Foto: Benny Box

Nature's carrying capacity is a new measure of sustainability

Monday 02 Mar 20
by Morten Andersen


Michael Zwicky Hauschild
Professor, Deputy Head of Division, Head of Section
DTU Management
+45 45 25 46 64

About research at DTU

Research and development of tools for assessing absolute sustainability are carried out at DTU Management in the Quantitative Sustainability Assessment (QSA) group, led by Professor Michael Hauschild.

  • The research is largely based on life cycle assessment (LCA) methods combined with limits for environmental sustainability, such as planetary boundaries.

  • The QSA Group is head of USEtox, the global model for estimating toxicity in a product’s lifecycle from cradle to grave.

  • The group advises the European Commission on the use of relevant sustainability assessment methods.



Absolute sustainability is based on nature’s actual carrying capacity. This makes it easier to distinguish between serious companies and those who strut in borrowed green plumes.


There is no shortage of companies that claim to be sustainable. But even for experts it can be almost impossible to recognize what’s what in the green profile. This has created an interest in the absolute sustainability research field, where nature’s carrying capacity is the definitive yardstick.

The great advantage is that a company working seriously with sustainability is provided with a clear goal for its strategy and initiatives. Today, after all, companies are working towards constantly moving targets. No sooner has a company reduced its energy consumption or the amount of wastewater by so and so many percent before the bar is raised once again. It can be frustrating to never get the feeling of having reached a satisfactory level,” says Professor Michael Hauschild, DTU Management. He is one of the world’s leading researchers within the absolute sustainability field.

The basic idea of the discipline is that nature’s carrying capacity defines a collective safe scope for how much humans can utilize and influence nature without giving rise to unacceptable consequences for the future quality and condition of nature. All of society’s activities are then allocated a share of the safe capacity. All activities should stay within their share to ensure that the sum of activities stays within nature’s carrying capacity. The most vital activities—such as providing food for the population—are allocated a larger capacity in relation to more peripheral activities. Based on this, it becomes possible for companies to assess their own placement in relation to the assigned capacity for the activities they work with.

The bad news is, from a company point of view, that few companies will be able to claim to be sustainable at the present time, as practically no companies are sustainable according to the carrying capacity measure. However, as mentioned, at least the good news is that the distance to the goal is made clear, enabling the companies to start a strategic process for how to achieve the goal,” comments Michael Hauschild.

Washing clothes in the EU

Michael Hauschild’s research group has, in collaboration with the Safety and Environmental Assurance Centre (SEAC), which coordinates work on sustainability in Unilever, developed and tested a new method of assessing absolute sustainability. The method is used to examine the sustainability of detergents and clothes washing.

What is more, not only has the sustainability of the production been examined, but the group has also looked at actual detergent use. Together, EU citizens wash their clothes 34.3 billion times a year. This figure illustrates how much is at stake. If detergent that allows consumers to wash at slightly lower temperatures or with a reduced electricity or water consumption is produced, the effect will be substantial.

In terms of research, it has been beneficial to look at a widespread and common activity and to look at it across a large geographical area, such as the European Union. Especially in relation to the capacity allocation, it would have been more difficult if we were to look more specifically at individual products in individual countries,” explains Assistant Professor Morten Ryberg, lead researcher of the development of the new absolute sustainability assessment method.

The parameters examined were, among other things, energy consumption—and thus the climate impact—contribution to ozone depletion, acidification of the oceans, air pollution, phosphorus and nitrogen emissions, and water consumption. Contribution to deforestation was also examined, as this parameter is a major factor in relation to detergents. This is because palm oil is the dominant raw material in the production of so-called surfactants, which are key ingredients in the type of detergent examined. The cultivation of palm trees contributes significantly to the deforestation of old-growth forests in Asia and South America. If all detergent used in the EU is produced in the same way as the examined type, approximately four per cent of the world’s palm oil would be used for detergent production.

Long way to sustainable detergent

"This is primarily a tool that companies can use to set targets and evaluate how well their work progresses."

According to the study, the current loads for the examined parameters are four to 21 times higher than the allocated capacity. In other words, even in areas where things are going well, reducing the load of the detergent to a fourth of the current level will be necessary.

As this type of assessment is still new and under development, the results have a high degree of uncertainty. Rather than being considered a definitive answer, the results should be considered as indications of the proportions of an activity’s environmental impact in relation to the allocated capacity,” explains Morten Ryberg.

The term ‘absolute’ in the method’s name should be understood in a mathematical sense. In other words, the distinctive characteristic of this method is that you work with absolute values rather than relative targets that aim at, e.g., reducing a given load by a certain percentage.

It’s true that we aim to determine the absolute sustainability of a particular activity. But at the same time, the limits keep changing over time. The population size is of great importance, for instance. Say there was only one billion people on the planet—the capacity allocated the individual activities would be on a much larger scale. With this in mind, the results we get do not have absolute validity. We must assume that the population will continue to increase, and thus the future capacity per person will be reduced,” says Morten Ryberg.

Strategic tool for businesses

In addition, the environmental impact of an activity depends to a large extent on factors beyond each company’s control. In the study, the researchers operate with eight different improvement scenarios. For example, one scenario is that electricity production based on fossil fuels in the EU will be reduced significantly.

If EU countries succeed in converting their electricity generation to renewable energy, thus reducing their climate impact significantly, the sustainability of all activities that use electricity, including washing clothes, will experience a considerable positive impact,” explains Morten Ryberg.

In addition to the uncertainty of society’s future development, the method’s obvious weakness is that there is no universal consensus on the importance of humanity’s activities in relation to each other. So all in all, the research group cannot provide any definitive answers.

This is primarily a tool that companies can use to set targets and evaluate how well their work progresses towards that target. We have yet to see the companies using our results in their marketing strategy,” says Michael Hauschild.

A challenging method

The DTU professor stresses that this is not a sponsored research project:

We have a really good cooperation with SEAC, but there is no money between us and Unilever. Among other things, they’ve provided an amount of production data for detergents which we would’ve had trouble obtaining on our own. In addition, we’ve had constructive discussions with them regarding the choice of methods, including the various scenarios for future development in the EU and the importance the different scenarios will have for the methods’ sustainability.”

Because the method focuses on the maximum load the environment can sustain, it differs from many other tools that companies use to assess whether their production is sustainable, stresses Michael Hauschild:

Other methods typically look at the effectiveness of what the company is already doing. Absolute sustainability will sometimes demonstrate that it is impossible to make the current production method sustainable. In other words, they may have to start over in terms of how the need that their production covers must be met. Expressed in popular terms, you go from ‘doing things right’—helped along by other methods—to ‘doing the right things’.”


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