By Torbjörn Rydberg
During my period as a teacher, my main interests have been open system thermodynamics and general systems theory for any system, including ecosystems, agricultural systems, energy systems, and economic systems. The method and theory for dealing with thermodynamics of open systems can be hard for many people to digest, but for natural scientists, classical thermodynamics with an analytical mechanistic worldview is still the dominating paradigm, which perhaps makes understanding general systems easier. The goal of this essay is to explain the shift from a quantitative mechanistic system perspective to a qualitative understanding of the web of life.
First we need to change our systems view from a mechanistic engineering view to an open systems perspective. We must broaden our view to include the world as one system full of processes interdependent upon each other, which works on different time scales as well as different size and spatial scales. This essay explains how I introduce fundamental concepts of self-organizing systems to students who are new to the discipline:
- Energy transformation and energy hierarchical organization, suggested as the fifth law of thermodynamics
- Maximum power and maximum empower, suggested to be the fourth law of thermodynamics for open self-organizing systems.
We need to use both of these concepts to understand sustainability of qualitative complex systems. These concepts impact how we measure and test systems performance such as productivity and efficiency.
Energy hierarchy and the energy problem–how do earth systems capture the sun’s energy?
What is energy? The practical definition of energy is something that can be converted 100% into heat. Heat is the invisible motion of molecules. The sun sends more than 10,000 times more energy to the earth per time unit in comparison with the total global consumption of fossil energy. So why can’t we use it all? One of the problems is that I can spend a whole day out there at the beach, and no matter how much energy I receive I will starve and die if I only count the energy of inflowing solar energy measured in joules that my body receive and the energy in the form of heat to my body. Is a joule always a joule? Are there no differences between the joules?
Since I’m not able to capture or “eat” the sun – who can capture the sun’s energy and who is able to digest solar energy? Plants capture the sun—at least that is what I learned in school. We spend a lot of time digging into the chemistry of photosynthesis, which shows that on a yearly basis globally, the net photosynthetic efficiency of the entire land and sea surface beneath the atmosphere is 0.1%. For forests the annual average is 1% and for cereal crops with good farming practices in a temperate climate, measure during the growing season only, the efficiency could be 3% of the total. That number is not high, because most of the solar spectrum consists of photons which are either too low energy or too high energy to be photosynthetically active. Theoretically, this leads to an optimum efficiency rate at 16%. Under very favorable conditions in a laboratory where factors such as water, temperature, and CO2 pressure, are optimized, a solar energy uptake can reach about 8 – 9%. But let us go back to the picture of the beach. We understand that a lot of energy is reaching the surface of the planet. We see a solar collector over the entire surface of the earth, through photosynthesis on both land (plants) and ocean (phytoplankton) as a result of a billion years of self-organization.
These surfaces collect both invisible and visible light from the sun. The visible light is the same light that the plants use in the photosynthetic process. The protein in our eyes that catches the light is very similar to the protein that catches the light in the plants. Dilute solar beams become concentrated and transformed.
The sunbeams heat the top layer of the water and winds evaporate water from the oceans and lakes. Thereafter the air loaded with moisture moves into new areas where the air can condense as clouds and become rain. The energy quality of solar radiation has changed into kinetic energy of flowing fluid. Clouds release their heat if the air surrounding if it is colder. Concentrated heat makes the air rise and this drives the circulation of the air.
These earth systems appear to be the result of a long time period of self-organization, which has optimized the proportion of different area types and the capturing process of the incoming solar beams. More than 70% of the earth’s surface is ocean. The oceans capture the solar energy and make atmospheric vapor, and later on this water is distributed over land as rain that transports and dissolves material and nutrients and feeds growing plants. Plants capture solar energy again in the form of wind for the evapotranspiration process or water that transforms into a quality that plants are able to use. Clouds transform the energy and land uses the rain and wind further in transformation processes.
What we see in the real world is that energies of different kinds work as needed inputs together in different processes to generate new forms of energy captured in plants, for example. Solar energy, wind energy, water energy, nutrient energy, soil energy, labor energy, machinery energy and information energy are all transformed beginning with humble plants, in increasing transformations and energy use. The energies necessary to drive plant processes come from different levels in the universal energy hierarchy. In order to compare these energies of different kinds generated from different levels in the energy hierarchy, we need to combine and account for them, and those varied energies all need to be expressed in units of one kind of energy. Therefore a new measure was defined. It is called Emergy and it is the available energy of one kind previously used up directly and indirectly to make a product or service. Most of the energies needed for a specific transformation are not found in the product or the service itself — Emergy is a measure, or the memory of the availability that was used up. Emergy is the measure or memory of the necessary support of the web of energy transformations in the geo-biosphere.
We can conclude that energies of different kinds are very different in their ability to support different processes in the geo-biosphere. Energy in the form of solar beams needs to be transformed in several transformation processes before it is in a form that is digestible for humans, for example. Each time energy is transformed, a large part of the energy is converted to heat and is now unable to do any more work. The energy that has been transformed and is now embodied at the next level of hierarchy retains less joules of another kind, typically of higher quality, that is able to feed into other processes, thus driving complexity.
When we look at the energy transformations we see that they are connected in a series. The outputs from one transformation are then mostly input to the next level. A portion of the new energy, however, acts as feedback to the input process, to interact and control the input. This type of organization is described as a hierarchy. The energy is transformed in a self-organizing process. The energy flow is decreasing in each energy transformation step. A systems ecologist, H. T. Odum, proposed the universal hierarchical self-organization of energy systems as the fifth energy law (Odum, 1987, 1988).
A squirrel in the forest – how do we measure efficiency?
