a high recycled content for steel. Consequently, the ICE database, which is ‘cradle-to-gate’ (Modules A1 – A3) only, recommends the implementation of an effective average recycled content for steel products and states: To implement this method effectively the same recycled content must be modelled for all different forms of (carbon) steel (e.g. rebar, sheet or section). Technological and economic factors often dictate where scrap materials are directed. The fact that a certain type of steel is almost exclusively manufactured from primary feedstock (iron ore) or secondary feedstock (scrap steel) becomes irrelevant. For example, steel rebar is often manufactured in an electric arc furnace (EAF) and therefore often has a recycled content of 100%. Conversely steel sheet is typically derived from a primary production route. An increase in the demand and production of steel rebar will not result in an increase in the global average recycled content for worldwide steel. Likewise, an increase in the demand and production of steel sheet will not reduce the global average recycled content. Scrap steel remains a valuable commodity and will be consumed regardless of the demand for certain types of steel. Consequently, changes in the demand of certain forms of steel (rebar, sheet or section) have no capacity to increase the global average recycled content. The consequences of this are that although rebar is normally made from recycled steel and sheet is typically made from virgin steel both materials are given an ‘effective market average recycled content’ within the ICE database.

Rationalisation of steelwork design is current, common practice on most projects in the UK. The main drivers for this are constraints on design fees and time and efficiencies in procurement and fabrication and erection of the steelwork.

There have been several recent studies looking specifically at the material efficiency of steel structures, see, for example, references [9-12]. These studies suggest that over-specification of sections can lead to an additional 30-40% of steel used within the structure and, therefore, to additional embodied carbon within the structure. While bespoke designs may contribute to reducing the upfront embodied carbon, there are good reasons to rationalise designs:

• from a safety point of view, less variability in member sizes reduces the possibility of human error during erection
• from an execution standpoint, the increase in the speed of construction
• from Other studies have investigated other factors including over-specification of loads and less conservative SLS criteria where SLS governs. While these aspects may help reduce embodied carbon within the structure, they are unrelated to rationalisation of the steelwork design.a sustainability or circular economy perspective, rationalised designs enable greater flexibility and adaptability of the building and enhance the reusability of the structural elements

It is noted that [10] concluded that rationalisation or repetition within the structure could not explain the over-specified mass of the steel frame rather it is the designers decision to limit the utilisation ratio to 0.8 that was the main cause. In addition, there is unused mass in cores, trimmers, ties, etc. and in edge beams which are under-utilised but are necessary for stability. Figure 5 (from [9]) shows the utilisation as a function of beam type from an analysis of 30 buildings.

Other studies have investigated other factors including over-specification of loads and less conservative SLS criteria where SLS governs. While these aspects may help reduce embodied carbon within the structure, they are unrelated to rationalisation of the steelwork design.

Fig. 5. Utilisation ratio as a function of beam type [10]

A circular economy is based on the principles of designing out waste and pollution, keeping products and materials in use, and regenerating natural systems. Figure 6, developed by the Ellen McArthur foundation, is one of the best accepted representations of circular economy concepts. The left hand (green) half of the figure represents biological cycles such as timber and the right-hand side (blue) represents technical materials, including, in the context of construction, concrete, metals, plastics, etc.

There are two fundamental concepts to highlight within the figure:

1. Leakage out of the circular system, to energy recovery or landfill, should be avoided wherever possible
2. Within the concentric circles, the smaller the diameter the more efficient the process

Steel has excellent circular economy credentials both as a material which is strong, durable, versatile and recyclable and, as a structural framing system, which is lightweight, flexible, adaptable and reusable.

While the focus of the circular economy in construction is on how to transition from a linear to a circular model, because of steel’s excellent recycling credentials [8] steel is already circular with very little ‘leakage’ out of the system. Recovery rates for structural steel, for reuse and recycling, are over 95% and, with steel recycling emitting only 20% of the carbon emissions compared to making steel from iron ore, steel is already helping significantly to reduce carbon emissions.

But the steel sector is not content with just recycling and is looking to improve its circular credentials further by encouraging greater steel reuse and designing to facilitate future deconstruction and reuse. Steel structures and structural steel elements are inherently demountable and reusable. While there are currently logistical and supply chain barriers to more mainstream reuse, reuse is technically viable, saves resources and carbon emissions and can save money.

To help facilitate structural steel reuse, SCI has recently published guidance documents:

• SCI P427 Structural steel reuse: a protocol for reusing existing structural steel
• SCI P428 Guidance on demountable composite construction systems for UK practice

Fig. 6. Representation of the circular economy – Ellen MacArthur Foundation

Recycling construction products is important to conserve resources and to reduce environmental impacts. Although most end-of-life building products are now recovered following demolition (it is estimated that >90% of UK demolition arisings are currently recovered and reused in some form), it is important to know how easy it is to recycle different products/materials and to understand the relative benefits of different forms of recycling and reuse.

Construction materials differ significantly in the ease with which can be recovered and recycled and if we ignore this aspect then, in effect, we are equating products that are recycled with products that are landfilled! Preserving resources through reuse and recycling is vital to achieve a more circular economy and to reduce greenhouse gas emissions.

The benefits of recycling and reuse are well understood and include:

• Reducing waste, i.e. diverting waste from landfill
• Saving resources, i.e. substituting primary production
• Saving energy and associated greenhouse gas emissions through less energy intensive reprocessing

Although these benefits apply to many commonly recycled materials, there are some important differences in material properties that influence the environmental benefit of recycling and particularly how these benefits are quantified.

