Wood construction as a climate saver

The interview

Jane-Beryl Simmer: Thank you also for recently honoring us with your presence at our handover event, where you presented highly interesting topics that really inspired all of the attendees. And there are still a few questions that remain. You also mentioned that the global average temperature already exceeded the 1.5 degree mark last year. That is also a guard rail. Is there still a way out? Is there still a way back, or what is your view? 

Prof. Joachim Schellnhuber: The 1.5 degrees were part of the Paris Climate Agreement. It was said that 1.5 degrees is just about manageable, especially for small island states that have to fear sea level rise. I was already skeptical at the time that it would be physically possible to keep it below this limit. Now, last year, we actually exceeded it in terms of global average temperature. It is possible that we will have two slightly cooler years again. This is related to the El Niño phenomenon in the eastern Pacific, where the winds sometimes blow in the opposite direction, so to speak. Warm water is then driven towards the coast of Peru, and then there is a La Niña. This is El Niño's cold sister, so to speak. It's an event where a lot of cold water swells up. This then causes temperatures to drop a little, perhaps by 0.1 or 0.2 degrees. It's possible that we'll slip back below 1.5 degrees, but that won't last, of course. In the long term, the majority of the energy from the enhanced greenhouse effect simply goes into the oceans, which act like a hot water tank. And I won't be able to get rid of this temperature, at least not in the short term. The oceans are heating up, and the Mediterranean is warmer than it has ever been. And I won't be able to get rid of these temperatures in the short term, this energy, and that's why we'll have to prepare ourselves for the fact that we'll be well above 1.5 degrees in the next 10 to 20 years. Unfortunately, I believe we'll also exceed the 2-degree mark, and then it will get really dangerous. 

Jane-Beryl Simmer: Thank you for your assessment. In your presentation and information, you also mentioned the forest-construction pump. Could you explain the principle and role of timber construction in this context in a little more detail, but still in a concise manner? 

Forest construction pump graphic

It's about linking forestry, sustainable forestry, with the construction industry, if you like, in a productive way. By burning so many fossil fuels, i.e. coal, oil, gas, we are essentially returning ancient biomass that formed 300 million years ago back into the atmosphere. Because coal seams are nothing more than dead biomass that has been compressed by geological processes and so on. We are now releasing this back into the atmosphere. Now imagine that when so much CO₂ is released back into the atmosphere, photosynthesis can work even better, because photosynthesis was invented by evolution over 3 billion years ago. In my opinion, it's the greatest invention of all time. What does it do? Plants that are capable of photosynthesis, or algae, take CO₂ from the air, take water and sunlight, and use them to form two components that are extremely important for all of us. They are even essential, because sugar is formed from the incredibly complex biomass that life can later live on, and oxygen. All we do is take this sugar. It is produced in agriculture, and we eat it and breathe it in. Breathing is oxygen, and then energy is produced, which we live on and use to move. And this biomass can be formed better and better the higher the temperatures are, the more water there is in the cycle, and the more CO₂ there is in the atmosphere. This means that the climate change we are currently driving forward, where it is getting warmer, where the water cycle is being stimulated, and where there is naturally much more CO₂ in the atmosphere, favors photosynthesis. Photosynthesis is mainly carried out by trees when they grow, i.e. when they produce wood. The idea is that we use this effect and reforest degraded areas so that we have more forests and more biomass on Earth, which we can then use for timber construction in particular. But why do I say “cycle”? Because it should be as closed a cycle as possible. Every tree I cut down is replaced by a new planting, of course, and in the process I can even convert the forest to make it more climate-friendly. We may introduce some Mediterranean trees, such as robinia and so on. And even if they are difficult to work with, as I know from timber farmers, there are many possibilities. This means that we would operate in a cycle, harvesting biomass on a large scale from sustainable forestry, but immediately replacing it with new plantings so that we have highly productive forestry that provides us with the raw materials we need to build with wood. Bamboo can of course do the same in the southern hemisphere, and that is now the second cycle we need. So we use it in construction, and in doing so we have essentially used CO₂ that we have extracted from the atmosphere through photosynthesis and can store this CO₂ in the long term. This means we are cleaning the atmosphere of previous emissions. That's great. But then it's important that I don't build the way they unfortunately still do in the US, where a house is simply burned down after 20, 30, or 40 years and used for thermal energy. Instead, we should build in such a way that this CO₂ is stored in the buildings for at least 100 or 200 years. That doesn't mean that the house always has to remain the same; a beam can be reused, for example. But circular construction doesn't mean using toxic adhesives; it's better to use screws. Your company is a global leader in this field, etc. So I can keep the basic elements of timber construction in the cycle for a long time, reuse them again and again, but at the same time ensure that these elements continue to store CO₂. The idea of two wheels turning, meshing with each other, and gradually, as I operate these wheels, pumping CO₂ out of the atmosphere again. And we have calculated that I have to do this pumping movement at least five times to remove enough CO₂ from the atmosphere to return us to a climate-neutral state, so to speak. 

