Greenhouse Gas Emissions in
Montgomery County, Pennsylvania
1990-2004
Sarah E. Knuth
M.S. Degree Candidate
Department of Geography
Penn State University
20 July 2006
i
©Copyright 2006
Sarah Elisabeth Knuth
This research was externally supported by a Science to Achieve Results (STAR) grant from
the US Environmental Protection Agency (#F5C20415) and a grant from the Teresa Heinz
Scholars for Environmental Research program, Heinz Family Foundation
ii
Introduction
This document presents the results of a greenhouse gas emissions inventory
compiled for Montgomery County from March 2005 to November 2006, using methods
described in the report Measuring Greenhouse Gas Emissions in Montgomery County
1990-2004: Technical Report (Knuth, 2006a). The inventory tracks county GHG
emissions from 1990 to 2004, investigating a number of emissions sources, sinks, and
drivers. This report presents overall inventory results, then examines more detailed
findings by sector. A Global Warming Plan of Action for Montgomery County,
Pennsylvania: Greenhouse Gas Emissions Reduction Strategies (Knuth, 2006c) presents
options for reducing the county’s GHG emissions.
Background Information
Earth’s temperature is regulated by a collection of trace atmospheric gases,
including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), that trap
outgoing heat in the atmosphere and re-radiate it back to the earth’s surface. Human
activities over the past 150 years, including burning fossil fuels for energy, deforestation,
intensive agriculture, and other processes, have dramatically increased atmospheric
concentrations of these natural greenhouse gases (GHGs) and added potent man-made
GHGs to the atmosphere. Scientific consensus indicates that continued high levels of
human GHG production will force significant and long-term alterations in Earth’s
climate; most directly, an increase in average planetary temperatures. Potential impacts
of this warming include increased incidence of heat waves, droughts, and severe storms;
melting of ice caps and global sea level rise; and species extinctions (IPCC, 2001). The
seriousness of these projected impacts is increasingly prompting citizens and
policymakers to take steps to reduce GHG emissions.
GHG emissions inventories establish places’ baseline GHG emissions and reveal
important emissions sources and sinks. Stakeholders may use this information to explore
trends in GHG emissions, target emissions reduction strategies, and track progress in
reducing emissions. Traditionally, inventories calculate GHG emissions by tracking
levels of known GHG emissions-producing/reducing activities, then multiplying these
activity data by nationally-derived emissions coefficients (e.g., EIIP, 1999). Emissions
are often expressed in metric tons of carbon-equivalent units (MTCE):
GHG Emissions (MTCE) = Activity Data * GHG Emissions Coefficients
Figure 1 shows GHG emissions sources and sinks inventoried for Montgomery County1
These include emissions from energy use, transportation, solid waste disposal and
wastewater treatment, agriculture, and forest management and land-use change.
1
Data unavailability prevented final inclusion of emissions from industrial processes and off-road
transportation.
2
Highway
Off-Road
Burning Waste
On-Site Fuel
Soils
Transportation
Electricity
Animals
Manure
Energy
Agriculture
Montgomery County
Greenhouse Gas
Emissions
Waste
Solid Waste
Forest
Industrial
Processes
Wastewater
+/- Land
Management
Figure 1: Montgomery County GHG Emissions Sources and Sinks
Overall Results
Montgomery County’s overall GHG emissions increased almost every year from
1990 to 2004. Total emissions grew from about 2.6 million metric tons of carbonequivalent GHG emissions (MTCE) in 1990 to almost 3.6 million MTCE in 2004, a 36
percent increase (Figure 2). Three GHG emissions sources – electricity consumption, onsite fuel use, and transportation – dominate Figure 2’s emissions trends.
