Tweet
                                               

The “forgotten” greenhouse gas emissions of our built environment will be a hard nut to crack

True or false? “A zero-carbon built environment means that no fossil fuels are used in the operation of buildings and infrastructure.” False, because this leaves out the embodied carbon emissions of building, maintaining and dismantling the built environment. But how would we know?

A whopping 40 per cent of all of Australia’s greenhouse gas emissions can be attributed to the built environment and there is increasing political consensus and will to reduce this liability swiftly.

“Zero-carbon” or “carbon-neutral” announcements for anything from buildings to cities are in vogue. But almost half of this 40 per cent figure are not even included in the discussion because they are indirect emissions, “hidden” in the supply chain of making buildings.

Our new research shows that 90 megatonnes of greenhouse gas emissions are emitted annually in constructing new buildings and infrastructure and maintaining the existing ones. This is almost a fifth of all of our annual emissions and of a similar magnitude to operational emissions from our buildings that account for 127 Mt CO2e a year.

Reducing this liability of “embodied” emissions will be much harder than building zero-carbon buildings. Here is why.

Zero Carbon – Really?

The NSW government’s announcement that NSW carbon emissions shall reach net zero levels by 2050 is an encouraging step. A recent poll in Victoria confirms that eight out of 10 Victorians support their government’s net zero emissions (and renewable energy) targets. Similar targets of “zero carbon” or “carbon neutrality” have been set for cities, precincts and buildings. This is in line with an increasing political momentum around reducing emissions from the built environment. These are significant as a recent report from ASBEC emphasises.

Over the past decade, considerable progress has been made in reducing the operational energy requirements of buildings and associated emissions. Residential electrical energy use, for example, has been declining due to improved building energy efficiency, increasing energy prices and the uptake of household solar power. Examples like 5×4 Haynes Lane show how renewable energies and efficient design can be integrated.

But what does “zero carbon” really mean? The aim of achieving no greenhouse gas emissions is usually defined as “net zero emissions” or “carbon neutral”. This refers to a situation where emissions have been reduced as much as possible and any remaining emissions are offset elsewhere with reduced or removed emissions from the atmosphere, such as through reforestation, renewable energy or energy efficiency. New National Carbon Offset Standards (NCOS) for precincts and buildings are being developed with the intention to help avoid the release of net emissions in new built environment projects and thus make them carbon neutral.

But what is often overlooked are the embodied emissions of the built environment. These emissions are released when building materials are manufactured, when heavy machinery is used to transport and assemble structural elements, or when clinker is produced at high temperatures in a cement kiln, for example. These emissions are considered to be “embodied” in a building, even before it is used. A carbon liability sticks to every piece of building component: footings, walls, frames, windows, doors, cladding – all of these have an invisible carbon label, a legacy rucksack full of carbon that can be very substantial indeed.

The Discussion Paper on the Review of Climate Change Policies recently published by the federal government ignores indirect emissions of the built environment completely, except for a scant mentioning of electricity usage. It may be that the full extent of embodied emissions is simply not known.

In a recent study we calculated the total carbon footprint of the construction industry in Australia. This included all emissions that occur within one year to enable the delivery of final construction products: commercial buildings, infrastructure and homes.

The analysis used an economy-wide approach, which means that all processes from cradle to grave were included: from the extraction of raw materials (mining of limestone), the manufacturing of building products (in Australia or abroad), transport, assembly, excavations to the demolition of old buildings to make way for new ones. Most embodied emissions come from the use of electricity and materials (Figure 1).

Fig.1. Carbon footprint of Australia’s construction sector in 2013. As the largest contributor, electricity is evidently an area for considerable emission reductions in the built environment, together with materials.

Does it matter?

These “indirect” or “embodied” emissions are not normally counted towards the built environment’s carbon liability. And why should they be? After all, building owners and operators can’t do much about the emissions that have already been released before the building is occupied.

There are several good reasons why embodied emissions in the built environment are important and why they should be considered:

  • they are a very substantial part of the total national emissions budget (numbers)
  • they affect the degree to which operational efficiency strategies are able to provide overall net emissions savings. Making a building zero carbon, under the current definition, might increase its total carbon footprint
  • to better inform the selection and development of design options and technologies such as low-carbon building materials, efficient floor plans, and energy supply systems that assist in achieving zero-carbon buildings
  • to enable smarter policies to be designed that take into account a more holistic view of emissions, ensuring they aren’t just being shifted from one sector to another.

But the most important reason is that all these embodied emissions would not exist if we didn’t build these buildings. They might be “indirect” and hidden from view, but they are directly associated with the built environment. With no building materials there is no building. It is similar for electricity; without a power generator there is no power. It is thus imperative that these embodied emissions are attributed to each and every building project that is ultimately responsible for them.

That last comparison also brings up a real dichotomy in the way we account for carbon: emissions from the use of electricity (and/or heat) are often accounted for, but not the other indirect, embodied emissions. These other indirect emissions are often treated as not inherently related in carbon accounting and offsetting standards. They are often seen as too difficult or not important enough to quantify. It’s almost as if no one dares to venture there or maybe that no one cares. The National Carbon Offset Standard (NCOS) is just one example of this.

However, this couldn’t be further from the truth. These indirect emissions matter, are easy to measure, and pose a potential carbon risk.

Where to from here?

If we, as a nation are going to meet our emissions reduction targets, there is a range of critical issues that must be tackled. To this end, we propose the following necessary actions:

  • Government/authorities: Provide national standards and guidelines on full indirect emissions accounting. In particular, the NCOS standard for buildings, precincts and cities (forthcoming) should be ambitious, clear and mandatory with regards to all emissions. Full emissions accounting could even be made a mandatory requirement in public tenders.
  • Construction industry: Account for and disclose full emissions on every construction project. Produce, support and use low-carbon construction materials (for example, timber or geopolymer concrete).
  • Industry associations: Targeted supply chain initiatives – requires collaboration between material manufacturers, builders, and architects (examples are the Australian Supply Chain Sustainability School and the new UK Green Building Council guidance on measuring and managing the embodied carbon with a focus on supply chains)
  • Research and training institutions: Data generation, collection and sharing, information and knowledge exchange, professional development, training and courses, etcetera.

We need to remove our blinkers so that we can see the complete picture when it comes to the real carbon liability of the built environment. If we continue to ignore embodied emissions it will be impossible to achieve a zero-carbon built environment, despite the appealing rhetoric.

We now have the means to better understand where and how these emissions occur. The question is, do we have the desire to do something about them?

Tags: , ,

Comments

2 Responses to “The “forgotten” greenhouse gas emissions of our built environment will be a hard nut to crack”

  • Tim Keating says:

    One of the largest carbon footprints of any material — perhaps the single largest — is imported tropical hardwoods (there are some exceptions, but in general, they are from logging of old-growth forests). Perhaps the second-largest is aluminium. Eliminating these two materials from buildings would go a long way towards net-zero emissions. Find out more at http://www.rainforestrelief.org and some alternatives at http://www.earthbilt.com.

  • Rick Walters says:

    Readers should be pleased to note that the Infrastructure Sustainability Council of Australia Infrastructure Sustainability rating scheme has always accounted for embodied emissions from its first version. In fact it was the first in Australia to go further and account for all lifecycle environmental impacts through its Materials Calculator based on lifecycle factors. So at least infrastructure is well catered for.

Comments are closed.

Have Your Say
Submit an Article »

More Articles on this Topic