Production and Delivery of Low-Carbon Gaseous Fuels
| Author | Romany M. Webb and Melinda E. Taylor |
| Pages | 670-691 |
Page 670 Legal Pathways to Deep Decarbonization in the United States
I. Introduction
Domestic use of natural gas has grown signica ntly in
recent years, with a decline in prices lead ing to its sub-
stitution for coal in various applications. Between 20 07
and 2017, natural gas use in the United States increased
by 18.5%, while coal use declined 39.1%.1 is shift has
had important environmental and public health benets
because, compared to coal, natural gas contains fewer
impurities and thus generate s less pollution when c ombust-
ed.2 With respect to climate-dama ging greenhouse gases,
the combustion of natural gas emits approximately ha lf as
much carbon dioxide as coal combustion.3 Despite this,
1. U.S. E I A (EIA), M E
R: J 2018, at 7 (2018) (DOE/EIA-0035(2018/6)) (indicat-
ing that 23.663 quadrillion British thermal units (Btu) of natural gas and
22.749 quadrillion Btu of coal were consumed in 2007 and 28.034 quadril-
lion Btu of natural gas and 13.862 quadrillion Btu of coal were consumed
in 2015), available athttps://perma.cc/F7W6-WTSP.
2. Natural gas combustion emits no mercury, virtually no particulate matter,
and signicantly less greenhouse gases than coal or oil. R K. L-
., C R S, M: A I-
E S R S 2 (2016),
available at https://perma.cc/6NWV-AG4C.
3. EIA, Frequently Asked Questions—How Much Carbon Dioxide Is Produced
When Diferent Fuels Are Burned? (indicating that natural gas combustion
emits 117.0 pounds of carbon dioxide per million Btu, whereas the com-
bustion of coal (anthracite) emits up to 228.6 pounds of carbon dioxide per
million Btu), https://perma.cc/5GM2-CHV4 (last reviewed June 8, 2018).
however, natural gas is not truly a “clean” fuel. Its combus-
tion still emits approximately 117 pounds of carbon diox-
ide per million British thermal units (Btu) of energy.4
Greenhouse gas emissions may also occur during natu-
ral gas production and tran sportation. Natural gas consists
primarily of methane, a hig hly potent greenhouse gas, with
a global warming potential up to 34 times that of carbon
dioxide over a 100-year time horizon.5 Methane is released
throughout the natural gas production process via acci-
dental leaks, intentional venting, and incomplete aring.
According to the U.S. Environmental Protection Agency
(EPA), natural gas systems6 were the largest industrial
source of methane in the United States in 2016, account-
ing for 24.9% of national emissions.7 at is a conservative
estimate; recent studies indicate that the EPA gures may
4. Id.
5. L ., supra note 2, at 2.
6. EPA, I U.S. G G E S: 1990-
2016, at 3-77 (2017) (EPA 430-R-18-003) (dening “natural gas systems”
to include “hundreds of thousands of wells, hundreds of processing facili-
ties, and over a million miles of transmission and distribution pipelines”),
available at http://perma.cc/VL4C-4PSW.
7. Id. at ES-6 to ES-8 (nding that total nationwide methane emissions were
654.4 million metric tons of carbon dioxide equivalent, of which natural gas
systems were responsible for 163.5 million metric tons).
Chapter 26
Production and Delivery of Low-Carbon Gaseous Fuels
by Romany M. Webb and Melinda E. Taylor
Summary
Recent increases in natural gas use in electricity generation and other applications have been widely heralded as a
vital step in the transition to a clean energy economy. Natural gas is often described as a “clean” fossil fuel because
its combustion emits signicantly less mercury and other air toxins than coal or oil. Natural gas combustion also
emits fewer greenhouse gases than other fossil fuels. Any savings at the point of combustion may, however, be o-
set by greenhouse gas emissions during natural gas production. Most of those emissions take the form of methane,
a highly potent greenhouse gas, released through gas leaks, venting, and aring (where there is incomplete com-
bustion). To reduce emissions, the Deep Decarbonization Pathways Project technical report recommends replac-
ing natural gas with renewable gases, such as biogas, hydrogen, and synthetic methane. is chapter discusses
various government policies that may be used to support the production and use of renewable gases.
