Will negative emission technologies fulfill their promise?

The Paris Agreement has set high standards for global action on climate change. Yet, as emissions continue rising, many people are out to explore novel solutions to bring about necessary changes. Negative Emissions Technologies (NETs), also called Carbon Dioxide Removal (CDR), are among these new approaches.

The basic premise is that we can decrease carbon contents in the atmosphere by burying CO2 underground, on land or in the oceans. NETs vary from nature-based solutions, like afforestation or biochar from agricultural waste, to technological ones, like converting CO2 into stone or increasing ocean alkalinity. The question is whether they can really serve their purpose adequately. Wouldn’t the new ingredient ruin the pie altogether?

Much progress has been made with NETs to date. The first large-scale negative-emissions plant was launched in Iceland last year and over 2,000 studies have been published on the topic. Recently, a team of 20 scientists published the first systematic review of NETs, covering ethical, technological, economic and other critical aspects of the emerging technology.

Scientists emphasize that NETs should not be considered geoengineering as these technologies “address the root cause of climate change by reducing atmospheric CO2 concentrations,” while geoengineering approaches like solar radiation management simply deal with the consequences and are often much riskier.

Geoengineering is adaptation. NETs are mitigation. And, according to their proponents, they are unavoidable if we want to achieve the optimistic scenario of limiting global temperature rises to 1.5°C. Without these technologies, it is argued, we are likely to see temperatures rise far above a devastating 2°C. Even if other measures prove workable, NETs will anyways be good options as they can provide a safe space for transition and keep the planet livable.

But there are also critics of NETs. First, there’s a long way to go from scientific reasoning to practical applications. Extra CO2 captured by phytoplankton thanks to ocean fertilization has often been later rereleased into the atmosphere through the food chain. Meanwhile, Direct Air Carbon Capture and Storage can provide reliable long term carbon storage, however the technology is little developed and comparably expensive at the moment. Even NETs proponents admit that most of the research is in its early stages.

Thus, there is a risk of “failing the scale”. Given too much weight, NETs might be implemented at the cost of more reliable solutions like switching to renewables or balancing consumption. Yet, without delivering the expected results, they may close the path to Paris targets altogether, as it might be too late for other activities to start delivering timely results.

Second, there are risks of dangerous responses from the natural cycles, while stopping halfway may just be impossible. Purposefully cooling the planet would hide the real impacts of warming for a while, and when we have grown the capacities of large-scale CDR or other technology, suddenly stopping these activities under political or economics circumstances might mean a drastic shift in ecosystem resilience, which could be extremely hard to predict or deal with.

Temperatures may start rising 3-4 four times faster above historical averages, leading to extreme weather events in many parts of the planet, according Christopher Trisos and his colleagues in a paper published in Nature Ecology & Evolution. If the risk of stopping doing something is so big, maybe it’s better not to do this at all?

And third, as a recent report by the European Academies Science Advisory Council states, NETs “will not compensate for inadequate climate change mitigation efforts”. CDR projects would allow us to continue with the business-as-usual of burning fossils, thereby coming to rely on an unstable technology while losing motivation for switching to renewables. 

Here, NETs are no longer considered as mitigation strategy as they do not address the real root causes, such as our continued dependence on fossil fuels. James Hansen, a leading climate change scientist and advocate notes that NETs should not provide a “get-out-of-jail-free card to policymakers”.

NET critics have gone as far as to model “deep mitigation pathways” to the 1.5°C scenario without the technology involved. Detlef van Vuuren and his colleagues emphasize the potential of solutions like change in lifestyles, non-CO2 greenhouse gas reductions, and increasing the speed of electrification based on renewables. They say going this way is both possible and feasible, while also contributing to other sustainability goals.

All in all, according to David Keith, a geoengineering expert at Harvard University, we have very little time left to apply the technology responsibly before more desperate and unregulated attempts go large-scale. And, if we are to seriously face climate challenges, discussions are urgently needed for well-thought-out and responsible actions.