Remember that hydrocarbons and NOx are the pollutants that lead to O3 formation. Hence, efforts to control O3 focus on controlling emissions of these precursors. For example, as we saw earlier, emissions of these compounds per automobile decreased greatly since the early 1970's, but vehicle miles have increased so much that actual decreases in total emissions were less than the decrease per vehicle would suggest.
Remember, as you read this, that in addition to helping to control ozone pollution, many of the measures described below (e.g., those that focus on improved fuel efficiency, decreasing reliance on cars, or switching to alternative kinds of fuels) will also help the battle against global climate change (since tropospheric ozone is a powerful "greenhouse gas," and sources of ozone precursors are also, often, sources of CO2. The same measures will, by and large, lessen our dependence on fossil fuels (fostering, perhaps, less political instability in the world). As an example, the CAFE (Corporate Average Fuel Efficiency, which is the average fuel efficiency of all vehicles of a given class produced by a given manufacturer -- e.g, passenger cars, or light trucks, etc.) standard increased from 18 to 27.5 mpg (for passenger cars; to 22.2 mpg for light trucks, including minivans, suv's and pickup trucks) between 1978 and 1985. Under legislation passed late in 2007, the average CAFE across passenger cars and light trucks is finally slated to increase again to 35 mpg by 2020; a 40% increase in the average efficiency -- hooray! The Union of Concerned Scientists estimates that this increase will save 1.1 billion barrels of oil per day in 2020, which is about half of what the US imports from the Persian Gulf, and which should decrease greenhouse gas emissions by as much as taking 28 million of today's cars and trucks off the road. Let's not be complacent though! Europe currently requires the equivalent of 40 mpg (and will soon -- as of 2008 -- increase that to 49 mpg), and it is expected that the Japanese standard will rise to 47 mpg in its 2015 version (Technology Review 15 Jan '08).
Auto emission standards in the US were first set in 1968 and became more and more stringent over time. A car in the early 1990's had about 1/5 the VOC and CO (carbon monoxide) and 1/2 -1/3 the NOX emissions of a car 25 yrs before that time (1993 data). However, urban miles travelled went up 100% over this 25 yrs so about ¼ of the decrease in CO and VOC and 2/3 of the decrease in NOX per car merely offset the increased miles driven!
Late in 1999 (or early in 2000), Federal legislation was passed that closed a loophole that had allowed SUV's (sport utility vehicles), minivans, and pickup trucks to emit three to five times more pollutants than passenger cars were allowed to emit. Emissions of NOx and fine particulates from these heavier vehicles are slated to decrease over a phase-in period, with reductions being complete by about 2008.
However, heavy duty diesel trucks and buses were still allowed to emit much more pollutants than other vehicles. One 18-wheeler, for example, can emit as much NOx and fine particulates as 150 passenger cars! (Air quality inside many diesel school buses is also notoriously bad, endangering the health of the children who ride these buses.) New regulations on such vehicles will, however, tighten emission standards for them as well, and went into effect beginning in 2007. These new vehicles should produce 75 - 90 % less NOX and 90% less particulates than those that were manufactured before 2007. In addition, oil refiners were required to decrease by 97% the sulfur content of the diesel fuel that these vehicles use by the year 2006, so that the pollution control devices on the new vehicles will work properly.
Incidentally, diesel electricity generators, both large (as are used for back up electricity production in times of regional energy shortages, as were experienced in California in 2001) and small, are major polluters. Other non-road diesel engines are also big polluters, including those used in agriculture, construction, and marine trasnport. Both the fuel that they burn and the burning and emissions technology are poor, and they are present poorly regulated. There are moves afoot to tighten restrictions on their emissions as well, which is important -- such sources produce more fine particulate pollutants than all other mobile sources combined! On a typical day, ships in the Los Angeles Basin release more ozone precursors than do one million cars! (2004 information)
PORTLAND, OREGON EXAMPLE:
Portland's ozone maintenance program has strategies to decrease VOC emissions :
MISCELLANEOUS "CAR STUFF:" CLEANER FUELS AND CLEANER CARS
One way to reduce tailpipe emissions is through catalytic conversion: most cars are equipped with three-way catalytic converters, which capture CO (carbon monoxide) and hydrocarbons (VOC's) by catalytic oxidation and NOx by catalytic reduction.
