- E85 vehicles reduce atmospheric levels of two carcinogens, benzene and butadiene, but increase two others - formaldehyde and acetaldehyde.
- E85 increased ozone-related mortalities in the United States by about 200 deaths per year compared to gasoline.
- This ES&T study was partially supported by NASA.
Stanford Report, April 18, 2007
Ethanol vehicles pose significant risk to health, new study finds
Ethanol is widely touted as an eco-friendly, clean-burning fuel. But if every vehicle in the United States ran on fuel made primarily from ethanol instead of pure gasoline, the number of respiratory-related deaths and hospitalizations likely would increase, according to a new study by Stanford University atmospheric scientist Mark Z. Jacobson.
His findings are published in the April 18 online edition of the journal Environmental Science & Technology (ES&T).
His findings are published in the April 18 online edition of the journal Environmental Science & Technology (ES&T).
"Ethanol is being promoted as a clean and renewable fuel that will
reduce global warming and air pollution," said Jacobson, associate
professor of civil and environmental engineering. "But our results show
that a high blend of ethanol poses an equal or greater risk to public
health than gasoline, which already causes significant health damage."
Gasoline vs. ethanol
For the
study, Jacobson used a sophisticated computer model to simulate air
quality in the year 2020, when ethanol-fueled vehicles are expected to
be widely available in the United States.
"The chemicals that come out of a tailpipe are affected by a variety of
factors, including chemical reactions, temperatures, sunlight, clouds,
wind and precipitation," he explained.
"In addition, overall health effects depend on exposure to these airborne chemicals, which varies from region to region. Ours is the first ethanol study that takes into account population distribution and the complex environmental interactions."
"In addition, overall health effects depend on exposure to these airborne chemicals, which varies from region to region. Ours is the first ethanol study that takes into account population distribution and the complex environmental interactions."
In the experiment, Jacobson ran a series of computer tests simulating
atmospheric conditions throughout the United States in 2020, with a
special focus on Los Angeles. "Since Los Angeles has historically been
the most polluted airshed in the U.S., the testbed for nearly all U.S.
air pollution regulation and home to about 6 percent of the U.S.
population, it is also ideal for a more detailed study," he wrote.
Jacobson programmed the computer to run air quality simulations comparing two future scenarios:
Deaths and hospitalizations
The results of the computer simulations were striking.
"We found that E85 vehicles reduce atmospheric levels of two
carcinogens, benzene and butadiene, but increase two others—formaldehyde
and acetaldehyde," Jacobson said. "As a result, cancer rates for E85
are likely to be similar to those for gasoline. However, in some parts
of the country, E85 significantly increased ozone, a prime ingredient of
smog."
Inhaling ozone—even at low levels—can decrease lung capacity, inflame
lung tissue, worsen asthma and impair the body's immune system,
according to the Environmental Protection Agency. The World Health
Organization estimates that 800,000 people die each year from ozone and
other chemicals in smog.
"In our study, E85 increased ozone-related mortalities in the United
States by about 200 deaths per year compared to gasoline, with about 120
of those deaths occurring in Los Angeles," Jacobson said. "These
mortality rates represent an increase of about 4 percent in the U.S. and
9 percent in Los Angeles above the projected ozone-related death rates
for gasoline-fueled vehicles in 2020."
The study showed that ozone increases in Los Angeles and the
northeastern United States will be partially offset by decreases in the
southeast. "However, we found that nationwide, E85 is likely to increase
the annual number of asthma-related emergency room visits by 770 and
the number of respiratory-related hospitalizations by 990," Jacobson
said. "Los Angeles can expect 650 more hospitalizations in 2020, along
with 1,200 additional asthma-related emergency visits."
The deleterious health effects of E85 will be the same, whether the
ethanol is made from corn, switchgrass or other plant products, Jacobson
noted. "Today, there is a lot of investment in ethanol," he said. "But
we found that using E85 will cause at least as much health damage as
gasoline, which already causes about 10,000 U.S. premature deaths
annually from ozone and particulate matter. The question is, if we're
not getting any health benefits, then why continue to promote ethanol
and other biofuels?
"There
are alternatives, such as battery-electric, plug-in-hybrid and
hydrogen-fuel cell vehicles, whose energy can be derived from wind or
solar power," he added. "These vehicles produce virtually no toxic
emissions or greenhouse gases and cause very little disruption to the
land—unlike ethanol made from corn or switchgrass, which will require
millions of acres of farmland to mass-produce. It would seem prudent,
therefore, to address climate, health and energy with technologies that
have known benefits."
https://news.stanford.edu/news/2007/april18/ethanol-041807.html
https://news.stanford.edu/news/2007/april18/ethanol-041807.html
This ES&T study was partially supported by NASA.
