Although we intuitively understand what pollution is, its essence is unclear. Without gaining an insight into the concept of pollution, we cannot find a solution to eliminate it. In this article, I first define what pollution is in terms of entropy and then examine the feasibility of material recycling and energy recovery of waste as the solution for waste disposal.
1. The Essence of Pollution
What is pollution? Can we define pollution in terms of physics? We often denounce unjust action as “dirty". Do this spiritual dirtiness and physical dirtiness have anything in common? This is the topic of this section.
1.1. Pollution as Material Entropy
Atsushi Tsuchida, a Japanese physicist, said an everyday expression that corresponds to entropy is pollution (汚さ). There are various forms of pollution; air pollution, water pollution, soil contamination, noise pollution, light pollution, thermal pollution, and so on. Among them, we can measure the degree of thermal pollution through entropy.
How about the other sort of pollution? Air pollution, for example, is not thermal pollution by itself. It is true that black pollutants absorb solar radiation and heat the air, but white pollutants reflect solar radiation and cool the air. Air pollution drops the temperature of the troposphere on the whole. Why do we feel air pollution is dirty, then?
For humans, oxygen or nitrogen spreading into the air is not pollution, but nitrogen oxide or sulfur oxide spreading into the air is regarded as pollution. Unlike the former, the latter causes pulmonary problems or acid rain. The photosynthesis of the cyanobacteria converted an anoxic state of the earth’s atmosphere into an anoxic state about 3 billion years ago. It must have been fatal air pollution for strict anaerobe at that time.
As the proverb goes, “one man’s meat is another man’s poison." Eutrophication of the sea is beneficial to aquatic vegetation or phytoplankton due to abundant nutrients, but harmful to fish and shellfish due to lack of oxygen. Some spend money listening to punk rock music, which is nothing but painful noise for others. How can we explain this relativity?
Whether a thing is harmful to a living system or not does not depend simply on its objective properties, but on its relation to the system. Even if it increases the physical entropy, it is not a pollutant for a living system, so long as it does not causally increase the entropy of the system. To sum up, pollutants are things that directly or indirectly increase the entropy of my (or our) systems. This proposition applies not only to the material entropy but also the information entropy.
1.2. Pollution as Information Entropy
As I explained before, the concept of entropy can be applied to information theory. Tsuchida opposed himself to stretching the definition of entropy, claiming that defining entropy as disorder or randomness is vague and barren because we cannot measure, for example, the disorder of randomly arranged books on a shelf.
When books on a shelf are arranged alphabetically, there is an order. As you take in and out them randomly, they become disorderly irreversibly, if you do not arrange them intentionally. This example is often used to illustrate the law of information entropy. We can measure its entropy by employing the probability to search a specific book. Suppose books on a shelf are arranged alphabetically and none of their titles are the same, then we can find the book by a binary search algorithm without fail, that is to say, with the probability 1 or the entropy 0. The binary search repeats the process of finding the median title, comparing it to the one you are searching for, and determining if it is anterior or posterior until it finally finds the title. The more disorderly the arrangement gets, the smaller the probability and the larger the entropy becomes. In this way, the disorder can be measured in terms of probability and entropy.
We feel an untidy room “dirty". Entropy can explain this dirtiness, but something more than a mathematical explanation might be necessary, because we consider a means-end relation, when we tidy up a room. Cups and mugs should be put into not clog cabinets but cupboards. The means-end relation is based on the cause-result relation. Just as whether something is a pollutant or not depends on the relation between the subject and the object, whether something is in order or not depends on the relation between means and ends.
1.3. Pollution as Social Entropy
Clifford Whittingham Beers (1876-1943) started the mental hygiene movement and reformed institutional care for the sake of mental health. Usually, hygiene aims at material cleanliness but the phrase suggests that mental cleanliness has something to do with material cleanliness. In fact, the increase in information entropy causes mental disease.
Living systems exclude alien invaders and thus maintain the difference between themselves and their environment. Our immune systems find and destroy pathogens, tumor cells, and so on in order that they can protect our health against infection. The healthy effect of catharsis is based on this mechanism of system maintenance. Crying and laughing have catharsis effects, because voice and tears are purged away. A bloodletting that has no medical merits was practiced in antiquity because of the catharsis effect.
Catharsis and purging scapegoats often contribute to maintaining social systems. The word “scapegoat" is a translation of “Azazel" that appears in chapter 16 of Leviticus, the Bible. It was a goat that escaped to the outside wilderness, with the sins of the people placed on it. By extension, it has come to mean any group or individual that innocently bears the blame of others.