4,000,000
GHG Emissions (MTCE)
3,500,000
3,000,000
Agriculture
2,500,000
Forest
Wastewater and Sludge
2,000,000
Municipal Solid Waste
1,500,000
On-Site Fuel
1,000,000
T ransportation
Electricity
500,000
0
1990
1992
1994
1996
1998
2000
2002
2004
-500,000
Figure 2: Montgomery County GHG Emissions (MTCE) 1990-2004
3
Figure 3 quantifies the sector GHG emissions shares shown in Figure 2. In
general, energy-related fossil fuel combustion dominates Montgomery County GHG
emissions. Electricity use, on-site fuel consumption, and transportation energy use were
the top three sources of GHG emissions in 1990, making up 33 percent, 44 percent, and
27 percent of total emissions, respectively (Figure 3). GHG emissions from wastewater
and sludge treatment and agriculture were much less significant at only 0.1 percent and 1
percent of total emissions. Solid waste disposal and forest management change were net
GHG emissions sinks in 1990.
In 2004, stationary energy use and transportation continued to dominate GHG
emissions (electricity made up 34 percent of total emissions, on-site fuel consumption 30
percent, and transportation 25 percent). Wastewater and sludge treatment and agriculture
remained minor emissions sources (0.1 percent and 0.3 percent of total emissions,
respectively). The primary difference between 1990 and 2004 GHG emissions shares
was the growing significance of GHG emissions from solid waste disposal and forest
management. Both of these sectors became net sources of GHG emissions over the last
fifteen years, making up 3 percent and 7 percent of 2004 GHG emissions, respectively.
Growth in the proportional importance of these sectors occurred at the expense of on-site
fuel consumption. GHG emissions in the latter sector remained fairly stable, and its
trends were outstripped by more pronounced trends in other sectors.
50%
40%
30%
1990
20%
2004
10%
0%
Ele
-10%
ctri
city
On
-Si
te F
u el
Tra
n sp
ort
a
Mu
n ic
tion
Fo
Wa
res
s te
t
ipa
wa
lS
ter
o li
a
nd
dW
Slu
ast
dg e
e
Ag
ric
u lt
ure
Figure 3: Montgomery County GHG Emissions (MTCE): Sector Percent Share in
1990 and 2004
As Figure 3 indicated, different sectors’ GHG emissions grew at different rates.
Figure 4 shows net growth in GHG emissions per sector between 1990 and 2004.
Montgomery County’s population grew about 14 percent over this period, increasing
from about 678,000 to 774,000 residents. Most sectors’ GHG emissions grew at a greater
rate than population. Electricity consumption and transportation emissions grew 42
percent and 25 percent, respectively, over the past fifteen years. Emissions from solid
4
waste disposal and forest management grew much more: 192 percent and 336 percent,
respectively. Because the inventory calculated GHG emissions from county wastewater
and sludge treatment using population trends, emissions from this sector showed the
same 14 percent increase as population over the past fifteen years. Finally, two sectors’
emissions decreased slightly between 1990 and 2004. GHG emissions from agriculture
fell 29 percent, and emissions from on-site fuel consumption decreased by 7 percent. Onsite fuel consumption’s emissions fluctuated substantially from year to year, so this
downturn is probably temporary and is at least in part an artifact of the two specific years
used to summarize GHG emissions trends.
400%
350%
300%
250%
200%
150%
100%
50%
0%
-50%
Ele
ctri
city
On
-Si
te F
u el
Tra
n sp
ort
a
Mu
n ic
tion
Fo
Wa
res
s te
t
ipa
wa
lS
ter
o li
a
nd
dW
Slu
ast
dg e
e
Ag
ric
u lt
ure
Figure 4: Montgomery County GHG Emissions: Percent Change 1990-2004
Electricity Consumption
Burning fossil fuels to generate electricity produces CO2 (Fuel impurities and
incomplete combustion can also produce small amounts of CH4 and N2O, but data to
calculate these emissions were unavailable at the county level.) The inventory measured
CO2 emissions from Montgomery County’s residential, small commercial and industrial
(SCI), and large commercial and industrial (LCI) electricity consumption between 1990
and 2004. Electricity consumed in Montgomery County is generated by plants in the
Pennsylvania-New Jersey-Maryland (PJM) Interconnection regional power pool and
distributed by PECO Energy Company/Exelon (PECO), PPL Electric Utilities
Corporation (PPL), and Metropolitan Edison Company. PECO serves the five-county
Philadelphia metropolitan area and is Montgomery County’s dominant electric utility.
