Carbon capture and storage technologies offer us an effective means of reducing CO2 emissions from power plants. They involve collecting CO2 at its source, transporting it safely, and injecting it into geologic formations for permanent storage.
CO2 is injected into basaltic rock formations where it reacts with minerals to form stable minerals that can be monitored over time and provide a robust storage mechanism.
Capture
Carbon Capture and Storage (CCS, or CCUS for short) uses proven technologies to lower emissions from power stations and industrial plants. The process involves collecting CO2 at its source before transporting and permanently storing it underground geological formations.
CO2 can be captured at various sources, from steel or cement plants, or post combustion (i.e. when fossil fuels have been burned to generate electricity). Once captured, captured CO2 must be treated, purified and compressed into liquid form for transport via pipelines or specially equipped ships.
CCS processes use considerable energy, meaning power plants with CCS require more coal to generate the same amount of electricity than non-CCS plants. This increases “upstream” environmental impacts such as mining pollution and transportation pollution while increasing costs of electricity generated at power stations; making CCS less competitive with renewable and other clean energy sources.
Compression
Compressing CO2 prior to transport to geological storage sites requires considerable energy, which is usually generated at power plants using similar processes as those used for electricity generation (compression).
CO2 gas captured is chilled and compressed further, changing it from solid to liquid form before being transported by pipeline to geologic storage sites such as old oil & natural gas reservoirs, deep saline formations or unmineable coal beds for safekeeping.
Once at its storage site, CO2 is injected deep underground in geological formations where it can be safely stored long term. A variety of processes may be employed to inject this gas, including reversing existing oil wells or drilling to deeper temperatures and pressure levels than usual – or by creating new wells where these parameters exceed standard. Structural trapping prevents the injected CO2 from migrating vertically towards the surface.
Transportation
Carbon capture and storage technology isn’t exclusive to power plants; it can also be applied in transportation systems. Buses running on natural gas, for instance, are being equipped with carbon capture devices which reduce emissions – this could pave the way towards greener methods of transportation such as electric vehicles.
Once CO2 has been captured and compressed, it must be transported to its storage site. Pipeline transport is often preferred as it offers strong economies of scale and lower unit costs than other modes; however, its energy penalty must also be considered when considering this mode.
CO2 can be stored in deep geological formations such as saline aquifers and depleted oil and gas reservoirs. Researchers are exploring methods such as mineral carbonation – using minerals to secure long-term storage of CO2.
Storage
Carbon capture and storage (CCS) involves extracting climate-warming CO2 from industrial exhaust gas or directly from the atmosphere and permanently storing it underground – an essential step toward creating a low carbon future.
At power plants, large fans channel air to machines that chemically separate CO2 before it exits through a smokestack. Once separated, this gas is compressed into liquid form before being transported by pipeline or specially-adapted ships to its storage site.
Once at its storage location, CO2 is pumped over 2,500 feet down wells into geological formations such as depleted oil and gas reservoirs or saline aquifers with specific characteristics that ensure long-term storage – such as being capable of safely holding large volumes over a wide area. Furthermore, injection into these formations may help increase oil production via enhanced oil recovery (EOR), with CO2 then permanently stored underground among rocks in its vicinity.