By Associate Professor and PhD Anders Hedegaard Hansen and Associate Professor and PhD Lasse Schmidt, both at AAU Energy
Photo: AAU Communication og Public Affairs

Construction machinery worldwide is renovating and building the cities and road networks of the future.

These machines emit large amounts of CO2 but this is often overlooked.

In 2020, the Danish Parliament adopted the Danish Climate Act. Denmark must reduce greenhouse gas emissions by 70 percent by 2030 compared to 1990 and achieve a climate-neutral society by 2050 at the latest.

It is therefore not a secret that we need to act quickly if we are to reach our goal.

Air transport's high climate footprint is probably the area that most Danes are aware of and want something done about.

Next comes agricultural emissions.

This was highlighted by the Minister for Climate, Energy and Utilities almost exactly two years ago on the ministry's website.

"We have to hit the mark in both the short and the long term, and we know where the difficulty lies. We’ve picked the low-hanging fruit, and the climate program clearly shows that we must reduce emissions in agriculture and transport. […] The task is complicated, and it must be done properly. But we must reach our goal," said Lars Aagaard, Minister for Climate, Energy and Utilities.

The largest low-hanging fruit

In May this year, the construction industry's emissions were also in focus because the government, with the support of a broad political majority, landed an agreement significantly tightening the climate requirements for new construction.

But from the researchers' point of view, the fruit tree hasn’t been shaken thoroughly enough.

There is a large, low-hanging climate culprit that we should pick as soon as possible. This can make a significant difference in the climate accounts.

Few Danes are aware that the large, heavy construction machinery like excavators, cranes, bulldozers, and other transport equipment from the construction industry are such huge climate sinners.

In fact, the large number of construction machines that work every day on construction sites and roadworks all over the world contribute to emitting such large amounts of CO2 that it is equivalent to the combined climate footprint of international aviation.

So, it’s a fruit worth picking.

The lost energy costs the climate accounts

In construction machinery, the hydraulic cylinders, pumps and motors are the muscle.

Research shows that huge amounts of energy are lost due to inefficient hydraulic systems.

The next generation of construction machinery is electric.

Therefore, the ability to do a full day's work on a single battery charge is important, but unfortunately, current hydraulic systems simply waste too much energy for this to be realistic.

As researchers, we want to change that.

Making machines more efficient and climate-friendly is a real possibility.

Unfortunately, research funding doesn’t appear out of nowhere for projects focusing on reducing the emissions of construction machinery.

Perhaps because few people know about the machines' problematic emissions.

We hope to open the public's eyes to the huge potential that lies in finding sustainable solutions to this problem.

We must ensure sustainable processes

More research and more funding are required if we are to achieve a future where buildings are sustainable from cradle to grave and the climate footprint can actually be reduced.

This transition involves not only sustainable materials and efficient use of energy. We must also ensure sustainable processes in the construction itself.

These processes are dependent on construction machinery whose emissions are often overlooked in the assessment of the building's overall climate footprint and sustainability.

A comprehensive study showed that large machines have an average efficiency of only 21 percent, while excavators, for example, which account for half of the total emissions from construction machinery, can have efficiency figures as low as 12 percent.

This means that the energy loss and related emissions of construction machinery correspond to almost 80 percent of the emissions from international aviation.

We therefore see great potential in reducing emissions in the construction processes themselves and the machines that do the work.

Stronger collaboration between research and industry

We hope that the next time decision-makers, foundations, and the industry itself sit down to discuss the sustainable transition, their eyes land on the large construction machines where perhaps the greatest, undiscovered potential for CO2 reductions lies.

Considering the numbers, sizes, and distinctive colours of the machines, they aren’t hard to spot.

The next step is to set the stage for even stronger collaboration between us researchers and the industry so that together we can develop the sustainable construction machines of the future with more energy-efficient hydraulic systems and thus only a minimal climate footprint.

The potential for reducing emissions in construction processes is enormous, and the low-hanging fruit is ready to be picked if the parties involved really want the sustainable transition.