Figure 5 reports CO2 emissions for PECO, PPL, and Metropolitan Edison electricity
customers, with PECO customers’ emissions reported by sector. CO2 emissions from
county electricity consumption grew from about 860,000 MTCE to 1.2 million MTCE
over the fifteen-year period. This emissions increase was uneven; growth periods (19925
1995 and 2000-2003) were punctuated by periods of stable or slightly declining
emissions (1990-1992, 1995-2000, and 2003-2004).
Examining forces driving electricity sector CO2 emissions helps explain Figure
5’s variable emissions trends. According to inventory calculations, Montgomery County
electricity consumption grew steadily between 1990 and 2004 (Figure 6). SCI electricity
use grew the most, LCI the least. Much of Figure 5’s variability stems from changes in
the average CO2 emissions intensity of the Pennsylvania-New Jersey-Maryland (PJM)
Interconnection’s electricity generation. Figure 7 tracks this intensity from 1990 to 2004
(hollow data points pre-1996 indicate intensities estimated due to data unavailability).
Electricity generation in PJM’s power pool grew steadily less CO2-intensive between
1996 and 2000 but reversed this trend between 2000 and 2003 (2004’s electricity
generation was slightly less CO2–intensive than 2003’s). When multiplied by electricity
use, these changing CO2 emissions coefficients alternately mitigate (1996-2000; 2004)
and exacerbate (2000-2003) electricity consumption’s emissions.
1,200,000
GHG Emissions (MTCE)
1,000,000
800,000
Met Ed
PPL
600,000
PECO - SCI
PECO - Res.
400,000
PECO - LCI
200,000
0
1990
1992
1994
1996
1998
2000
2002
2004
Figure 5: Montgomery County GHG Emissions (MTCE) 1990-2004: Electricity
Consumption
6
3,500
3,000
2,500
2,000
LC I
R esid.
1,500
SC I
1,000
500
0
1989
1994
1999
2004
Figure 6: Montgomery County Electricity Consumption (PECO Service Area) 19902004
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
1989
1991
1993
1995
1997
1999
2001
2003
2005
Figure 7: PJM Interconnection CO2 Emissions Intensity: 1990-2004
On-Site Fuel Consumption
Residential, SCI, and LCI sector facilities burn fossil fuels (most commonly
natural gas, petroleum fuels, and coal) on-site for a variety of purposes (e.g., space
heating, water heating, and industrial processes). Fossil fuel combustion produces CO2
as well as small amounts of CH4 and N2O from fuel impurities and incomplete
combustion. The inventory measured CO2 emissions from Montgomery County’s
residential, SCI, and LCI on-site fuel consumption. Data constraints prevented the
inventory from including CH4 and N2O emissions in the GHG inventory. PECO provides
utility natural gas service to Montgomery County. UGI Utilities, Inc. (UGI), the only
other gas utility in the region, served slightly over 1,600 Montgomery County natural gas
customers in 2004 (UGI, 2004), an insignificant share next to PECO’s 152,000 county
customers (PECO, 2004b).
Therefore, the inventory does not include UGI’s
Montgomery County customers or consumption in the inventory. Numerous smaller,
7
non-utility companies provide oil, coal, and other renewable and non-renewable fuels to
Montgomery County customers.
To calculate CO2 emissions from Montgomery County on-site fossil fuel use, the
inventory first determined Montgomery County residential, SCI, and LCI sector
consumption of natural gas, petroleum fuels (i.e., residual fuel oil, distillate fuel oil,
liquefied petroleum gas, and kerosene), and coal from 1990 to 2004. It then multiplied
fuel consumption in million British Thermal Units (BTU) by each fuel’s carbon (C)
content and proportional oxidization to CO2 using EIIP (1999) coefficients to express
emissions in MTCE.
According to inventory calculations, GHG emissions from on-site fuel
consumption fluctuated from year to year but averaged about 1 million MTCE annually
(see Figure 8). Each sector showed similar year-to-year variability. Due to inventory
methods, these shifts are linked to trends in overall gas use by PECO customers. Figure 9
estimates different fuel types’ contribution to GHG emissions in each sector in 1999.
