Beneath Deep Space

Author: Lewis Dartnell

Imagine that the world as we know it died tomorrow. A world-wide catastrophe occurs: a pandemic, an asteroid impact, or nuclear annihilation. Most of the people died, civilization collapsed, and the survivors in the post-apocalyptic era found themselves in a post-apocalyptic world: cities were deserted, people robbed each other, and the law of the jungle became the new law of survival.

As bad as it sounds, this is not the end of humanity and we will always come back. As has happened countless times in history, sooner or later peace and order will be reestablished, stable communities will gradually take shape, and the technological foundations will be painfully rebuilt from scratch. But here's the question: How far can such a society go? In a post-apocalyptic society, is there any chance to rebuild a technological civilization?

To put it more concretely, we have today consumed most of the easily accessible oil and a considerable portion of our shallow, easily accessible coal reserves. Fossil energy is both central to the organization of modern industrial society and a key player in the birth of industrialization itself. And this is a unique role - even if we can do without fossil energy to some extent today (which we cannot), whether we can regain today's technological level without fossil energy at all is another question.

So, is it possible to achieve a new industrial revolution on a planet that does not rely on fossil energy reserves to rebuild civilization? In other words, what if the people of Earth never had oil and coal energy? Will our civilization inevitably stagnate in the pre-industrial era before the 18th century?

It's easy to underestimate how dependent the world today is on fossil energy. When it comes to fossil energy, we always think of their most intuitive uses in fuel-driven vehicles and thermal power generation provided by coal and natural gas. But we also rely on a wide range of industrial raw materials, which in most cases require extremely high temperatures to convert into usable products, such as making glass and metal products, cement, fertilizers, etc. Most often, the heat energy required for these manufacturing processes comes from fossil fuels: petroleum, coal, natural gas, and oil.

The problem doesn't stop there. From pesticides to plastics, a large number of the chemical products that the modern world needs to function are organic matter derived from crude oil. As world crude oil reserves dwindle further, arguably the most wasteful use of these limited resources is to burn them. For these precious organic compounds, people have to be very careful to preserve the remaining limited resources.

But the topic of this article is not what we should do now - probably everyone knows that people must transition to a low-carbon economy no matter what. What I want to answer is a (hopefully) more theoretical question: Does the rise of a technologically advanced civilization necessarily depend on easily accessible ancient energy? Is it possible to build an industrial civilization without fossil energy? The answer is: maybe—but extremely difficult.

Sun and wind: How far can sustainable energy take us?

The first is a natural thought. Many alternative energy technologies are already well developed. For example, more and more roofs are equipped with solar panels for home or commercial use. A tempting idea is, can Civilization 2.0 directly pick up the legacy of previous generations from the ruins and use renewable energy as the starting point of industrialization?

Well, in a very limited sense it is possible. If you were a survivor in a post-apocalyptic world, you could indeed collect enough solar panels to live on for a while and maintain an electrified lifestyle. Photovoltaic cells have no moving parts, require little maintenance, and are resistant to harsh environments. But they also wear out over time: moisture erodes their appearance, and sunlight itself reduces the purity of the silicon layer. The power it provides drops by about 1% per year. After a few generations, all solar panels passed down will become They will all be worn out and unusable. What to do then?

Making new solar panels from scratch is a daunting task. Solar panels require extremely pure, thin silicon wafers. Although the raw material is just common sand, complex and sophisticated technology is required to process and refine the silicon. This technical capability is pretty much what we need to make modern semiconductor electronic components. It has taken a long time to develop this technology, and it will probably take just as long to restore it. So a society in the early stages of industrialization may not be able to produce photovoltaic solar energy.

Starting with electricity, though, might be the right approach—most of today’s renewable energy technologies produce electricity. In the course of our own history, the core phenomena of electricity were discovered in the first half of the nineteenth century, well after the early development of steam machinery. Heavy industry at that time already relied on machinery based on internal combustion, and since then electrical energy has played a mainly supporting role in the process of organizing our economic structure. But can this order be changed? Does the process of industrialization require thermal machinery to appear first?

On the face of it, it is not impossible that an advancing society would be able to build electric generators, connect them to simple windmills and waterwheels, and later develop wind turbines and hydroelectric dams. In a world without fossil energy, we could envision an electric civilization that largely bypasses the history of the internal combustion engine. Its transport infrastructure relies on electric trains and trams to support long-distance and urban transportation. I say "to a large extent" because we can't completely bypass it.

While electric motors may be able to replace coal-fired steam engines for mechanical applications, as we have seen, our society still relies on heat to drive many essential chemical reactions and physical transformations. How could an industrialized society produce key building materials like steel, bricks, mortar, cement and glass without coal?

You can certainly use electricity to produce heat. We already use electric furnaces and electric kilns, and modern electric arc furnaces are already used to produce cast iron and recycled steel. The question is not whether electric energy can be converted into thermal energy, but meaningful industrial production requires the support of a huge amount of energy. If only renewable energy generation is used as a source of thermal energy, such as wind and hydropower, it will be quite stretched.

