Carbon accounting without life cycle analysis

Life cycle analysis (LCA) is deeply embedded in carbon accounting. LCA is valuable for qualitatively understanding technologies' environmental footprints. However, ambiguities and insatiable data requirements make it ill-suited for quantitative analysis. Fortunately, accounting without LCA is possible, for example, by demanding that for every ton of carbon coming out of the ground, another ton must be sequestered. This "Carbon Takeback Obligation" (CTBO) policy would eliminate the need for tracking carbon through supply chains. With all supply chains already carbon balanced, it is sufficient to quantify the amount of carbon sequestered without subtracting upstream emissions. Our modeling shows that once full carbon neutrality is demanded, market forces alone will eliminate counterproductive sequestration technologies, approaches that release more CO2 than they store. Complications arise during the transition where some carbon extraction is not yet balanced out by sequestration, as under some policies, counterproductive technologies could be introduced solely to game the system. We explore the economics of four transition pathways: a simple CTBO, a CTBO combined with permits required for all unbalanced carbon, a CTBO combined with a futures market, and permit-future hybrid schemes. A simple CTBO that does not add an economic burden on unmitigated carbon would incentivize low-cost, counterproductive technologies. Contrastingly, a CTBO policy that includes permits and/or futures will render such technologies uneconomical at any point in the transition. A policy with controlled futures would allow for rapid permit phaseout. Hybrid systems could lessen the initiation shock and bridge the transition time when market demand exceeds sequestration capacity. Carbon accounting without life cycle analysis (LCA) is possible by requiring one ton of sequestration for each extracted ton of carbon. A carbon takeback obligation eliminates the need to track carbon through the supply chain.