Reaching negative CO₂ emissions

I appreciate David Kramer’s informative article “Negative carbon dioxide emissions ” (Physics Today, January 2020, page 44). It appears that negative emission technology (NET) will be needed. However, I am puzzled by one phrase—“achieving Paris goals without retarding economic growth.” Isn’t it obvious that perpetual economic growth in our finite terrarium/aquarium is not possible? Long-time Physics Today readers will remember several items by Albert Bartlett about exponential growth (see, for example, Physics Today, July 2004, page 53 , and March 1994, page 92 ). Such growth—economic and other—is a primary driver of increasing carbon dioxide emissions and thus of climate change.

Kramer quotes Julio Friedmann: “We have to create an industry the size of the oil and gas industry that runs in reverse.” The oil and gas industry generates its output to make a profit. The “reverse output” of the NET industry—tens of gigatons of CO₂ sequestered annually—is not a marketable product to be sold for up to $100 per ton. A carbon fee may be needed to fund NET.

Would use of CO₂ for enhanced recovery of oil make up any significant fraction of tens of gigatons per year? How much CO₂ would be released in burning the additional oil produced? Does the CO₂ come back up with the oil? Then what?

Kramer mentions “improved forest management” but doesn’t explain it. In the western US, politicians and others often use that phrase as code for “more logging.” (They usually avoid the word “logging” in favor of “thinning,” “forest health,” or similar language.) A purported goal is to reduce the fuel available to forest fires. Proposals to increase CO₂ storage by reforestation and large-scale tree planting on public land are incompatible with demands for forest-fire fuel reduction. Studies by wildfire scientists and ecologists ^{1 , 2} show that such fuel reduction is generally ineffective in reducing large fires and is ecologically damaging. It is not improved management.