Global emissions of greenhouse gases such as CO2 have been rising continuously since the 1960s. In order to halt the associated acceleration of climate change, various efforts are under way to reduce energy requirements. Approaches include energy efficiency measures and digital technologies. In addition, renewable energy sources, biomass or even hydrogen are set to replace fossil fuels. However, these efforts alone are far from enough. Unavoidable and historical emissions need to be countered by “negative” emissions, and the technology to achieve this is becoming increasingly important. But how do negative emission technologies (NETs) work, why are they negative, and what are the challenges of these novel methods?
Everyone’s talking about net zero right now. Net zero means that the emission of CO2 into the atmosphere and the absorption of CO2 in natural or engineered reservoirs balance each other out. Especially since the 26th UN Climate Change Conference of the Parties (COP26), there has been an exponential increase in the commitments of companies and countries to be net zero by 2050. Such ambitious targets, however, beg the question: What is the concrete roadmap for achieving net zero?
Why do we need to talk about negative emissions?
At the 21st UN Climate Change Conference (COP21), the global community voted to adopt the Paris Agreement, an international treaty on climate change. Under the agreement, 197 countries agreed to limit global warming by 2100 to well below 2, preferably to 1.5°C, compared to pre-industrial levels. According to a special report by the Intergovernmental Panel on Climate Change (IPCC), the 1.5-degree target has significant advantages over the 2-degree target. At the current level, however, the world’s activities will lead to warming of about 2.7°C compared to pre-industrial levels. Therefore, global greenhouse gas emissions must be cut drastically – to net zero by mid-century – if we are to meet the science-based climate target by 2100. So far, however, many of the necessary transformations have failed to materialize (see also the outcomes of COP26). To reach ambitious climate goals, we need to embrace efficiency measures and reduce our use of fossil fuels, but also to tighten climate policies and adopt new technologies. This is where negative emissions come into play.
What are negative emissions?
Another way to describe negative emissions is the term “carbon dioxide removal” (CDR). CDR, i.e., the retrieval of CO2 from the atmosphere, is the opposite of carbon emissions – hence the term “negative emissions”. Negative emission technologies (NETs) remove carbon dioxide from the atmosphere and store it permanently. While processes that remove other greenhouse gases, such as methane, from the atmosphere are also being discussed and researched internationally, the IPCC special report on the impacts of global warming of 1.5 °C and this article focus on the removal of CO2 as the most significant and long-lived greenhouse gas.
Negative emissions go one step further than carbon credits, which have been embraced by governments all over the world as a way to limit industrial CO2 emissions. Although carbon credits and CO2 certificates help to compensate for emissions, any existing or produced CO2 remains in the atmosphere. And that’s where NETs come in to play with a major advantage: they actually eliminate the existing footprint by permanently removing CO2 from the air.
Negative emissions are indispensable if we are to limit global warming to no more than 1.5 degrees
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