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CO₂ Could Become a Useful Raw Material

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The use of fossil fuels is the main cause of climate change since their burning releases carbon dioxide (CO₂), the most important greenhouse gas. It may be necessary to extract massive amounts of CO₂ from the atmosphere to combat climate change. Fortunately, we won’t have to store the gas, because it could be put to better use in the future.

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KLAUS Æ. MOGENSEN

Senior Futurist, Editor

Posted Apr 14, 2020 in Environment & Resources Article from Scenario 06:2019

One of the great climate sins is the release of
CO₂ in the atmosphere. CO₂ isn’t the only greenhouse gas nor the most effective – for example, methane is many times worse – but the massive release of CO₂ from burning fossil fuels is the primary source of global warming.

Radical reduction of CO₂ emissions is the best and simplest way to combat global warming, but with a growing global middle class and the associated growing energy consumption, not a lot suggests that it will happen in the necessary degree. Hence, more and more
speak of the necessity of extracting CO2₂ from the atmosphere as an important measure for avoiding extreme climate change. A problem with this is that it is expensive to extract CO2 from the atmosphere and store it underground, and the energy costs are so great that the net reward is modest. Other methods could prove not just cheaper, but even capable of transforming the CO₂ into useful materials.

The simplest solution is to plant more trees which absorb CO₂ and transform it into wood. There is a lot of variation in how much different tree species grow in a year and hence, how much CO2 they absorb; for instance, a Douglas fir absorbs around 16 tons a year, where an oak tree absorbs 8 tons. If the trees are used for firewood or left to rot where they fall, the benefit is short term, but wood is an excellent material for making both furniture and buildings, e.g. as an alternative to concrete which has a high climate footprint. Danish researchers have calculated that if woodland areas in Denmark are increased from 14 percent to 25 percent, it will reduce carbon emissions per Dane by 2 tons a year – corresponding to a 30 percent reduction.

Another option is to turn Another option is to turn CO₂
into fuel. For instance, scientists from Rice University in
Houston, Texas have succeeded in binding CO2 to hydrogen by using a catalyst, producing formic acid, which is an efficient liquid fuel with almost 1,000 times the energy density of gaseous hydrogen. The formic acid can be used in fuel cells where the acid reacts with oxygen and creates electricity, water, and CO₂.
The process produces electricity corresponding to 42 percent of the energy that was used to create the formic acid, and there is considerable energy loss in the process, but it can be useful for storing excess energy from variable sources such as solar and wind power while also creating a compact fuel for e.g. cars into fuel. For instance, scientists from Rice University in Houston, Texas have succeeded in binding CO2 to hydrogen by using a catalyst, producing formic acid, which is an efficient liquid fuel with almost 1,000 times the energy density of gaseous hydrogen. The formic acid can be used in fuel cells where the acid reacts with oxygen and creates electricity, water, and CO₂. The process produces electricity corresponding to 42 percent of the energy that was used to create the formic acid, and there is considerable energy loss in the process, but it can be useful for storing excess energy from variable sources such as solar and wind power while also creating a compact fuel for e.g. cars.

In Australia, researchers have found an effective way to extract pure carbon from CO₂ using nanoparticles of the element cerium dissolved in the metal gallium, which is liquid at 30° C. The process requires neither high pressure nor high temperature. The produced carbon is pure enough to be used in supercapacitors for electric cars or for making the miracle material graphene, which among other things potentially can be used to make superconductors. Whether the market for such materials is large enough to make a real difference in the climate account is another question.

Scientists from the University of Toronto have found a way to turn CO₂ into plastic. Offhand, this doesn’t sound particularly ecofriendly, but plastic is normally made from oil and other fossil fuels, so if it could instead be made from Scientists from the University of Toronto
have found a way to turn CO₂into plastic. Offhand, this doesn’t sound particularly ecofriendly, but plastic is normally made from oil and other fossil fuels, so if it could instead be made from CO₂, you don’t just remove CO₂ from the atmosphere, but also reduce the use of fossil fuels. The scientists use copper as a catalyst to combine CO₂ with hydrogen to ethylene, a precursor to the widely used plastic polyethylene, so the method has a lot of potential.