______
One of the major reasons for encouraging the use of biofuels has been
the positive effects their use is expected to play in reducing
greenhouse gases and also air pollutants, with concomitant improvements
in health. The speakers in the workshop’s fourth session offered details
on how the production and use of biofuels should affect greenhouse gas
levels, air quality, and health.
BIODISTALLATE FUELS AND EMISSIONS
In the first presentation, S. Kent Hoekman, research professor in the
Division of Atmospheric Sciences at the Desert Research Institute,
discussed biodistillate fuels and emissions. The term biodistillate is a more general term than biodiesel, he explained, and it includes not only biodiesel but also related biofuels.
Background
Hoekman began by offering some basic background on biodiesel and other
biodistillate fuels, beginning with the drivers. “Why are we interested
in biodiesel? I think today the simplest and most direct answer is
because it’s the law.” In particular, the U.S. Environmental Protection
Agency (EPA), in implementing several congressional mandates, has
requirements for the use of renewable fuels divided into conventional
biofuels, cellulosic biofuels, biomass-based diesel, and other advanced
biofuels.
The ultimate drivers for the use of biofuels—that is, the reasons behind
the political decision to impose requirements for the use of
biofuels—include concerns about greenhouse gas emissions, the desire to
develop renewable or sustainable energy sources, the desire to develop
secure domestic fuel supplies, and an interest in rural development.
Interestingly, Hoekman said, neither air quality concerns nor health
concerns have been major factors in the push to increase the use of
biofuels. “They are somewhat important, but they have not been the main
drivers.”
Terminology
Next, Hoekman went over some basic terminology related to biofuels in
order to clarify exactly what is meant by various terms. According to
ASTM International, biodiesel fuel refers to “mono-alkyl esters
of long-chain fatty acids derived from vegetable oils and animal fats.”
The term can also refer to trans-esterified triglycerides or to fatty
acid methyl esters (FAMEs), which are both closely related to ASTM’s
definition. Biodiesel fuel is sometimes referred to as B100.
Renewable diesel is produced from the same feedstocks as
biodiesel, Hoekman said, but it is produced through hydroprocessing
technologies so that the product is a hydrocarbon (HC), not an ester. It
is also referred to as “green diesel.”
Co-processed renewable diesel is a form of renewable diesel that
is produced by adding vegetable oils or animal fats to feedstocks that
are being hydrotreated to produce diesel fuel, creating a single product
that is a mixture of bio and fossil HCs.
Cellulosic biodiesel fuel, or synthetic biodiesel, is produced by
pyrolysis or gasification of lignocellulosic feedstocks, such as
grasses and woods. The resulting liquid generally requires rather
considerable additional processing or upgrading before it can be blended
into petroleum fuel stock.
Biodistillate Production Technologies
A variety of different production methods are used to produce the
different types of biodistillates. Hoekman illustrated them with a
single figure that showed the feedstocks, processing methods, and
resulting fuels (see Figure 4-1).
FIGURE 4-1
Biodistillate production technologies beginning with feedstock used,
processing technology used, fuel produced, and chemical type. NOTE: ag =
agricultural, FAME = fatty acid methyl ester, F-T = Fischer-Tropsch, HC
= hydrocarbon, H2 = molecular hydrogen, (more...)
Hoekman pointed out that, as the figure indicates, there are many
different types of fats and oils that can be used to produce
biodistillates. “And this is an abbreviated list shown here,” he said.
The line at the top of the figure represents the traditional biodiesel
production pathway that uses methanol in a trans-esterification pathway
to produce biodiesel and glycerin. “We haven’t heard a lot about that,”
he said, “but glycerin is the main byproduct of biodiesel production.
About one-tenth as much glycerin is produced as biodiesel.” None of the
rest of the production pathways produces glycerin, he noted.
Furthermore, he noted that other than the biodiesel produced in that
first production pathway, the rest of the fuels produced are HCs. It is
only biodiesel that is oxygenated.
At present, he said, biodiesel remains by far the most commonly produced
biodistillate. In the United States, soy oil is the main feedstock used
to produce biodistillates, with some waste cooking oil, sunflower oil,
and other oils used as well. In Europe, the main feedstock is rapeseed,
while in much of the rest of the world palm oil is the dominant
feedstock.
In the United States production of biodiesel is at an all-time high,
with more than 1 billion gallons produced in 2011 and 2012, up from next
to nothing a decade earlier. To put that in context, Hoekman said, the
total U.S. petroleum diesel fuel production is about 60 billion gallons
per year, and gasoline is about double that amount.
Biodistillate Properties and Composition
Biodiesel and renewable biodiesel differ from petroleum-based diesel in a
number of ways. One of the most important is the presence of oxygen.
Neither petroleum diesel nor renewable biodiesel contains oxygen, while
biodiesel is roughly 11 percent oxygen by weight. Another important
difference can be found in the energy content of the different fuels.
Petroleum diesel has a high energy content of 130,000 BTU per gallon.
