What Does Net-Zero Carbon Really Mean?

The consensus among climatologists is that the world needs to reach net-zero greenhouse gas emissions by mid-century. We are hopeful for meaningful and realistic legislation in Virginia to achieve this goal. We are particularly interested in The Virginia Energy Plan; relating to the Commonwealth Energy Policy (VEP) and The Virginia Clean Economy Act (VCEA).

The VEP (SB94) establishes greenhouse gas emissions reduction standards that target net-zero emissions carbon across all sectors of Virginia’s economy by 2045. It passed subcommittee and the full senate on January 24, with support from Dominion Energy, but only after a change in the target for the electric power sector from “zero carbon by 2040” to “net-zero carbon by 2045”.

The VCEA (HB1526 and senate version SB851) establish a Renewable Portfolio Standard (RPS), which steadily increases the electrical generation to 100% renewable energy by 2050. (It is widely believed that the bills will allow zero-carbon nuclear production from existing plants to continue, but unfortunately this is not clearly spelled out.)

A draft alternative to the VCEA, reportedly being circulated by Dominion Energy, advances the RPS scheduled to 2045, but it makes the following changes:

55% Zero Carbon by 2030
65% Zero Carbon by 2036
100% Net-Zero Carbon by 2045

What are we giving up by replacing “zero” carbon with “net-zero” carbon in these bills?

The meaning of zero carbon is clear: it means producing power without emitting any carbon to the atmosphere. Wind, solar, hydro, and nuclear are all zero-carbon sources of electric power. Virginia’s potential for hydropower is limited. Nuclear currently produces about 30% of Virginia’s power. Although nuclear power is a reliable (non-intermittent) and clean energy source, significant expansion of nuclear energy faces political hurdles. Wind and solar are expected to undergo major expansion over the next three decades, largely due to rapidly falling costs. However, over-reliance on intermittent energy sources poses reliability risks, even if combined with substantial energy storage capacity. Achieving true zero-carbon energy by mid-century is likely to require either major technological advances in energy storage or a renaissance in nuclear power or both.

Lacking these developments, achieving net-zero carbon emissions is a more realistic target. Net-zero carbon emissions is widely understood to mean offsetting any emissions of carbon by a corresponding removal of carbon from the atmosphere. For example, ‘net-zero’ would allow natural gas peaker plants to fill the gaps between energy demand and intermittent renewable energy supply, thereby dramatically improving power reliability. Combining peaker plants with carbon capture or the use of biogas could substantially reduce, but would not eliminate, carbon emissions.

Technologies to offset carbon emissions by carbon removal from the atmosphere are currently unproven. But improvements in technologies to reduce carbon emissions by carbon capture at the source and to remove carbon from the atmosphere would expand the potential pathways to achieve reliable power with net-zero carbon emissions. Developing these carbon removal technologies, needed for net-zero emissions, would also provide the potential to achieve net-negative emissions.

Replacing zero carbon with net-zero carbon emissions would appear to be a worthwhile compromise to set realistic goals and get legislation passed. Notably, however, the language in SB-94 and in Dominion’s draft alternative for the VCEA does not state net-zero carbon emissions, and it does not define net-zero carbon. For example, Dominion is pushing their electric school bus program, which on balance, is laudable. Could Dominion claim net-zero carbon, even while their own carbon emissions actually increased, by offsetting their carbon emissions with reductions of carbon emissions in other sectors, such as electrification in the transportation sector? If a cap and trade market for carbon emissions is established, could Dominion purchase carbon emission credits and claim a net-zero carbon with no decrease in its own carbon emissions? These are not acceptable net-zero strategies.

Net-zero carbon must be defined as balancing carbon emissions with carbon removal in Virginia’s code. With that in place, establishing carbon reduction targets as part of clean energy standards are effective policy for reducing greenhouse gas emissions.

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