The squirrel collects nuts and fruits. He stores the yield in holes in trees, and buries some of it down in the soil. Most of his harvest is never found. During winter he feeds himself from his stored energies. In this photo, it appears as though he has forgotten where he put the harvest. If we analyze the percentage of his harvest that the squirrel uses and we will find that the rate of “nut recovery” is very low. Only a few percent of the harvest will be found and eaten by the squirrel. Why is the efficiency of the squirrel’s harvesting work so low? Shouldn’t it be closer to 100% than closer to a few percent?
In fact, someone else may have already eaten some of the collected nuts and fruits, and some of it may never be found by animals, left to germinate or decompose, all of which serves the complexity of the larger system of the forest. What is a proper degree of efficiency for squirrel buried nut recovery? In order to look at that efficiency, we need to broaden our view to the larger system that the squirrel is working in. We have to zoom out using our “em-lens” and see other processes at the same time. The digging action from the squirrel means that the squirrel helps with planting of new trees and bushes. More trees will germinate faster and that will ensure more fruits and nuts for the next harvesting period for the squirrels and other creatures. Some of the fruits and nuts are digested by insects and soil organisms and will not be available for the squirrel. This transformation of the harvest will improve the soil fertility both directly and indirectly, which will improve the quality of the trees and bushes that the squirrel is fed from. The entire forest ecosystem is improved by the action of the squirrel and the production and capacity of the system improves. If we use that type of system view and make a new analysis that views the whole system, we now understand that efficiency that is measured only on a single sub-process can be misleading. When we broaden our view, our measure incorporates more complexity to what is probably a very efficient system. What would happen if we theoretically could improve the efficiency of the squirrel in a narrow-minded mechanistic systems view?
When we consider systems containing several scales like this forest ecosystem with plants, trees, insects, mammals, and microorganisms which all run on different time and spatial scales, the maximum empower principle proposes that self-organization develop designs to maximize empower of each scale at the same time. The hypothesis is that the importance of an exchange between scales is in proportion to the empower involved. In an ecosystem like a forest ecosystem the emergy flow is equal on all hierarchical levels. Empower is emergy flow per time unit.
The tractor and the sheep – the lack of systems understanding
From hundreds of scientific studies and reports we are told that we can grow biomass and harvest the biomass and still have more than enough energy to feed the tractor. Some reports based upon traditional energy analyses, or, as I prefer to call them, partial fuel-budgets, also claim that bio-fuel makes a good substitute for fossil fuels. I call them partial because they do not even take into account the fuel needed to support the people involved in the process. Some studies suggest that we do not need more land to grow energy for the tractors than we needed for feeding the horses when they were doing the hard field work.
Let’s dissect the energy basis for biomass tractor fuel. First I place my hay-bale in front of the tractor and wait for a while and hope that the tractor will crank up and be able to run. The hay-bale has enough of energy, when looking at the numbers of joules available, and so that shouldn’t be the problem. The problem might be that we need to transform the hay into a form that tractors can consume. It needs to be in a liquid form similar to diesel, petrol or burnable gas. We can convert the hay, and make our fuel for the tractor and it might be true that the land needed for this is about the same amount needed for feedstuffs for the horses many years ago. What this type of argument misses is the need for the many other kinds of energy, material and services needed to have the fuel altered to a form that works in the tractor engine.
The farmer needs to grow the hay, sow the seeds, apply fertilizer, till the soil, harvest the hay, dry it, collect it, and so on. In addition to the hay process, we also need to analyze the tractor and its requirements in terms of resources. The tractor needs metals of different kinds, rubber, plastic, glass, electronics, processors and much more. Furthermore the tractor needs industries that connect the tractor with all the necessary goods, including a highly developed infrastructure of roads, railways, world-wide web communication, and well-educated factory workers and engineers. All of these processes demand a functioning environment that can provide ecosystem services for not only us and but also for this complex economy. We can only hope that this type of arrangement doesn’t negatively interfere with our life-support environment. It would be very misleading to claim that the hay bale (read bio-fuel in general) could run the tractor.
Since the tractor fueled by hay didn’t work out, we can move the same hay bale in front of a flock of sheep. The hay bale attracts the sheep and they start to eat it. Inside the sheep the hay becomes transformed into energy that fits the metabolism of the animal. The sheep start to move. But this transformation not only generates mechanical motion but also meat, wool, milk, and even recycled manure for the hayfield. The hay is transformed within a complex system that supports itself, develop its owns spare parts and creates feedback, through a self-organizing sheep with eyes and a brain and a body that is responsive and communicative with its surrounding. The sheep can also generate its own new prototype for the next growing season. No extra industry is needed, no extra infrastructure, no extra mining industry is needed for this type of technology. The sheep is an example of a system that has a good fit with the hay bale. The sheep operates at a distance from thermodynamic equilibrium. In contrast, the tractor is an example of a system that has a very low degree of fitness with the hay bale. The tractor is a system that is very close to thermodynamic equilibrium. But the tractor is not able to do things by itself — needs a fully developed industrial society that fuels itself mostly using non-renewable resources. The sheep is a multi-functional system far from thermodynamic equilibrium while the tractor is a technology that generates heat that is converted to mechanical work.
Our choices in how we view the system and the evaluation method we use are critical when we attempt to analyze any kind of system. The network of all energy transformations forms a hierarchical series that explains the capacities of available energy of different kinds to do work–any kind of work, not just the theoretical mechanical work that the traditional physics deal with.
Emergy accounting measures what is required to make something, by measuring work of differing quality, in comparable units, from differing scales. Emergy measures the real wealth generated by nature and by humans. Measures like Emergy are needed to develop a fuller and more comprehensive systems view to deal with issues related to sustainability.