The big problem with these methods is that they require extracting CO₂ from the atmosphere before it can be turned into useful products. A team of researchers from Kyoto University may have a solution for that: They have produced a so-called porous coordination polymer (PCP) from zinc ions, which is ten times as effective in extracting CO₂ from the atmosphere than earlier known PCPs. The energy use for this process is supposedly very small, though the research article in Nature doesn’t specify exactly how low. The collected CO₂ can be used to make organic polymers, which in turn can be used to make polyurethane, a plastic often used in textiles and packaging – and the PCP can be reused to collect more CO₂.

Think Green

Even though the above high-tech methods certainly may have their place, we will most likely get the most bang for the buck by using plants to absorb and transform CO₂. It is an efficient method that has evolved through billions of years; it is easy, and it requires no other energy than sunlight. As mentioned above, planting forests may be a solid contribution to reduce the net emission of CO₂, but there are many other methods that also require attention.

As an example, the Chilean designer Margarita Talep has developed a sustainable and biodegradable alternative to disposable plastic packaging. It is a transparent, plastic like material made from agar extracted from red algae. With the proper choice of organic additives, the material can be used for both hard trays and soft bags, which can be coloured with plant extracts. The material is broken down in nature in two to three months, or a little longer in cold climates. It isn’t suitable for wet goods since liquid accelerates degradation, but it can be used for basically all other goods where disposable plastic packaging is used today. In addition, the material is entirely free of toxins and endocrine disruptors. It is limited how much this material directly contributes to CO₂ reduction in the atmosphere since the CO₂ that the red algae absorbs during growth is released again once the material degrades – but as an alternative to oil-based plastic, it can become very important.

Algae are quite varied, and of an estimated 300,000 algae species in nature, only about 100 species are used by mankind. Hence, the potential is great for finding algae that can produce useful raw materials while extracting CO₂ from the atmosphere or reduce the use of fossil fuels. Experiments are done with placing algae tanks on the outside walls of buildings, where the algae absorb CO₂ as they grow. The algae can then be used to produce bioplastic or biogas that can be used to heat the building.

Even though trees absorb a lot of CO₂ over their lifetimes, other plants grow faster and absorb more CO₂ per hectare per year. One such is hemp, which is among the fastest growing plants in the world. Hemp can be grown without using fertiliser and doesn’t require weed killer since it outcompetes weeds. Hemp has been cultivated for millennia as a source for textiles and rope, but was miscredited in the 20th century because some varieties of hemp could be used to produce cannabis – something that made many countries ban growing all varieties of hemp, even those that don’t contain useful quantities of psychoactive substances. It ought to be uncontroversial to allow cultivating these hemp varieties, also known as industrial hemp.

Hemp has a very large content of cellulose and can, among other things, be used to make paper. Hemp paper doesn’t need bleaching, doesn’t yellow with age, and can be recycled up to eight times versus just three for paper made from wood pulp. Textiles from hemp fibre are soft and durable and don’t shrink when washed. Hemp is also used in the building material hempcrete, a light and eco friendly concrete-like material that is used as insulation between inner and outer walls; in addition, hemp seeds are useful as a food supplement because of their high content of omega-3, amino acids, protein, and fibre.

Methods for turning CO₂ into raw materials are an excellent contribution to reducing greenhouse gases in the atmosphere, but we should not see them as solutions to the climate problem – they are far too inadequate for that. Planting forests is a good idea, but every year, global forest areas of around 50,000 square kilometres are cleared – greater than the total area of Denmark – and this deforestation is responsible for an estimated 12-17 percent of global net emissions of greenhouse gases. Quite a lot of new forest needs to be planted just to keep pace with global deforestation. It is also nice if the 100 million tons of polyethylene that are produced every year could be made from CO₂ – but it makes little difference compared to the almost 40 billion tons of CO₂ sent into the atmosphere every year. Adding to this is that all the methods – even planting and processing trees or hemp – requires energy and could end up increasing overall global energy consumption, unless the raw materials can replace other, more energy-intensive raw materials?

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