Natural gas from utilities and oil are the most important fuels used in the area,
respectively contributing 53 and 45 percent of GHG emissions in the residential sector,
56 and 42 percent in the SCI sector, and 39 and 60 percent in the LCI sector. Coal is a
minor contributor in each sector at 1 percent or less of total GHG emissions, and bottled
gas/liquid petroleum gas (LPG) is a minor source of residential GHG emissions at 2
percent of total sector emissions. In the residential and SCI sectors, use of utility natural
gas increased relative to oil from 1990 to 2004. This proportional increase moderated
residential and SCI GHG emissions because natural gas combustion produces fewer
GHG emissions than oil combustion. Data unavailability precluded the inventory from
tracking changing fuel-type importance in the LCI sector.
1,400,000
GHG Emissions (MTCE)
1,200,000
1,000,000
Resid.
800,000
SCI
600,000
LCI
400,000
200,000
0
1990
1992
1994
1996
1998
2000
2002
2004
Figure 8: Montgomery County GHG Emissions (MTCE) from On-Site Fuel
Consumption 1990-2004
8
70%
60%
50%
Gas
40%
Oil
30%
Coal
20%
LPG
10%
0%
Residential
SCI
LCI
Figure 9: GHG Emissions from On-Site Fuel Consumption 1999: Emissions Share
by Fuel Type
Transportation
Transportation-related fossil fuel consumption produces CO2 and small amounts
of CH4 and N2O from fuel impurities and incomplete combustion. The inventory tracked
Montgomery County’s on-road CO2, CH4, and N2O emissions for gasoline- and dieselburning passenger cars, light trucks, and heavy trucks. It calculated emissions based on
total miles of travel. County-level data constraints did not permit reporting motorcycle
and bus GHG emissions as separate categories, although having this information would
have been useful to inform mitigation strategies. The inventory was unable to include
several smaller sources of transportation GHG emissions. First, idling in traffic produces
excess fuel consumption and a small amount of extra GHG emissions; this information is
summarized in Appendix A. The inventory also did not report GHG emissions from nonroad modes of transportation (e.g., airplanes, boats, trains, farm and construction
equipment, snowmobiles), due to a combination of data unavailability at the county level
and boundary allocation problems (judging who is responsible for marine and air travelrelated GHG emissions is difficult to impossible at the local level).
To calculate CO2 emissions from Montgomery County on-site fossil fuel use, the
inventory first determined annual on-road vehicle miles traveled (VMT) in Montgomery
County, then determined the proportion of VMT contributed by different vehicle types.
It multiplied VMT by vehicle type by the inverse of EPA fuel economy by vehicle type to
calculate gasoline and diesel use. It then used EIIP (1999) formulas and emissions
coefficients to calculate CO2 emissions from fuel consumption, and CH4 and N2O
emissions from VMT by vehicle type.
Transportation GHG emissions grew from about 700,000 MTCE in 1990 to
almost 900,000 MTCE in 2004 (Figure 10). Light-duty gasoline vehicles (i.e., passenger
cars) accounted for, on average, 61 percent of total emissions, with light-duty gasoline
trucks a distant second at 21 percent. Heavy-duty diesel vehicles and heavy-duty
gasoline vehicles contributed smaller amounts to total emissions – 10 percent and 8
percent, respectively. GHG emissions from light-duty diesel vehicles and trucks were
9
relatively insignificant. These emissions shares corresponded roughly to different vehicle
types’ proportional contributions to VMT. However, relatively low vehicle fuel economy
in light-duty gasoline trucks and, especially, heavy-duty gasoline and diesel trucks
inflates the significance of these sources’ GHG emissions relative to their share of VMT.
Figure 11 demonstrates this relationship by comparing county GHG emissions and VMT
in 2003. At 6.9 billion, Montgomery County’s 2003 VMT was the second highest in
Pennsylvania (only surpassed by Allegheny County), 1 to 2 billion higher than any other
county in the Philadelphia area.