California has had real troubles with meeting O3 standards, and as part of the solution, cars sold in CA must meet stricter emissions standards than in other states. (However, several states have also adopted the CA standards.) CA is trying to achieve reductions not only by improving emissions reductions capacity on conventional fueled vehicles (catalytic converters) but also by gradually phasing in over recent years cars that are between 50-85% less polluting than the strictest national standards on the books today.
CA recently stiffened its auto emissions standards again -- including imposing limits on CO2 emissions. In 2002, CA became (rather, tried to become!) the first state to regulate "global warming potential" of vehicles, requiring auto makers to cut emissions of CO2, CH4, nitrous oxide (N2O), and several other pollutants by at least 30% by 2016, with the first decreases to show up in 2009 models. As of this writing (late 2008), several other western states, including WA and OR had signed on to the CA standards, but the regulations were declared illegal by the Federal government -- the legal battle continues (if you use this link, scroll way down in text to find the material relevant to this discussion).
See some links to interesting car "stuff" in the section of notes that deals with your Resource Use Reduction Project.
Information on ways to improve your fuel efficiency can be found at cleanenergy and at seven-ways.
Click "green" to find information on "environmental friendliness" of various car models, ranging from hybrids to SUV's (see the Green Center within that site).Additional useful information is at a site called Clean Cars for Oregon
These vehicles are fueled with hybrid (gas + electric) technologies or with alternative fuels (methanol, ethanol, natural gas, hydrogen) which:
(1) Are reformulated to have lower reactivity (lower ozone forming potential) and evaporation rates (volatility). Reformulated gas can burn as cleanly as methanol or ethanol blended with gas in flexible fueled cars. Decreasing fuel vapor pressure decreases the generation of vapors in the fuel system, which decreases evaporative emissions from the system, which are about 50% of a car's VOC emissions! In fact, hydrocarbon emissions are sometimes greater when the car is not running than when it is. This is a phenomenon called "hot soak," which occurs after the engine is turned off but when it is still hot. Diurnal breathing is also involved, in which the fuel tank breathes in air as it cools at night and breathes out air and gas vapor as warms in day.
(2) burn cleaner--especially concerning VOC's. In fact, some of these fuels actually produce more NOx than conventional fuels, although this isn't universally true. (Molecules in these alternative fuels are smaller and simpler than gas, with fewer c-c bonds, so they burn more cleanly than conventional gasoline. More complex molecules have more complex combusition and more chance of incomplete combustion.)
Decreasing sulfur content of fuels is also important, because sulfur interferes with efficiency of catalysts for VOC's, CO and NOx, damaging catalytic converters. While the US has the strictest auto emission standards in the world, it also permits the highest sulfur content in fuels, negating many of the gains made in clean car technology. CA regulates fuel sulfur content, allowing a maximum of 40 ppm sulfur, while gasoline sold in the rest of the country averages (or did until recently) about 330 ppm. It is estimated that reducing sulfur content of fuel nationwide to the CA standard would be equivalent to taking 53 million cars off the road, in terms of reduced pollutant emissions!! For OR, the gain would be equivalent to removing about 1/3 of the vehicles from the Salem-Portland area! Late in 1999, a Federal ruling did require oil companies to produce cleaner burning fuel with lower sulfur content, and the new rules concerning diesel trucks and buses will require, as mentioned above, a 97 % decrease in the sulfur content of diesel fuels as well.
Regulation tends to focus on hydrocarbon (VOC) emissions, which can generally be reduced more readily than can NOx emissions. The main control strategy for NOx from stationary sources is to change the combusion conditions largely by reducing temperatures, which reduces NOx production. "Lean burn" strategies, which minimize the amount of air mixed in when burning can be effective.
(Incidentally, adding MTBE (methyl tertiary butyl ether) or other oxygenates decreases CO emissions but has little effect on atmospheric reactivity and O3 formation, and sometimes increases NOx emissions.)
