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People And Nature ☭ Part 5 of Decarbonising the Built Environment: a Global Overview, by Tom Ackers.


Globally, the built environment’s greenhouse gas emissions comprise those from construction, and those from the operational use of buildings (for electricity, heating and cooling, cooking, etc).

By weight, building and infrastructure construction creates by far the largest “stock” of materials, globally.
The Heidelberg cement factory, Germany. Source: 
Heritage calling / Creative Commons

In this part, I look at the historical growth in material stocks (section 5.1); the maintenance and replacement of these stocks (section 5.2); how these stocks have accumulated in different countries (section 5.3); and then the impact of land use on emissions (section 5.4). After that I then turn to the present state of man-made emissions in the built environment (section 5.5). Finally, I outline what I see as the big issues raised by decarbonisation (section 5.6).

5.1. A history of material stocks

Much of the greenhouse gases emitted in the history of the fossil economy is embedded in material stocks of metals, building materials and waste. To quantify the emissions, we need to quantify the scale of these material stocks and the flows that produced them. To do so I will draw on work by a team of researchers mostly based at the Vienna Institute of Social Ecology.

A series of studies shows that, globally, about 1000 billion tonnes (1000 Gt) of physical materials are embedded in buildings and infrastructure. One such study, published in Nature in 2020, was reported with the headline: “Human-made materials now outweigh Earth’s entire biomass”.[1]

There are bound to be discrepancies in such stock calculations, due to different estimates of the baseline weight of pre-industrial construction, the scale of informal settlements, reporting gaps, and so on (see also part 3, footnote 4). But, in terms of the overall scale of stocks, all the studies came to similar conclusions.

The study by Krausmann et al also contained this remarkable Sankey diagram, which shows the estimated global balance of stock accumulation, versus dissipative use and waste, out of materials extracted globally, for the period 1900-2015.

Source: Fridolin Krausmann et al. (2018). NAS = net additions to stocks

The sum of global material extraction just in 2015 (biomass, fossil fuels, metallic and non-metallic minerals) was around 90 Gt, according to estimates in the same article.

China has over the last 20 years played an outsized role in the accumulation of world material stocks and their associated emissions, as outlined in part 4.

By 2015, around 50% of the world’s gross additions to stocks (GAS) (by weight) were taking place in China. You can see this in Fig. 2(b) below: China’s share is coloured green. Data assembled by materialflows.net shows that, in China as well as globally, just under half of extraction by weight consists of construction minerals.

Stock-flow dynamics, 1900-2015. Source: Dominik Wiedenhofer et al (2021)

China’s accumulation of stocks has also been incredibly rapid. Over those last 20 years, Chinese material stocks have grown at least twice as fast as any other comparable region or economic group. Material stocks in China now comprise around 35% of the global total weight of built stocks: this is shown in the graphic, Fig. 2(a).[2]

However, on a per capita basis, China’s total material stocks (as yet) remain below those of most early-industrialising economies. In 2015 China had around 220 tonnes of material stocks per person, against around 300 tonnes/person in Europe, and 450 tonnes/person in North America.[3]

More than half (55%) of that sum of stocks in China is concrete, as shown below in Fig. 2(c). This compares to 41% for the world as a whole. But the proportion is surprisingly at variance with the combined material stocks profile of the USA, Canada, New Zealand and Australia, which is labelled “Ind. New World”. For those countries, more than half (52%) of accumulated stocks are assessed to be from primary (“virgin”) sand and gravel, 16% from concrete, and 16% from asphalt.[4]

Cement and concrete are central to modern construction, as discussed in part 3. At ~41% of global material stocks, concrete is the most plentiful manufactured substance on the planet, and the second most consumed substance on Earth, after water.

Of the 90 Gt total material extraction in 2015, just under half (43 Gt) was used by the global construction industry, according to a report by the UN Environment Programme. And that is just the physical bricks and mortar, before you even consider the industry’s consumption of fossil fuels.

But of that 43 Gt, only around 30 Gt was added to stocks. So about 30% of extraction meant for stock-building goes to waste. Almost all of that is solid and liquid waste. (See the first graphic in this article, above).

That 30 Gt is the net gain to stocks, after demolition. We also need to factor in so-called end-of-life (EOL) building waste streams – where old stocks of buildings and infrastructure, along with their embodied carbon, are literally wasted, junked. These are quantified in the graphs below.

The built environment’s end-of-life stocks.
Source: Dominik Wiedenhofer et al (2021)

These waste flows are dominated by concrete, asphalt, bricks and aggregates (Fig. 5(a), above). Steel is a smaller proportion by weight – and although this high-energy, high-carbon product is readily and widely recycled, when it is in the form of concrete reinforcing bars, the concrete around it gets smashed apart.

Demolished concrete can be crushed and “down-cycled” as construction aggregate, but lots goes to landfill. Asphalt concrete is readily recycled, as the bitumen binder can be reactivated by heating – although usually with a reduction of quality, due to accumulated dirt. Road construction is also a large sink for downcycled materials, especially in roads’ lower layers.

Extraction, processing, use and waste of stock materials.
Source: Barbara Plank et al (2022)

The next diagram above shows the estimated flow of global primary construction materials for 2016, including production waste flows, but excluding end-of-life waste flows.