Another possible idea is to directly use solar energy to produce high temperatures. Rather than relying on photovoltaic panels, solar thermal farms can use giant mirrors to concentrate the sun's rays into a small spot. Thermal energy concentrated in this way can be used to drive specific chemical or industrial processes, or to create steam that drives generators. But even so, it would be difficult for this system to generate, say, the high temperatures required inside a blast furnace for melting iron. It is also obvious that the energy efficiency of solar thermal concentration is also heavily dependent on the local climate.

Unfortunately, when it comes to generating the "white heat" needed for modern industry, we don't really have many good options other than burning things.

But that doesn't mean we have to burn fossil energy.

The power of burning: Can we return to the age of wood?

Let’s take a quick look back at the “prehistory” of modern industry. Long before coal, charcoal was widely used to melt metals. It actually has advantages in many aspects: it burns at a higher temperature than coal and has far fewer impurities. In fact, impurities in coal were one of the main factors that slowed down the Industrial Revolution - impurities released during combustion could contaminate the heated product. During the melting process, sulfur impurities can penetrate into the molten iron, making the finished product brittle and brittle, causing safety issues during use. People spent a long time solving the problem of how to use coal in industrial production, and during this period of history, charcoal performed perfectly.

But then, we don't use charcoal. Looking back, it's a bit of a shame. As long as charcoal comes from sustainable sources, it is inherently carbon neutral because it releases no new carbon into the atmosphere—although this was not a concern for early industrial civilizations.

But not all charcoal-based industries died. In fact, it's alive and well and enjoying a renaissance in Brazil. Due to its rich iron ore reserves and scarce coal mines, Brazil is the world's largest charcoal producer and the ninth largest steel producer. This is not a small workshop-style industrial production, so the Brazilian case provides our thought experiment with An inspiring example.

The trees used to make charcoal in Brazil are mainly fast-growing eucalyptus species, bred specifically for this purpose. The traditional method of making charcoal is to pile chopped and naturally dried wood into a dome-shaped pile. While the wood is smoldering, it is covered with turf or soil to isolate the air flow. Brazilian companies have greatly expanded the scale of this traditional skill so that it can be used in industrial production. The dried wood blocks are stacked in low, cylindrical masonry kilns, arranged in long rows to facilitate sequential loading and unloading. The largest production sites can accommodate hundreds of such kilns. After the wood is placed, the entrance and exit are sealed and lit from above.

The charcoal production technique actually involves retaining just enough air inside the kiln for the reaction. There needs to be enough heat of combustion to generate enough heat to drive away moisture and volatile materials and pyrolyze the wood, but not so high that it burns the wood directly into a pile of ash. Kiln managers need to monitor the combustion status at all times, carefully monitor the smoke emitted from the kiln mouth, and open or seal the vents with clay at any time to regulate the entire process.

Haste makes waste, and this low-temperature charcoaling method of strictly controlled smoldering takes about a week. Similar methods based on this have been used for thousands of years, but the uses for the fuel produced are very modern. Charcoal made in Brazil is trucked out of the forest and delivered to blast furnaces where the ore is smelted into pig iron, the basic raw material for modern mass production of steel. These "Made in Brazil" products are exported to countries around the world, where they are processed into cars, sinks, bathtubs and kitchenware.

About two-thirds of the charcoal produced in Brazil comes from sustainable farming systems, giving charcoal the reputation of “green steel” for its modern uses. Unfortunately, the remaining one-third comes from unsustainable clearing of native forests. Nonetheless, the Brazilian case does provide an example: besides fossil energy, what other ways can we supply the raw materials needed by modern civilization.

Additionally, wood gasification may also be a relevant option. The use of wood to provide heat is as old as human history, and burning wood alone utilizes only a third of its energy; the rest is blown away in the wind as gases and steam are released during combustion. Even smoke is flammable under the right conditions. We don't want to waste it.

Promoting the pyrolysis of wood and capturing the gases produced is better than simply burning it. If you light a match, you can observe this basic principle: the bright flame does not appear directly on the wood: it floats above the match stem, with a clear gap between the two, and the flame is actually formed by The gas is supported by the heat provided by the pyrolyzed wood, and the gas only burns when combined with oxygen in the air. It's fun to look at a match up close.

To release these gases under controlled conditions, we roast the wood in an airtight container. Oxygen is tightly controlled so that the wood does not catch fire directly. It undergoes a complex chemical molecular decomposition process called pyrolysis, and then the high-temperature carbonized charcoal at the bottom of the container reacts with the decomposed products to produce flammable gases such as carbon monoxide and hydrogen.