Biodiesel is 6 to 7 percent less—121,000 BTU per gallon for biodiesel
and 122,000 BTU per gallon for renewable biodiesel.
With respect to the chemical composition of the various types of diesel
fuel, two critical factors influence the physical properties and
performance attributes of the fuels, including their emissions. The
first is the length of carbon chains in the molecules of the fuels. In
conventional diesel the chains are typically 12 to 24 carbons long,
although some molecules are somewhat shorter or somewhat longer.
Biodiesel, being made from fatty acids, tends to have molecules with
carbon chains that are 16 or 18 carbons in length. The second important
factor is the degree of unsaturation, which is, roughly speaking, a
measure of how many fewer hydrogen atoms a molecule with a certain
number of carbon atoms has than it could have if the carbon atoms were
arranged to maximize the number of hydrogen atoms in the molecule. The
degree of unsaturation is important, Hoekman explained. Having too much
unsaturation makes for an oxidatively unstable product, while having too
little unsaturation results in a product with poor low-temperature
performance—that is, it tends to “wax up” when the temperature drops.
Compared to biodiesel, conventional diesel has lower unsaturation
overall, and it has more branching of the HCs, he said. “Those are
important for physical and chemical properties.”
Different oil feedstocks lead to biodiesels with different chemical
compositions. For example, soybean oil is dominated by linoleic acid
entities, consisting of an 18-carbon chain with two double bonds.
“That’s rather highly unsaturated in terms of fuel stability,” Hoekman
said. By contrast, rapeseed is mainly oleic acid, a molecule with an
18-carbon chain but only one double bond, so it is not so highly
unsaturated.
Emissions Standards and Controls
Diesel engine and vehicle emissions are regulated by the EPA as well as
by some states, most notably California, Hoekman said. Different sets of
standards are defined for different applications and purposes. For
example, there are different emissions standards for different engine
sizes—light-duty, medium-duty, and heavy-duty application—and, in fact,
each of these categories has subsets with their own sets of standards.
There are also different standards for on- and off-road applications.
Off-road applications make up a significant part of diesel fuel usage,
he said, and they include railroads, mining, and farming.
Historically, four different types of emissions have been regulated for
diesel uses: HC, carbon monoxide (CO), nitrogen oxide (NOx), and
particulate matter (PM). Of those four, Hoekman said, the latter two
have been of the greatest concern and have been under regulatory
scrutiny for the longest time, principally for reasons related to air
quality.
The emissions standards are not static sets of numbers, he said. They
have been steadily evolving. In particular, emissions standards have
become much more stringent during the past 25 years, and the maximum
allowable emissions of NOx and PM have been reduced by almost two orders
of magnitude during that time. For example, in the late 1980s, NOx was
regulated at 10.5 grams per brake horsepower-hour; today, the standard
is 0.2 grams per brake horsepower-hour. Similarly, the standard for PM
went from 0.6 to 0.01 grams per brake horsepower-hour.
Those emission standards apply only to new engines and vehicles, he
noted. They are not automatically applied to fleet vehicles already in
use, and fleet turnover is very slow, particularly for heavy-duty diesel
vehicles.
The large reductions in emissions required by the standards have been
achieved by a combination of engine improvements and improvements in
emission control systems. Engine improvements have included the adoption
of high-pressure, common-rail fuel injection; variable injection
timing; and electronic monitoring and control systems. A recently
developed emission control system used to reduce particulate emissions
is the particulate trap. Particulate traps require regeneration, Hoekman
noted, and there have been some issues regarding the regeneration of
those traps. To control NOx, engines are now being built with selective
catalytic reduction systems. These use urea injection to reduce NOx to
molecular nitrogen. Those are significant changes that have taken place
in just the past couple of years, he said.
Another change that has made it possible to dramatically reduce
emissions has been the introduction of ultra-low-sulfur diesel (ULSD).
“The primary reason for having that is to enable satisfactory long-term
operation of those sophisticated emission control systems,” Hoekman
said. “It’s analogous to getting the lead out of gasoline so that
catalytic control systems can function properly.”
Effect of Biodiesel on Engine Emissions
The traditional understanding of how using biodiesel in an engine
affects tailpipe emissions comes from a 2002 EPA draft report (2002)
that was “rather famous but never officially published in a final
version,” Hoekman said. That report showed that as the blending level of
biodiesel is increased from B0 (0 percent) all the way to B100 (100
percent), there are significant reductions in HC, CO, and PM emissions,
while there is a slight increase in NOx emissions. “That increase in NOx
has been a source of tremendous controversy in a lot of studies over
the years,” Hoekman said. In most real-world applications, he noted,
biodiesel is used at low concentrations, usually B5 to B20. So, it is in
that range that it is most important to understand what happens to
emissions.
Recently, the Desert Research Institute, working on behalf of the
Coordinating Research Council, conducted an updated literature review in
order to examine more recent and comprehensive information concerning
the effects of using biodiesel on engine emissions. The review, which
Hoekman was a part of, examined more than 1,000 literature sources and
analyzed the data with various sorting and statistical analysis methods.
