For a million reasons, ranging from the industrial revolution to an unhinged consumerist mindset, the Earth has exceeded the previously critical threshold of 1.5 degree of warming. The natural warmth of the planet’s atmosphere has been disrupted by an accelerated production of the greenhouse gases: carbon dioxide, methane, nitrous oxide and hydrofluorocarbons (remember we protected our ozone from this villain once?). It’s the classic problem of too much of anything is bad. This excess is predominantly composed of CO2, which we have released too much of, turning Earth’s warmth for us into raging heat.
Thankfully, in more pockets than before, there are pledges and promises to reduce any further additions. Some of us are trying to control the damage we will most definitely inflict on the planet. Cue all the words synonymous with Net Zero Targets, Carbon-neutral, Low-carbon future et al; let’s call them the Net Zero Troop. These are a set of strategies designed to curtail the rising emissions from industrial processes of manufacturing, transportation, and agriculture. While there are numerous roadblocks in actually reducing emissions from these processes, for the purpose of this entry, let’s believe they are somewhat successful.
Despite an ambitious deceleration in emissions, the problem of extant CO2 enmeshed in our atmosphere will persist. The reduction in emissions will ensure less ensuing damage; the damage that has already been done cannot be addressed through ambitious targets and strategies. It is here, in this additional capacity, that Carbon Dioxide Removal enters the damaged stage. CDR, in short, refers to a set of technologies that, true to their name, seek to remove carbon dioxide from the air. This differs from Carbon Capture, Use, and Storage (CCUS); that character, which is a part of the Net Zero troop, seeks to capture CO2 from industrial processes and use it in relevant industries or store it underground. CCUS is a tool to reduce CO2 emissions from current industrial processes; CDR is designed to remove the CO2 from the air.
The CDR troop includes two kinds of technologies: Closed System and Open System. The more prominent Closed System Actor is the fancy, more infrastructure-heavy technology called the Direct Air Capture, or DAC. Quite literally, the associated infrastructure is designed to capture CO2 from the air, directly. (These Carbon-tech families have very lucid names, no?) This technology has predominantly taken off, by which I mean established, in developed economies:
Courtesy: DACC Map – Direct Air Capture Coalition
The good folks at Direct Air Capture Coalition (DACC) who have mapped the extent of this technology, expect 93 such plants to be operational by 2030 “with a combined capacity of 6.4-11.4 MtCO2/yr”. As on date, the median production of DAC plants is at “100 tCO2/yr”. The captured CO2 is injected into the ground, geological storage.
Another Closed System Actor is the somber Biochar, which leverages biomass waste to capture CO2. The biomass waste is carbonized under high temperatures, also called the pyrolysis process, to produce Biochar. This intervention operates in a closed-setting of minimum oxygen, to capture the carbon dioxide in the lookalike of charcoal. Biochar is then applied to agricultural fields as an alternative to fertilizers to improve soil health. The settings in the pyrolysis system determine the effectiveness and longevity of carbon captured. Research suggests that Biochar can capture between 2-3GtCO2/yr, upon global application.
Unlike the Closed System Actors that are characterized by controlled environments, the Open System Actors operate in a more variable environment relying on natural processes to sequester CO2. These actors include: Enhanced Rock Weathering (ERW), Oceanic CDR, and Afforestation. Of these, ERW has gained prominence, perhaps competing with the popularity of Afforestation – often misrepresented as a catch-all solution through monoculture plantations. Forests are ecologically diverse and better positioned to sequester carbon over extended periods compared to the plantations, which are typically harvested at predetermined times, releasing stored carbon back into the atmosphere.
ERW attempts to leverage the mineralization property of rocks to remove and store CO2 geologically. The popular application in recent times has been that of ground basalt in agricultural fields. While this has observable benefits for the agricultural produce and soil health, its carbon removal process is a bit like voodoo. The theory is that absorbed carbon dioxide reacts with the basalt to form carbonic acid, which eventually through permeation into groundwater or run-off through rivers will form stable bicarbonate ions in the ocean, storing the removed carbon. ERW is expected to remove up to 2GtCO2/yr annually, once scaled.
Now, there are many questions that arise with respect to the entire CDR clan:
- Each of these actors has a deep, jargonized process. For instance, what is pyrolysis as used in biochar? Biomass is of varied kinds. Do all of them make similarly potent biochar? Likewise, does ERW perform similarly across soil types?
- How do these compare in terms of effectively removing and storing carbon for millenia? (I’m jk, but we need them locked forever, ideally, and for a long time, definitely). The measurement, reporting and verification (MRV) system for this family is still being developed, and isn’t ripe for etching their strengths in stones. (Geddit?) Biomass-based approaches like Biochar, Afforestation, and ERW are dependent on soil quality and permanence of land use decisions. DACS is more dependent on ensuring that its inherent construction and storage of carbon doesn’t negate the quantity removed from the air. Until we get into this question, here’s a very well-made diagram from WRI:
Courtesy: New Developments in Carbon Dioxide Removal | World Resources Institute
- How does one lay adequate emphasis on CDR and its credits being an additionality and yet maintain the importance of mitigation strategies? The net-zero clan’s rightful center-stage prominence?
We are lucky that the CDR clan is living rent-free with my two brain cells for the rest of this month. We are going to take these questions sequentially, with a focus on the Indian markets, and appear enlightened at the end of all three. The first question is a set of biographies, laden with scientific jargon. Armour yourself with persistence, we are in for a ride!