Net-Zero Emissions? What does it mean?

Net-Zero emissions have become a buzz phrase used by Presidential Candidates, state governments, and utilities as a goal to be achieved in the not too distant future.  How far in the future?  30 years from now according to the Paris Agreement that the U.S. pledged to in December 2015.  The U.S. pledged to reduce greenhouse gas emissions by 26%-28% below 2005 levels by the year 2025.  Trump then rescinded the agreement and withdrew the U.S. from the Paris accord.  If another President is elected in 2020 it could very well be reinstated.  Regardless, 200 countries agreed to the accord (Syria and Nicaragua did not).  Net-Zero emissions doesn’t mean zero emissions; just that every ton of CO₂ we do emit must be matched by a ton that we remove from the atmosphere.

The U.S. is the second-largest carbon emitter after China.  Together China and the U.S. emit more than 45% of the greenhouse gasses in the world.  Electricity generation in the U.S. accounts for 26% of the U.S. greenhouse gas emissions with industry and transportation accounting for most of the rest.  Therefore, the electrical generation must be at the forefront of lowering greenhouse gas emissions.  Due to this, nearly 550 coal-fired power plants have closed since 2010.  Some of the closures were due to emissions issues and the increased EPA requirements.  The other issue is increasingly cheap natural gas.  Natural gas coincidently is a much cleaner fuel as far as greenhouse gasses compared to coal.

So how is this to be accomplished?  How do we replace 26% of our greenhouse gasses from electrical generation?  The three major categories of energy for electricity generation are fossil fuels (coal, natural gas, and petroleum), nuclear energy, and renewable energy sources.  Most electricity is generated with steam turbines using fossil fuels, nuclear, biomass, geothermal, and solar thermal energy.  Other major electricity generation technologies include gas turbines, hydro turbines, wind turbines, and solar photovoltaics.  Hydro and Nuclear are the largest single sources of electricity that are carbon-free.  Only about 30% of our total electricity comes from those forms of energy, however.  There are a finite number of hydro locations and a nuclear power plant has not been built in this country in decades.  Solar and wind provide about 10-15% of the energy.  As was hypothesized though, solar and wind can be sporadic at best.

So, to really reduce our emissions to the levels agreed to in the Paris accord will require “cleaning up” natural gas and coal-fired power plants or investing heavily in renewable sources.  Barring new technologies, the only way to lower fossil fuel emissions is the Clean Energy Standards (CES) or renewable portfolio standards.  Most states have shifted to a “clean” energy policy rather than a “renewable” energy standard.  This allows new nuclear, hydro or solar/wind to be built vice limiting them to only solar/wind.  Another way is to update the grid to a more modern approach where energy can be “moved” more efficiently to where it is needed.  This allows users to benefit from off-peak and shifting demand when consumers need power.

Many states have already used the CES to lower emissions by requiring lower SO₂ and mercury emissions.  CO₂ will be next, but at the time of this writing, a viable form of CO₂ capture is not available commercially.  Aggressive renewable energy policy must take up the slack to ensure we meet the set goals.  Solar and wind are becoming more and more important with many new incentives for power producers to invest.  The incentives are necessary, however, because solar and wind currently are not very efficient.  Only about 30% compared to coal at nearly 70%.  Solar costs almost three times as much money as coal to produce electricity. Clean, limitless power sources such as solar energy are the kinds of technology that will lead our cities into the future.  However, to replace fossil fuel energy sources such as coal, they must be made much more efficient and cost-effective.