Almost always, old parts of the built environment are demolished so that something new can be built in their place, bringing in an entirely new round of embodied material and carbon footprints. In 2015, at the world scale, there was around 16 Gt of end-of-life waste. Of that, around 8 Gt of built stocks were trashed in China; around 4.5 Gt were trashed in Europe, Japan and South Korea combined.

Sixteen billion tonnes (16 Gt) is an awful lot of prior construction, sacrificed on the altar of new construction. On top of that 16 Gt of end-of-life waste, 13 Gt of extraction for construction also goes straight to waste.

The amount of waste is alarming – though presumably some degree of material waste is inevitable in the production of material stocks.

In addition to the waste, the rate of stock building, and both the absolute and relative scale of construction, are staggering: the 30 Gt of new built stocks added each year is a whole 3-4% of the entire ready-existing stock of buildings and infrastructure.

That is: a fresh 3-4%, annually, of existing stocks, are commissioned and deposited into the built environment. This is simply in order to construct whatever new buildings and infrastructure get made every year. Simply to keep the existing form of economic growth and development on the road.

Out of the 30 Gt of annual stock additions, about 4 Gt is CO2-intensive cement. About 0.6 Gt of the 30 Gt is steel, plus smaller quantities of other metals such as aluminium and copper, for which the extraction processes are intensely polluting and the manufacturing processes hugely energy-intensive.

Regional, country, annual statistics of cement consumption in the twentieth century are also instructive (Fig. 2, below).

Cement consumption: China and the world.
Source: Zhi Cao et al (2017)

In these indices, you can see some clear disparities of stock accumulation internationally – a tangible physical record of the history told in part 3. You can see the “rise of concrete” after the second world war.

Again, China’s annual absolute consumption of cement after the 1990s is an order of magnitude greater than all other regions – scaled separately on the right-hand side of the graph.

5.2 Maintenance and replacement

We can also compare the per capita per year laydown of material stocks, versus “maintenance and replacement” flows – see Fig.3, below. The black graph lines (scaled on the right-hand axes) give the per capita cumulative stock levels for each region.

Expansion, versus maintenance and replacement.
Source: Dominik Wiedenhofer et al (2021) (see footnote no. 4 for region definitions)

The peaks of the black graph lines in Fig. 3 also give an apparent window into the different “stock saturation” points for different countries and regions – the points at which the rates of increase of total stocks in the built environment have plateaued or declined.

“Stock saturation” can speak to many different varieties of stock-flow relations, and many different levels of stock-flow efficiency, with regard to human needs and the delivery of services.

For example, the US has a very high level of “stock saturation”: per capita, the weight of material stocks is very high.

Meanwhile, the stocks that exist in the US – notably, roads – require very high levels of annual maintenance and replacement. As such, the built environment in the US has very poor stock-flow efficiency.

I have mentioned already how, in the US, road maintenance has proven to be fiscally bankrupting to states and cities, in the absence of federal assistance. The US is notorious for the degraded state of its infrastructure more broadly.

And yet, looking at the blue graphs in Fig. 3, annual “maintenance and replacement” flows are distressingly high throughout the “developed” world.

The world would benefit from stocks that require far less maintenance and replacement – and from services provided on a more efficient material basis. That is, the world would benefit from much better “stock-flow service efficiencies”.

5.3 An unequal distribution of the built environment

And look at the distribution of the built environment. For example, sub-Saharan Africa has a miniscule per capita level of built stocks, and a tiny level of maintenance and replacement flows, compared to the rich countries.

Today, just as we find the world economy drastically ill-formed, we also find the built environment dramatically mis-shapen: quantitatively mal-distributed, and qualitatively distorted, with respect to social and environmental needs.

Construction is over-accumulated where it is not needed. Developments threaten to “lock in” tremendous inefficiencies in operational usage and maintenance flows associated with those built stocks.[5]

Alongside those sorts of over-accumulation, we find the under-accumulation of suitable construction where it is needed. And yet still, what does get built, in such circumstances of “underdevelopment”, is invariably tailored by boosterish ideologies – not toward the provision of essential services and needs, but toward the highly questionable, and environmentally calamitous, economic lever of expanded material throughput.

For despite claims to the contrary, by the UN amongst others, world poverty – by any reasonable measure – has continued to increase alongside the boom in world output after 2000. Using ActionAid’s measure, that anyone with income under $10 a day is in poverty, that now includes two-thirds of the world’s population (or 84% of people in low and middle income countries).

The material and social links are key: between stocks, flows, the provision of “services” and human wellbeing.

5.4 Emissions and land-use change

Before turning to the details of the embodied and operational emissions of the built environment, we need to consider the built environment’s role in land-use change, and the loss of carbon sinks due to processes such as deforestation.

In 1850, effective emissions from the loss of land-based carbon sinks were around 2.54 billion tonnes of CO2, against around 197 million tonnes of CO2 from burning fossil fuels. Effective annual emissions from land-use change have been surprisingly steady worldwide ever since, and through the post-war period: in fact they peaked around 1960 and since 2000 have been lower than they were in 1950. (See section 3.2 above.)