1,000,000
GHG Emissions (MTCE)
900,000
800,000
Light Duty Diesel T rucks
700,000
Light Duty Diesel Vehicles
600,000
Heavy Duty Gas Vehicles
500,000
Heavy Duty Diesel Vehicles
400,000
Light Duty Gas T rucks
300,000
Light Duty Gas Vehicles
200,000
100,000
0
1990
1992
1994
1996
1998
2000
2002
2004
Figure 10: Montgomery County GHG Emissions (MTCE) from Transportation
1990-2004
10
80%
70%
60%
VMT
50%
40%
G HG Emissions
30%
20%
10%
0%
Light D uty Light D uty
G as
G as
Truc ks
Vehic les
Heavy
D uty
D ies el
Vehic les
Heavy
D uty G as
Vehic les
Light D uty Light D uty
D ies el
D ies el
Truc ks
Vehic les
Figure 11: Montgomery County Vehicle Miles Traveled and GHG Emissions 2003:
Percent Share by Vehicle Type
Solid Waste Disposal
GHG emissions from solid waste disposal are determined by three emissions
sources and one emissions sink. First, solid waste that municipalities deposit in landfills
releases CH4 as a result of anaerobic waste decomposition; rates of landfill CH4
emissions depend on total landfill waste in place, climate, and other landfill
characteristics. Landfill CH4 can be removed by CH4 flaring and recovery for waste-toenergy programs. Industrial waste disposal and decomposition also produces CH4
emissions, and incineration of municipal sold waste releases CO2 and N2O. Finally,
municipal solid waste disposal in landfills also acts as an emissions sink because it
sequesters C for long periods. In calculating GHG emissions from Montgomery County
waste disposal, the inventory considered all landfills to which Montgomery County
exports waste, both within county boundaries and in other Pennsylvania counties. It
tracked all types of waste deposited in municipal landfills, including municipal waste,
residual waste, sewage sludge, infectious waste, construction waste, ash residue, and
asbestos. Data was not available to compute waste deposited at out-of-state landfills; it
was assumed that this total is small. This boundary allocation decision links GHG
emissions from waste disposal to Montgomery County consumption. The inventory did
not account explicitly for waste diverted from the waste stream via recycling and did not
attempt to calculate GHG emissions produced during the entire lifetime of disposed
products (e.g., energy needed to extract and process raw materials, transport products,
etc.).
The inventory calculated CH4 emissions from municipal solid waste disposal to
landfills by multiplying cumulative waste at Montgomery County destination landfills by
EIIP (1999) emissions coefficients estimating CH4 emissions per unit of waste (MTCE).
It determined CH4 emissions from industrial solid waste disposal to landfills using the
previous equation’s results and an EIIP (1999) proxy method. The inventory calculated
CO2 and N2O emissions from municipal solid waste incineration by multiplying annual
Montgomery County waste incineration by EIIP (1999) emissions coefficients. Finally, it
11
established C sequestration from solid waste disposal to landfills by multiplying
Montgomery County annual municipal solid waste disposal to landfills by EIIP (1999)
emissions coefficients estimating C sequestered per unit waste.
Montgomery County GHG emissions from solid waste disposal increased from
about -54,000 MTCE in 1990 to 104,000 MTCE in 2004 (Figure 12). Solid waste
disposal was a net GHG emissions sink in 1990 and 1991 because carbon sequestration
from landfilled municipal waste exceeded CH4 emissions from municipal and industrial
waste landfilling and CO2 and N2O emissions from waste incineration. Although total
municipal waste disposal increased steadily between 1990 and 2004 (Figure 13), the
amount of waste sent to landfills declined after the Montenay Energy Resources of
Montgomery County, Inc. (MERMCI) incineration facility opened in 1991. This shift
simultaneously reduced annual landfill carbon sequestration and landfill CH4 emissions
(the latter less so, because landfill CH4 emissions are dependent on cumulative waste in
place and are therefore less sensitive to year-to-year changes). Industrial landfilling
remained a minor source of CH4 emissions. Waste incineration also produced CO2 and
N2O emissions. The waste sector produced positive GHG emissions from 1992 to 2004.
As MERMCI reached maximum annual capacity, increasing total waste disposal diverted
more waste to landfills, and landfill CH4 emissions and carbon sequestration increased
again. Finally, landfill CH4 recovery programs at most of Montgomery County’s major
destination landfills significantly reduced total emissions, lessening the GHG emissions
impact of increasing waste disposal to landfills.