An often-cited example of the scapegoat is the Witch-hunting in Medieval Europe. A witch was believed to apply a special ointment to her body, fly in the air riding blooms, and join the Sabbat. The ointment meant an aphrodisiac; the broomstick a penis; flying in the air orgasm; the Sabbat the sexual orgy.
They thought such Dionysian disorder resulted from witches transgressing the boundary of sexual norms. When the boundary between a system and its environment comes to fade, the system falls into crisis. Burning witches at the stake was a ritual necessary for the system to differentiate itself from its environment and re-create the order.
We feel illegal activities are “dirty". If agents of a social system begin to break laws, they become unable to anticipate others’ behaviors mutually. This increase in social entropy makes us feel social systems are polluted. Punishment can decrease social entropy, but punishing the innocent increases social entropy in the long run.
The medieval witch-hunt was most frequent when the Little Ice Age caused a harvest failure. The ruling classes had to accuse somebody of the starvation crisis to evade their responsibilities. The scapegoats that the medieval Christian power chose were the heathen magicians that were aliens and peripheral to it.
Some scapegoats were male but most of them were female. There are two reasons for it. First, women had a peripheral status in those days. Second, sterile women were associated with crop failure. That’s why they were the most likely candidates for witches. Anyway, they were innocent.
Purging innocent scapegoats can bring about a temporal catharsis effect, but it does not contribute to maintaining the social system. Here again, we must take causality into consideration. Because the witches were not the true cause of the disasters, the catharsis had no enduring effects, so that people had to repeat the purging, until they realized it had nothing to do with the disasters.
Any selection can reduce entropy in itself. The selection we consider to be good is what directly or indirectly reduces the entropy of our systems. To sum up, pollution is what directly or indirectly increases the entropy of the estimator, whether the entropy is material or informational.
2. Recycling of Materials
Recycling in a wide sense is reusing materials and objects in original or changed forms. Here, however, I take the word in a narrow sense, so that it does not include reuse, but only implies the process by which wastes are collected and used as raw materials for new products. This chapter examines whether recycling is the ultimate solution to the waste problems or not.
2.1. The Ideal of Zero Emissions
In 1991 Gunter Pauli launched the concept of zero emissions for industry and in 1994 created the Zero Emissions Research and Initiatives under the guidance of Heitor Gurgulino de Souza, then Rector of the United Nations University. Can our industry emit no waste? Their project is an endeavor to convert the industry into a sort of perpetual motion machine, that is to say, impossible.
In modern Europe, engineers tried to invent perpetual motion machines, only to fail. Although two principles of thermodynamics prove it impossible to make perpetual motion machines, we still find many people professing to succeed in inventing perpetual motion machines.
Two perpetual motion machines are corresponding to two principles of thermodynamics.
- The first kind of perpetual motion machine is against the principle of energy conservation. The Fast Breeder Reactor is represented as the first kind of perpetual motion machine that allegedly reproduces more fuel by consuming it.
- The second kind of perpetual motion machine is against the principle of maximum entropy. The zero-emission industry by recycling is represented as the second kind of perpetual motion machine that allegedly produces no waste and does not pollute the environment at all.
The zero-emission industry is not the first kind but the second kind of perpetual motion machine. Of course, the second law of thermodynamics just says that entropy never decreases in an isolated system and does not go so far as to say entropy always increases in an isolated system. So, the zero-emission industry is theoretically possible, but in reality impossible.
You might think that, though recycling cannot realize the zero-emission industry, it could realize less emission industry. If recycling increases less entropy than the previous production, recycling proves to be a desirable solution to the waste problem. Unfortunately, it is not always the case.
2.2. Problems of Recycling
While the recycling movement is spreading all over the world, it turns out that recycling has some problems. Here I take up three problems, namely, problems of safety, resource-saving, and profitability.
- Recycled products tend to be unsanitary or dangerous. Think of recycling cotton goods. Bacteria or viruses often remain in used cotton goods. Since cotton has a similar nature to bacteria, it is very difficult to disinfect them without destroying cotton. Nor can recycling remove the chemical poison that soaks into the used materials, so that repeating recycling accumulates poison in the materials. If you liquefy or gasify the materials, you can easily detect the poison and remove it, but even cutting-edge technology has difficulty detecting poison in solid materials. Moreover, because the quality of used materials is not homogeneous, sampling inspection is unavailable.
- Recycling often wastes rather than saves resources. That is to say, recycling often requires more time and energy, emitting more wastes than making new products from virgin materials. Recycling plastic bottles, for example, emit three times as much waste as the production of virgin materials. To recycle plastic bottles, you must wash the dirty used bottles, carry them to factories, reprocess them, and distribute them to stores. Meanwhile, you spend a lot of energy and emit waste including heat and gas. If the only emission is invisible heat and gas, the process seems to achieve zero-emission recycling, but actually, it is not zero-emission.