Metals, for example, are infinitely recyclable, i.e. they can be recycled again and again into functionally equivalent products. This is the most environmentally beneficial form of recycling and is called closed-loop recycling. By carefully blending scrap steel it is also possible to produce new steel with superior properties and higher value, e.g. engineering and stainless steels. This is called upcycling.

Other construction products are downcycled into new products that are only suitable for lower grade, lower values applications because the recycled product has different, usually lower, material properties. Although waste is diverted from landfill by downcycling, only lower grade primary resources are saved. For example, crushing bricks and concrete for hardcore, sub-base or general fill saves aggregates but does not save the resources required to make new bricks or new concrete.

For recycling to be sustainable in the long term, it is important that the recycling process is financially viable. This is frequently the biggest hurdle to recycling, particularly for products and materials that are downcycled into lower grade, low value applications. These products often require incentives or regulation to encourage recycling.

Steel scrap, on the other hand, has a high economic value that ensures it is always highly recycled. This process is enhanced by steel’s magnetic properties that allow it to be easily recovered from mixed waste streams. An established infrastructure exists to collect, sort and process scrap efficiently.

The methodology generally used in construction to quantify these relative recycling or circular economy benefits of different products is called Module D and is explained in the next FAQ Why are UK sections produced via the primary (BF-BOF) production route?

Reusing structural steel makes good environmental sense and can save money. Reuse, as opposed to the current, common practice of recycling structural steel by remelting, offers significant potential in terms of both resource efficiency and carbon emission savings.

Structural steel sections are inherently reusable. The process is straightforward. For example, deconstructed sections are inspected to verify their dimensional properties, tested to determine their mechanical properties and the section is then generally shot or sand-blasted to remove any coatings, and refabricated and primed to the requirements of the new project.

Despite the viability of reusing structural steel, there are many barriers to more widespread reuse. These include the availability of reclaimed sections particularly of the desired size, volume and location, and issues relating to the quality, traceability and certification of reclaimed sections. The additional time/programme and cost of using reclaimed steel are also barriers. Extra time, in general, incurs additional cost and there are many barriers centred around the increased programme associated with reclaiming and reusing structural steel including:

• The current approach of ‘just-in-time’ supply (of new steel) by stockholders and steelwork contractors
• The additional design, procurement and testing/certification time required compared to using new steel
• Increased automation in steelwork fabrication which is far less efficient when using reclaimed steel sections
• Insufficient time within new development programmes to allow for deconstruction and recovery of the steel elements rather than demolition

Despite the barriers, structural steel remains one of the most viable candidate products for mainstream reuse and without question, reuse will become more commonplace in the future as we embrace circular economy principles. To help facilitate the reuse of existing structural steel, SCI has published a protocol (SCI P427) setting out recommendations for data collection, inspection and testing to ensure that reclaimed structural steelwork can be reused with confidence.

More can also be done to facilitate reuse in the future and work is underway within the sector to support this. The proportion of recovered products that are reused will increase as design for deconstruction is better understood and a stronger market for reusable steel construction products is stimulated. The ability of the steel construction sector to reuse structural steelwork is enhanced by the standardisation of components and connections.

To help facilitate design for deconstruction and reuse, SCI has developed guidance on the design of demountable composite construction systems (SCI P428).

Responsible sourcing of construction products is assessed under BREEAM Mat 03 under which up to 3 credits are achievable. Credits are awarded as follows:

The scope of assessment of the superstructure is defined as:

To assess a building, the assessor has to establish the BREEAM-recognised responsible sourcing certifications scheme (RSCS) certification or environmental management system (EMS) certification, if any, relevant to each product/material within the scope.

Recognised schemes are listed in BREEAM Guidance Note GN18. GN18 lists the following schemes which are currently recognised by BREEAM and their scoring.

Where the construction product has no certification, is non-compliant with the broken chain (see below) requirements or the certification type is not listed in Guidance Note 18, the score is zero.

Broken chain

There are situations where a product/material (or constituent product/material) specified by the design team (or chosen by the constructor) is certified at manufacture but is supplied by one or more organisations that have no relevant certification. This reduces the level of assurance because the chain-of-custody/traceability is broken (so-called broken chain). For example, this would apply where a steelwork fabricator, without responsible sourcing certification, is using material from a certified source.

To recognise responsible sourcing certification where it does exist in the supply chain, while reducing the risks associated with a broken chain, it is permissible to use the upstream certification score in the Mat 03 calculator where the downstream risk to responsible sourcing is considered to be low.

Specifically, it is acceptable for the following types of organisations in the supply chain (that are downstream of the organisation with certification) not to have their own responsible sourcing certification:

1. Organisations that only handle or transport
2. Organisations that only fabricate, assemble or install and are using a recognised quality management system to ensure the mixing and substitution of the certified upstream source with uncertified sources has not occurred
3. Are operating in a jurisdiction that can demonstrate relatively robust and well enforced environmental, social and economic controls. For example:

• States which are members of the EU
• States that have declared adherence to the OECD Guidelines for Multinational Enterprises.

For the case of structural steel therefore, full benefit for responsible sourcing under BREEAM can be achieved as long as the steel producer is certified to a recognised responsible sourcing scheme (point 2 above) as long as they have a recognised quality management system in place. In the UK this is generally BES 6001 certification which the major steelwork suppliers to the UK market (British Steel, ArcelorMittal Long products Europe, Spartan UK and Tata Steel) currently have.

The full list of steel companies currently certified to BES 6001 can be seen here BRE Group: Responsible Sourcing League Tables