未来能源研究所-农业生物能源的政策前景（英）-2024.5-9页

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The Policy Landscape for

Agricultural Bioenergy

Issue Brief 24-03 by Emily Joiner, Michael Toman, and Suzanne Russo — May 2024

Key Points

• Agricultural (ag) bioenergy has received financial

and technical support from the Energy Title of

the Farm Bill, first established in 2002. At present,

however, the primary drivers of ag bioenergy

are incentives in federal energy legislation (the

Renewable Fuel Standard or RFS) and California

legislation to reduce the greenhouse gas intensity

of transportation fuels (the Low Carbon Fuel

Standard or LCFS), along with policies administered

by the US Environmental Protection Agency.

• The RFS creates requirements for incorporating

various categories of renewable sources,

including ag biofuels, into liquid transportation

fuels. A complex credit program based on sales

of qualifying renewable sources facilitates the

achievement of those requirements. The thresholds

for qualifying (20, 50, or 60 percent lower estimated

lifecycle greenhouse gas intensity) are coarse-

grained and thus coarsely targeted for providing

incentives to reduce greenhouse gas intensity.

• The LCFS also uses a credit system to achieve

targeted reductions in lifecycle greenhouse

gas intensity over time. However, the emissions

intensities of qualifying renewable sources are

based on technology pathways, with careful

assessments of actual emissions that provide

incentives for reducing actual emissions intensity.

Nevertheless, the measurement of reductions

in emissions intensity is only as good as the

baseline used for comparison—a concern that has

been expressed over the calculation of negative

emissions intensity for manure-derived biogas.

• There is vigorous debate about the overall

reduction in greenhouse gases achieved with

conventional bioethanol made from corn. Lower-

carbon technologies remain costly to use at scale.

Adverse environmental impacts also can arise

from producing biofuels, some of which raise

environmental justice concerns.

1. Introduction

Bioenergy is energy produced from biologic feedstocks

processed into liquid fuel, or process heat or electricity

from combustion. Various refining or processing

techniques go into producing bioenergy. Agricultural

bioenergy (ag bioenergy) uses agriculturally derived

feedstocks, either crops grown explicitly for their use as

energy or waste by-products such as manure. Biofuels

and biogas are the two most common ag bioenergy fuels.

Renewable biomass energy from forestry is another

bioenergy source (Wear and Bartuska 2020). However,

our focus in this issue brief is on ag bioenergy from farms

and ranches.

Current ag bioenergy policy in the United States reflects

several motivations. It creates a favorable regulatory

climate for production and sale of additional products

from the agricultural sector. Domestic bioenergy,

including ag bioenergy, is seen as improving the security

of US energy supplies by reducing imports—though

we raise questions about that rationale in Section 5. A

third very influential motivation is the potential for ag

bioenergy to reduce carbon intensity and total emissions

of greenhouse gases (GHGs) in the United States.

Resources for the Future — The Policy Landscape for Agricultural Bioenergy 2

This issue brief provides a brief typology of bioenergy

and then summarizes and discusses key elements in the

nonagricultural policy landscape that have expanded

production of ag bioenergy. It also highlights some

important questions needing further consideration.

We focus on a time frame of roughly the next 5 to 10

years, taking an agnostic view here on bigger longer-

term issues such as the role for ag bioenergy vis-à-vis

electricity in decarbonizing ground transportation.1

2. Types of Bioenergy

Biofuels include both ethanol and diesel fuels.

Traditional, or conventional, ethanol relies on a

distillation of food starches to fuel. Ethanol also can

be made from cellulosic feedstocks, which results in

a considerably lower lifecycle GHG intensity relative

to conventional ethanol.2 Cellulosic feedstocks can

be grown on lower-quality lands, which may reduce

competition between food and fuel crops on existing

agricultural lands, as well as GHG emissions compared

with the eects of more extensive land use to scale up

food crops for ethanol production. However, cellulosic

ethanol production remains low because of continuing

technical hurdles.

Alternatives to petroleum-derived diesel fuels can be

made from waste oils and grease from food preparation,

various plant-based oils, and animal fats. Biodiesel is a

product made from these sources through the chemical

process of transesterification. Limited amounts of

biodiesel can be blended into petroleum-based diesel

fuel. Renewable diesel is made via processes that yield

a product fully interchangeable with petroleum-based

diesel. Both fuel types are ag biofuels, though raw

vegetable oils and waste products from food preparation

are quite dierent feedstocks. Oils extracted from

nonfood energy crops (e.g., jatropha) can be another

source of ag biofuels.

1 We also do not delve into the possible role of ag bioenergy in energy sources for aviation and marine transport or ethanol derived

from low-carbon hydrogen sources.

2 Lifecycle analysis (LCA) of GHGs from bio energy includes emissions from land use change (such as forest clearing), agricultural

practices (N2O and CH4 emissions), and soil carbon sequestration benefits from biofuel crop production. It also includes emissions

associated with transportation of feedstocks to refineries for biofuel production, and operation of the refining facilities (e.g.,

CO2 released during feedstock fermentation to produce ethanol). The properties of the models underlying LCA results and the

fundamental assumptions these models make are in dispute.

Biogas is a mixture of methane, CO2, and other

impurities resulting from decomposition of biomass in a

low-oxygen environment. This anaerobic decomposition

is found in landfills and sewage treatment plants, but the

main source of ag biogas is decomposition of livestock

manure. If the manure is collected and placed in a biogas

digester, the resulting biogas can be collected and used.

