"Energy derived from green sources is not specifically delivered to the customers who choose it, but to the power grid, which displaces power that would have otherwise been produced from traditional [fossil fuel] generating sources."
(Source: Stan Wise, Georgia PSC Commissioner)
While all proponents of renewable energy emphasize the importance of displacing/reducing fossil fuel use, several key points are often overlooked or not understood:U.S. Electricity Generation by Fuel Source
The "Big Picture" on Air Pollution: Most proponents of Green Energy also fail to communicate that ~90% of all Electric Utility pollutants of NOx, CO2, SO2, and mercury come from coal fired generation. Below is data focusing on CO2 emissions to illustrate this point, where the carbon intensity of coal is almost 2 times greater than natural gas.
Not all renewable energy technologies (e.g., solar vs.
biomass) displace the same fossil fuels;
Not all fossil fuels produce the same level of pollution
(coal power plants pollute more than natural gas).
In results of numerous national surveys, most consumers are unaware that the majority of U.S. electricity generation comes from coal. Also, arguments by Green Energy proponents for "reduced foreign oil dependence" really don't fit the electricity industry -- as oil only represents ~2% of generation.
"Energy Independence" arguments for natural gas are also non-factual. About 82% of all natural gas consumed in the U.S. comes from domestic resources -- with Canada (an economy closely linked to the U.S.) providing almost all of imports.
U.S. Electricity Generation
Carbon Intensity by Fuel Type
(Lbs. of Carbon/MBtu)
Another way of stating this above information is that electricity generation from oil and natural gas is only emitting ~10% of air pollutants from the electric utility industry.Carbon Storing of Tree Energy Crops
Understanding Electricity Generation and Air Emissions: The below graph illustrates the concept of how electricity providers dispatch their power plants to meet demand of customers. While the Graphs' data is from California, the "bell type shape" of electricity demand is representative of most "load shapes" for Utilities throughout the U.S. (e.g., lower demand at night, increasingly higher demands for electricity during the day).
The different colors within the below graph represents the different type of generation type (e.g., the brown area represents nuclear generation) that is run/dispatched to meet electricity demand. This is called the "dispatch stack".
While nuances exist with each Utility to meet electricity demand, generally, a Utility decides on which power plant to dispatch/run based on a unit's marginal cash operating cost -- where the cost of fuel is the largest component. Power Plants are generally ranked into three categories of (1) Base-load units which have the lowest operating costs; (2) Intermediate-load units; and (3) Peaking-load units which have the highest operating costs (but with fast start-up, are very flexible in generating electricity to the grid quickly).
In the Southeast U.S., large coal-fired and nuclear power plants are very representative of base-load units, and are dispatched/run at high capacity factors (~60 to 80%). For example, a base-load unit may run 24 hours a day for the entire year except for times when maintenance is being performed on the unit. Conversely, smaller MW peaking-load units such as a natural gas or oil fired combustion turbine will have lower capacity factors (primarily running to meet summertime air conditioning load).
Paradigm/Model of Electricity Generation and the Environment: Understanding load shapes, how power plants are dispatched and run (e.g., cycling) to meet demand, and how Power Providers plan new generation capacity additions is extremely important in understanding the paradigm/model of "electricity generation and the environment", where:
Biomass co-firing will directly reduce/displace fossil fuel use from high capacity factor, base-load power plants. With co-firing in Florida and the Southeastern U.S., the fuel displaced will overwhelmingly be coal, which typically has higher emission levels of NOx, SO2 and CO2 than peaking or intermediate-load natural gas fired units.
Generally, renewable energy generation facilities such as wind or solar PV have capacity factors between ~20% to ~35% as a result of natural resource limitations (e.g., sunlight, wind speeds) – often producing electricity during peak demand day-light hours.
Implementing solar photovoltaic or wind turbine projects (where top wind speeds occur during afternoon peaking hours) will not generally displace generation from large MW base-load coal or nuclear units -- but rather displace existing generation from natural gas fired peaking and intermediate-load units (i.e., combustion turbines, combined cycle) in the dispatching of power plant resources to meet demand. [see DOE Report on this subject]
Also, recognizing the reality that the overwhelming majority of new power plant construction is peaking and combined cycle units, placing in-service new wind or solar facilities will displace or reduce in size, the amount of new natural gas-fired capacity built to meet demand (often referred to as “avoided capacity additions”).
