Hybrid nature-engineering carbon removal: An effective strategy for climate mitigation and sustainability?

Recent policies such as the US bipartisan Inflation Reduction Act (IRA) provide unprecedented level of funding to Carbon Dioxide Removal (CDR). Unfortunately, these policies define boundaries only for oil and gas industry centered technologies such as Direct Air Capture (DAC), with little attention to nature-based methods, despite their broad appeal. Here we review the challenges facing biological carbon sequestration methods such as leakage, permanence, and verification that hinder their practical implementation and effectiveness. We suggest that a more proactive management strategies will be needed for Biomass Carbon Removal and Storage (BiCRS).

We discuss biomass burial and storage, a hybrid nature-engineering method that is low-cost ($30-100/ton), with a potential for 2-10 GtCO2/year. A durability of 1000+ years can be achieved by storing sustainably sourced woody biomass in anoxic, dry, or frigid conditions. We illustrate the feasibility with 4 examples:(1) Thinning and storage of wood in the fire-prone America West; (2) Burial of waste wood from urban-suburban tree removal; (3) Mix-use of regrowth forests on past deforested Amazon with sustainable harvesting and burial; (4) Burial of agroforestry waste in Indonesia. These all have environmental co-benefits while providing green jobs, with the largest potential in the Global South.

We will discuss the research and experiments needed to formulate best practices and guide ongoing or anticipated attempts in current and future carbon markets, including the following key questions: What are the best ways to ensure the longevity of stored wood, and how to verify? What are the most cost-effective ways of operation? How to do full carbon accounting of a proposed method to ensure no ‘leakage’? How to apply the method to solve other problems with co-benefits?