Negative Emissions Technologies

Negative emissions technologies or techniques (NETs, also known as Carbon Dioxide Removal (CDR) or Greenhouse Gas Removal (GGR)) are means of accelerating the removal of greenhouse gases from the atmosphere. They are central to the possibility of net-zero climate goals, but involve many technical, political and environmental complexities

I have been working on NETs as a tool for climate policy for over a decade. As a consultant, in 2011, I undertook one of the earliest comprehensive review and asesessment of NETS, examining the technological readiness, capacity, costs and side-effects of more than 30 potential techniques, including biochar, direct air capture, ocean calcination and tree burial. 

That early research - first published by Friends of the Earth, and subsequently in the PSEP academic journal - concluded that NETs would be needed to avoid too great a risk of dangerous climate change, that the global capacity of NETs is limited (for example by the availability of geological storage for carbon dioxide, and the sustainable supply of biomass), that the costs of NETs will typically be much higher than those of mitigation, and that much development effort is needed to bring NETs to scale.

The report argued that development of NETs should be actively pursued as a supplement to mitigation. It identified techniques which appeared to offer most promise. Recognising the serious moral hazard / mitigation deterrence risk involved, it also made recommendations for reducing that risk. The full report 'First Stop Digging' is available as a PDF through the links below, as is a summary of the assessment spreadsheet. The research was undertaken in parallel with the compilation of a short report (also available below) on the same topic for Friends of the Earth (England, Wales and Northern Ireland).

More recently, I have contributed to continuing research into NETs and the mitigation deterrence problem in and beyond the AMDEG project, and in collaboration with scholars in continental Europe and the USA. 

In the linked files below there are also presentations regarding specific NETs: bioenergy with carbon capture and storage (BECCS), and direct air capture (DAC). In January 2022 I gave evidence to the Environmental Audit Committee in the UK Parliament regarding the risks in unquestioning pursuit of such technologies.

I am also currently collaborating on research into justice aspects of NETS in an international context with the LUNETS project at Linköping University in Sweden.


McLaren D. and W. Burns, ‘It would be irresponsible, unethical and unlawful to rely on NETs at large scale instead of mitigation’. Chapter 18 in Debating Climate Law (eds Mayer and Zahar, 2021), Cambridge University Press.

Boettcher, M., K. Brent, H. J. Buck, S. Low, D. McLaren and N. Mengis (2021). Navigating Potential Hype and Opportunity in Governing Marine Carbon Removal. Frontiers in Climate 3(47).

McLaren, D. ‘Capturing the Imagination: Prospects for direct air capture as a climate measure’. Chapter 17 (pp113-118) in Geoengineering Our Climate: Ethics, Politics and Governance (eds. Blackstock and Low; 2019), Earthscan Routledge: London.

McLaren, D. A comparative global assessment of potential negative emissions technologies, Process Safety and Environmental Protection 90(6): 489-500. November 2012

Linked Files