Renewable natural gas is biogas processed to remove

impurities and is fully interchangeable with conventional

(fossil) natural gas in various applications, including as a

transportation fuel (compressed natural gas).

3. Federal Policy Background

for Ag Bioenergy

The Energy Title of the Farm Bill was established in

2002 to accelerate production of biofuels, primarily

corn-based ethanol. It is Title IX in the current Farm

Bill, the Agriculture Improvement Act of 2018 (Pub.

L. No. 115-334). Title IX supports, among other goals,

cultivation of bioenergy feedstocks, technological

processes for biofuel refinement, and research and

education (CRS 2022).

Title IX programs targeted at ag biofuel production

include loan guarantees and Commodity Credit

Corporation payments for advanced biofuel production

and payments for biomass cultivation and bioenergy

conversion. The 2018 Farm Bill also established the

Carbon Utilization and Biogas Education Program to

support education on biodiesel and on filtering multiple

sources of waste into a single stream of biogas. Other

research eorts focus on stimulating production of new

biofuels and other biomass derivatives.

CRS (2021b) shows the biofuel funding allocation over

various years in which an energy title was included in

Farm Bill authorization. The 2018 Farm Bill continued

a trend of providing less mandatory program funding

Resources for the Future — The Policy Landscape for Agricultural Bioenergy 3

than in 2008. As explained in Section 3, the mandatory

funding reduction coincided with the introduction

of energy-focused legislation that led to significant

expansion in US biofuel production. Title IX in the 2018

Farm Bill is largely a complementary policy focused on

funding research and education.

One key energy-related policy for stimulating ag

biofuel production is the Renewable Fuel Standard

(RFS), established in the Energy Policy Act of 2005.

The RFS subsequently was expanded in the Energy

Independence and Security Act of 2007. The RFS

system is administered by the US Environmental

Protection Agency (EPA), which also sets requirements

for incorporation of ethanol into motor fuels to improve

engine performance and reduce tailpipe emissions by

promoting more complete fuel combustion.

The RFS requires fuel suppliers to provide a minimum

volume of total renewable fuels and of several specific

categories of renewable fuels. The requirements

were specified by statute through 2022, with rising

obligations over time. From 2023 onward, EPA has set

the volume requirements by balancing various factors

listed in the statute (AFDC 2024c; EPA 2023; CRS 2023).

The categories are conventional renewable fuels

(mostly corn-based ethanol) and advanced renewable

fuels, which include as subcategories fuels made from

cellulosic feedstocks and biomass-based diesel.3 The

specified types of biofuels qualify for inclusion in these

categories only if they meet certain lifecycle emissions

reduction thresholds compared with conventional

petroleum fuel (gasoline or diesel). The threshold for

conventional renewable fuels is a 20 percent reduction,

whereas the thresholds for various categories of

advanced renewable fuels are 50 or 60 percent.

3 Some renewable natural gas from farm-based manure biodigesters as well as landfills and wastewater treatment plants are

included in the cellulosic category.

4 This is a highly simplified overview of what is in practice a very complex regulatory system.

5 Among those measures, the IRA continues existing tax incentives for biofuels including biodiesel through 2024, and it sets up a

new clean fuel production tax credit (45Z) for 2025 (Pub. L. No. 117-169).

6 The 45Q credit is also applicable for bioenergy operations that rely on the burning of biomass, which often share feedstocks with

advanced biofuels.

In practice, rather than each supplier having to meet

each of those Renewable Volume Obligations (RVOs)

in its own sales, the requirements are met through

a system of tradable credits. Supplies of renewable

fuels covered by the RFS are assigned Renewable

Identification Numbers (RINs) when they are sold into

the fuels market. These numbers allow EPA to track the

volumes and carbon intensities. Fuel suppliers then can

purchase certificates based on the RINs as an indirect

way of meeting their volumetric obligations based on

their own fuel sales.

Revenues received by renewable fuel suppliers equal

the sum of payments for the fuels and payments for the

RIN certificates. The prices of the certificates indicate

the indirect subsidies required to draw the RFS-required

volumes of the covered renewable fuels into the

market (AFDC 2024c, 2024d; CRS 2023; Stock 2015).4

The requirements for conventional ethanol stopped

increasing in 2015, as the demand for ethanol became

constrained by EPA’s current requirement of 10 percent

ethanol blending into motor gasoline. Other advanced

fuels have since played a larger role.

In addition to the RFS, the Inflation Reduction Act

of 2022 (IRA) contains numerous production- and

infrastructure-related tax breaks for biomass-based

“clean energy” sources, including biogas (AFDC

2024b).5 The IRA expands a previous tax credit

(known as 45Q) for the use of carbon capture,

utilization, and storage (CCUS). This has strong

appeal to corn ethanol producers because the cost of

capturing CO2 from ethanol fermentation is low—an

important consideration, since emissions from ethanol

fermentation are estimated to be close to 1 percent of

total US CO2e emissions (Irwin 2024).6

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摘要：

ThePolicyLandscapeforAgriculturalBioenergyIssueBrief24-03byEmilyJoiner,MichaelToman,andSuzanneRusso—May2024KeyPoints•Agricultural(ag)bioenergyhasreceivedfinancialandtechnicalsupportfromtheEnergyTitleoftheFarmBill,firstestablishedin2002.Atpresent,however,theprimarydriversofagbioenergyareincentivesinf...

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