![]() ![]() This is more than a quarter of total annual global energy demand for all uses, of around 550EJ. On this basis, the paper says that capturing 12 billion tonnes of CO2 equivalent (GtCO2e) per year (around a third of annual global emissions) would require 156 exajoules (EJ) of energy. Or, perhaps, as much as 12GJ/tCO2 once inefficiencies and other stages of the process are taken into account. Jospe tells Carbon Brief: “The big question in people’s minds is cost…That’s the potential nail… the coffin DAC.”Īccording to a 2016 Nature paper, DAC would require a theoretical minimum of 0.5 gigajoules (GJ) of energy to remove and store each tonne of CO2. (This view of high costs is disputed, however – see below). This is often thought to mean that the costs and energy needs for DAC will be many times larger than for CCS. ![]() These estimates are based on extrapolating what we know about carbon capture and storage (CCS) at power plants, where CO2 levels in flue gases are much higher than in ambient air. ![]() Academic estimates for the cost of CO2 capture, transport and storage, along with regeneration of chemicals used in the process, range from $400 to $1,000 per tonne of CO2. There is a widely held perception that it is extremely costly, in both energy and financial terms. Yet direct capture also has an achilles heel. “You have an unambiguous carbon sink, whereas trees can get cut down.” points out that DAC avoids the complex question of biomass carbon accounting, which clouds the other leading negative emissions option, bioenergy with CCS (BECCS). It has a number of attractive features, including a limited land footprint, the ability to site units near to CO2 storage sites and a clarity around how much CO2 it sequesters, in contrast to negative emissions that use biomass.Ĭhristophe Jospe, an independent consultant and former chief strategist at the Center for Negative Carbon Emissions at Arizona State University. (Last year, Carbon Brief produced a series of articles on the need for negative emissions, the options available and whether they are feasible – or merely a distraction that encourages complacency).ĭirect air capture (DAC) is one of those options, with DAC machines often described as “sucking CO2 from the air” or “artificial trees”. Some estimates suggest as much as five billion tonnes of CO2 (GtCO2) would have to be removed from the atmosphere, and then locked away underground, each year by 2050. This has sparked a growing realisation that so-called negative emissions might be necessary to meet the goals of Paris, where an overspend against the carbon budget is paid back by pulling CO2 from the air. The accord also calls for a “ balance” between greenhouse gas emissions sources and sinks in the second half of the century, equivalent to reaching global net-zero emissions.Įven before Donald Trump said the US would pull out of the deal, national climate pledges, when viewed cumulatively, fell far short of what would be needed, with the carbon budget for 1.5C set to be used up within as little as four years. Under the 2015 Paris Agreement on climate change, nearly 200 countries agreed to limit warming to “well below” 2C above pre-industrial levels and to aim for no more than 1.5C. It aims to be capturing 1% of global CO2 emissions each year by 2025.Ĭarbon Brief travelled to the opening of the plant and interviewed co-founder Christoph Gebald to find out more about Climeworks’ ambitions, how the technology works and how it might contribute to global climate goals. This is partly covered by selling the CO2 to a nearby fruit and vegetable grower for use in its greenhouse.Ĭlimeworks hopes to get this down to $100/tCO2 by 2025 or 2030. On the roof of a waste incinerator outside Zurich, the Swiss firm Climeworks has built the world’s first commercial plant to suck CO2 directly from the air.Ĭlimeworks says that its direct air capture (DAC) process – a form of negative emissions often considered too expensive to be taken seriously – costs $600 per tonne of CO2 today. ![]()
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