Cement and Concrete

People seem to have a reluctant relationship with Earth’s natural world. We know that nature provides us with our necessary food. But most of us buy it in shops. And, with most of us living in cities, even our homes and workplaces are removed from nature. For these, concrete is the most effective separator. It’s a human invented material that is the foundation for most of our civilization.

Concrete results from mixing cement with water and with a suitable filler such as sand or gravel. Its use in the Roman era Pantheon demonstrates its durability. Its longevity can be further enhanced as we use rubble from destroyed concrete structures as filler for new concrete structures. However, cement can’t be re-used. New concrete requires new cement. And cement is costly.

Let’s scale the cost. Annually we produce over 4×109 tonnes of cement, equivalent to the cement for about 1000 dams the size of the 3 Gorges Dam. This amount is to remain constant to well past 2050. Its production calls for an annual expenditure of 3.5GJoules of energy per tonne. This amounts to an allocation of 1.4×1019Joules of energy annually, about 3% of total energy consumption. As most of the energy comes from fossil fuels then there’s resulting pollution at a rate of 0.54t of CO2 per tonne of cement, about 8% of global CO2 emissions. Because of this, cement is a significant parameter when modeling future climate change. Over history, humans have used about 128×109 tonnes of cement to enable living apart from nature, which is almost a thousand times greater than the weight of all humans. Concrete is costly both in energy consumption and pollution emission.

Concrete separates us from nature. And estimates are that we will continue this separation for decades to come. Should we continue to separate ourselves from the ecosystem? Or are you willing to fight this apparent primal urge to treat nature as a threat? For a prosperous future, we recommend you look for ways to live with nature rather than apart.

Solar on More Than Tops of Buildings

Singapore may soon get 20% of its energy from solar parks in Australia. The plan is to cover 10,000 square kilometres of outback with solar collectors and send the resulting 10GW of energy through a 4370 kilometre long undersea cable. With this, Singapore, covering a land area of only 725 square kilometres, would make a strong step toward becoming carbon neutral by using large areas of a far away land.

Expand this idea further and there’s great potential. Globally about 15% of Earth’s land surface is barren, i.e. not able to support life. If we cover this land with solar collectors then it would generate 138% of the total primary energy that humans used in 2018. While most of the barren lands occur slightly north of the equator, e.g. the Sahara desert, most people live in temperate climates further away from the equator. So conducting electricity for thousands of kilometres is essential. But this and others seem to be simple engineering challenges that are keeping us from this potential.

Now imagine a future where every major population centre is tied to solar parks in barren lands throughout the world. If this were achieved then we’d have a very good chance of achieving net-zero carbon emissions by 2050. Are you ready to place your reliance upon solar parks in far away lands rather than on far away oil fields?

Ouarzazate
Ouarzazate – James Allen, NASA

Hydrogen Energy

We rely upon energy to get things done. It powers our bodies and it powers our industries. We’ve developed many methods to transport and store energy for our industries. Some methods come quite naturally such as using wood from trees. Other methods are pure human genius as with using hydrogen gas and fuel cells. Let’s look at this energy genius.

While hydrogen is the first element on the periodic table and a key constituent of our Sun, there’s not much of it floating freely in Earth’s atmosphere. Actually, given its volatile nature, this is a good thing. Nevertheless, we can expend energy to isolate and store it. Then, as need, we release the energy in the hydrogen gas by oxidizing it. The oxidation’s end product is water so the claim is that using it doesn’t pollute.

However, we must use energy to isolate and store hydrogen gas as its not floating free. Typically we use a natural gas formation process to do this. Simply, the process transfers the energy of the natural gas to become energy in the hydrogen gas. This formation process has the usually debilitating fossil fuel pollution products, i.e. carbon monoxide and carbon dioxide. Thus, using hydrogen in our energy distribution network results in the same problems as using natural gas directly. That is, hydrogen doesn’t remove the pollution from energy usage, we simply move the location of the polluter.

When thinking about sources of energy, hydrogen is not directly a source, it’s a carrier. Nor is it truly pollution free. We can store and transport energy by forming hydrogen gas. But we have many other methods to store and transport energy without having to build a new distribution network. Perhaps its not genius. Instead, let’s decrease the pollution at source or reduce our energy demands or do both. Thus our energy usage would minimize pollution of the future. This would be genius.

Trees

Do you ever wonder if we’d run out of trees? Seems like a ridiculous notion given that they seem to be growing nearly everywhere. Yet today satellites give us extraordinary views of Earth’s land cover. They clearly show that the trees, or more accurately the forests, are changing and the change may startle you.

First, let’s look at broad numbers. Currently, the Earth’s land cover could be set into thirds; a third is barren or glacier covered, a third is use by people for agriculture and a third is forest. A third is a huge amount, about 43 million square kilometres. While the forest area is huge, it’s a change. It’s only about half the forested area of pre-human days. And we’re continuing to decrease forested area by 0.2 million square kilometres each year. Hence, broadly speaking, in about 200 years the forests will be gone; that is, we’d run out of trees!

Probably all conservationists, and most people, want to keep forests. Not only do they harbour wildlife, they also rejuvenate Earth’s atmosphere. We can keep forests in two obvious ways. One way is to stop forest degradation. This is the aim of REDD+. The other is to grow forests, i.e. to plant trees. This is the aim of the Trillion Tree Initiative. Let’s look at the latter.

The Trillion Tree Initiative is for people to plant a trillion trees. Simple enough. But where do we plant them? Assume on average that a hectare can support 600 trees. Thus, a trillion trees would need about 17.5 million square kilometres of land, another huge amount! On the plus side, these trees would sequester carbon thus reducing atmospheric carbon dioxide. And they’d store about 7.3×1021 Joules of potential energy. On the negative side, the Earth has no available land area; all habitable land is already allocated. And we’re changing 0.2 million more square kilometres each year from forest cover to agriculture cover. Thus, planting a trillion trees won’t likely occur given our reliance on today’s agriculture and food industry methods.

What this exercise shows us is the mathematical simple yet realistic challenging way to save trees. Trees, much as with animals, need land to grow. As we change natural land cover to suite our needs, we reduce the number of trees. And yes, trees can go extinct. So, while we can run out of trees, are we willing to act to prevent this and to regrow forests?

Before / After:

Solar Power Generation

Solar power generation is on a growth spurt. In 2018, it produced over 584 TWh of energy. Its capacity is nearly doubling every two years. Some see solar power as being the solution for global energy needs.

However solar power comes with costs. For one, there’s the need to fabricate panels, construct the collector facilities and then maintain operations. For another, all life forms below the solar panels will die-off as the Sun is their only source of energy and the panels capture all the sunlight. Thus, solar power usage needs to be rationalized with costs of other energy supplies.

Can we scale our energy challenge? Certainly; let’s see. In 2018, we consumed over 160,000 TWh of primary energy and it is increasing by about 1.5% annually. If solar power supplies all this then we’d need cover about 14 million square kilometres of land with solar arrays and then maintain operations.

This operational area is huge, greater than all of Europe. Further, implementing this solution would drastically, negatively affect the Earth’s biodiversity. Thus solar power generation has its place in the global energy supply mix but we need other, less costly, means to satisfy our energy challenge.