Life Cycle Energy and Climate Change Implication of Nanotechnologies: A Critical Review

Summary The potential environmental and health impacts of nano-technologies triggered a recent surge of life cycle assessment (LCA) studies on nano-technologies. Focusing on the energy use and greenhouse gas emissions impacts, we reviewed 22 LCA-based studies on nano-materials, coatings, photovoltaic devices, and fabrication technologies that were published until 2011. The reviewed LCA studies indicate that nano-materials have higher cradle-to-gate energy demand per functional unit, and thus higher global warming impact than their conventional counterparts. Depending on synthesis method, carbon-based nanoparticles, i.e., carbon nano-fibers, carbon nano-tubes and fullerenes require 1-900 giga joule per kilogram (GJ/kg) of primary energy to produce, compared with ~200 mega joule per kilogram (MJ/kg) for aluminum. This is mainly attributed to the fact that nano-materials involve an energy intensive synthesis process, or additional mechanical process to reduce particle size. Most reviewed studies ascertain, however, that the cradle-to-grave energy demand and global warming impact from nano-technologies in a device level is lower than from conventional technologies because nano-materials are typically used in a small amount to improve functionality and the upgraded functionality offers more energy efficient operation of the device. Due to immature status of most nano-technologies, the studies reviewed here often rely on inventory data estimated from literature values and parametric analyses based on laboratory or prototype production, warranting future analyses to confirm the current findings.