According to the Global Carbon Project, land-use change since the advent of fossil capitalism is responsible for about a quarter of all sociogenic carbon emissions, through the loss of land-based carbon sinks.

However, in contrast to the 1850 baseline, only an estimated 60% of those land-use changes are direct – that is, deliberately caused by humans. The most significant of these are the clearance of tropical forests for agriculture. The remaining roughly 40% comes from indirect drivers such as climate change.

The point is that while some of the net loss of forest cover in recent years is due to urban sprawl and resource extraction – for example in eastern China – “at the global scale, the growth of urban areas accounts for a small fraction of all land changes”, as a US-based research team showed recently.

It seems fair to infer that rural and other non-urban elements of the built environment, such as roads and infrastructure, will still have a meaningful effect on land-use CO2 flux – but these effects still appear to be much smaller than the effects of agricultural expansion and climate change.

5.5 Built environment emissions

Globally, then, the built environment’s greenhouse gas emissions are almost entirely captured by the embodied carbon of the flow of building materials into building stocks; and the operational carbon flows of building and infrastructure use. In this section, I will use the available data to quantify these as accurately as possible.

The International Energy Agency (IEA) makes comprehensive calculations of the built environment’s global emissions footprints, the best that I know of. Most other analyses defer to the IEA, look only at buildings or at particular materials, or only at material use and not at emissions. The UN Environment Programme (UNEP) partners with the IEA for its work on the built environment, and they jointly publish reports as the Global Alliance for Buildings and Construction (GlobalABC).

The IEA’s built environment analysis focuses mostly on energy. It is based on energy-related CO2 emissions, and does not include non-CO2 emissions. The global picture is set out in the panel below.

⏺ Graph (a) below shows the most up-to-date estimate of total global greenhouse gas emissions for 2018 (in blue), and its various components.

⏺ Graph (b) shows some important components of that total. This includes the GlobalABC’s estimate for the total CO2 energy-related emissions from the built environment in 2018 (in orange).

⏺ Graph (c) gives a breakdown of that GlobalABC data, to show where the different components of those energy-related built environment emissions come from, for 2018. To that I have also added estimates for four other categories of emissions: the CO2 “process” emissions from cement and steel manufacture; the methane emissions associated with the operational use of buildings, globally; and a recent estimate for the non-renewable CO2 wood combustion emissions associated with household cooking.

CO2 wood combustion emissions are a component of the category “land-use, land-use change and forestry” (LULUCF). They are not included in the IEA’s “energy-related CO2 emissions” data.

Note that the operational emissions shown are only for buildings, while the embodied emissions come from the construction of both buildings and infrastructure.

For more detail on the graphs, and how these emissions totals are worked out, see Appendix 3, in the PDF version.

Sources: * Global Carbon Project / Jan C. Minx et al (2021) (EDGAR dataset); ** IEA, Global Energy & CO2 Status Report 2019; § IEA / UNEP (2019), IEA / UNEP (2021); △ Robbie M. Andrew (2019); O Global Carbon Project (2020) Supplemental data; §§ Global Carbon Project / Jan C. Minx et al (2021), IEA (2020a), IEA (2020b), IEA (2020c), IEA (2021a), IEA (2021b), IEA (2022); §§§ Alessandro Flammini et al (2023); §§§§ IEA (2020) (note: this is the 2019 figure – see Part 7) Note: based on global warming potentials with a 100-year time horizon from the IPCC Fifth Assessment Report (AR5).

The main takeaway from this chart is that the annual embodied and operational CO2 carbon footprints of the global built environment are of comparable magnitudes. Embodied CO2 emissions are about 8.4 Gt CO2; operational emissions are about 11 Gt CO2.

And the rough picture of built environment emissions as a share of the total is: out of 58 Gt CO2e of sociogenic emissions in 2018, the construction, maintenance and inhabitation of the built environment globally was responsible for about 17.5 Gt CO2e in energy-related emissions, and about 1.8 Gt of process-based CO2 emissions from concrete and steel combined.

And to be clear: this picture is a snapshot from 2018. We are looking here at the components of built environment emissions, and their proportions.

The crucial historical fact is the continual drive upwards, globally, of the absolute level of global emissions. That is what needs to be reversed, as a matter of urgency.

5.6 Decarbonising the global built environment

This graph, from an International Energy Agency (IEA) report, represents the proposed decarbonisation of buildings and construction, over the next half century (considering only CO2, but not other greenhouse gases).

Source: IEA (2020)

This graph, like all of the IEA’s recent work on decarbonisation, reflects the agency’s Sustainable Development Scenario, which aims to integrate the Paris Climate Accords with the UN’s Sustainable Development Agenda. This includes a technological and policy agenda for reaching “net zero” by 2070, plus the aim of universal access to modern energy by 2030.

So we are talking about the emissions from construction, and the operational carbon of buildings use. There are also the operational emissions of various services provided by infrastructure. Operational emissions involve the energy sector; construction emissions involve large-scale industry, and again, in turn, the energy sector.

There are differences between the issues facing the older, richer, economically dominant countries and others.