- Recycled products are often expensive for their low quality so that they cannot sell without subsidy. Recycling presupposes volunteer activity including fractionation of garbage. Their time spent adds the opportunity costs to recycling. You might think environmental merits justify the high costs, but, generally speaking, high costs indicate a high environmental load. Producing a picture worth one million dollars seems to have less impact on the environment than producing a piece of steel worth the same amount of money. But producing a picture worth one million dollars actually increases so much material entropy, because it requires bringing up many artists and drawing many trials.
2.3. Recycling and Entropy
I defined pollution in terms of entropy. So, I can explain three problems of recycling in terms of entropy.
- The problem of safety is concerned with entropy. Although poison harms living things and thus increases material entropy, it is harmless, so long as it is gathered at a place and kept away from us. If it is scattered and its existence becomes more uncertain, it gets dangerous for us. Recycling is dangerous because its circulation increases the information entropy of poison. In this respect, the circulation of recycling is contrary to the liquid circulation in a body. The former tries to make resources from waste and scatters poison, while the latter concentrates it and excretes it out of the body. The former increases the entropy of our systems, while the latter decreases it. Needless to say, what we need is the latter circulation.
- The problem of resource-saving is a typical matter of entropy. Those who believe recycling is unconditionally good regard resources as things. If resources were to be things, the repeated use of the things could save resources. Resources are, however, not things but low entropy. Recycling is the same process as production in that the more increase in entropy of the environment must compensate for the decrease in entropy of products. Recycling as well as production emits exhaust heat and pollutes the environment. What is important is which increases less entropy than which.
- The problem of profitability is an economic matter. As I wrote before, economic value expresses the low entropy of goods or services. Here again, whether recycling is better than production from virgin materials or not depends on whether the former increases less entropy than the latter. Although economic costs are not necessarily proportional to the environmental burden, energy efficiency usually makes the production process profitable. So, we must doubt whether unprofitable recycling can really lead to sustainability.
There are some cases where recycling clears up all these problems. An excellent and successful example is aluminum recycling.
- Retrieved aluminum products are melted in a furnace to produce molten aluminum so that impurities are easily eliminated. By the end of the process, the recycled aluminum is indistinguishable from virgin aluminum. It is not contaminated, poisonous or degraded.
- The electrolysis to make virgin aluminum from bauxite consumes a lot of energy while recycling aluminum saves 95 percent of the energy.
- The recycling of aluminum is profitable even when the cost of collection, separation, and recycling is taken into account. It cuts hidden costs of landfill disposal.
If products are made of rare elements, they are worth recycling. But recycling products made from carbohydrates are mostly unsanitary, wasteful, and uneconomical because the elements of carbohydrate are abundant around us so that it is difficult to liquefy or gasify them without reducing their commercial value. In such a case, energy recovery is a better option.
3. Energy Recovery from Waste
Energy recovery is the waste treatment that captures energy in the form of electricity or heat from waste. There are many technologies for energy recovery. In this chapter, I discern the merits and the demerits of each technology.
3.1. Direct Combustion
Incineration was the most common way to dispose of waste. It enables us to reduce the volume of the original waste by more than 90%. If we leave waste material, it accumulates on the earth, polluting our environment and thus increasing the entropy of our systems more and more, as time elapses. We must, therefore, convert material entropy into thermal entropy, so that we can throw waste into outer space.
Today, we can use the heat of incineration to generate electricity. Recovery of thermal energy from waste has two advantages over material recycling.
First, the troublesome classification of waste is unnecessary. All you have to do is separate general waste from metallic waste, of which the former should be burned and the latter should be recycled. It can reduce the opportunity cost of consumers.
Second, the average distance from consumers to incinerators can be shorter than the distance to recycling facilities. The more special a recycled product is, the less its recycling facilities are and the longer the average distance to them, increasing transportation cost. The waste for direct combustion energy recovery is so general that incinerators can gather enough fuel from neighbors.
The average distance from incinerators to consumers can also be shorter than the distance from recycling facilities. The more special a recycled product is, the less its shops are and the longer the average distance to them, increasing transportation cost. The demand for the product of direct combustion energy recovery, namely electricity, is so general that incinerators can send it to neighbors. Cogeneration is possible thanks to the proximity to consumers.
Energy recovery by direct combustion is, however, not clean. Incinerators emit various toxic substances such as nitrogen oxides, sulfur dioxide, heavy metals, soot particles, dioxin, and furan. More advanced Thermochemical technologies are expected to solve this problem.