Focusing just on the data for NOx emissions, Hoekman noted that there
was “tremendous scatter” in the data. That is, there was no smooth curve
that could describe what happened to the emissions as the percentage of
biodiesel increased from 0 to 100 percent; instead, the data points
were scattered all over the graph. This was not particularly surprising,
he observed, because the data were from a wide range of literature
sources. The various studies were done under a very wide range of
conditions, with many different forms of biodiesel blended into
different base fuels, and many other differences as well. And the data
scatter was just as large for HC, CO, and PM emissions, he noted.
Still, it was possible to discern a trend in the NOx emissions. The data
showed an upward trend in NOx as the percentage of biodiesel increased
in the category of heavy- and medium-duty engine dynamometer emissions.
However, the trend was the opposite for the category of heavy- and
medium-duty chassis dynamometer emissions. The main difference between
the tests lies in where the dynamometer is mounted during the
test—coupled directly to an engine that is independent of a vehicle,
versus coupled to the power train of a vehicle through the drive wheel
or wheels without removing the engine from the frame of the vehicle.
This difference in observed NOx effects, depending on the testing
methodology used, is one illustration of why it is so difficult to
determine the “true impacts” of fuel changes on engine emissions when
applied across the entire vehicle fleet, Hoekman said.
The study found significant decreases in HC, CO, and PM emissions with
increasing percentage of biodiesel, which were in “reasonably good
agreement” with the earlier EPA findings. “So, I think this is probably
the best idea you can get as to the impact of biodiesel use on emissions
across the whole fleet,” Hoekman said.
Emissions from B20 Fuel
Hoekman then focused specifically on the issue of emissions from B20
fuel because “that’s the upper end of the most common range of biodiesel
usage levels.”
He discussed a study by Robbins and colleagues (2011),
in which the results were broken down by engine class: medium- and
heavy-duty engine, medium- and heavy-duty engine on a chassis, and
light-duty engine. Overall, there were large reductions in HC, CO, and
PM emissions, with a slight increase in NOx emissions, although there
was a large scatter in the results. The results in the study by Robbins and colleagues (2011) (HC, –17.4; CO, –14.1; PM, –17.2; NOx, +1.8) generally agreed quite well with the results from the earlier EPA study (EPA, 2002) (HC, –21.1; CO, –11.0; PM, –10.1; NOx, +2.0).
Given that the review involved more than 1,000 individual studies,
Hoekman said, it was possible to sort the studies according to various
criteria, including the feedstock used for the biodiesel (soy oil,
rapeseed oil, yellow grease, palm oil), the base fuel into which the
biodiesel was mixed (No. 2 diesel, ULSD, California Air Resources Board
[CARB] certified diesel), the engine year (as a proxy for the
certification levels for the emissions and, particularly, the NOx
certification level), and the test cycle load (light, medium, heavy).
When Hoekman and his colleagues examined how these different criteria
affected the emissions levels from the various biofuels, they found that
there was so much data scatter in the results that it was difficult to
detect significant effects across the whole fleet. To illustrate, he
showed graphs of how B20’s effects on emissions varied by the type of
feedstock used, the type of base fuel, the engine year, and the test
cycle load. In each case, the error bars were larger than the effect
sizes, so it was impossible to conclude that any of these factors had an
influence on how B20 affected emissions.
Moving on, Hoekman spoke briefly about mobile source air toxic (MSAT)
emissions from biodiesel. There are dozens of MSATs, but those of
greatest interest with respect to biodiesel are polycyclic aromatic HCs,
aldehydes (formaldehyde, acetaldehyde, proprionaldehyde, and acrolein),
and the total PM discussed previously. Oxygenated organics, such as
biodiesel, might be expected to produce higher levels of oxygenated
MSATs, Hoekman said, but there is very little relevant experimental data
that address this issue. The existing data suggest that the use of
biodiesel does not consistently increase emissions of these MSATs, he
said.
Hoekman concluded his presentation with a number of general observations
about biofuels emissions. First, he said, although biodiesel—the FAME
version—is currently the dominant form of biodistillate being produced,
he believes that in the future the nonoxygenated biodistillates are
likely to grow in use and perhaps even become the dominant form of
biodistillate.
Recent reviews of the biodiesel literature have confirmed what the EPA
and others have been saying for many years—that the use of biodiesel
reduces emissions of HC, CO, and PM while increasing NOx emissions by a
small amount. Although data on the emissions of renewable biodiesel—that
is, the non-oxygenated, HC biodistillates—are sparse, it does appear
that renewable diesel provides emission reduction benefits that are just
as big as, if not bigger than, those from biodiesel.
Exhaust emission standards for diesel engines and vehicles have become
much more stringent during the past 25 years, which has resulted in the
development of advanced emission control systems that reduce emissions
dramatically, much more so than a change in the fuel composition to
include biodistillate fuels.
