Trucks at Work
The real GHG culprits

The real GHG culprits

The household sector, which accounted for almost a third of total emissions in the U.S. in 2006, has seen no significant gains in [greenhouse gas] emissions efficiency during the past decade. Even though emissions per household are low, the cumulative effect of the U.S. household sector’s consumption of energy is large.” –From the Commerce Department’s report U.S. Carbon Dioxide Emissions and Intensities Over Time issued this past April

It’s one of those critical factoids overlooked amid the ballyhooed effort by President Obama’s administration to create fuel economy and greenhouse gas (GHG) emission standards for medium- and heavy-duty trucks: they aren’t the biggest producers of GHGs within the U.S. economy.


Know who is? You, me, and every other average homeowner and/or car and light-truck driver in the nation. Yep, we’re the biggest producers of GHGs – bigger even than the MANUFACTURING sector of the U.S. economy; those evil titans of industry with their big factories supposedly spewing out global warming gases by the metric ton.

Turns out the lowly homeowner is responsible for most of the CO2 being produced in this country – and that’s according to data compiled by the GOVERNMENT; the very same folks that now drawing a CO2 line in the air (if you will) for truckers.

In its U.S. Carbon Dioxide Emissions and Intensities Over Time report issued this past April, the Commerce Department calculated that energy-related CO2 emissions in the U.S. increased from about 5.6 billion metric tons (Bmt) in 1997 to almost 6.0 Bmt in 2007, an increase of 7.4% percent over the decade or an average annual increase of about 0.7% per year.

The Commerce Department’s research also indicated that manufacturing and households are the two highest-emitting CO2 sectors in the U.S. economy – higher even than transportation. Yet household emissions are now LARGER than those of manufacturing!


Manufacturing was responsible for one-quarter (25%) of total CO2 emissions in 2006, down 30% from 1998. However, the household sector was by far the largest producer of energy-related CO2 emissions in 2006, responsible for 30% or roughly 1.8 Bmt worth per year – over DOUBLE the amount the transportation sector produces (some 912 million metric tons [Mmt] annually).

Here’s another critical statistic the Commerce Department uncovered: The household sector has NOT become more energy efficient. In 1997, manufacturing emitted more CO2 than any other sector. But by 2006, households were the largest CO2 emitting sector. During these years, while manufacturing was reducing its emission per dollar of output, CO2 emissions per household increased, Commerce noted.

What comprises “household emissions” you ask? It’s the combined consumption of all primary fuels—electricity, natural gas, fuel oil, propane, etc.—for heat and power, as well as the consumption of gasoline and diesel fuel for light-duty vehicles (LDVs), primarily automobiles and light-duty trucks.

For 1998, 2002 and 2006, on average, according to Commerce’s data, approximately one-third of all household emissions resulted from fuel consumption in LDVs, with the remaining two-thirds of the emissions were from utility use for heat and power.


Between 1998 and 2006, emissions levels grew from both of these sources, with “emissions intensity” from household use of LDVs increasing by a total of about 7%, with emissions intensity related to household use of utilities in residential structures increasing by 2%.

In terms of the CO2 growth, within households, about 45% of the increase came from an increase in gasoline usage, with the remaining 55% arising from higher utility usage.

Manufacturing, however, displayed a 10.5% drop in total CO2 emissions from 1998 to 2006. As a result, manufacturing’s share of total CO2 emissions dropped from 30% to 25% between 1998 and 2006 – demonstrating a greater decline (5 percentage points) in its share of emissions than its overall economic share, which declined by 3 percentage points between 1998 and 2006.

One of the reasons why emission intensities of households may have increased over the 1998 to 2006 period is that household size has increased in each of those years as well, Commerce’s researchers noted. In 1998, there were 2.59 persons per household; by 2002, 2.63 and by 2006, 2.67, according to U.S. Census Bureau figures. By 2010, household size should again increase, up to an estimated 2.69 persons.

And yet … what are we focusing the harsh lens of regulation upon? Why, commercial trucks of course! Even though they (apparently) are NOT the largest source of CO2 emissions in the U.S.!

The problem, though, is that the transportation sector had the largest proportional increase in CO2 emissions over the 1998-2006 period, posting an increase of 16.1%, or 127 Mm. However, households posted the largest absolute increase with a net gain of 210 Mmt (a 12.9% jump) which accounted for almost two-thirds of the 328 Mmt increase within the entire economy.


Yet let’s face it – trucks make an easy target. The distribution of emissions within the transportation industry, according to the data compiled by the Commerce Department, shows that by far, trucks are the greatest emitter of CO2 within this economic sector – responsible for 47% of the 912.1 Mmt of CO2 emissions in 2006 from this sector. Air transport, by contrast, is a distant second at 22%, with water transport responsible for just 10%, warehousing, 8%, and rail a measly 5%.

Commerce found, it should be noted, that the water transportation industry showed significant increases in emissions intensity between 1998 and 2006, with the trucking sector also becoming less efficient over this time period.

However, trucking has a pretty good excuse – complying with Environmental Protection Agency standards to cut oxides of nitrogen (NOx) and particulate matter (PM) emissions. Those efforts, it must be noted, resulted in poorer fuel economy and higher CO2 emissions.


The key to reducing GHG emissions – of which CO2 is a major component – boils down to improving fuel efficiency of the entire transportation network, Allen Schaeffer, executive director of the Diesel Technology Forum, told me earlier this year.

“Reducing carbon emissions is a direct function of reducing GHGs. You do that by burning less petroleum fuel,” he explained. “But from a GHG perspective, you are no longer looking at controlling emissions from just a diesel engine by itself – you are looking at the fuel efficiency of the entire vehicle, which includes how it’s operated.”

In some ways, too, this focus on GHG reduction is creating a major emission policy contradiction, Schaeffer noted. “We’ve spent the last two decades controlling PM and NOx emissions in trucking, which led to reductions in fuel economy,” he pointed out. “Now, we’re looking to control GHGs, requiring improvements in fuel economy. If we’d started with this goal first, we wouldn’t have done what we did over the last 20 years.”

A good point, but the emissions ship is sailing a new course now, though the particulars are still vague. What comes next in terms of specific fuel economy and GHG standards is when we’ll find out how smooth the sailing is going to be, or if the waters are going to be a lot rougher than expected.