That is, attention is being paid both to cleaner fuels and to cleaner cars. Instead of focusing only on the car, focus on what we put in it to burn!
Methanol is made most cheaply from natural gas and also from coal, wood, or agricultural wastes.
Ethanol is often made from corn, but also from other biomass. As is true for methanol, ethanol is a simpler molecule than gasoline, so it burns cleaner. The energetics of using ethanol as a fuel source (in addition to gasoline or alone) is complex -- it depends on what is being used to make the ethanol and on what that land was being used for (or not used for!) before it was used to grow crops to make fuel. Think, for example, about all the energy that goes into corn production! Instead of using corn, which could be used to feed people either directly or indirectly, as livestock feed, interest is growing in using other biomass to produce ethanol -- including woody biomass -- in which case the energetics may turn out to be more positive than when the ethanol is produced using corn. There is a LOT of attention being paid to "biofuels" these days -- largely ethanol manufactured from biomass (ranging from corn to wood debris) and biodiesel. While it is possible that use of some sources of biomass as fuel could help decrease dependence on fossil fuels -- and also help decrease CO2 emissions, in most cases that I've read about so far, the savings just aren't clear -- and it is certianly hard for me to understand using crops that could be used for food to make fuel. Early in 2007, a team of economists from OSU published "Biofuel Potential in Oregon: Background and Evaluation Options," a report that examined the energetics and emissions associated with biofuels and was not optimistic about their prospects -- the authors suggest that simply increasing fuel efficiency of conventional cars (even modestly -- 1 mile per gallon!) would likely be far more effective. See also the editorial in the November 2006 issue of BioScience. (OSU is, by the way, one of five universities in the US that receives funds from the US government under a "Sun Grant." This allows OSU to serve as a regional center for the study and development of sustainalbe and environmentally friendly biofuels [or other bio-based energy alternatives.].) (I've added quite a bit more information on the energetics of plant-based ethanol to the section of notes that deals with land limitatons in agriculture, because there is competition between energy and food production goals for land.)
Natural gas -- vehicles powered with natural gas have much lower NOx, VOC, and CO2 emissions than do convertional gaoline-powered vechicles. GM, Chrysler and Ford all have natural gas vehicles on the road now, as do other manufacturers -- note the natural gas powered buses at the Portland, OR airport! These produce about 80% less emissions of NOx and VOC than conventinally fueled cars and are about 30% less expensive/mile to operate than conventional gas-fueled cars. As of 2005, ~ 250 "gas" stations in CA provide natural gas.
Some of the techniques to decrease emissions of NOx, CO and VOC's tend to increase car weight, however, and may decrease fuel efficiency. For example, compressed natural gas has to be stored under high pressure, which requires heavy tanks (if you want decent driving range on a tank). Cars run on methanol also need bigger tanks because methanol only contains 1/2 the energy per volume that gas does (is 30% > efficient, though, so may balance out). However, use of new light weight plastic composites for body construction to decrease weight could counterbalance some of these problems.
Diesel -- Many kinds of diesel vehicles are very efficient in terms of fuel economy -- diesel contains ~ 10 times more energy per unti volume than does conventional gasoline. However, diesels have historically been quite "dirty" -- producing much greater emissions of fine particulates ('soot") and NOx than conventionally-fueled vehicles. However, both the fuels and the engines and exhaust sytems have been improved greatly in recent years, and I've read of one kind of diesel bus that rivals a natural gas powered bus in terms of cleanliness of emissions. (See above -- near the top of this section of notes -- about changes in diesel technology and fuel that went into effect by 2007 in the US and that will clean these vehicles up greatly!)