Determining the effects of fuel-type fleet-wide emissions is difficult
because of the variability of engine and vehicle types, test cycles,
emissions control systems, and other factors. The variability in the
data prevents drawing firm conclusions about the effects of biodiesel
feedstock, base fuel type, the engine model year, or the test cycle on
diesel emissions when using B20. In the case of aldehyde emissions,
although the data are sparse, the use of biodiesel does not appear to
affect the emissions in a consistent or significant way. The effects of
biodiesel on polycyclic aromatic HC emissions are hard to ascertain, but
the few data that exist suggest little effect, if any.
Finally, Hoekman offered a recommendation. The various advanced diesel
emission control systems, such as the selective catalytic reduction
device and the particulate trap, have been in use for only a couple of
years, he reiterated. “I believe that additional research and study
monitoring is needed to assess the long-term effects of biodiesel and
its impurities on the performance of those systems. If those systems
fail over a shortened lifetime, that would have significant effect.”
Discussion
Following Hoekman’s presentation, there was a discussion period devoted
to just his talk. The first question, which came from an audience
member, was whether any work had been done to study the effect that
contaminants in biofuels might have on health. In particular, the
question concerned biofuels produced from things such as frying oils
used for french fries and other foods, which could have a variety of
contaminants.
Hoekman replied that he was not sure if any data exist concerning the
health effects of such contaminants. However, he noted that there is a
rather long and stringent list of specifications for biodiesel fuel—as
there is for petroleum-based diesel—because the diesel engines are
expected to run for half a million miles or even longer on these fuels
without breaking down. “The feeling is if there are excessive levels of
salts or metals, they may impede the performance of emission control
systems,” he said. “They may use some of the capacity of the trap,
thereby reducing its overall efficiency.”
In a follow-up question, Hoekman was asked about the difference between
more versus less unsaturated feedstocks for biofuels. Plant-derived
biofuels can vary in how unsaturated they are, depending on which plants
they are derived from. So the question was whether that difference
could lead to a difference in emissions from the biofuels.
Hoekman answered that there has been quite a lot of work looking at how
the extent of unsaturation affects total emissions and, especially, NOx
emissions. The results have been somewhat equivocal, he said, but there
is some evidence that the higher the unsaturation, the more NOx
emissions there may be. However, he added, “what’s much more important
with respect to unsaturation is the physical property—the oxidative
stability of the fuel. Can you keep it out in the marketplace? Is it an
acceptable fuel regardless of what happens when you burn it?”
In response to a question about whether automotive manufacturers are
willing to warranty engines used with a biodiesel mix, Hoekman said that
his understanding is that most manufacturers of heavy-duty engines now
accept up to B20. In fact, he said, the international standards
organization ASTM has developed standards for biodiesel in the range of
B6 to B20. “So, in that range, I believe biodiesel is accepted by all
the U.S. heavy-duty engine manufacturers,” he said. However, he did not
know whether manufacturers of light-duty vehicles have yet reached the
same point.
REGIONAL IMPACTS OF BIOFUELS ON HEALTH AND CLIMATE CHANGE IN BRAZIL
In the next presentation, Elliott Campbell, an assistant professor at
the School of Engineering at the University of California Merced Energy
Research Institute, moved from the micro-level issue of tailpipe
emissions to the macro-level question of how the use of biofuels might
affect health and climate change on a regional scale.
To begin, Campbell noted that much of the current discussion related to
the effects of biofuels on climate change concerns those changes on the
global scale. It concerns issues such as carbon cycle in the use of
biomass feedstock and land-use change. But there is also emerging
interest in examining the effects of biofuels use at a regional
scale—for example, in studying how the broad use of E85 (a fuel with 85
percent ethanol and 15 percent gasoline) might affect air quality in a
region such as Los Angeles and surrounding areas (Jacobson, 2007) or looking at the regional climate impacts from the widespread use of second-generation cellulosic biofuels products (Georgescu et al., 2011).
Noting that there has been quite a bit of this sort of work done on the
regional scale in the United States, he said that his talk would be
focused instead on some emerging analysis of the regional climate and
health impacts of biofuels production in Brazil.
Background
He began by providing some basic background on biofuels in Brazil. As can be seen in the top section of Figure 4-2,
the consumption of liquid fuels has steadily increased during the past
decade, as has the production, and in recent years production and
consumption have been approximately equal. As can be seen in the bottom
section of the figure, hydroelectricity produces a large majority of the
country’s electricity, with fossil fuels a distant second. Nuclear
power accounts for a very small percentage of the total electric power
and is a smaller proportion than renewable energy sources other than
hydroelectricity and nuclear. Two energy-related concerns in Brazil are
the export of biofuels and diversifying local electric power production.