200,000
GHG Emissions (MTCE)
150,000
100,000
Municipal Landfilling
Waste Incineration
50,000
Industrial Landfilling
0
Landfill C Sequestr.
-50,000
-100,000
-150,000
1990
1992
1994
1996
1998
2000
2002
2004
Figure 12: Montgomery County GHG Emissions from Solid Waste Disposal 19902004
12
1,200,000
1,000,000
800,000
Incinerators
600,000
Landfills
400,000
200,000
0
1990
1992
1994
1996
1998
2000
2002
Figure 13: Montgomery County Annual Municipal Solid Waste Disposal (Tons)
1990-2003
Wastewater and Sludge Treatment
Processing municipal sewage sludge and wastewater produces small amounts of
N2O and CH4 emissions. Processing practices that minimize anaerobic decomposition or
recover gases produced can reduce GHG emissions, but local data availability did not
permit including these emissions-reducing methods.
To calculate CH4 emissions from Montgomery County wastewater and sludge
treatment following EIIP (1999) methods, the inventory multiplied total county
population by average per capita waste production, the proportion of waste kept as
wastewater and removed as sludge, and, for each, CH4 produced per unit of waste and the
average proportion of waste treated anaerobically. It subtracted CH4 recovered from
these totals. To determine N2O emissions from wastewater and sludge, the inventory
multiplied average United States per capita protein consumption by the percent N in
protein, Montgomery County population, and an emissions factors that converted N to
N2O emissions.
Montgomery County CH4 and N2O emissions from sludge and wastewater
treatment were insignificant relative to most other GHG emissions sources. However,
wastewater and sludge emissions grew steadily between 1990 and 2004, driven by
increasing county population (Figure 14).
13
3,100
GHG Emissions (MTCE)
3,000
2,900
2,800
2,700
2,600
2,500
2,400
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Figure 14: Montgomery County GHG Emissions from Wastewater and Sludge
Treatment 1990-200
Forest Management
Forests sequester C in trees and forest canopy, undergrowth, roots, and forest
soils. When forests are altered so that the forest ecosystem stores less C per acre or total
acres of forest land are reduced, these changes are expressed as CO2 emissions (i.e.,
releases of stored C). The inventory measured Montgomery County C sequestration and
CO2 emissions from contiguous forested areas. Although street trees and other
vegetation types also sequester C, lack of data precluded including these emissions sinks
in Montgomery County’s inventory.
Using a basic version of EIIP (1999) formulas, the inventory calculated C
sequestration/C-equivalent CO2 emissions released from forest management and land-use
change by multiplying average C storage per unit of forest land by total forest land from
1990 to 2004. It expressed gains in C storage as negative CO2 emissions and losses in C
storage as positive CO2 emissions.
Montgomery County’s forest sector changed from a GHG emissions sink in 1990,
registering a 74,000 MTCE increase in carbon sequestered in trees, undergrowth, and
forest soils, to a CO2 source in 2004, emitting over 247,000 MTCE (Figure 15). Loss of
forested land in the county drove this trend toward decreasing forest carbon sequestration
and increasing GHG emissions. Land-cover trends indicate that the county has lost
almost 25 percent of its forest land over the last fifteen years (see Figure 16; emphasized
data points indicate land-cover inventory years). Increasing average carbon storage per
forest acre (the inventory measured a 13 percent increase between 1990 and 2004)
14
exerted a moderating influence on forest GHG emissions. Increasing carbon storage per
forest acre drove the inventory’s early trend toward carbon sequestration, but the
magnitude of county forest loss converted the forest sector to a net emissions source in
1996. Since then, growing annual loss of forest land has produced increasingly large
GHG emissions.
Montgomery County CO2 Emissions (MTCE) from Forest
Management 1990-2004
300,000
GHG Emissions (MTCE)
250,000
200,000
150,000
100,000
50,000
0
-50,000
-100,000
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Figure 15: Montgomery County CO2 Emissions (MTCE) from Forest Management
1990-2004
35,000
30,000
25,000
20,000
15,000
10,000
5,000
0
1989
1991
1993
1995
1997
1999
2001
2003
2005
Figure 16: Change in Montgomery County Forest Land (Hectares) 1990-2004.
