Carbon dioxide emissions from anthropic activities have accumulated in the atmosphere in excess of 800
Gigatons since preindustrial times, and are continuously increasing. Among other strategies, CO2 capture
and storage is one option to mitigate the emissions from large point sources. In addition, carbon dioxide
extraction from ambient air is assessed to reduce the atmospheric concentration of CO2. Both direct and
indirect (through photosynthesis) pathways are possible.
Geological sequestration has significant disadvantages (high cost, low public acceptance, long term
uncertainty) whereas carbon dioxide recycling (or utilization) is more consistent with the basic principle
of industrial ecology, almost closing material cycles.
In this article, a series of technologies for CO2 capture and valorization is described as integrated and
optimized pathways. This integration increases the environmental and economic benefits of each
technology. Depending on the source of carbon dioxide, appropriate capture and valorization processes
are evaluated based on material and energy constraints.