**Emergy**, a concept developed by ecologist Howard T. Odum, is the measure of the energy used directly and indirectly in the production of a product or service. Odum defined it as the "available energy of one kind previously used up directly and indirectly to make a service or product." Essentially, emergy quantifies all the energy inputs—whether solar, fossil fuel, or biological—that are required to sustain a system, a process, or a product, translating them into a common unit called **solar emjoules** (seJ), which standardizes the energy inputs in terms of the amount of solar energy required. ### Emergy and Complex Systems Odum’s idea of emergy highlights the importance of **embodied energy** in maintaining complex systems. In ecosystems and human-built systems alike, it is not just the immediate energy input that matters but also the cumulative energy history—the energy required to create the components and processes that sustain the system. For example, a forest doesn’t just require the sun’s energy each day to thrive; it also depends on nutrients, water cycles, and atmospheric interactions that have developed over long periods of time. These resources and interactions, in turn, are the result of countless prior energy transformations in the system—such as the decomposition of organic matter, the movement of water through the hydrological cycle, and even geological forces shaping the land. Similarly, producing a single unit of food doesn’t just involve the energy spent growing the crops; it also involves the energy used to produce the fertilizer, transport the materials, and even the energy in creating the machinery used for farming. In Odum's view, understanding emergy is key to understanding how systems—including ecosystems and economies—are sustained and how their complexities develop over time. **Energy flows, embodied in the form of emergy**, underpin all processes in nature and human society, from ecosystems to global economic systems. The transformation of energy through these systems allows for the development of complexity and structure, in much the same way as Ilya Prigogine’s concept of dissipative structures describes. ### Relationship Between Energy, Information, and Complex Systems In complex systems, energy and information are intertwined. The flow of **energy** drives the processes that sustain and organize complex structures, while **information**—in the form of feedback mechanisms, genetic code, or patterns of interaction—guides how energy is used and distributed within the system. Odum's emergy concept directly ties energy to the structural "memory" or information embedded in a system: how past energy investments (emergy) have shaped the system's ability to organize and sustain itself. Odum extended this idea to the understanding of ecological and economic systems, where **information** is seen as the system's capacity to capture and store energy, while **complexity** emerges from the system's ability to handle more energy inputs efficiently. Ecosystems, for example, are complex precisely because they have evolved to efficiently capture and recycle energy flows through feedback loops, trophic levels, and nutrient cycles. In human societies, similar principles apply: technological systems, for instance, represent stored energy from past processes and inventions that allow for increasingly efficient use of energy over time. ### Emergy and Autotrophic Biosphere Communities in the Late 21st Century Looking ahead to **autotrophic biosphere communities** of the later 21st century—communities that are largely self-sustaining, relying primarily on internal energy sources—Odum's concept of emergy becomes especially relevant. Autotrophic communities are those that harness energy from non-organic sources (like solar energy, wind, or geothermal) to sustain themselves, much like how plants (autotrophs) use sunlight for photosynthesis to drive their energy needs. In such communities, emergy would help quantify the **efficiency** and **sustainability** of energy use. Communities would need to maximize their energy return on investment (EROI) by ensuring that their energy systems (such as solar, wind, and bio-based systems) are highly efficient and capture the maximum amount of energy for the least emergy investment. A sustainable autotrophic system would aim to minimize the emergy footprint by recycling materials, using renewable energy, and creating closed-loop systems for water, waste, and nutrients. Moreover, Odum's emergy theory suggests that these communities would need to maintain a balance between **complexity** (such as technological development or infrastructure) and the **natural energy flows** they harness. A community that depends too much on high-emergy systems (e.g., fossil fuel-driven infrastructure) may ultimately deplete its resources and become unsustainable, while one that invests emergy wisely in renewable, low-emergy technologies could evolve into a stable, self-sustaining system. Autotrophic biosphere communities would, ideally, integrate **ecological principles** into their energy systems, resembling natural ecosystems in terms of their **energy efficiency** and **cybernetic feedback** processes. Systems for capturing solar energy, recycling nutrients, managing water, and storing information would work synergistically to maintain the community’s complexity and function without relying on external (high-emergy) inputs like fossil fuels. ### Emergy and Energy Dissipation in Future Systems In Odum's framework, emergy also relates to how energy dissipation occurs in ecosystems or human-made systems. Autotrophic biosphere communities would need to be designed to **efficiently dissipate energy**, much like ecosystems do. For example, waste heat from industrial processes might be captured and reused, while agricultural systems could be designed to recycle nutrients and organic matter. The goal is to create a system where energy inputs are minimized and reused at every level, mimicking the **circular energy flows** found in nature. In these future communities, energy and emergy flows would be closely monitored to ensure that the system remains within its **carrying capacity**, and emergy analysis could provide a tool to assess the overall sustainability of the system. By tracking how much energy is required to produce various goods and services, communities can make informed decisions about resource use, technological investments, and environmental impact, ensuring that they remain resilient and self-sustaining over time. ### Conclusion Howard T. Odum’s concept of **emergy** offers a profound framework for understanding the relationship between **energy, information, and complexity** in both natural and human-made systems. As we look towards the possibility of **autotrophic biosphere communities** in the later 21st century, emergy provides a crucial lens through which to assess the sustainability and resilience of these systems. By using emergy to evaluate the cumulative energy investments in technology, infrastructure, and ecosystems, these communities can strive to efficiently harness energy flows while maintaining their complexity and capacity to self-organize—key principles that will be vital for thriving in a future shaped by renewable energy and ecological sustainability.