Thursday, March 18, 2021

Carbon Capture and Storage: The Negative Carbon Option?

There used to be one coal-fired electricity generating plant in the US using carbon capture and storage (CCS) technology, the Petra Nova plant outside of Houston, Texas. It's now been shut down. It's not that the plant was a roaring technology success; for example, the process for scrubbing out the carbon required so much energy that the company had to build a separate natural-gas power plant just for that purpose. Still, I was sorry to see it go. There are other US plants, not coal-fired, learning about carbon capture and storage. But the way to learn about new technologies is to use them at scale. 

Here, I'll take a look at the Global Status of CCS 2020 report from the Global CCS Institute (December 2020) and the Special Report on Carbon Capture Utilisation and Storage: CCUS in clean energy transitions from the International Energy Agency (September 2020). These reports make no effort to oversell carbon capture and storage. Instead, the argument is that in specific locations and for specific purposes, carbon capture and storage technology could be a useful or even a necessary part of reducing carbon emissions. 

Brad Page, chairman of the Global CCS Institute, notes: "Just considering the role for CCS implicit in the IPCC 1.5 Special Report, somewhere between 350 and 1200 gigatonnes of CO2 will need to be captured and stored this century. Currently, some 40 megatonnes of CO2 are captured and stored annually. This must increase at least 100-fold by 2050 to meet the scenarios laid out by the IPCC." Nicholas Stern adds: "We have long known that CCUS will be an essential technology for emissions reduction; its deployment across a wide range of sectors of the economy must now be accelerated."

The basic point here is that even if there can be an enormous jump in non-carbon energy production for most purposes, there are likely to remain a few uses where it is extremely costly to substitute away from fossil fuels. Common examples include the iron, steel, and concrete industries, as well as back-up power-generating facilities that are needed for stabilizing power grids. For those purposes, carbon capture and storage technology can keep the resulting emissions as low as possible. Carbon capture and storage might have a role to play in a shift to hydrogen technology: hydrogen generates electricity without carbon, but using coal or natural gas to make the hydrogen is not carbon free. Moreover, it would be useful to have at least a few energy technologies that are carbon-negative. Examples would include if it is possible to combine biofuels with carbon capture and storage technology, or perhaps even in certain locations to use a cheap but local noncarbon energy source (say, geothermal energy) to capture carbon from the air. 

The IEA report summarizes the current situation in the US for carbon capture and storage technology this way: 

The United States is the global leader in CCUS development and deployment, with ten commercial CCUS facilities, some dating back to the 1970s and 1980s. These facilities have a total CO2 capture capacity of around 25 Mt/year – close to two-thirds of global capacity. Another facility in construction has a capture capacity of 1.5 Mt/year of CO2, and there are at least another 18-20 planned projects that would add around 46 Mt/year were they all to come to fruition. Most existing CCUS projects in the United States are associated with low-cost capture opportunities, including natural gas processing (where capture is required to meet gas quality specifications) and the production of synthetic natural gas, fertiliser, hydrogen and bioethanol. One project – Petra Nova – captures CO2 from a retrofitted coal-fired power plant for use in EOR though operations were suspended recently due to low oil prices. ...  All but one of the ten existing projects earn revenues from the sale of the captured CO2 for EOR operations. There are also numerous pilot- and demonstration-scale projects in operation as well as significant CCUS R&D activity, including through the Department of Energy’s National Laboratories.
I found the IEA discussion of potential options for removing carbon from the atmosphere to be especially interesting. as they state: "Carbon removal is also often seen as a way of producing net-negative emissions in the second half of the century to counterbalance excessive emissions earlier on. This feature of many climate scenarios however should not be interpreted as an alternative to cutting emissions today or a reason to delay action."

Basically, there are nature-based and technology-based options. The nature-based solutions involve finding ways to absorb more carbon in plants, soil, and oceans. The main technology solutions are bioenergy carbon capture and storage, commonly abbreviated as BECCS and direct air capture with storage, often abbreviated as DACS. The IEA writes: 

While all these approaches can be complementary, technology solutions can offer advantages over nature-based solutions, including the verifiability and permanency of underground storage; the fact that they are not vulnerable to weather events; including fires that can release CO2 stored in biomass into the atmosphere; and their much lower land area requirements. BECCS and DACS are also at a more advanced stage of deployment than some carbon removal approaches. Land management approaches and afforestation/reforestation are at the early adoption stage and their potential is limited by land needs for growing food. Other non-technological approaches – such as enhanced weathering, which involves the dissolution of natural or artificially created minerals to remove CO2 from the atmosphere, and ocean fertilisation/alkalinisation, which involves adding alkaline substances to seawater to enhance the ocean’s ability to absorb carbon – are only at the fundamental research stage. Thus, their carbon removal potentials, costs and environmental impact are extremely uncertain.

Here are a few words from the IEA on BECCS and on DACS:

BECCS involves the capture and permanent storage of CO2 from processes where biomass is converted to energy or used to produce materials. Examples include biomass-based power plants, pulp mills for paper production, kilns for cement production and plants producing biofuels. Waste-to-energy plants may also generate negative emissions when fed with biogenic fuel. In principle, if biomass is grown sustainably and then processed into a fuel that is then burned, the technology pathway can be considered carbon-neutral; if some or all of the CO2 released during combustion is captured and stored permanently, it is carbon negative, i.e. less CO2 is released into the atmosphere than is removed by the crops during their growth. ... The most advanced BECCS projects capture CO2 from ethanol production or biomass-based power generation, while industrial applications of BECCS are only at the prototype stage. There are currently more than ten facilities capturing CO2 from bioenergy production around the world . The Illinois Industrial CCS Project, with a capture capacity of 1 MtCO2/yr, is the largest and the only project with dedicated CO2 storage, while other projects, most of which are pilots, use the captured CO2 for EOR [enhanced oil recovery[ or other uses. ...

A total of 15 DAC plants are currently operating in Canada, Europe, and the United States. ... Most of them are small-scale pilot and demonstration plants, with the CO2 diverted to various uses, including for the production of chemicals and fuels, beverage carbonation and in greenhouses, rather than geologically stored. Two commercial plants are currently operating in Switzerland, selling CO2 to greenhouses and for beverage carbonation. There is only one pilot plant, in Iceland, currently storing the CO2: the plant captures CO2 from air and blends it with CO2 captured from geothermal fluid before injecting it into underground basalt formations, where it is mineralised, i.e. converted into a mineral. In North America, both Carbon Engineering and Global Thermostat have been operating a number of pilot plants, with Carbon Engineering (in collaboration with Occidental Petroleum) currently designing what would be the world’s largest DAC facility, with a capture capacity of 1 MtCO2 per year, for use in EOR [enhanced oil recovery] ...
Reducing carbon emissions isn't likely to happen through any single solution, but rather through a portfolio of actions. It seems to me that carbon capture and storage has a small but meaningful place in that portfolio. For a couple of earlier posts on this technology, see: