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
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.
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.