By Sirui Ma
Moving toward circular economy, rethinking and redesigning the production and recycling cycle is crucial to diminishing externalities. In order to “close the loop”, a variety of efforts are concerned, including materials used in production, easiness to dismantle disposed products, etc. Among all efforts that contribute to a “closed loop”, introducing renewable energy to the production process is one of the most essential. The significance of renewable energy is not limited to the concept “renewable”, which is often related with less carbon emission. One other advantage of renewable energy is its peculiar characteristics: LOCAL.
Why Renewable Energy?
Carbon emission is one of the major barriers to “close the loop” since a large percentage of manufacturers are still heavily relying on burning fossil fuels such as coal and refined oil products. In the perspective of reducing carbon output into the environment, introducing renewable energy input in the production line has gained its importance more than ever before. According to EIA statistics, 1364 million metric tons of carbon dioxide was produced by coal power plants in 2015, accounting for 71 percent of carbon emission by the national electric power sector. Given the huge quantity of carbon emission by coal burning, it is intuitive to imagine how renewable energy can reduce carbon emission at an extraordinary scale.
From Global to Local
However, in the process of replacing traditional energy with renewable energy, several properties of renewable energy need to be addressed: energy density, energy storage and transportation, as well as the match-up of energy suppliers and end-users.
While it is hard to generalize the characteristics of all renewable energy, different type of renewable energy has different advantages and limits. Among all renewable energy, hydroelectric power is one of the most stable energy types with a relatively high energy density. Wind power is strong but relatively unstable due to variation of wind speed and direction. Solar power has a smaller density but overall a stable output. Based on limits and advantages of different types of renewable energy, it is essential to characterize the type of energy demand of a specific type of production and find the most appropriate renewable energy to serve a local industry. The process of determining the energy source(s) for a factory should thus be added into the “rethinking” procedure of circular economy agenda.
In rethinking and redesigning of the industry, it is also momentous to understand the characteristics in the production and transportation of renewable energy. Fossil fuel, which stores energy in a condensed form, often needs a series of energy “dilution” steps before it can be used in daily life, in the form of electricity. Renewable energy, on the other hand, is in a relatively loose form with energy density of equal or less than 1 kW/m2 in its original state. Although the energy density cannot be compared with fossil fuels, the level of energy may be used directly by households without extra steps of “dilution”. Avoiding the “dilution” process can significantly increase the efficiency of energy use. What’s more, because of global scattering of fossil fuel reserves, the energy often experiences a “long haul” before reaching users. A huge energy loss is induced in the transportation process. In the case of renewable energy, “long haul” is definitely not an ideal choice. Based on the fact that long distance transportation is both technically difficult and costly, the use of renewable energy should be concentrated on the local economy.
Circular Economy is not just about reducing the environmental externalities of an industry. In fact, reducing energy loss is also vital in the idea of “closing the loop”. By relying more on renewable energy, an appropriate match between renewable energy and end-user demand can significantly improve the efficiency of energy use. In a well-designed circular economy structure, raw materials and energy resources are all from local suppliers. Appropriate match-ups between energy suppliers and end-users should be designed beforehand. For existing manufacturers, retrofitting the energy and raw material supply based on current circumstances is also promising and cost-effective. Overall, a more efficient management system is required to approach the goal of localizing circular economy, either designing or retrofitting.