Carbon Dioxide Removal Features Improved in En-ROADS
By
Charles (Skuk) Jones
February 4, 2021
As part of our continuous improvement of the En-ROADS simulator, this month we released added detail for a carbon dioxide removal (CDR) technique called enhanced mineralization. CDR has been in En-ROADS from the start, divided between afforestation and “technological” approaches. With this release, we improved the model formulation of enhanced mineralization and added some graphs that help clarify the resources needed for many kinds of CDR. This is just one example of the way En-ROADS can be and will be improved in reaction to the latest science, public interest, and policy discussions.
We were motivated to improve enhanced mineralization because articles last year touted its “vast” potential for CO2 removal (e.g. in the Guardian).
Mineralization, also called weathering, is part of the natural carbon cycle – certain minerals react with carbon dioxide and water to form carbonates, which wash into the deep ocean or underground, moderating atmospheric CO2 levels over geological time frames.
Enhanced weathering or mineralization is proposed as a method to deliberately accelerate this normally slow process. The “enhanced” part of the process includes grinding rocks to increase their surface area and then spreading the ground rock over fields, beaches, or other open land so it can react and capture CO2. Mineralization advocates hope this effort would make a meaningful contribution to keeping temperature change below 2°C.
As we have done before with afforestation, we want to ground hope on a potential climate solution in knowledge of what the intervention takes, and how much it can accomplish. In the new model structure for enhanced mineralization, we represent the time it takes for the practice to be adopted and the infrastructure to be built. After adoption, the gross amount of CO2 removed by mineralization is a function of the land area the ground rock is applied to and the amount of rock per area. Additionally the chemistry of rock weathering is considered. The net CO2 captured is the gross amount of CO2 removed minus the emissions from energy used to grind and spread the rock. You can adjust all these parameters and assumptions in the latest release of En-ROADS.
How do I use the new enhanced mineralization features in En-ROADS?
Enhanced mineralization is, as it was before, under Technological carbon removal. The main slider increases mineralization along with other carbon removal techniques. If you want more control you can open the advanced settings menu (the three dots toward the right of main slider), select the “Use detailed settings” switch, and adjust each technique individually with its respective slider.
In addition, to the percent of maximum and the start year sliders for enhanced mineralization, you can adjust other parameters in the Simulation > Assumptions > Mineralization settings menu.
“Maximum area” and “rock application” together determine the tons of rock spread every year.
“Energy intensity of mineralization”—along with the energy system characteristics as influenced by other En-ROADS inputs—determines the emissions from producing the rock to be spread, which counteracts some of the CO2 absorbed.
“Specific mineralization potential” concerns the chemistry of weathering. For example, some minerals or smaller grain sizes can absorb more CO2 per ton than our default assumption that basalt is used. The other minerals usually have a higher energy cost.
The “Time to deploy mineralization” represents how fast farmers are willing to change practices, and how fast infrastructure can grow along with demand.
With the detailed controls, you can test the mental models of participants who have detailed opinions about enhanced mineralization. For example, want to add deployment on beaches in addition to fields? Just increase the maximum area, the chemistry is the same. Want to mix in some other mineral with the assumed basalt? Increase the specific potential, but be sure to increase energy intensity as well. And as always, when someone wants to talk in detail about their favorite solution, push them to uncover how it fits in with multisolving. What do they think mineralization does for health and jobs and justice?
When you move any of the CDR sliders in En-ROADS, there are some key graphs you want to look at, found in the “Removals and Land Use” section. “Bulk material for Mineralization” shows the amount of rock it takes every year to achieve the selected removals. Most CDR techniques can be seen on one or the other of the land graphs. “Land for Growing CO2-Removal Biomass” shows a stacked graph of the land that is required for techniques that compete with farmland and other available land. “Land for Farming with CO2 Removal” has lines that are not stacked, because these techniques can be used together and on the same land as land used to grow food.
One way to use these graphs is to show your audience the scale of effort these techniques would require. See how the land needed quickly surpasses the area of India(!), or how bulk material rivals the entire coal industry in tons of stuff moved every year—all to save a few tenths of a degree. This is not to say there is no place for CDR among climate solutions—it takes many flowers to grow a garden—just that nothing is an easy alternative to keeping fossil fuels safely in the ground. Take a look at En-ROADS and explore for yourself.
We are interested to know what we might change or improve in developing these or any other policies we might build out in the future. We welcome ideas for how to improve En-ROADS and what policies you think are important parts of the current conversation. Let us know on the forum.
