A new approach to assessing greenhouse gas emissions from
coal, wind, solar, and other energy technologies paints a much more precise
picture of cradle-to-grave emissions and should help sharpen decisions on what
new energy projects to build.
The method—a harmonization of widely variant estimates of
greenhouse gas emissions by the U.S. Department of Energy’s (DOE) National
Renewable Energy Laboratory (NREL)—is being heralded as an important step
forward in lifecycle assessments that paints a clearer picture of the
environmental penalties and benefits of different technologies.
NREL analysts looked at more than 2,000 studies across
several energy technologies, applied quality controls, and greatly narrowed the
range of estimates for greenhouse gas emissions.
The harmonization found that cradle-to-grave
greenhouse-gas emissions from solar photovoltaics are about 5% of those from
coal; that wind and solar are about equal in emissions; and that nuclear energy
is on a par with renewable energy.
And the analysis succeeded in narrowing the huge range of
estimates—in some cases by 80% to 90%—to a robust median, improving precision,
and giving stakeholders a much clearer look at the likely environmental impacts
of various projects.
NREL’s findings appear in six articles.
Also helping with the findings were subcontractors and
researchers from the DOE’s Brookhaven National Laboratory.
“As a society, we need to better understand what the
effects of our energy choices are,” said Garvin Heath, a scientist with NREL
and a leader of the project. “Greenhouse gases and climate change are a part of
the discussion. As we try to envision what our future energy system will look
like, we need an accurate picture of what that transition will mean.”
Renewables such as solar and wind produce far fewer
greenhouse gas emissions than coal, oil, or natural gas while in operation.
But the meta-analysis by Heath, Technology Systems, and
Sustainability Analysis Group Manager Margaret Mann, and their team looked
deeper, at emission estimates starting with the manufacture of solar panels,
wind turbines, coal plants or natural gas lines, all the way to the emission
estimates for decommissioning the sites. Increasingly, lenders, utility
executives, and lawmakers are scrambling to get the best, most precise
information on greenhouse gas emissions from various sources of energy. And
they are frequently frustrated by the huge range of those estimates.
State and local lawmakers, weighing the merits of a new
coal-fired plant versus a wind farm, for example, are eager to know not just
the relative financial costs, but the impacts to the environment over the
decades the project.
“This methodology allows you to arrive at a better
precision, so you can say with more certainty that this is the benefit you get
from using this technology rather than that technology,” Heath said.
Project developers, investors, manufacturers, and
utilities all can use the harmonization estimates as building blocks to making
their own estimates of specific projects or to guide policy.