Jane-Beryl Simmer: Impressive! In your opinion, is there also a graphic or diagram that shows at a glance how essential timber construction is for our climate? 

Prof. Joachim Schellnhuber : Of course, you can take a picture of this pump, which I showed you briefly, but it's very technical. However, it shows how these two flywheels mesh and then combine to form a pump, so to speak. There may be another graphic that I can provide you with.

Graphic 1

We calculated what would happen if the human population were to grow by another 2 billion, mainly in the Global South, mainly in Africa. And we calculated what would happen if we were to house these 2 billion people, essentially with reinforced concrete, plastic, aluminum, and glass, assuming they could afford it, of course, and how much additional CO₂ would be released into the atmosphere as a result. We came to the conclusion that this alone would be 70 billion tons of CO₂. That's an enormous amount. And then we looked at the reverse scenario, and you can make really nice bar charts for that, which I'd be happy to share with you. 

Graphic 2

The reverse scenario means that we now build from wood instead. The stairwells can still be made of concrete, and I assume your screws are made of steel, which doesn't matter at all. you can build hybrid structures, but if the majority of the building is made of wood, then you can show that you are not only avoiding these emissions from reinforced concrete, which is called substitution, meaning that these emissions are eliminated, but in addition, I have stored the same amount of CO₂ through photosynthesis. This means that I am even offsetting previous emissions on the same scale. I heal them, so to speak, and then you get 70 + 70, which is around 140 billion tons of CO₂, which, incidentally, is the budget we still have available worldwide if we want to stay below the 1.5-degree line. That's roughly the order of magnitude. That's just the people who are now being added. These 2 billion people. If they build with wood, whether it's multi-story buildings, flat buildings, whatever, and are housed, then we would avoid an enormous amount of CO₂, so to speak, and even make up for previous climate sins. I think in English they have a nice way of saying “value proposition,” and I can't imagine a better value proposition than that. 

Jane-Beryl Simmer: Impressive. What I would like to know now is what realistic contribution can each of us make to the climate on a daily basis? Is there an idea of how each of us can do this? 

Prof. Joachim Schellnhuber: There is a whole portfolio, of course. I would say that you shouldn't necessarily drive around in an old diesel car, because there has always been debate about that, but if you drive the cars to the end of their life, 20 years in the production of electric cars, greenhouse gases are also emitted and so on. There is a new study that shows that the climate debt is amortized incredibly quickly, so to speak, with electric cars. After 2.5 years. That means that when you produce a conventional car, you don't generate as much CO₂ during manufacturing as you do with an electric car. Because of the battery. But in operation, after two and a half years, you've basically paid back that climate debt. If a car like that runs for 10 years or more, you're definitely in the black. So electric mobility makes sense, no matter what horror stories some people keep telling. The same applies to renewable energy, of course. Photovoltaics will probably be the dominant form of electricity worldwide in 10-20 years. We bought an old house in Italy with friends and converted it completely to geothermal energy, photovoltaics, and electric mobility. There's a wallbox where I'll charge my car. I'm not going to say which electric car it is, but there are so many options available now. But the most important decision, the most important decision an individual can make, and here I come back to you. Once in a lifetime, as the saying goes, you build a house, and that house should be built from organic, renewable raw materials. That's a big decision, because a single-family home weighs about 100 tons, and conventional building materials release 100 tons of CO₂ in the process. If you choose wood construction, and if you have a hybrid construction, we say that about 70% of the material is organic, then you've done the climate a huge favor. But you also live in a house that is more beautiful, healthier, feels good, smells good, and can even be reused. 

Jane-Beryl Simmer: Great, thank you very much, Professor. 

Prof. Joachim Schellnhuber: You're welcome.