Most built stocks, including buildings, exist in the countries that are most “developed” on the model of the fossil economy – mostly the older, richer economies, plus the rapidly developing “emerging markets”.

Meanwhile, the areas now being integrated into the world economy have lots of new construction. Other, “underdeveloped” countries and regions have the eye of capital on them, and are desired locations for future construction.

Poorer regions are also often in tremendous need of new infrastructure and housing – an agenda often rhetorically collapsed into capital accumulation and/or the project of economic enlargement, although these projects are really distinct.

These “developing” and poorer countries are likely to be, and in most cases need to be, the location for most new construction. Their futures therefore contain the largest share of “mitigation potential” when it comes to embodied carbon.

On the other hand, the highest immediate mitigation potential for operational carbon is in the rich countries, with their vast accumulated stocks of buildings and infrastructure.

It is in the interests of the world’s poor, especially, to mitigate the carbon load, and the operational costs, of using buildings, alongside decarbonising energy systems – especially now, as fossil fuel prices rise. That applies all the more to populous countries, and those experiencing the most rapid growth in population – many of which are poor.

Out of all buildings-related emissions worldwide, operational emissions presently comprise around 75%, with embodied emissions at around 25%.[6] This means that, while the greatest immediate operational emissions mitigation potential is with rich countries, it is the populous countries, with the fastest-growing populations, where the greatest long-term mitigation potentials exist: for embodied emissions and for operational emissions.

And the “long term” starts now – especially where countries already face enormous deficits in the provision of housing and other services.

As the Intergovernmental Panel on Climate Change (IPCC) Working Group III on mitigation stresses, in respect of both operational and embodied emissions, “the 2020-2030 decade is critical”.

To date, around two-thirds of countries have included operational building energy codes as part of their Nationally Determined Contributions (NDCs) under the Paris Agreement net-zero pledges. But the UN Environment Programme (UNEP) notes that building materials, and therefore embodied emissions, are insufficiently addressed, and the legal extent of commitments is patchy. (This on top of the blatant and deliberate inadequacy of net-zero in providing a sufficiently rapid path to zero emissions.)

UNEP in 2021 highlighted Viet Nam for having an NDC Roadmap, “that lays out a low-carbon, climate-resilient buildings and construction sector”. Papua New Guinea has “extensive detail” about buildings in its most recent NDC.

The NDCs of Colombia, the EU, Lebanon, Maldives, Montenegro, Panama and Vanuatu also “mention efforts to either improve energy efficiency in buildings or reduce building-related emissions.” The 2018 Caribbean Regional Energy Efficiency Building Code (CREEBC) – a measure to address operational carbon – is being implemented now.

However, a large proportion of future construction is forecast to take place in countries without the protections of mandatory environmental building codes or buildings-related NDC commitments. This is a significant problem with meeting the Paris goals.

For example, the most recent NDCs of the USA, India, Nigeria and Bangladesh, all have some mention of buildings’ energy efficiency, but little about broader adaptive measures. The USA explicitly removed previous commitments during the 2017-21 Trump era; so did Canada.

In the following parts of this series, I will look more specifically at the embodied and operational emissions of the built environment – and what removing the emissions from each could or should look like.

🔥 Go to part 6

🔥 Go to Contents and Introduction

Download the whole series as a PDF here

[1] The study in Nature, by Emily Elhacham et al, used a figure of 1100 billion tonnes (Gt). Another study (Fridolin Krausmann et al., 2018) estimated that there were around 925 Gt of physical material stocks worldwide in 2015. A third study (Dominik Wiedenhofer et al, 2021), found total material stocks, across nine world regions, of 1050 Gt as of 2015. The vast majority were building materials: aggregates for building and road foundations were 49% of total stocks (~514.5 Gt); concrete about 28% (~294 Gt); and asphalt concrete (ie, bitumen-based road asphalt / tarmac) 11% (~115.5 Gt). All metals, including iron and steel, comprised ~4% of total stocks (~42 Gt) – smaller than the others by weight, yet they provide a “functionally crucial role” across manufacturing industry and in the built environment.

[2] Non-industrialised and pre-industrial stock construction is under-reported, as mentioned above and in part 3. Nevertheless, they are massively outweighed by newer and industrial stocks

[3] See research by Dominik Wiedenhofer et al (2021)

[4] In the next two graphs, “Industrial Old World” = most of Europe, plus Japan and South Korea; “Industrial New World” = “the affluent Anglo-American colonial settler societies USA, Canada, New Zealand and Australia with relatively low population densities”

[5] An example of both these tendencies is that UK material stocks continue to expand by ~1% per year (in 2016, about 374.1 Mt). Gross annual additions to asphalt stocks are typically about 10-12% of this. In 2016 they were ~40.2 Mt; but of this, only ~21.4 Mt were for new roadway additions. The rest went on repair and maintenance to existing stocks, replacing surfaces lost to wear and tear. The UK, with 0.85% of the world’s population, accounted for about 1.9% of the world’s asphalt concrete consumption (see Barbara Plank et al, 2022).

[6] See Appendix 3, Step 3, in the PDF version, for more details.