Biodiesel -- Still another kind of fuel is receiving increased attention as well, and that is diesel fuel, but with a difference: biodiesel fuel. This is a diesel fuel that is based on vegetable oil, and can be made using used ("waste") vegetable oil, as from restaurants, or raw vegetable oil, including oil derived from crops that are produced "cheaply" in terms of water and fertilizer inputs. It burns cleanly (more cleanly than conventional diesel) and can be locally produced and distributed, lessening dependence on imported fossil fuels (on fossil fuels in general). Biodiesel produced ~ 75 % less CO2 per mile than does conventional diesel, making it, potentially, relatively friendly in terms of global climate change potential. Further, even though it does lead to some CO2 emission, the CO2 isn't ancient stored CO2 (as in fossil fuels) but is CO2 taken up relatively recently by the crop, hence more "balanced" as a CO2 source. Biodiesel uses less fossil fuel energy to produce per unit of fuel energy obtained (put out) than other fuels -- you get about 3.24 units of energy "out" per unit of energy put "in" to its production http://www.biodiesel.org/.
Biodiesel can be used "straight" (B 100 = pure biodiesel) or in mixtures such as B 20, which is 20% biodiesel/80% regular diesel. Both result in lowered emissions relative to conventional diesel (except for NOx...). I've heard that it lags a little bit behind regular diesel fuel in some measure of power, but for most vehicle applications this wouldn't be noticeable.
To run biodiesel in a conventional diesel vehicle, all that is needed is a change in fuel line fittings from rubber to another substance, since biodiesel corrodes rubber. See http://www.greaseworks.com for a local biodiesel business.
ALTERNATIVE VEHICLES
Electric Vehicles -- Cars run on electricity are referred to as "ZEV's" for zero emission vehicles. ) By law, 2% of CA's annual new car production (about 40,000 cars) was supposed to be electric by 1998 with that percentage to increase to 10% by 2003. Similar laws were in place for NY and MA, with 2% of their new vehicles to be electric by 1998. However, the increased popularity of hybrid vehicles (run on a combination of gasoline and electric energy sources; see below) -- and possibly other political/economic forces -- decreased the emphasis on purely electric cars. Some of the alternative technologies, in particular hybrids, avoid problems with limited driving range and limited access to recharging sites that are associated with electric vehicles. However, as of 2008, we're starting to hear more and more about electric cars again -- and Corvallis has at least one public "plug in" site -- down on 2nd street in front of that fancy new high rise building.
While they are called "ZEV's", that is a bit misleading, in my opinion. Yes, they don't emit pollutants as they drive around, but electric vehicles aren't totally benign from an environmental perspective: most electricity generation produces pollution, just at a different site than out of the car's tailpipe, or is associated with hydroelectricity and its problems. However, some analysis suggests that, because most car charging would occur at night, when many power plants are basically "idling" compared to their production during peak hours, and because extra electricity from car batteries could be fed back into the grid during peak hours, electric cars might actually reduce the need for electrical generation (ask Steve Cook in OSU's Geosciences Department about this!) In addition, there was early concern about lead impacts for those that are fueled with lead-acid batteries -- impacts associated with mining, processing, recycling etc. for the lead. Alternative kinds of batteries are now in place (e.g., nickle-metal hydride batteries), which, as I understand it, are less problematic and, while expensive, give better performance in cold temperatures.
Range of travel between recharges is a major issue for some uses of electric vehicles, however ranges have improved; in CA, a consortium of aerospace firms, electric utilities and government agencies have produced an electric car with a range of 220 km. Some manufacturers are experimenting with electric vehicles with solar panels on their roof, but I gather that, so far, these have low power (6 sq m of photovoltaics on a roof generates about 500 watts or <1 horse power...)
Light electric vehicles (LEV's) are beginning to find their place in the commuter market. These are generally two passenger city cars, with ranges of 50-80 km and top speeds of 50-100 km/hr. They weigh 1/2 as much as a regular car, and are made of a plastic composite that is actually stronger and more flexible than steel (so should be pretty safe). Challenges still include short range of driving between charges, the lack of public charging facilities, and the cost of installing charging units in your home.