The resulting "producer gas" is a versatile fuel: it can be stored or transported via pipelines, used in street lights or heating systems, and used in complex machinery such as internal combustion engines. During the gasoline shortage during World War II, more than a million wood gas vehicles around the world ensured the operation of civilian transportation. In Denmark during the occupation, more than 95% of farm machinery, trucks and fishing boats were powered by wood gas. About three kilograms of wood (depending on its dryness and density) contain about the same energy as a liter of gasoline, and gas-powered cars consume energy in miles per kilogram of wood rather than miles per gallon. Wartime gas-powered cars could travel about 1.5 miles per kilogram of wood, and today's designs are further improvements on this basis.

But in fact, "wood gas" has great potential besides driving cars. In fact, it is suitable for any of the aforementioned manufacturing processes that require heat energy, such as powering the kiln that makes lime cement bricks. Wood gas generator sets can easily power agricultural and industrial equipment as well as various pumps. Sweden and Denmark are world leaders in the sustainable use of forest and agricultural waste, using this energy to run steam turbines in power stations. Once the steam is used in the Combined Heat and Power Plant (CHP), it is transported to nearby towns and factories for heating, allowing the CHP power plant to achieve 90% energy efficiency. Such a plant represents a remarkable industrial prospect that completely eliminates dependence on fossil energy.

But how much wood do we have available?

So does this count as a solution? Can we rebuild a new society based on wood energy and renewable energy power? Maybe, if the population was fairly small. But there's another problem here. These alternatives presuppose the survivors' ability to build efficient steam turbines, combined heat and power plants, and internal combustion engines. Of course we know how to make these things, but if civilization was destroyed, who knows if the knowledge of these crafts would disappear with it? If knowledge disappears as well, how likely is it that future generations will be able to reconstruct it?

The first successful application of the steam engine in our own history was for pumping water from coal mines. This was a very fuel-rich environment, so it didn't matter that the original design was extremely inefficient. Increasing coal production was used first to melt raw iron and then to shape the iron into shapes. Iron components were used to build more steam engines, eventually used to mine mineral deposits or drive blast furnaces in iron foundries.

And, apparently machine shops also used steam engines to build more steam engines. Only after the steam engine was built and put into use could subsequent engineers begin to improve its efficiency and energy conservation. Various methods were subsequently developed to reduce the volumetric weight and use it for transportation or factory production. In other words, there was a positive feedback loop at the heart of the Industrial Revolution: the production of coal, iron, and steam engines all supported each other.

In a world without existing coal mines, people might not even get the chance to test the extravagant steam engine prototypes that would become more sophisticated and efficient over time. Without trying its hand at the simpler external-combustion steam engine—a steam engine with a separate boiler and cylinder and piston—what hope could a society have of fully understanding thermodynamics, metallurgy, and mechanics to create more complex and precise What about efficient internal combustion engine components?

In order to reach the height of contemporary technology, we have consumed a lot of energy, and it would probably take a lot of energy to do it all over again. Without fossil energy, our future world will require an alarming amount of wood.

In a temperate climate like the UK, one acre of broadleaf trees can produce four to five tonnes of biofuel per year. If fast-growing varieties such as willow or miscanthus are cultivated, yields can be quadrupled. The trick to maximizing timber production is to use the "coppice method": cultivating species such as ash or willow that grow out of their own piles and can be cut down again in 5-15 years. This ensures a continuous supply of wood without worrying about cutting down surrounding trees and causing an energy crisis.

But here’s the rub: Coppice techniques were well developed in pre-industrial England. It cannot keep up with the rapid development of society. The core problem is that forests, no matter how well managed, conflict with other land uses - mainly agricultural land. The double dilemma of development is that as the population grows, people need more farms to provide food and more wood to provide energy, and these two demands compete for the same land.

In our own history, here's how things went: Starting in the mid-16th century, Britain responded to this dilemma by mining massive amounts of coal—essentially tapping the energy of ancient forests beneath the ground without reducing agricultural output. One acre of grove can produce the energy equivalent of 5-10 tons of coal in a year, but the latter can be dug directly from the ground much faster than waiting for the grove to grow back.

It is this thermal energy supply limitation that will become the biggest problem for societies without fossil energy trying to industrialize. This is true in our post-apocalyptic world, or in any hypothetical world without access to fossil energy. For a society to industrialize without these conditions, it would have to focus its efforts on a specific, highly advantaged natural environment—not an island riddled with coal mines, like England in the 18th century, but rather, say, Scandinavia or Canada. , there are both hydraulic energy provided by fast water flow and sustainable thermal energy provided by vast vegetation.

Even so, the Industrial Revolution without coal reserves would have been very difficult to say the least. Today our use of fossil fuels is actually growing, and many of the reasons for concern are too familiar to need repeating here. It is imperative to move towards a low-carbon economy. But at the same time, we should also know how these accumulated thermal energy reserves have supported us step by step to get where we are today. If they had never been available, one might have taken the hard path of slowly advancing mechanization using renewable energy and sustainable biofuels, which might have eventually succeeded—but it might not have. We had better hope that the future of our own civilization is optimistic, for we may have exhausted all the resources needed for any successor society to follow in our footsteps.

Author: Lewis Dartnell

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