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Quantifying Material Use, Emissions, And The Scale Of Decarbonisation

People And Nature ☭ Part 5 of Decarbonising the Built Environment: a Global Overview, by Tom Ackers.


Globally, the built environment’s greenhouse gas emissions comprise those from construction, and those from the operational use of buildings (for electricity, heating and cooling, cooking, etc).

By weight, building and infrastructure construction creates by far the largest “stock” of materials, globally.
The Heidelberg cement factory, Germany. Source: 
Heritage calling / Creative Commons

In this part, I look at the historical growth in material stocks (section 5.1); the maintenance and replacement of these stocks (section 5.2); how these stocks have accumulated in different countries (section 5.3); and then the impact of land use on emissions (section 5.4). After that I then turn to the present state of man-made emissions in the built environment (section 5.5). Finally, I outline what I see as the big issues raised by decarbonisation (section 5.6).

5.1. A history of material stocks

Much of the greenhouse gases emitted in the history of the fossil economy is embedded in material stocks of metals, building materials and waste. To quantify the emissions, we need to quantify the scale of these material stocks and the flows that produced them. To do so I will draw on work by a team of researchers mostly based at the Vienna Institute of Social Ecology.

A series of studies shows that, globally, about 1000 billion tonnes (1000 Gt) of physical materials are embedded in buildings and infrastructure. One such study, published in Nature in 2020, was reported with the headline: “Human-made materials now outweigh Earth’s entire biomass”.[1]

There are bound to be discrepancies in such stock calculations, due to different estimates of the baseline weight of pre-industrial construction, the scale of informal settlements, reporting gaps, and so on (see also part 3, footnote 4). But, in terms of the overall scale of stocks, all the studies came to similar conclusions.

The study by Krausmann et al also contained this remarkable Sankey diagram, which shows the estimated global balance of stock accumulation, versus dissipative use and waste, out of materials extracted globally, for the period 1900-2015.

Source: Fridolin Krausmann et al. (2018). NAS = net additions to stocks

The sum of global material extraction just in 2015 (biomass, fossil fuels, metallic and non-metallic minerals) was around 90 Gt, according to estimates in the same article.

China has over the last 20 years played an outsized role in the accumulation of world material stocks and their associated emissions, as outlined in part 4.

By 2015, around 50% of the world’s gross additions to stocks (GAS) (by weight) were taking place in China. You can see this in Fig. 2(b) below: China’s share is coloured green. Data assembled by materialflows.net shows that, in China as well as globally, just under half of extraction by weight consists of construction minerals.

Stock-flow dynamics, 1900-2015. Source: Dominik Wiedenhofer et al (2021)

China’s accumulation of stocks has also been incredibly rapid. Over those last 20 years, Chinese material stocks have grown at least twice as fast as any other comparable region or economic group. Material stocks in China now comprise around 35% of the global total weight of built stocks: this is shown in the graphic, Fig. 2(a).[2]

However, on a per capita basis, China’s total material stocks (as yet) remain below those of most early-industrialising economies. In 2015 China had around 220 tonnes of material stocks per person, against around 300 tonnes/person in Europe, and 450 tonnes/person in North America.[3]

More than half (55%) of that sum of stocks in China is concrete, as shown below in Fig. 2(c). This compares to 41% for the world as a whole. But the proportion is surprisingly at variance with the combined material stocks profile of the USA, Canada, New Zealand and Australia, which is labelled “Ind. New World”. For those countries, more than half (52%) of accumulated stocks are assessed to be from primary (“virgin”) sand and gravel, 16% from concrete, and 16% from asphalt.[4]

Cement and concrete are central to modern construction, as discussed in part 3. At ~41% of global material stocks, concrete is the most plentiful manufactured substance on the planet, and the second most consumed substance on Earth, after water.

Of the 90 Gt total material extraction in 2015, just under half (43 Gt) was used by the global construction industry, according to a report by the UN Environment Programme. And that is just the physical bricks and mortar, before you even consider the industry’s consumption of fossil fuels.

But of that 43 Gt, only around 30 Gt was added to stocks. So about 30% of extraction meant for stock-building goes to waste. Almost all of that is solid and liquid waste. (See the first graphic in this article, above).

That 30 Gt is the net gain to stocks, after demolition. We also need to factor in so-called end-of-life (EOL) building waste streams – where old stocks of buildings and infrastructure, along with their embodied carbon, are literally wasted, junked. These are quantified in the graphs below.

The built environment’s end-of-life stocks.
Source: Dominik Wiedenhofer et al (2021)

These waste flows are dominated by concrete, asphalt, bricks and aggregates (Fig. 5(a), above). Steel is a smaller proportion by weight – and although this high-energy, high-carbon product is readily and widely recycled, when it is in the form of concrete reinforcing bars, the concrete around it gets smashed apart.

Demolished concrete can be crushed and “down-cycled” as construction aggregate, but lots goes to landfill. Asphalt concrete is readily recycled, as the bitumen binder can be reactivated by heating – although usually with a reduction of quality, due to accumulated dirt. Road construction is also a large sink for downcycled materials, especially in roads’ lower layers.