FIGURE 4-2
Energy in Brazil: (a) liquid fuels production and consumption
(2002–2014); (b) electricity generation, by fuel type (2001–2011).
SOURCE: EIA, 2012.
Brazil produces large amounts of sugarcane whose sugar is used in the
production of ethanol, and one issue of importance to Brazilian policy
makers is what to do with the parts of the sugarcane plant that are not
converted into ethanol. At present, Campbell said, about half of the
sugarcane crop is subjected to pre-harvest burning, which makes the
harvesting process much easier and less expensive and also returns
nutrients to the soil. However, it produces massive amounts of air
pollution during the time of the pre-harvest burning, and it is also
wasting a large amount of energy that could be captured and used
elsewhere.
Reducing the amount of pre-harvest burning would lead to much larger
quantities of available sugarcane residue, which could be turned into
energy in two ways: it could be burned in electricity-generating plants,
or it could be turned into cellulosic ethanol. Converting the residue
into electricity has greater greenhouse gas benefits than using the
residue to produce ethanol, he said, and, furthermore, converting the
residue into electricity could have a massive impact on Brazilian energy
security.
The Level of Direct Emissions
After providing that brief overview, Campbell took a more careful look
at the emissions caused by the field burning of sugarcane (Tsao et al., 2012).
One way to understand these direct emissions, he said, is to use a
bottom-up approach that combines emissions factors from the GREET
(Greenhouse Gases, Regulated Emissions, and Energy Use in
Transportation) model from Argonne National Laboratory, maps of
sugarcane production, and basic conversion factors generated from other
agronomic and life-cycle assessment data. When the calculations are
done, they show that field burning does indeed release massive amounts
of various gases: CO, volatile organic compounds, NOx, PM, and carbon
dioxide. So, field burning is a very important component of the direct
emissions associated with the production of biofuels, he concluded.
During the past decade, he said, the emissions of various gases have
grown despite the move to mechanization, and he illustrated this with a
figure that showed emissions over time in the Brazilian state in which
most of the sugarcane production takes place (see Figure 4-3).
This increase in emissions is due to the expansion of the areas in
which sugarcane is grown, so that even with growing mechanization, the
amount of field burning has been increasing.
FIGURE 4-3
Estimated life-cycle emissions of ethanol in Brazil from crop year 2000
to 2008 (crop year is from April to January the following year). NOTE:
(a) Emissions of volatile organic compound (VOC), nitrogen oxide (NOx),
particulate matter less than 10 microns (more...)
Researchers have used various methods to estimate the direct emissions
from field burning, Campbell said. One such method has been remote
sensing from satellites. This is a convenient method because it makes it
possible to get estimates from many different sugarcane-growing regions
with relatively little additional effort over what it takes to get
estimates from just one area. However, the top-down data from such
satellites have proven to significantly underestimate the emissions
versus the bottom-up estimates.
“One important question is ‘Why the difference?,’ because we would love
to be able to use the remote sensing data,” Campbell said. There are a
number of factors at play. One is that the remote sensing comes up with
significantly different estimates for the size of the burned areas than
the bottom-up approach. There are also major differences in the
estimates of the fuel load (the amount of biomass per unit area) and the
emission factors (total emissions per kilogram of biomass).
Regional Health and Climate Impacts
With a growing understanding of the emissions from pre-harvest burning,
the next question is, What might the health and climate impacts of these
emissions be? To answer that question, Campbell said, one begins by
trying to understand what the change in air quality is—not just how the
emissions change, but how atmospheric species change in concentration
and how those concentrations vary in space and time. The next steps in
quantifying the human health effects are to determine the exposed
populations, estimate the health effects, and determine a health
baseline incidence. “You can try to gather these data at a variety of
spatial scales in Brazil,” he said, including city-level,
province-level, or country-level data.
There are a number of studies that estimate the health effects of
various levels of atmospheric pollution, Campbell noted, “and the change
in the atmospheric concentration comes from these regional atmospheric
models that I talked about previously.” To illustrate, he showed a map
of PM levels in Brazil in January, during the sugarcane growing season,
and in May, when the pre-harvest burning takes place.
Combining models of this sort with estimates of the health effects for
various levels of PM in the atmosphere, it is possible to derive
estimates of the health effects of the pre-harvest burning of sugarcane
based on the following approach: health effect = (air quality change) ×
(exposed population) × (health effect estimate) × (health baseline
incidence). In looking at annual mortality changes, “you get somewhere
between 20 and 4,000 deaths per billion gallons of ethanol,” Campbell
reported. To put these numbers into perspective, it is helpful to review
a study that compared deaths associated with operating gasoline-fueled
vehicles versus those fueled with a blend of 85 percent ethanol (E85)
based on modeling for 2020. Jacobson (2007) found
that E85-fueled vehicles increase ozone-related mortalities by about
185 deaths per year, which corresponds to a 4 percent increase over the
U.S. projected death rate of operating gasoline vehicles. Campbell noted
that there is obviously much uncertainty in the exact number of deaths
from the air quality effects of the pre-harvest burning, but from this
preliminary analysis there appears to be significant potential for the
health impacts to be quite large.
