Land‐based climate solutions for the United States

Abstract

Meeting end-of-century global warming targets requires aggressive action on multiple fronts. Recent reports note the futility of addressing mitigation goals without fully engaging the agricultural sector, yet no available assessments combine both naturebased solutions (reforestation, grassland and wetland protection, and agricultural practice change) and cellulosic bioenergy for a single geographic region. Collectively, these solutions might offer a suite of climate, biodiversity, and other benefits greater than either alone. Nature-based solutions are largely constrained by the duration of carbon accrual in soils and forest biomass; each of these carbon pools will eventually saturate. Bioenergy solutions can last indefinitely but carry significant environmental risk if carelessly deployed. We detail a simplified scenario for the United States that illustrates the benefits of combining approaches. We assign a portion of non-forested former cropland to bioenergy sufficient to meet projected mid-century transportation needs, with the remainder assigned to nature-based solutions such as reforestation.Bottom-up mitigation potentials for the aggregate contributions of crop, grazing, forest, and bioenergy lands are assessed by including in a Monte Carlo model conservative ranges for cost-effective local mitigation capacities, together with ranges for (a) areal extents that avoid double counting and include realistic adoption rates and (b) the projected duration of different carbon sinks. The projected duration illustrates the net effect of eventually saturating soil carbon pools in the case of most strategies, and additionally saturating biomass carbon pools in the case of forest management.Results show a conservative end-of-century mitigation capacity of 110 (57-178) Gt CO 2 e for the U.S., ~50% higher than existing estimates that prioritize nature-based or bioenergy solutions separately. Further research is needed to shrink uncertainties, but there is sufficient confidence in the general magnitude and direction of a combined approach to plan for deployment now.

Global warming intensity of biofuel derived from switchgrass grown on marginal land in Michigan

“…As they are defined in our study, marginal lands clearly can produce crops for biofuel production to mitigate GHG emissions. This finding is consistent with the existing literature and suggests carbon‐negative biofuels derived from switchgrass grown on marginal land could contribute to keeping the global temperature increase below 1.5°C (Intergovernmental Panel on Climate Change, 2018; Robertson et al, 2022). Furthermore, concentrating this energy crop production on marginal lands can reduce potential food‐versus‐fuel conflicts, further improving the environmental and societal benefits of such systems.…”

Ten new insights in climate science 2022

“…For example, in the United States, improved forest, cropland and rangeland management could provide ~45.8 (16.4–88.1) Gt CO 2 -eq of mitigation by 2100 (Robertson et al, 2022). In Canada, land use related to the conservation, management and restoration of natural systems could provide an emission reduction potential of ~78.2 (41.0–115.1) Tg CO 2 -eq/year by 2030, equivalent to the emissions of all heavy industry in 2018 (Drever et al, 2021).…”

Long‐term changes in soil carbon and nitrogen fractions in switchgrass, native grasses, and no‐till corn bioenergy production systems

“…With a changing climate, research that improves our ability to estimate the impacts of land‐based negative emission technologies such as bioenergy with carbon capture and storage (BECCS), whereby the C in biomass is captured and stored in geologic formations when biomass is converted to fuel or electricity, are becoming increasingly salient (Robertson et al., 2022). Our study suggests that bioenergy systems with high root productivity and the tendency to form large aggregates that persist following the cessation of tillage may provide the largest soil C and N accretion gains.…”

“…Bioenergy production is central to all shared socioeconomic pathways scenarios from the United Nations Intergovernmental Panel on Climate Change with a greater than 67% chance of meeting a 2°C end‐of‐century target (IPCC, 2018; Robertson et al., 2022), and grass‐based cropping systems comprise the greatest source of biomass in all projections. Primarily these include purpose‐grown perennial grasses such as switchgrass ( Panicum virgatum L.), miscanthus ( Miscanthus × giganteus ), and sugarcane ( Saccharum officinarum L.) but also included is biomass from restored prairie and other native species communities and from residues of cereal crops like corn ( Zea mays L.) and wheat ( Triticum aestivum L.) (Robertson et al., 2017; U.S. Department of Energy, 2016).…”