Extraction, processing, use and waste of stock materials.
Source: Barbara Plank et al (2022)

The next diagram above shows the estimated flow of global primary construction materials for 2016, including production waste flows, but excluding end-of-life waste flows.

Almost always, old parts of the built environment are demolished so that something new can be built in their place, bringing in an entirely new round of embodied material and carbon footprints. In 2015, at the world scale, there was around 16 Gt of end-of-life waste. Of that, around 8 Gt of built stocks were trashed in China; around 4.5 Gt were trashed in Europe, Japan and South Korea combined.

Sixteen billion tonnes (16 Gt) is an awful lot of prior construction, sacrificed on the altar of new construction. On top of that 16 Gt of end-of-life waste, 13 Gt of extraction for construction also goes straight to waste.

The amount of waste is alarming – though presumably some degree of material waste is inevitable in the production of material stocks.

In addition to the waste, the rate of stock building, and both the absolute and relative scale of construction, are staggering: the 30 Gt of new built stocks added each year is a whole 3-4% of the entire ready-existing stock of buildings and infrastructure.

That is: a fresh 3-4%, annually, of existing stocks, are commissioned and deposited into the built environment. This is simply in order to construct whatever new buildings and infrastructure get made every year. Simply to keep the existing form of economic growth and development on the road.

Out of the 30 Gt of annual stock additions, about 4 Gt is CO2-intensive cement. About 0.6 Gt of the 30 Gt is steel, plus smaller quantities of other metals such as aluminium and copper, for which the extraction processes are intensely polluting and the manufacturing processes hugely energy-intensive.

Regional, country, annual statistics of cement consumption in the twentieth century are also instructive (Fig. 2, below).

Cement consumption: China and the world.
Source: Zhi Cao et al (2017)

In these indices, you can see some clear disparities of stock accumulation internationally – a tangible physical record of the history told in part 3. You can see the “rise of concrete” after the second world war.

Again, China’s annual absolute consumption of cement after the 1990s is an order of magnitude greater than all other regions – scaled separately on the right-hand side of the graph.

5.2 Maintenance and replacement

We can also compare the per capita per year laydown of material stocks, versus “maintenance and replacement” flows – see Fig.3, below. The black graph lines (scaled on the right-hand axes) give the per capita cumulative stock levels for each region.

Expansion, versus maintenance and replacement.
Source: Dominik Wiedenhofer et al (2021) (see footnote no. 4 for region definitions)

The peaks of the black graph lines in Fig. 3 also give an apparent window into the different “stock saturation” points for different countries and regions – the points at which the rates of increase of total stocks in the built environment have plateaued or declined.

“Stock saturation” can speak to many different varieties of stock-flow relations, and many different levels of stock-flow efficiency, with regard to human needs and the delivery of services.

For example, the US has a very high level of “stock saturation”: per capita, the weight of material stocks is very high.

Meanwhile, the stocks that exist in the US – notably, roads – require very high levels of annual maintenance and replacement. As such, the built environment in the US has very poor stock-flow efficiency.

I have mentioned already how, in the US, road maintenance has proven to be fiscally bankrupting to states and cities, in the absence of federal assistance. The US is notorious for the degraded state of its infrastructure more broadly.

And yet, looking at the blue graphs in Fig. 3, annual “maintenance and replacement” flows are distressingly high throughout the “developed” world.

The world would benefit from stocks that require far less maintenance and replacement – and from services provided on a more efficient material basis. That is, the world would benefit from much better “stock-flow service efficiencies”.

5.3 An unequal distribution of the built environment

And look at the distribution of the built environment. For example, sub-Saharan Africa has a miniscule per capita level of built stocks, and a tiny level of maintenance and replacement flows, compared to the rich countries.

Today, just as we find the world economy drastically ill-formed, we also find the built environment dramatically mis-shapen: quantitatively mal-distributed, and qualitatively distorted, with respect to social and environmental needs.

Construction is over-accumulated where it is not needed. Developments threaten to “lock in” tremendous inefficiencies in operational usage and maintenance flows associated with those built stocks.[5]

Alongside those sorts of over-accumulation, we find the under-accumulation of suitable construction where it is needed. And yet still, what does get built, in such circumstances of “underdevelopment”, is invariably tailored by boosterish ideologies – not toward the provision of essential services and needs, but toward the highly questionable, and environmentally calamitous, economic lever of expanded material throughput.

For despite claims to the contrary, by the UN amongst others, world poverty – by any reasonable measure – has continued to increase alongside the boom in world output after 2000. Using ActionAid’s measure, that anyone with income under $10 a day is in poverty, that now includes two-thirds of the world’s population (or 84% of people in low and middle income countries).

The material and social links are key: between stocks, flows, the provision of “services” and human wellbeing.

5.4 Emissions and land-use change

Before turning to the details of the embodied and operational emissions of the built environment, we need to consider the built environment’s role in land-use change, and the loss of carbon sinks due to processes such as deforestation.

In 1850, effective emissions from the loss of land-based carbon sinks were around 2.54 billion tonnes of CO2, against around 197 million tonnes of CO2 from burning fossil fuels. Effective annual emissions from land-use change have been surprisingly steady worldwide ever since, and through the post-war period: in fact they peaked around 1960 and since 2000 have been lower than they were in 1950. (See section 3.2 above.)

