Carbon dioxide removal–What’s worth doing? A biophysical and public need perspective

Abstract

Carbon dioxide removal (CDR) has become a focal point for legislators and policymakers who are pursuing strategies for climate change mitigation. This paper employs a policy framework of collective biophysical need to examine two broad categories of CDR methods being subsidized and advanced by the United States and other countries: mechanical capture and biological sequestration. Using published data on these methods, we perform a biophysical input-outcome analysis, focusing on the U.S., and compare methods on the basis of three criteria: effectiveness at net carbon removal, efficiency at a climate-relevant scale, and beneficial and adverse co-impacts. Our findings indicate that biological methods have a superior return on resource inputs in comparison to mechanical methods. Biological methods are both more effective and more resource efficient in achieving a climate-relevant scale of CO2 removal. Additionally, the co-impacts of biological methods are largely positive, while those of mechanical methods are negative. Biological methods are also far less expensive. Despite their disadvantages and a track record of failure to date, mechanical CDR methods continue to receive large subsidies from the US government while biological sequestration methods do not. To achieve more optimal CDR outcomes, policymakers should evaluate CDR methods’ effectiveness, efficiency, and biophysical co-impacts. We present tools for this purpose.

Bad science and good intentions prevent effective climate action

“…These approaches may become more viable in the future-e.g., if diets change, permitting the reforestation of the vast tracts of land used to feed livestock; if breakthroughs raise efficiencies and reduce costs; and/or if much higher (i.e., realistic) carbon prices increase the cost competitiveness of these technologies. Sekera et al (2023) argue that biological sequestration methods, such as the restoration of forests, grasslands, and wetlands and regenerative agriculture, are more effective, resource efficient, and cheaper ways to achieve large-scale CO2 removal than techno-mechanical methods. Moreover, the co-impacts of biological methods are largely positive, while those of mechanical methods-which use machinery and chemicals to capture CO2-are largely negative.…”

Solar-Powered Direct Air Capture: Techno-Economic and Environmental Assessment

“…Direct air capture (DAC) refers to technologies that separate and concentrate atmospheric carbon dioxide solely through mechanical and chemical processes, thus excluding the use of biogenic sources for this purpose. − Although biomass-based processes are significantly more mature and less expensive, DAC does not present biophysical limitations that endanger crop production or biodiversity when massively scaled up. − CO 2 from both technologies can be sequestered or used as a feedstock. If a sequestration process is included, the technologies are often referred to as direct air carbon capture and storage (DACCS) and biomass with carbon removal and storage (BiCRS). , Since their ultimate goal is to remove carbon dioxide from the atmosphere, they are considered carbon dioxide removal (CDR) technologies, just like nature-based approaches such as enhanced weathering of minerals. ,, While CDR is a critical tool to address climate change, atmospheric carbon utilization is also considered a key enabler of the energy transition, as chemicals and fuels derived from nonfossil CO 2 could be carbon-neutral. , These synthetic fuels are considered crucial for decarbonizing hard-to-abate sectors in most energy transition plans. ,− …”

“…Direct air capture (DAC) refers to technologies that separate and concentrate atmospheric carbon dioxide solely through mechanical and chemical processes, thus excluding the use of biogenic sources for this purpose. 1 − 4 Although biomass-based processes are significantly more mature and less expensive, DAC does not present biophysical limitations that endanger crop production or biodiversity when massively scaled up. 5 − 9 CO 2 from both technologies can be sequestered or used as a feedstock.…”

Funding research using climate change mitigation: The case of the Carbone boréal research infrastructure

“…NBS have the potential to reduce GHG emissions by 8-14 Gt CO 2 -eq yr -1 between 2020-2050 [1], which represents 32-82% of the emission gap by 2030 to limit global warming between 1.5-2˚C by 2100 compared with the preindustrial era [2]. In addition to CO 2 removal from the atmosphere, NBS also render valuable ecosystem services such as biodiversity conservation, water and nutrient cycling regulation and soil preservation [3][4][5][6]. Several positive impacts on human well-being and sustainable development goals can also be achieved through NBS [1].…”