Hybrid vehicles -- Much of the interest in electric cars was displaced at least temporarily by a burgeoning interest in "hybrid-fuel vehicles" which have gasoline engines as well as electric engines. You can't walk down a street in Corvallis these days without seeing one of these -- a fast change in a few years!! There are various versions of these on the market and in testing, but the general concept is that either engine can be used, and the gasoline engine (ultra efficient version, of course) is used to recharge the battery (nickle-hydride), so it doesn't need to be plugged in to recharge. For some, the battery is also recharged by a "regenerative" braking system -- the electric motor works to help stop the car (along with the breaks) and that motor acts as a generator, cpaturing the excess energy when the driver slows and applies the brakes, with this energy being used to recharge the battery. The gasoline and electric engines are run in parallel or in series, depending on the particular car. Power isn't a problem with these vehicles -- for added passing power or for starts from a standstill, the electric motor kicks in with a burst of power, and the vehicle then switches to the gasoline engine at higher speeds. Gas mileage on the freeway is high because the gas engine is smaller than usual. In city driving, fuel efficiency is even higher, becasue the electric motor takes over at low speeds. Various auto makers, including Honda, Toyota, Ford, Chrysler and GM have hybrid cars on the market, and some have even released hybrid SUV's, minivans, and pick up trucks.A web site that I found useful for learning about hybid cars is at howstuffworks.
Hydrogen and hydrogen fuel-celled cars: DISCLAIMER -- Notes on hydrogen fuels and fuel cells below are sketchy -- I don't pretend to be an engineer!! If you find important concepts that are either mispresented here, or omitted, please let me know!!
For the not-too-distant future (prototypes exist, including those manufactured by Ford, Honda, GM, Daimler-Chrysler, Mazda, BMW and others), we can look forward to hydrogen-powered vehicles, which, in some models, produce nothing but drinking-quality water.
These vehicles can run on either liquid or compressed gas forms of hydrogen, requiring a heavy, high pressure tank to carry the fuel. This extra weight is, however, compensated by not needing all the weight that comes with a catalytic converter and other exhaust system components. While hydrogen is the most abundant element on Earth, it must be isolated from other elements before it can be used. Currently, hydrogen for vehicle fuels is isolated from water, methane (natural gas) or gasoline ... but producing the hydrogen takes a good deal of energy -- sometimes more energy than is contained in the hydrogen itself. Eventually, it is hoped that it will be obtained from hydrolysis of water, using renewable energy to complete the hydrolysis, in which case it will be a zero emissions fuel (zero not counting water..). Vehicles that run on hydrogen as of ~ 2006 must either contain on-board reformulators to get the hydrogen from natural gas, or visit filling stations where hydrogen is produced from natural gas.
Hydrogen-fueled vehicles are considered by some to be transitional to hydrogen fuel-cell powered vehicles.
Fuel cells produce electricity from an added fuel, unlike standard batteries whose ingredients are sealed inside and eventually run down. By contrast, in a fuel cell, when the fuel gets low, you just add more. Hydrogen fuel cells produce electricity from an electrochemical reaction between hydrogen and oxygen, producing only water as a byproduct. They split hydrogen into protons and electrons, creating an electric current. The cell doesn't discharge as a battery does, and it continues to produce power as long as fuel (hydrogen, in this case) is supplied. Sounds kind of perfect, eh? One uncertainty is (as for straight hydrogen powered vehicles, above) where the hydrogen comes from. In the prototypes developed so far, sources include methanol and natural gas. In this case, the hydrogen fuel-cell driven vehicle will still rely on fossil fuels, and will emit CO2 in addition to water (CO2 of concern, of course, because of climate change prospects). IF, however, the hydrogen is generated using renewables, such as photovoltaics, then this can be a perfect zero-emission loop, with water the only byproduct! Most folks think that the initial offerings will be cars that contain a "reformer" that makes hydrogen for the fuel cell from gasoline or methanol, allowing local service stations to continue suplying these vehicles. Eventually envisioned are stations that offer liquid or compressed gas forms of hydrogen directly, but that may be down the road a piece.
Some concern has been expressed about how much water vapor will be produced by hydrogen fuel cell powered vehicles, given that water vapor is a powerful greenhouse gas. However, it is estimated that if all US passenger vehicles were fuel cell powered, the water emitted would be about 0.005 % of the rate of natural evapotranspiration from the continental US. In fact gasoline engines also porduce water vapor -- more water per mile than would a hydrogen fuel cell powered vehicle.
