Emergy and States
Howard T. Odum was an American ecologist and systems theorist. He developed the principles of emergy beginning in the 1950s in response to an inadequate representation of the quality variation among various forms of energy. Emergy is defined as the amount of energy consumed in direct and indirect transformations for the production of a product or service. Its standard unit is the emjoule, measured in a consistent form of energy (typically solar energy). Emergy is then a measure of the amount of solar energy required to produce a particular energy source.
I found the concept a bit opaque based on the Wikipedia page. The International Association for the Advacement of Emergy provides a nice example that helped me understand the idea. Consider a log. The available energy in the log is the heat it can provided through the process of its combustion. Its emergy is measured as the required input energy through sunlight and transpiration to grow the tree, harvest the tree, and process that tree into a log (and other contributions for it to reach your home). We can think of emergy as an input measurement equivalent to the energy output we typically consider in analysis. The objective inherent in emergy is to provide a consistent comparison between the usefulness of different products or services, as well as their energy efficiency. For example, the energy in a log measured in Joules is not readily comparable to that embodied in human metabolism because they do not produce comparable outputs (heating in the case of a log and heat, movement, and various other outputs in the case of human metabolism). Emergy lets us consider the inputs in a common unit based on the required solar energy.
A nice metric we can derive from emergy is transformity, measured as the remaining energy in the product compared with its input energy - measured in se/J. From the second law of thermodynamics, we know that available energy decreases with each transformation. However, the emergy at the start of the process will remain fixed. As a result, the transformity (se/J) of the remaining available energy tends to increase with each transformation - more emergy is required per unit of energy. This makes sense to me if we consider progressive steps down the line. For example, the emergy required for a unit of human metabolism will be a function of the conversion rate of food energy into human energy; food production will require some energy from fertilizers, water, transportation, etc.; each of these products will require some amount of energy from electricity, sunlight, etc.; and so on. A given quantity of energy produced via human metabolism will require a greater input of solar energy (emergy) than a similar quantity of energy for fertilizer, as there are energy loses along the intermediate steps and inputs to human metabolism that are separate from its fertilizer requirements.
Another concept I’d like to write about today is the steady state economy. The idea here is that an economy can be defined that is constant in its population and capital stocks. I was reminded of this concept while reviewing a chapter of the Nebraska Climate Plan today. They discussed the idea of “sustainable growth”. By including the term “growth”, the discussion is already framed in a context of non-steady state sustainability. If we consider the IPAT equation (Impact = Population x Affluence x Technology), “sustainable growth” requires that technology play an inordinate role to ensure stable, or preferably declining impacts, because neither population nor affluence are held at steady state conditions. The growth mindset is unfortunately baked into many analyses. We see it in IEA/EIA forecasts - not just growing population but growth of the “good things” (renewables, electric vehicles, energy efficiency, etc.) into the future. The only variation is by how much these various quantities are assumed to grow. Even the paragon of capitalist economics, Adam Smith, believed national economies would reach stationary conditions. Herman Daly, a prominent ecological economists, argued for a steady state economy, based on natural resource flows, that would impose hard limits on resource use. This view differs from the classical view beginning with Smith, which believed that conditions would evolve without government intervention. While Daly’s approach seems restrictive and infeasible in a democratic society, I also believe it naive to assume that stationarity will naturally evolve as a function of standard market evolution. In my work, I am starting to examining these views from a microeconomic perspective through econometric model estimation. While not a perfect solution to the forecasting problem inherent in the discussion, this approach does allow us to operationalize various steady state mechanisms as simulations based upon empirical data and structural behavioural assumptions.