Page 671
understate methane emissions from both natural gas and
petroleum systems by up to 60%.8
e Deep Decarbonization Pathways Project (DDPP)
technical report for the United States indicates that, in the
future, natural g as should be replaced with lower emission
alternatives.9 Possible alternative gases include biogas, pro-
duced through the anaerobic digestion (AD) or thermal
gasication (TG) of organic materials, a nd hydrogen and
synthetic methane, produced using renewable electricity
via the chemical process of power-to-gas (P2G). Substitut-
ing these so-ca lled “renewable gases” for natural ga s would
almost certai nly result in a decline in greenhouse gas emis-
sions.10 Past life-cycle assessments (LCAs) have found that
both biogas and P2G facilities have lower greenhouse gas
emissions than natura l gas systems.11
Despite the potential benets of switching to renew-
able gas, there is currently little government support for
its production. Rather, many existing government policies
impede renewable gas production, including by preventing
or delaying the construction of new AD, TG, and P2G
facilities and imposing restrict ions on facility operation.12
ere are also numerous impediments to the delivery of
renewable gas to industrial and other users.13 e safest,
most ecient, and lowest cost method of delivery is via
the existing natural gas pipeline system. Current pipeline
interconnection rules and quality standards may prevent
the delivery of renewable gas, however.
is chapter explores law and policy change s required
to support renewable gas production and delivery. It begins
with an overview of the key met hods for producing renew-
8. Ramón A. Alvarez et al., Assessment of Methane Emissions From the U.S. Oil
and Gas Supply Chain, S. (June 21, 2018).
9. J H. W ., P D D
U S, U.S. 2050 R, V 1: T R 20
(Deep Decarbonization Pathways Project & Energy and Environmental
Economics, Inc., 2015), available at http://usddpp.org/downloads/2014-
technical-report.pdf [hereinafter DDPP T R].
10. U.S. D A ., B O R-
: V A R M E I
E I 14 (2014) [hereinafter B O
R] (estimating that the current 239 AD systems, producing bio-
gas from livestock waste in the United States, reduce methane emissions by
two million metric tons of carbon dioxide equivalent annually), available at
https://perma.cc/CK5P-6F3C.
11. See, e.g., Andrea Tilche & Michele Galatola, e Potential of Bio-Methane as
Bio-Fuel/Bio-Energy for Reducing Greenhouse Gas Emissions: A Qualitative As-
sessment for Europe in a Life Cycle Perspective, 57 W S. T. 1683,
1689-90 (2008) (estimating net life-cycle emissions from production of bio-
gas via AD in Europe); Gerda Reiter & Johannes Lindorfer, Global Warming
Potential of Hydrogen and Methane Production From Renewable Electricity Via
Power-to-Gas Technology, 20 I’ J. L C A 477 (2015)
(estimating cradle-to-gate emissions from production of hydrogen and syn-
thetic methane via P2G in Europe).
12. See infra Section V.B.
13. See id.
able gas in Section II. Section III then discusses renewable
gas’s role in a decarbonized economy, outlining possible
uses for the gas, as well as exploring its climate and other
benets. e regulatory framework for renewable gas pro-
duction and use is outlined in Section IV, after which Sec-
tion V identies potential regulatory barriers to increased
reliance on renewable gas and reforms needed to elimi nate
those barriers. Section VI concludes.
II. What Is Renewable Gas?
e term “renewable gas” is used in this chapter to describe
gaseous fuels fabricated from renewable sources (i.e., as
opposed to being extracted from geologic reservoirs) that
can be substituted for natural g as. Natural gas is composed
primarily of methane, a chemical compound made up of
one carbon atom and four hydrogen atoms. It could be
replaced with biogas, a gaseous m ixture consisting primar-
ily of methane, which is produced through the AD or TG
of organic materials, or with synthetic methane produced
through P2G. A high-level overview of the AD, TG, and
P2G processes is provided in this section.
A. Biogas
Biogas is typically produced through the AD of organic
materials such as agricultural waste, energy crops, forest
residues, sewage sludge, and municipal waste (biomass).
During AD, the biomass is broken down by microorgan-
isms in an environment deprived of oxygen, releasing a
gaseous mixture, usually composed primarily of methane
and carbon dioxide.14 e process can ta ke from a few days
to several weeks and involves four key stages:
1. Hydrolysis, wherein large organic polymers in the
biomass (e.g., carbohydrates and proteins) are con-
verted into simpler monomers (e.g., glucose, fatty
acids, and other small molecules). e conversion
is made possible by hydrolytic enzymes that break
down the chemical bonds in complex molecules.
2. Acidogenesis, wherein the products of hydrolysis a re
converted into carbon dioxide, hydrogen, ammo-
nia, and various organic acids. e conversion is
performed by anaerobes (i.e., organisms that do
not require oxygen for growth) known as acido-
14. G T I, T P R G: B-
D F B F U P
Q 19 (2011), available at https://perma.cc/A5W5-8LFC.
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