Under Federal and Florida Environmental Law, while older coal-fired power plants are “grand-fathered” for air quality requirements, all new power plants (primarily natural gas units) are required to implement “best available control technology” (BACT) for air emissions.
Carbon Sequestration and Energy Crops: When crops are grown and used for biomass energy, two aspects of carbon management occur. First, the above-ground crops harvested for fuel use are “carbon cycle neutral” -- just like other renewable options. However unlike other renewables, carbon is also sequestered or stored below ground. For example, for every 10 tons of fuel harvested from our tree farm (e.g., the above ground mass), 6 additional tons of tree mass (through the trees’ root systems) has been stored in the soil.
Recognizing that approximately 50% of tree mass (on a dry basis) is carbon, tree energy crops represent an extremely useful tool for carbon management – having an additional sequestration component which solar and wind energy do not have.
Putting It All Together: By using the above information, a paradigm/model based on sound-science and sound-engineering can be formed.
Carbon Reductions of Renewable Energy Options
First, using U.S. Department of Energy data on air pollution emissions, a major environmental objective of renewable energy should be the displacement of coal -- after all, ~90% of all air pollution in the U.S. comes from coal fired generation.
Second, also per U.S. Department of Energy information, the operating characteristics of solar photovoltaics primarily result in natural gas displacement on the integrated resource power grid. Common sense dictates that biomass co-firing in coal power plants displaces coal use.
Third, while small nuances exist in opinion, all renewable energy options (including biomass) are considered "carbon cycle neutral". Thus, by using data developed by the Electric Power Research Institute (EPRI) on "typical" CO2 emission rates for fossil fuel technologies (e.g., natural gas combustion turbines, pulverized coal) -- "CO2 displacement values" for solar and biomass co-firing technology options can be determined.
Fourth, by using University of Florida data on carbon sequestration, the EPRI data can be modified to show the "CO2 displacement value" for biomass energy crops co-fired in a coal unit.
Three Renewable Energy technology options are compared below using this paradigm of displacement and sequestration: (1) Solar PV; (2) Biomass co-firing using biomass waste streams; (3) Biomass co-firing using energy crops.
Understanding the above chart is straight forward (again, remembering that both solar and biomass energy are carbon cycle neutral). The value of solar photovoltaics is the CO2 emissions avoided from running a natural gas combustion turbine unit. For both biomass options, the value is avoided CO2 emissions from a pulverized coal unit -- with the energy crop option reflecting the additional below ground carbon sequestration benefit.
Regional CO2 Emissions by
The Need to Develop Biomass Energy in the South: Readers may wonder why a Wind Energy option was not included in the above comparisons. The reason is simple. Currently, we are unsure if any "broad generalization" can be made on wind energy due to the site specific nature of wind speeds. For example, for existing wind projects in California, capacity factors can reach ~90% during peak demand periods from 1 to 7 P.M.
Thus, the generation displaced by wind energy in California most likely would be natural gas combustion turbines or combined cycle units.
However, for wind energy projects in other U.S. Regions where (1) peak wind speeds occurred at night (or off-peak); and (2) significant coal-fired generation existed -- the fossil fuel displaced would likely be coal.
The variability in site wind speeds and the region that wind projects are located (e.g., the Regional Power Grid) leads to an interesting question. Perhaps not all wind projects are equal in their ability to achieve environmental objectives. For example, a wind energy project in Kentucky where top winds occurred off-peak would likely have a greater ability to reduce coal use than a wind energy project located in California.
We believe the facts are clear on the special need to develop biomass energy projects in the Southeastern U.S. such as:
High capacity factor Landfill Methane Projects.
Biomass Co-Firing in Base Load Coal Units.
Increasing Capacity Factors in existing Biomass Units.
The Use of Energy Crops.
Recognizing the role of the South's Electric Utilities in total U.S. CO2 emissions (largely attributable to coal use) the need for base load renewable energy resources becomes even more evident. Clearly, in order to meet the national and global challenge of Climate Change, the South must play a critical role in better managing its use of coal.
U.S. Electric Utilities