Emphasized data points represent years for which data was present; other points
are interpolated or extrapolated.
15
Agriculture
Various agricultural practices release GHG emissions. Livestock emit CH4
during digestion (enteric fermentation), particularly ruminant livestock (e.g., cattle and
sheep). Manure management produces various levels of CH4 and N2O emissions,
depending on total volume of manure and the type of manure management system
utilized (e.g., pit storage, solid storage, anaerobic lagoon, etc.), which varies by region
and livestock type. Some farmers cultivating wheat, rice, and sugarcane burn agricultural
crop waste, releasing CO2 and N2O emissions (of these crops, only wheat is produced in
Montgomery County). Finally, various agricultural soil management practices produce
GHG emissions. Nitrogen (N) fertilizer application to agricultural crop and pasture land
produces N2O emissions directly, via leaching and runoff, and through volatization to
NH4 and NOx (N in these gases eventually converts to N2O). Livestock manure applied
to agricultural soils through daily spread operations or in pastures also contributes to N2O
emissions directly, through leaching and runoff, and via volatization to NH4 and NOx.
Incorporation of crop residues into agricultural soils and cultivation of N-fixing crops
(e.g., soybeans, alfalfa, lentils) produce N2O emissions directly. Finally, lime application
to agricultural soils produces CO2 emissions. The inventory measured Montgomery
County agricultural GHG emissions from all sources described above. Rice cultivation is
an important source of agricultural CH4 emissions, but Montgomery County produces no
rice. Also, lack of county-level data prevented the inventory from including N2O
emissions from soil management practices including organic fertilizer use and cultivation
of high-organic content histosols; these omissions are probably minor.
First, the inventory calculated CH4 emissions for each type of livestock by
multiplying livestock populations by CH4 production per head (EIIP, 1999). It
determined CH4 emissions from manure management by multiplying livestock
populations by average animal mass (TAM), volatile solids (VS) produced, and CH4producing capacity to find maximum potential CH4 emissions, then multiplied this total
by percent use of different manure management systems and each system’s CH4 percent
conversion factor. The inventory found N2O emissions from manure management by
multiplying livestock populations by average animal mass, N produced per unit of mass,
the percent of manure managed, and the amount of N in manure unvolatized to find total
N in managed manure, then multiplied this total by the percent of manure in each
management system and each management system’s N2O emissions factor. Next, it
calculated CO2 emissions and N2O emissions from agricultural waste burning in
Montgomery County by multiplying county production of crops whose waste is burned
by EIIP (1999) coefficients estimating total residue produced, amount burned, percent
dry matter produced, burning efficiency, combustion efficiency, and C content (for CO2
emissions) or N content (for N2O emissions). Finally, the inventory calculated N2O and
CO2 emissions from agricultural soils using several equations. First, to estimate direct
N2O emissions from soil management practices, it first multiplied annual synthetic
fertilizer use by an EIIP (1999) coefficient calculating N2O emissions. It found
additional N2O emissions by multiplying the total N content of county livestock manure
by the percent of manure managed as daily spread and an N2O emissions coefficient for
this practice. The inventory determined N2O emissions from integrating crop residues
into soil by multiplying crop production by EIIP (1999) coefficients estimating the
16
amount of residue each crop produces, the fraction of residue incorporated back into the
soil, the residue’s N content, and the amount of N that converts to N2O emissions
(MTCE). Finally, the inventory found N2O emissions from cultivation of N-fixing crops
by multiplying annual production of these crops by EIIP (1999) coefficients estimating
total residue production, N content, and N conversion to N2O emissions (MTCE).
Second, to calculate N2O emissions from animal manure deposited on pasture, range, and
paddock, it multiplied the N content of county manure by the EIIP (1999) estimated
percent of manure deposited on pasture, range, and paddock and N2O emissions
coefficient for this practice. Third, it used synthetic fertilizer application, manure
production, and N content information calculated in previous equations with EIIP (1999)
emissions coefficients to calculate the fraction of N in fertilizer and manure that volatizes
to NOx and NH4, and the fraction that is removed from the soil in leaching and runoff
(both processes eventually produce N2O emissions). Finally, the inventory determined
CO2 emissions from lime application to agricultural soils by multiplying county lime use
by an EIIP (1999) CO2 emissions factor.
