The key environmental indicators in sustainable material selection

Here, Samir Jaber, Content Writer at Matmatch, explores the most common environmental sustainability indicators in a materials selection process and how they are quantified.

As defined in the Brundtland Report in 1987, “sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”

Today, sustainability has long passed the mere association with minimising carbon and greenhouse gases. Discussions about sustainability are concerned with various matters of the environment, the economy, and the society. These are commonly known as the 'three pillars of sustainability', as they all demand consideration and proper management to ensure a sustainable future.

But one question remains: How can we properly measure sustainability, quantify its impacts, and set meaningful and appropriate goals?

Well, measuring sustainability is no easy task. It is a multifaceted process that involves dozens of considerations and indicators. As more ambitious sustainability targets are being set by governments, organisations and companies alike, the challenge of measuring the impacts and meeting demands has become increasingly difficult yet ever important.

No matter what industry you are in, sustainable material selection has become a fundamental course of action in your work scheme. Accordingly, here are some of the key and most common environmental sustainability indicators that can go into the material selection process.

Carbon footprint

The carbon footprint of a material refers to the total greenhouse gas (GHG) emissions produced throughout the different stages of the material’s lifecycle, including production, processing, use and end-of-life.

Over the whole lifespan, several GHGs can emanate, including carbon dioxide, methane and nitrous oxide. Such gases have different heat-trapping capacities that contribute to the overall global warming phenomenon. These are measured as Global Warming Potentials (GWPs) in units of carbon dioxide equivalents (CO₂e). This allows for straightforward comparison of carbon footprints of different materials accounted for by single units.

As climate change has become one of the world’s major challenges, mitigating GHGs and adapting to climate change are now of paramount importance. Initiatives targeted at alleviating GHGs primarily depend on emission quantification, monitoring, reporting and verification. For that, the International Organisation for Standardisation (ISO) issued the ISO 14060 family of standards that not only offers a clear and consistent approach to the measures mentioned above but also enhances the environmental integrity, credibility and transparency of these measures.

Other indicators under the umbrella of carbon footprint include carbon reduction, carbon offset and carbon neutrality. While carbon reduction is, as its name implies, the reduction of carbon emissions, carbon offset is that reduction made particularly to counterbalance emissions produced somewhere else. The ideal result from carbon offsetting is known as carbon neutrality, which is net zero carbon emissions.

Embodied energy

The embodied energy of a material is the sum of the direct and indirect energy inputs involved in resource extraction, transportation, production, processing and delivery of the material. Embodied energy can also be defined in a way that incorporates the whole lifespan of the material. However, such a measurement is relatively complex to calculate as it depends on the product the material was used to make. Either way, it is crucial to reduce the embodied energy of a material or product as much as possible to minimise its environmental impact.

Such a sustainability indicator is most commonly found around applications of building and construction, but it is also utilised in other application areas. It is expressed in units of megajoules (MJ) or gigajoules (GJ) per unit weight (kg or tonne) or per unit area (m²). In construction applications, this characterises the measurement of non-renewable energy input per unit of building material or system.

Embodied energy should not be confused with what is known as embodied carbon. Embodied carbon is, basically, the carbon footprint of the material, but it differs based on which part of the material’s lifecycle is considered. It is important to distinguish it from embodied energy as it indicates the carbon emissions involved not the energy.

Recycled content

Also known as recycled material input, recycled content represents the proportion of material in a product that has been redirected from the solid waste stream. This can happen in two different stages, leading to two different categories of recycled content.

One is pre-consumer recycled content,also known as post-industrial. This is when the material is redirected during manufacturing, before it reaches the consumers. The other one is post-consumer recycled content (PCR),which refers to materials recycled after consumer use.

Recycled content is generally expressed as mass fraction in percent. Common materials that incorporate recycled content include plastics (PET, PP, HDPE, ABS), metals (aluminium, steel), and glass.

The process of recycling materials, whether they fall under post-consumer or post-industrial, plays a significant role in promoting sustainability practices and attaining sustainable materials. It effectively helps in reducing energy consumption and depletion of non-renewable resources.

Given all these metrics, they can all be put together into what we call as an Environmental Sustainability Index (ESI), which is a measure of the overall progress towards environmental sustainability. This composite index presents a combination of environmental, socioeconomic and institutional indicators that have quantifiable impacts on environmental sustainability at a national level.

At Matmatch, we have begun to incorporate sustainability indicators in our materials database to help engineers make more sustainable choices. We put together a guide to sustainable materials selection and we are currently collecting data from materials suppliers to make some of the indicators mentioned in this article searchable.

For example, leading aluminium producer Nature Alu is committed to producing fully environmentally friendly and contributing to sustainable development. Its high-purity aluminium (P0101 up to 4N+) has a very low carbon footprint, but it is also designed with the health and safety of employees in mind and the needs of the client in mind. Similar suppliers can be found on our database.

By finding the most sustainable materials and identifying their environmental impact, we can contribute to more environmentally friendly and economically viable production. Aspects such as the carbon footprint, embodied energy and recyclability of a material are all very important considerations for any engineering project that is concerned about the wellbeing of the society and the planet at large.