Estimating climate effects caused by the emissions from pre-harvest
burning is even more difficult. “It requires advanced climate modeling,”
Campbell said, “but if you use climate forcing factors based on
emissions for black carbon from the fields and from the boilers at the
ethanol refineries, the climate forcing per unit energy of ethanol for
sugarcane can increase from what we think it is now to something that
may exceed regulatory thresholds.”
Indirect Emissions
In addition to the direct emissions from pre-harvest burning, there are also indirect emissions caused by indirect land-use change, meaning,
in essence, a change in the use of land from forest or some other
non-cultivated land to cultivated cropland. Such land-use change
generally involves the clearing of forest or other land, which in turn
involves cutting down and burning trees or other vegetation, which
releases carbon and other elements into the atmosphere.
Calculations show that rangeland converted to biofuels production in
Brazil led to a significant amount of PM released into the atmosphere,
Campbell said, but that the conversion of forest to rangeland accounted
for far more emissions.
When the indirect emissions from indirect land-use change are included
in the calculations for total emissions in the life-cycle of sugarcane
ethanol, a very different picture emerges. For PM (in particular, PM2.5,
which refers to particles less than 2.5 micrometers in diameter),
including indirect land-use change in the calculations may nearly double
the estimated emissions due to the production of biofuels. To put this
in perspective, Campbell compared the indirect emissions of PM from
biofuels production to the emissions of PM caused by Amazonian
deforestation. “Adding a billion gallons of ethanol is potentially on
the order of all the emissions from deforestation in roughly the last
decade,” he said.
In summing up his presentation, Campbell offered the following takeaway messages:
- The emerging trade regime for biofuels, with Brazilian biofuels being exported to developed nations, presents important “leakage” challenges with respect to regional health and climate impacts.
- Previous burning estimates may underestimate the burned area by a factor of four.
- Sugarcane regional health impacts are potentially much larger than those of other biofuels, although a great deal of work remains to produce better estimates.
- The regional climate impacts from biofuels production may mean that sugarcane ethanol, instead of providing a significant reduction in climate impacts relative to the fossil fuels that it replaces, is actually causing climate warming, at least at a regional scale.
Finally, Campbell offered several research recommendations:
- Regional climate and health impacts research should focus on Brazil, given the potential for relatively high impacts there.
- The critical research gaps that should be addressed include top-down studies of burned area (in order to resolve the difference from bottom-up estimates), observation-based emissions factors (because they vary widely), and three-dimensional atmospheric modeling.
- Integrate research and policy to address leakage issues for regional impacts (e.g., air quality, aerosol forcing) in addition to the current focus on global impacts (e.g., carbon dioxide).
Discussion
Campbell’s presentation was followed by a discussion period. Christopher
Portier, director of the National Center for Environmental Health,
Centers for Disease Control and Prevention, began by asking whether
Campbell’s climate forcing model with which he examined the effects of
field burning included carbon black. It only included carbon, Campbell
replied, which is one of the weaknesses of that analysis. There have
been some very simple ballpark estimates of the climate forcing of
carbon black that have been public, he said, and applying those
estimates implies that field burning “can potentially exceed some
thresholds for life-cycle greenhouse gas emissions.” However, Campbell
said, what is really needed is to run a regional climate model “because
the climate forcing from these species varies so much depending on the
domain, the time of year, the timing of the emissions, all of these
kinds of factors.” Thus, the jury is definitely still out on the effects
of these carbon black emissions.
Carlos Santos-Burgoa from the Pan American Health Organization asked
whether there were any changes that could be made to the sugarcane
ethanol production process that would improve the emissions.
One approach would be to continue reducing the amount of pre-harvest
burning, Campbell said. There has been a pretty dramatic shift over the
past decade away from pre-harvest burning and toward mechanization.
“Brazil has a voluntary program that’s trying to move toward those
better cultivation approaches,” he said, “but it’s unclear what the
future trends would be if sugarcane cultivation expanded rapidly to try
and meet demand for export of biofuels.”
Roundtable member Bernard Goldstein referred to Campbell’s statement
that the residue-based ethanol made in Brazil and shipped to the United
States has little impact on the energy security of the United States but
would have massive impact on Brazil’s energy security if it were not
exported. Goldstein then suggested that economists would likely respond
to this situation by saying that energy security is not being priced
appropriately.
Al McGartland responded that the EPA does include an analysis of energy
security in the ethanol regulations when it sets a mandate. There are a
variety of security benefits to ethanol production, he said, including
making the economy less vulnerable to the price of oil and potentially
decreasing military expenditures in the Middle East if imported
petroleum is less vital to the national interest. The value of these
security benefits “is not a trivial number” for the United States, he
said, although he was not familiar with the case of Brazil.
