PNNL

Abstract

The Carbon Management Study Group (CMSG) was formed early in the conduct of Energy Model Forum Study 37 (EMF 37) to explore interactions between potentially key technologies and United States energy system pathways to net-zero carbon dioxide (CO2) emissions in 2050. Three technology groups were identified to be explored by the CMSG: carbon dioxide capture and storage (CCS), hydrogen systems (H2), and direct air capture of carbon dioxide (DAC). Seven sensitivity scenarios were designed to explore the role these three technology suites played in shaping the larger technology mix in scenarios that successfully led the U.S to achieve its net-zero CO2 emissions goal in 2050 (NZ). Important insights emerged from the CMSG scenarios. These insights included the following: Negative CO2 emission technologies (NET) also known as carbon dioxide removal (CDR) technologies were consistently a major part of successful pathways to net-zero U.S. 2050 emissions. The models all used afforestation/reforestation as part of their strategy to achieve net-zero U.S. 2050 CO2 emissions. Many models included bioenergy with CCS (BECCS) and/or DAC as part of their technology solutions. Many models added CDR technologies over the course of the EMF 37 study to better represent net-zero technology options. Achieving the net-zero goal without some form of CCS was shown to be impossible for most models. A few models also found it impossible to reach net-zero without DAC. When CCS and/or DAC were available, they were part of the overall energy strategy to meet 2050 net-zero goals. The marginal cost associated with net-zero CO2 emissions exhibited considerable variation across models. Nonetheless, the marginal cost of achieving net-zero in 2050 was between two and 10 times HIGHER without CCS and/or DAC available. When CCS was not available, CO2 prices ranged from $1300 - $2100/tCO2. When CCS was available, CO2 prices for Net Zero in 2050 ranged from $120 -$880/tCO2 in most models. Models deployed CCS technologies at a large scale. The average CO2 capture rate across all models in 2050 in the net-zero reference scenario was 1.3 GtCO2/yr. This is two orders of magnitude greater than current capacity and implies a substantial upscaling of capacity to move and store CO2. Cumulative captured emissions through 2050 across models and scenarios ranged up to 42 GtCO2. Such volumes do not challenge existing storage resources, though matching capture sites and storage sites could be challenging. More work is needed to examine the implications of better representations of CO2 storage capacity and reservoir fill rates. Hydrogen sensitivity scenarios showed that H2 constituted a relatively small share of the overall U.S. energy system. However, H2 deployed in very high value applications, facilitating transition towards net-zero emissions.