3.2. Thermochemical Conversion
Direct combustion technology transfers the heat of combustion into steam and generates electricity, while thermochemical technology makes hydrogen from biomass by reacting the biomass at high temperatures with steam without oxygen.
In the gasification process, carbon in biomass reacts with steam to produce carbon monoxide and hydrogen.
C + H2O → H2 + CO
Carbon monoxide further reacts with steam to produce carbon dioxide and hydrogen.
CO + H2O → H2 + CO2
Hydrogen can generate electricity utilizing fuel cells. I will explain fuel cells in detail later.
Gasification is an efficient method for extracting energy from many different types of biomass. Dioxins, furans, pathogens, and other pollutants are completely cracked into harmless compounds. High temperature may gasify dangerous heavy metals, such as mercury and cadmium, but, when they pass through bag-filters, they are cooled and liquefied or solidified, so that the bag-filters can remove them. Metal components in the waste stream are selectively collected and reused.
3.3. Biochemical Conversion
Another way to make fuel gas from waste is the biochemical conversion by anaerobic digestion (fermentation). The organic wastes such as excrement or dead bodies of animals, kitchen garbage, wood, when put into the sealed container, generate mainly methane and carbon dioxide under anaerobic conditions as a result of the fermentation of bacteria.
C6H12O6 → 3CO2 + 3CH4
In developing countries, simple home and farm-based fermentation is widely practiced, because it offers methane as fuel, destroys pathogens, and reduces the volume of waste. Burning methane is cleaner than coal and emits less carbon dioxide per unit of energy, while emitting methane has more greenhouse effect than burning it.
When the residue of fermentation includes inorganic nutrients, especially potassium and phosphorus, it can serve as manure for agriculture. But most of the residue usually consists of useless dead bacteria. Biochemical conversion of waste is inappropriate where there is no wide field to scatter the residue. Biochemical conversion is suitable to rural areas, while thermochemical conversion is suitable to urban areas.
Let me conclude this part. We decrease the entropy of our systems and increase the entropy of the environment. The increase in entropy of the environment is called pollution. To purify pollution, we must convert waste material into waste heat and emit it into outer space. We must recycle and reuse materials themselves, of which plants can recycle carbohydrates and humans must recycle inorganic materials, the residue of energy recovery.
I applied the concept of pollution as entropy to social systems. When members of a social system offend law, social entropy increases. Law, a social medium of value exchange, must punish the offender to decrease the social entropy but also rehabilitate him or her. The rehabilitation of offenders is the social recycling of human resources. If the crime is very grave and the offender is unlikely to be rehabilitated, the death penalty is applied. The death penalty is not material recycling, but it is a warning against future possible crime and thus reduces social entropy. It is resource recovery from the social disorder.
When it comes to environmental crime, it increases material, informational and social entropy. Environmental goods are public goods that are non-rivalrous and non-excludable. Since uncoordinated markets are unable to provide these goods, the government has to intervene in free economic activities. We will discuss later what a nation or the international community has to do.
- Clifford Whittingham Beers. The Mental Hygiene Movement (Classic Reprint). Forgotten Books (August 6, 2018).
- Jorgensen, Finn Arne. Recycling (The MIT Press Essential Knowledge series). The MIT Press (November 12, 2019).
- Ciuta, Simona, Tsiamis, Demetra, Castaldi, Marco J. Gasification of Waste Materials: Technologies for Generating Energy, Gas, and Chemicals from Municipal Solid Waste, Biomass, Nonrecycled Plastics, Sludges, and Wet Solid Wastes. Academic Press; 1st edition (October 24, 2017).
- Eccleston, George, Eccleston, George. Gasifiers Wood Gasification & Off Grid Power: A Beginners Guide. April 17, 2018.
- Nicolas Georgescu-Roegen. The Entropy Law and the Economic Process. Harvard University Press; Reprint 2014 edition (February 5, 1971).
- Nicolas Georgescu-Roegen. From Bioeconomics to Degrowth (Routledge Studies in Ecological Economics). Routledge; 1st edition (March 28, 2011).
- Atsushi Tsuchida (槌田 敦) 『エントロピーとエコロジー ―「生命」と「生き方」を問う科学』ダイヤモンド社 (1986/07). p.27
- Atsushi Tsuchida (槌田 敦) 『エントロピーとエコロジー ―「生命」と「生き方」を問う科学』ダイヤモンド社 (1986/07). p.16.
- Clifford Whittingham Beers. The Mental Hygiene Movement. Forgotten Books (October 29, 2017).
- Read my article for detail: “How can we improve recycling ?" NagaiToshiya.com.
- “Zero Emissions Research and Initiatives."