Fuel cells are typically 30 - 40 % efficient when made in automobile sizes, which is about twice the efficiency of the standard gasoline powered internal combustion engine.
For a hydrogen-based fuel system, however, we face a "chicken or egg" problem: to get many such cars on the road, there must be adequate numbers of fueling stations; fueling stations won't be built, however, until there are adequate numbers of such vehicles....CA Governor Schwarzenegger signed an order to develop the CA Hydrogen Highway Network by 2010 -- intended to speed the commercialization of hydrogen fuel celled vehicles. This has been funded by a public/private partnership.. We'll see what happens!
Improving fuel efficiency would also help reduce emissions of ozone precursors, since less fuel would be burned. Between 1978 and 1985, the Corporate Averge Fuel Efficiency (CAFE) standards for passenger cars increased from 18 to 27.5 mpg, so we know that the auto makers can improve efficiency fast when needed. It's estimated that if the CAFE standards increased from the current 27.5 up to 40 mpg over the next 10 years, we would save more oil than we import from the Persian Gulf and could get from drilling in the Arctic National Wildlife Refuge combined!!
Much of the above reduces to four basic approaches to dealing with autos and air quality:
Cars are becoming a bigger problem globally as well. Globally, transportation consumes 20% of all fossil fuel energy that is produced. (Think of all the land that gets paved for roads and parking each year too........)
In Bangkok, Thailand, the average motorist sat in his/her car, going nowhere, for the equivalent of 44 eight-hour work days per year (this is basically time spent idling at traffic lights, and so forth). Further, the number of cars on Bangkok's streets was increasing by 300-400 per day during the year 2000. Congestion is so bad, that ~ 145 of Bangkok's traffice police have recieved training in midwifery -- hundreds of babies have been born in cars over the past few years!
In London, the average speed at which cars move within the city is not much faster than the average speed achieved by horse-drawn carriages! In fact, the Mayor of London recently (~ 2003) imposed a "congestion charge" of ~ $12 (? $ 16?) (US dollars) on cars driving into the city center during the workday hours (7 a.m. to 6 p.m.). It is enforced by video cameras that read the license plates of vehicles driving into the city center. By summer 2006, traffic in the city center had decreased by 30%, traffic delays had been cut in half, bus ridership had increased by 35% and air quality had improved. The mayor, in February 2007, announced that he is doubling the area encompassed , so that it will now be 6.5 square miles -- and he hopes to increase the fee as well. (Fines for violations are on the order of $200). The number of car trips into the city center decreased by ~ 15% almost immediately, and public transit use increased accordingly.
We are not immune from such traffic nonsense here in the US either -- in 2004, it was reported that the average US motorist spends 46 hours per year in traffic jams, with a consequent wasting of ~ 5.7 billion gallons of gasoline! In Portland, OR, it was estimated that drivers experience an average of 39 hours delay per year (basically a full work week) due to congestion per year (2005). An analysis of 16 studies conducted across 11 U.S. cities found that the average time required for a motorist to find a parking place on a downtown street is 8 minutes -- multiply that by the number of motorists, and you get the picture! A study of one 15 block area in LA found that cars hunting for parking spaces on that street drove 945,000 miles in one year -- the equivalent of 38 trips around the Earth! (Utne Reader, Nov-Dec. '06). What would happen if cities began charging more for parking??? Make it less attractive, people will use alternatives....
Overall, controlling ozone is a difficult task. There is no simple relationship between emissions of precursors and and ozone concentrations. The complex atmospheric chemistry of its production and transport depends on what else is in the soup (is some intermediate limiting??) and on wind and weather. Continued efforts toward decreasing precursor emissions are, however, bound to pay off in the end!
To move to the next section in these notes, which begins our study of stratospheric ozone depletion, change, click on "Stratosphere," here. To move to the overall Table of Contents for this BI301 home page, click "Contents" and for reminders on how to move about within and among these pages, click "Navigate."
This page is maintained by Patricia Muir at Oregon State University. Page last updated (partially) Feb. 22, 2009.