Goldstein then asked if it is correct that a drop in the price of oil
would mean there would be less of a push for biofuels. McGartland
replied that this is the case. Right now, biodiesel would not be made
without a mandate because it costs more than petroleum-based diesel, but
if the price of regular diesel fuel went up enough, biodiesel would be
made without a mandate.
Goldstein next asked how to get air pollution and other health issues
considered more in the discussion concerning biofuels. Stephen Reynolds
suggested that life-cycle assessments (LCAs) might offer a way in. “The
whole concept of life-cycle assessments has become pretty popular these
days,” he noted. “In fact, it’s mandated by certain regulatory agencies
that some form of LCA must be done to evaluate the broader impacts of
fuels or other technology introductions.” These LCAs have tended to
focus more on greenhouse gases and energy balances and not so much on
“mobile-source air toxics,” Reynolds said. So, one place to start
getting more attention to health issues in the discussion on biofuels
would be to work to get more consideration of toxic emissions in LCAs.
An audience member elaborated on the importance of persuading decision
makers—and especially the economists who advise them—that air quality
needs to be taken into account as a serious policy concern. “I think
that air quality is one of a class of health-related issues that
traditionally have been marginalized,” he said, “in part because
although economists will pay lip service to issues of health and
productivity, I’m not sure that the current economic theory really
believes it.” The result is that economic models often minimize or leave
out health considerations. If people are removed from a labor market
that is already glutted with free labor, for example, that does not have
much overall economic impact. Thus, more work needs to be done to
health and productivity and economic development. “Some progress is
being made in health and productivity studies of the type that are being
done in industry to relate health promotion to productivity,” he said,
“but that so far has been very narrow and very rich-country-oriented. I
think we need a far more robust economic approach.”
Another audience member immediately challenged those comments. “With all
due respect to the last speaker, most of what he said is really quite
wrong from an economics perspective. The environmental economics
community … would never think about valuing health in the way that was
described. We know that it is absolutely wrong to think about the
benefits from loss of life or illness as something as simple as lost
life years or lost productivity. It’s wrong from an economic analysis
perspective. It feels in-the-gut wrong, and it is wrong. So, I don’t
want to give you a big long lecture, but that notion is really not an
accurate depiction of the state of the field.”
In reality, the commenter said, the benefits of improved human health
are very well understood as belonging in cost-benefit analysis, and
there are many studies doing this.
Goldstein offered a relevant anecdote. Forty years ago, as a young
investigator at the U.S. Office of Management and Budget (OMB), he gave a
talk about the effects of sulfur dioxide and mentioned the infants who
had died in the London great smog event of 1952. “I was asked by the OMB
economists whether they were male infants or female infants, and when I
looked horrified, and … asked why would that be a question, it was
pointed out that females did not contribute to gross domestic product,
but males did. So, OMB has come a long way.”
REFERENCES
- Campbell E. Regional impacts of biofuels on health and climate change; Presentation at the Institute of Medicine Workshop on the Nexus of Biofuels Energy, Climate Change, and Health; Washington, DC. 2013.
- Georgescu M, Lobell DB, Field CB. Direct climate effects of perennial bioenergy crops in the United States. Proceedings of the National Academy of Sciences of the United States of America. 2011 10.1073/ pnas.1008779108. [PMC free article] [PubMed]
- EIA (U.S. Energy Information Administration). Brazil. 2012. [July 29, 2013]. Available at http://www
.eia.gov/countries/cab .cfm?fips=BR. - EPA (U.S. Environmental Protection Agency). A comprehensive analysis of biodiesel impacts on exhaust emissions: A draft technical report. 2002. [October 10, 2013]. (EPA420-P-02-001). Available at http://www
.epa.gov/otaq /models/analysis/biodsl/p02001.pdf. - Hoekman SK. Biodistillate fuels and emissions in the United States; Presentation at Institute of Medicine Workshop on the Nexus of Biofuels Energy, Climate Change, and Health; Washington, DC. 2013.
- Jacobson MZ. Effects of ethanol (E85) versus gasoline vehicles on cancer and mortality in the United States. Environmental Science and Technology. 2007;41:4150–4157. [PubMed]
- Robbins C, Hoekman S, Ceniceros E, Natarajan M. Effects of biodiesel fuels upon criteria emissions. 2011. (SAE Technical Paper 2011-01-1943). [Cross Ref]
- Tsao CC, Campbell JE, Mena-Carrasco M, Spak SN, Carmichael GR, Chen Y. Increased estimates of air-pollution emissions from Brazilian sugar-cane ethanol. Nature Climate Change. 2012;2:53–57.
Copyright 2014 by the National Academy of Sciences. All rights reserved.
https://www.ncbi.nlm.nih.gov/books/NBK196452/
https://www.ncbi.nlm.nih.gov/books/NBK196452/
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