Parameter-minimal analysis of carbon dioxide removal through direct air capture

TL;DR

The paper tackles the risk of multistationarity (steady-state multiplicity) in the Earth’s carbon cycle under direct air capture (DAC) by applying parameter-minimal Chemical Reaction Network Theory (CRNT). It builds a five-pool box model and constructs a corresponding power-law CRN, enabling analysis that relies on network topology and kinetic structure rather than detailed rate constants. The study demonstrates that the DAC-enabled system is a deficiency-zero, weakly reversible network with a positive steady state, and it derives simple, parameter-free criteria based on kinetic-order ratios $R_p$ and $R_q$ to assess multistationarity. These insights offer a fast, graph- and kinetics-based screening tool for evaluating various negative emissions technologies and for understanding properties like absolute concentration robustness and atmospheric carbon reduction. The approach provides policymakers with a rapid method to compare NETs without resorting to computationally expensive Earth system models.

Abstract

The potential for multistationarity, or the existence of steady-state multiplicity, in the Earth System raises concerns that the planet could reach a climatic `tipping point,' rapidly transitioning to a warmer steady-state from which recovery may be practically unattainable. In detailed Earth models that require extensive computation time, it is difficult to make an a priori prediction of the possibility of multistationarity. In this study, we demonstrate Chemical Reaction Network Theory (CRNT) analysis of a simple heuristic box model of the Earth System carbon cycle with the human intervention of Direct Air Capture. CRNT leverages parameter-minimal analysis, relying primarily on the graphical and kinetic structure of the reaction network system, to identify necessary conditions for steady-state multiplicity. The analysis reveals necessary conditions for the combination of system parameters where steady-state multiplicity may exist. With this method, other negative emissions technologies (NET) may be screened in a relatively simple manner to aid in the priority setting by policymakers. Beyond multistationarity, the analysis provides insights into key system properties, such as absolute concentration robustness and some conditions for atmospheric carbon reduction.

Figures (1)

• Figure 1: In the box model, the boxes represent the different pools, solid arrows indicate the transfer of carbon from one pool to another, and dashed arrows indicate the pools that influence a carbon transfer.

Theorems & Definitions (5)

• Remark 2.1
• Remark 2.2
• Proposition 3.1
• Proposition 3.2
• proof