Carbon capture and storage – a viable emissions reduction technology?
Reducing greenhouse gas (GHG) emissions from the energy sector is one the biggest challenges in fighting climate change. According to the International Energy Agency (IEA), the global power sector accounted for nearly two-thirds of emissions growth in 2018.
Rising emissions are causing global temperatures to rise, and without drastic measures to mitigate the impacts of climate change, the world faces a “global cascade of tipping points” that could lead to devastating impacts on human societies and ecosystems.
No single technology or strategy will provide all the emissions reductions needed, but carbon capture and storage (CCS) is one such tool. However, due to factors such as cost and scalability, there are not many large scale carbon capture and storage plants in operation worldwide. The reality of CCS does not match up with the expectations of the technology, and as a result, has not been widely adopted.
What is carbon capture and storage?
CCS is the process of capturing and storing carbon dioxide (CO2) from large industrial sources before it is released into the atmosphere. There are three main methods of capturing carbon dioxide from power plants: post-combustion, pre-combustion and oxy-fuel combustion.
The most familiar form of CCS is its use in fossil fuel power plants. The technology aims to capture carbon emissions directly from the source, but due to slow development and high-profile problems, there is a sense that CCS processes might be too complicated, expensive, and technologically challenging to succeed.
How does carbon capture and storage work?
Carbon dioxide is captured, compressed into liquid state, and transported by pipeline, ship, or road tanker for storage. The liquid is then injected into storage sites typically made of porous rock formations with impermeable rocks above that ensure the carbon dioxide remains stored over time. Sites include depleted oil and gas fields, coal-beds, or deep saline aquifers located deep underground (about 1km).
Source (ABC Australia, 2012)
How effective is carbon capture and storage from fossil fuel plants?
Fossil fuel plants generate different amounts of carbon dioxide emissions. This is dependent on the type of fuel used, the type of power generation, the size of the plant, and how efficient it is. Research has shown that CCS technology has the potential to reduce carbon dioxide emissions from a coal-fired power plant by more than 85 percent, compared to a plant without CCS.
However, in order to achieve this reduction, the capture unit needs to consume about 30 percent of the energy produced by the plant. This means that a coal-fired power plant with CCS would need to burn more fuel to generate the same amount of energy as a plant without this added technology.
Carbon capture industry claims are misaligned with reality
Currently, there are 51 large-scale CCS facilities globally. Of these, 19 are operating, four are under construction, and 18 are in early development. The industry claims this technology can capture up to 90 percent of carbon dioxide emissions from fossil fuel plants, but in reality this has not been the case.
An example of this is Petra Nova, a newly-operational carbon capture plant near Houston, Texas which began construction in 2014 and came online in 2016. This plant was built alongside a pre-existing conventional coal power unit, and uses a pre-existing Mitsubishi/Kansai developed process to scrub carbon from the flue gases, making it “post-combustion”, or “the world’s largest post-combustion carbon capture facility installed on an existing coal-fuelled power plant”.
According to the project’s own figures, it captures 90 percent of the carbon dioxide from an adjacent 240MW coal unit – 4776 metric tonnes a day or 1.6 million tonnes annually. However, in the first two years of full operation, Petra Nova only managed to capture between 65 percent and 70 percent of the carbon dioxide. According to research conducted by the Institute for Energy Economics and Financial Analysis (IEEFA), this doesn’t take into account the emissions from the natural gas turbine used to run the carbon capture equipment. With these additional emissions, Petra Nova is actually capturing about 50 percent of carbon dioxide emissions from the plant.
SaskPower’s Boundary Dam CCS plant has come under fire for similar issues. The project was expected to capture 90 percent of the carbon dioxide emitted from the plant, but instead, captured less than half that amount. Ongoing issues with Boundary Dam have resulted in the plant being shut down several times.
Challenges and opportunities in using carbon capture and storage
The IEA and IPCC agree that CCS will be necessary to meet ambitious climate targets as CCS technologies prove great alternatives in the sequestration of carbon process. However, electricity produced by power plants with carbon capture technology is several times higher than the cost of existing carbon-free technologies. It is both a financial and political risk, especially because coal is already losing on price to renewable energy sources such as wind.
The main issue with CCS is its high upfront cost, with initial investments at around several billions of dollars. Large-scale projects also require long lead times. Projects can take up to a decade to develop. Building carbon capture technology into existing power plants may sound achievable, however this still requires a pipeline and storage infrastructure at scale, resulting in additional costs to any carbon capture and storage project.
There are also several physical risks associated with CCS projects. Carbon dioxide stored underground has the potential to leak and contaminate groundwater. It can also induce seismic activity due to pressure built up from the large volume of carbon dioxide injected underground. Stored carbon dioxide could also impact the climate through slow or large releases of carbon dioxide to the surface, further impacting soil, trees, and other vegetation.
If carbon capture can be added to an existing coal plant in an economically viable way, a future price on carbon could make the capture part of CCS viable as technology develops and costs fall.