According to the Global Carbon Project, land-use change since the advent of fossil capitalism is responsible for about a quarter of all sociogenic carbon emissions, through the loss of land-based carbon sinks.

However, in contrast to the 1850 baseline, only an estimated 60% of those land-use changes are direct – that is, deliberately caused by humans. The most significant of these are the clearance of tropical forests for agriculture. The remaining roughly 40% comes from indirect drivers such as climate change.

The point is that while some of the net loss of forest cover in recent years is due to urban sprawl and resource extraction – for example in eastern China – “at the global scale, the growth of urban areas accounts for a small fraction of all land changes”, as a US-based research team showed recently.

It seems fair to infer that rural and other non-urban elements of the built environment, such as roads and infrastructure, will still have a meaningful effect on land-use CO2 flux – but these effects still appear to be much smaller than the effects of agricultural expansion and climate change.

5.5 Built environment emissions

Globally, then, the built environment’s greenhouse gas emissions are almost entirely captured by the embodied carbon of the flow of building materials into building stocks; and the operational carbon flows of building and infrastructure use. In this section, I will use the available data to quantify these as accurately as possible.

The International Energy Agency (IEA) makes comprehensive calculations of the built environment’s global emissions footprints, the best that I know of. Most other analyses defer to the IEA, look only at buildings or at particular materials, or only at material use and not at emissions. The UN Environment Programme (UNEP) partners with the IEA for its work on the built environment, and they jointly publish reports as the Global Alliance for Buildings and Construction (GlobalABC).

The IEA’s built environment analysis focuses mostly on energy. It is based on energy-related CO2 emissions, and does not include non-CO2 emissions. The global picture is set out in the panel below.

⏺ Graph (a) below shows the most up-to-date estimate of total global greenhouse gas emissions for 2018 (in blue), and its various components.

⏺ Graph (b) shows some important components of that total. This includes the GlobalABC’s estimate for the total CO2 energy-related emissions from the built environment in 2018 (in orange).

⏺ Graph (c) gives a breakdown of that GlobalABC data, to show where the different components of those energy-related built environment emissions come from, for 2018. To that I have also added estimates for four other categories of emissions: the CO2 “process” emissions from cement and steel manufacture; the methane emissions associated with the operational use of buildings, globally; and a recent estimate for the non-renewable CO2 wood combustion emissions associated with household cooking.

CO2 wood combustion emissions are a component of the category “land-use, land-use change and forestry” (LULUCF). They are not included in the IEA’s “energy-related CO2 emissions” data.

Note that the operational emissions shown are only for buildings, while the embodied emissions come from the construction of both buildings and infrastructure.

For more detail on the graphs, and how these emissions totals are worked out, see Appendix 3, in the PDF version.

Sources: * Global Carbon Project / Jan C. Minx et al (2021) (EDGAR dataset); ** IEA, Global Energy & CO2 Status Report 2019; § IEA / UNEP (2019), IEA / UNEP (2021); △ Robbie M. Andrew (2019); O Global Carbon Project (2020) Supplemental data; §§ Global Carbon Project / Jan C. Minx et al (2021), IEA (2020a), IEA (2020b), IEA (2020c), IEA (2021a), IEA (2021b), IEA (2022); §§§ Alessandro Flammini et al (2023); §§§§ IEA (2020) (note: this is the 2019 figure – see Part 7) Note: based on global warming potentials with a 100-year time horizon from the IPCC Fifth Assessment Report (AR5).

The main takeaway from this chart is that the annual embodied and operational CO2 carbon footprints of the global built environment are of comparable magnitudes. Embodied CO2 emissions are about 8.4 Gt CO2; operational emissions are about 11 Gt CO2.

And the rough picture of built environment emissions as a share of the total is: out of 58 Gt CO2e of sociogenic emissions in 2018, the construction, maintenance and inhabitation of the built environment globally was responsible for about 17.5 Gt CO2e in energy-related emissions, and about 1.8 Gt of process-based CO2 emissions from concrete and steel combined.

And to be clear: this picture is a snapshot from 2018. We are looking here at the components of built environment emissions, and their proportions.

The crucial historical fact is the continual drive upwards, globally, of the absolute level of global emissions. That is what needs to be reversed, as a matter of urgency.

5.6 Decarbonising the global built environment

This graph, from an International Energy Agency (IEA) report, represents the proposed decarbonisation of buildings and construction, over the next half century (considering only CO2, but not other greenhouse gases).

Source: IEA (2020)

This graph, like all of the IEA’s recent work on decarbonisation, reflects the agency’s Sustainable Development Scenario, which aims to integrate the Paris Climate Accords with the UN’s Sustainable Development Agenda. This includes a technological and policy agenda for reaching “net zero” by 2070, plus the aim of universal access to modern energy by 2030.

So we are talking about the emissions from construction, and the operational carbon of buildings use. There are also the operational emissions of various services provided by infrastructure. Operational emissions involve the energy sector; construction emissions involve large-scale industry, and again, in turn, the energy sector.

There are differences between the issues facing the older, richer, economically dominant countries and others.