Montgomery County’s agricultural GHG emissions declined from 1990 to 2004,
from about 17,000 MTCE annually to just under 14,000 MTCE (Figure 17). GHG
emissions from almost all agricultural sources – including livestock direct emissions,
manure management, burning of crop residues, nitrogen-fixing crop production, and lime
application to agricultural soils – also declined from 1990 to 2004. Decreases can be
attributed to declining crop production for most crops and livestock population over the
past fifteen years (see Figure 18 and 19, respectively). Corn production does not follow
this general decline. Rather, it fluctuates from year to year. In addition, the populations
of some types of livestock (i.e., horses, sheep, goats, and mules) increased slightly
between 1990 and 2004. However, more significant decreases in cattle and swine
production outweigh these minor increases. GHG emissions from synthetic nitrogen
fertilizer use fluctuated over the study period as fertilizer use changed from year to year
(see Figure 20). These trends in fertilizer use may be tied to weather or economic
conditions. In contrast, agricultural lime use declined over the past fifteen years. In
conclusion, a variety of driving forces overlap to determine agricultural GHG emissions;
emissions from this source are at once the most complex and (with the exception of
wastewater and sludge) the least significant overall.
17
20,000
18,000
GHG Emissions (MTCE)
16,000
14,000
Crop Residue Burning
12,000
Agricultural Soils
10,000
Manure Management
8,000
Livestock
6,000
4,000
2,000
0
1990
1992
1994
1996
1998
2000
2002
2004
Figure 17: Montgomery County GHG Emissions (MTCE) from Agriculture 19902004
1,200,000
1,000,000
800,000
C orn
S oybeans
600,000
Wheat
400,000
200,000
0
1989
1994
1999
2004
Figure 18: Montgomery County Grain Crop Production (Bushels) 1990-2004
18
14,000
12,000
10,000
C attle
S wine
8,000
Horses
S heep
6,000
G oats
M ules
4,000
2,000
0
1989
1994
1999
2004
Figure 19: Montgomery County Livestock Populations 1990-2004
3000
2500
2000
1500
1000
500
0
1989
1991
1993
1995
1997
1999
2001
2003
Figure 20: Montgomery County Synthetic Nitrogen Fertilizer Consumption (Tons)
1990-2004
Recapitulation
This chapter has presented the results of Montgomery County’s GHG emissions
inventory, evaluating changes in and the significance of various GHG emissions sectors,
sources, and sinks. The chapter has also explored forces driving changes in each sector’s
GHG emissions. Knuth (2006c) explains how these GHG emissions inventory results to
guide Montgomery County’s climate change mitigation planning process.
19
References
EIIP (1999). Estimating Greenhouse Gas Emissions. EIIP Documentation Series, Volume
VIII. Washington, DC: Greenhouse Gas Committee, Emissions Inventory
Improvement Program, and US Environmental Protection Agency.
http://www.epa.gov/ttm/chief/eiip/techreport/volume08/index.html.
Intergovernmental Panel on Climate Change (IPCC) (2001).
Knuth, Sarah (2006a). Measuring Greenhouse Gas Emissions in Montgomery County
1990-2004: Technical Report. Report compiled for the Montgomery County
Planning Commission.
Knuth, Sarah (2006c). A Global Warming Plan of Action for Montgomery County,
Pennsylvania: Greenhouse Gas Emissions Reduction Strategies. Report compiled
for the Montgomery County Planning Commission.
PECO. (2004b) Gas Annual Report of PECO Energy Company (Harrisburg, PA,
Pennsylvania Public Utility Commission), available at
<http://www.puc.state.pa.us/PcDocs/538597.xls>.
UGI (2004) Gas Annual Report of UGI Utilities, Inc. (Harrisburg, PA, Pennsylvania
Public Utility Commission), available at
<http://www.puc.state.pa.us/PcDocs/540078.xls>.
20