Most built stocks, including buildings, exist in the countries that are most “developed” on the model of the fossil economy – mostly the older, richer economies, plus the rapidly developing “emerging markets”.

Meanwhile, the areas now being integrated into the world economy have lots of new construction. Other, “underdeveloped” countries and regions have the eye of capital on them, and are desired locations for future construction.

Poorer regions are also often in tremendous need of new infrastructure and housing – an agenda often rhetorically collapsed into capital accumulation and/or the project of economic enlargement, although these projects are really distinct.

These “developing” and poorer countries are likely to be, and in most cases need to be, the location for most new construction. Their futures therefore contain the largest share of “mitigation potential” when it comes to embodied carbon.

On the other hand, the highest immediate mitigation potential for operational carbon is in the rich countries, with their vast accumulated stocks of buildings and infrastructure.

It is in the interests of the world’s poor, especially, to mitigate the carbon load, and the operational costs, of using buildings, alongside decarbonising energy systems – especially now, as fossil fuel prices rise. That applies all the more to populous countries, and those experiencing the most rapid growth in population – many of which are poor.

Out of all buildings-related emissions worldwide, operational emissions presently comprise around 75%, with embodied emissions at around 25%.[6] This means that, while the greatest immediate operational emissions mitigation potential is with rich countries, it is the populous countries, with the fastest-growing populations, where the greatest long-term mitigation potentials exist: for embodied emissions and for operational emissions.

And the “long term” starts now – especially where countries already face enormous deficits in the provision of housing and other services.

As the Intergovernmental Panel on Climate Change (IPCC) Working Group III on mitigation stresses, in respect of both operational and embodied emissions, “the 2020-2030 decade is critical”.

To date, around two-thirds of countries have included operational building energy codes as part of their Nationally Determined Contributions (NDCs) under the Paris Agreement net-zero pledges. But the UN Environment Programme (UNEP) notes that building materials, and therefore embodied emissions, are insufficiently addressed, and the legal extent of commitments is patchy. (This on top of the blatant and deliberate inadequacy of net-zero in providing a sufficiently rapid path to zero emissions.)

UNEP in 2021 highlighted Viet Nam for having an NDC Roadmap, “that lays out a low-carbon, climate-resilient buildings and construction sector”. Papua New Guinea has “extensive detail” about buildings in its most recent NDC.

The NDCs of Colombia, the EU, Lebanon, Maldives, Montenegro, Panama and Vanuatu also “mention efforts to either improve energy efficiency in buildings or reduce building-related emissions.” The 2018 Caribbean Regional Energy Efficiency Building Code (CREEBC) – a measure to address operational carbon – is being implemented now.

However, a large proportion of future construction is forecast to take place in countries without the protections of mandatory environmental building codes or buildings-related NDC commitments. This is a significant problem with meeting the Paris goals.

For example, the most recent NDCs of the USA, India, Nigeria and Bangladesh, all have some mention of buildings’ energy efficiency, but little about broader adaptive measures. The USA explicitly removed previous commitments during the 2017-21 Trump era; so did Canada.

In the following parts of this series, I will look more specifically at the embodied and operational emissions of the built environment – and what removing the emissions from each could or should look like.

🔥 Go to part 6

🔥 Go to Contents and Introduction

Download the whole series as a PDF here

[1] The study in Nature, by Emily Elhacham et al, used a figure of 1100 billion tonnes (Gt). Another study (Fridolin Krausmann et al., 2018) estimated that there were around 925 Gt of physical material stocks worldwide in 2015. A third study (Dominik Wiedenhofer et al, 2021), found total material stocks, across nine world regions, of 1050 Gt as of 2015. The vast majority were building materials: aggregates for building and road foundations were 49% of total stocks (~514.5 Gt); concrete about 28% (~294 Gt); and asphalt concrete (ie, bitumen-based road asphalt / tarmac) 11% (~115.5 Gt). All metals, including iron and steel, comprised ~4% of total stocks (~42 Gt) – smaller than the others by weight, yet they provide a “functionally crucial role” across manufacturing industry and in the built environment.

[2] Non-industrialised and pre-industrial stock construction is under-reported, as mentioned above and in part 3. Nevertheless, they are massively outweighed by newer and industrial stocks

[3] See research by Dominik Wiedenhofer et al (2021)

[4] In the next two graphs, “Industrial Old World” = most of Europe, plus Japan and South Korea; “Industrial New World” = “the affluent Anglo-American colonial settler societies USA, Canada, New Zealand and Australia with relatively low population densities”

[5] An example of both these tendencies is that UK material stocks continue to expand by ~1% per year (in 2016, about 374.1 Mt). Gross annual additions to asphalt stocks are typically about 10-12% of this. In 2016 they were ~40.2 Mt; but of this, only ~21.4 Mt were for new roadway additions. The rest went on repair and maintenance to existing stocks, replacing surfaces lost to wear and tear. The UK, with 0.85% of the world’s population, accounted for about 1.9% of the world’s asphalt concrete consumption (see Barbara Plank et al, 2022).

[6] See Appendix 3, Step 3, in the PDF version, for more details.

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Climate change Decarbonisation People And Nature Tom Ackers

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