Water and Transportation Fuels

View my white paper on Sigma Xi regarding the water consumption required for various types of alternative fuels. See: http://www.sigmaxi.org//programs/issues/King.pdf. (also see below for full text of article if link).

In this white paper I refer to an article I wrote in Environmental Science and Technology on this same subject of the Water Intensity of Transportation. In this paper I calculate the "gallons of water per mile" that are embodied via consumption (meaning mostly evaporated) and withdrawal (taken from a water source and returned to the source) during farming, mining, processing, and refining of feedstocks into fuels.

Feedstocks studied are petroleum, coal, natural gas, sun, wind, biomass (corn and soy).
Fuels studied are ethanol, gasoline, diesel, biodiesel, electricity, hydrogen, and natural gas.


FULL SIGMA XI ARTICLE:
On the Water Consumption for Transportation Fuels
Carey W. King, Ph.D.
University of Texas at Austin
Center for International Energy and Environmental Policy

Driving light duty vehicles (LDV) on most alternative fuels and energy sources will
consume more water per mile driven than by driving on gasoline and diesel1. The
exceptions are using compressed natural gas with natural gas powered pumps, electricity
derived from non-thermal renewable electricity (e.g. solar PV and wind), and hydrogen
derived from either electrolysis of water using non-thermal renewable electricity or steam
methane reforming. To effectively plan for the environmental consequences of moving
from high energy density petroleum to lower quality fossil fuels and biomass, we must
not unduly distribute fuels with low energy return on investment. Water consumption is
just one environmental attribute for focus, but an important one from a quantity and
quality perspective.

In 2003 the average fuel efficiency of the U.S. LDV fleet was 20.5 mpg of gasoline.
These gasoline vehicles consume, via embodied water in mining and refining, 0.1-0.2
gallons of water per mile (gal H2O/mile). Using tar sands, coal, and oil shale converted to
liquids consumes 0.3-0.5 gal H2O/mile. If using electricity from the average U.S.
generation mix, driving a car using an electric motor from a battery consumes 0.2-0.3 gal
H2O/mile. If the grid electricity is used for electrolysis of water to create hydrogen, using
that hydrogen in a fuel cell vehicle results in consumption of 0.4-0.5 gal H2O/mile. Using
non-thermal renewable electricity for electric and fuel cell vehicles consumes less than
0.05 gal H2O/mile, and obtaining the hydrogen from steam methane reforming of natural
gas consumes just under 0.1 gal H2O/mile.

The other major category of potential LDV fuels is biofuels. If the biomass feedstock is
irrigated, using so-called “blue water” from aquifers and reservoirs, the water
consumption for corn-based ethanol (E85) and soy-based biodiesel is orders of magnitude
higher than other fuels with U.S. averages of 28 and 8 gal H2O/mile, respectively. Note
that only 10% of soy and 15-20% of corn bushels are irrigated in the U.S. However, some
highly irritating regions of the U.S. could embody over 100 gal H2O/mile by growing
irrigated corn converted to E85. Cellulosic-based irrigated grasses could result in 1-9 gal
H2O/mile of consumption. Without irrigation, fueling today’s fleet of LDVs using E85
ethanol and soy biodiesel would consume 0.1-0.4 gal H2O/mile, comparable to
unconventional fossil conversions.

For almost any product or application, but certainly for agriculture, the embodied water is
essentially transferred to drier regions. For instance, in providing food aid to developing
nations, the U.S. essentially becomes a net exporter of water – that is water embodied in
the exported food. If a given region does not have the climate, or irrigation water source,
1 King, C. W. and Webber M. E. Water Intensity of Transportation. Env. Sci. & Tech. Online
9/24/08 at: http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/asap/abs/es800367m.html.
for growing a certain crop, importing that crop may be a good option. However, should
the irrigation water be drawn from a fossil aquifer, the same crop grown under a different
circumstance will not be sustainable in the long term and should be considered a fossil
fuel itself simply based upon its supply chain, or life cycle. The irrigation of biomass
represents the growing of that biomass in areas with insufficient rainfall. This
relationship itself does not necessarily imply a lack of sustainability. For instance,
diverting nearby river water into a reservoir can create a stable supply source that can
withstand the normal climactic variations in rainfall.

The embodied water concept for agriculture can also be applied to biofuels but with
additional focus upon thermodynamics and energy return on investment (EROI). Many
regions may import some sugar cane-based ethanol from Brazil, yet don’t have the
climate to grow the sugar cane. Because of the relatively high EROI of cane ethanol over
corn ethanol, international shipping can make sense. Thus, the history, or supply chain, of
the biofuel is important, not just its final properties. The supply chain of fossil fuels will
also become more important over time as lesser quality resources are extracted. There
was no need to pay attention to EROI from the early coal beds and oil wells because they
so clearly allowed increased lifestyle and leisure relative to the world before the
industrial revolution.

In the concept of moving to non-petroleum fuel sources, the Renewables Fuels Standard
(RFS) of the Energy Independence and Security Act (EISA) of 2007 has been both good
and bad from a policy perspective:

Bad in the sense that the RFS initially pushes a feedstock-fuel combination, corn
ethanol, that has detrimental environmental consequence in terms of nutrient runoff
and low EROI. But, the consequences of runoff can be minimized by not overfertilizing,
more widespread use of better tilling practices, and buffer strips next to
major rivers.

Good in the sense that the RFS has pushed forward the scrutiny of how we use energy
resources, biomass included, and focused much attention on how we can create better
biomass to fuel conversions. It has also raised worldwide awareness on the ethics of
how agricultural land should be used: food, fuel, or both?

Today, the struggle for new fuel supplies is clouded because it is not obvious what
options best provide for increased or even continued levels of lifestyle and leisure. What
is more obvious is that there are geographic regions that can sustainably grow certain
kinds of biomass that other regions simply cannot. Unconventional fossil resources such
as tar sands and oil shale have lower EROI and higher water consumption needs than
conventional petroleum. The need for more water in industrial fuel systems is an
indicator of moving to lower energy efficient sources.

Lawmakers creating future policy regarding agriculture and energy need to be cognizant
that the tie between energy and water will only increase into the future. Generally, energy
sources with lower energy density tend to require more water for mining, farming,
refining, and processing. Certainly an increase in vehicle fuel efficiency decreases the
“gallons of water per mile” traveled, but in then end, fresh water sustainability is
measured on only one “per” basis: “gallons of water per Earth”.

PHEV/EVs and water - Finally a good article

It seems that the first paper (regarding water for electric vs. gasoline miles) on our work on the "water intensity of transportation" has gotten quite a bit of attention in the media. I've reported on this already, but included here is finally a good and responsible article that properly demonstrates the scope of the issue.

For an example of an article that does a good job, see the following:

ScienceNOW published this article - online today (3/10/08)

Bottom line (I repeat), electric and plug-in hybrid electric vehicles will use more water because people will charge their cars from the general electric grid. This grid is dominated by thermoelectric power plants (coal, natural gas, and nuclear), and these plants consume and withdraw water as part of cooling. To lessen the water impact, we can focus on (1) generating electricity in thermoelectric plants using technology that consumes and withdraws less water and (2) using electricity from sources that don't consume and withdraw water (wind, PV solar).


For examples of articles that do a poor job, see any of the following:

Popular Mechanics

- The quote below is very misleading and incorrect. The water intensity, or gallons/mile, for withdrawal is 17 times greater. This is not a 17-fold increase in water demand, even if all light duty vehicles (cars, trucks, SUVs) ran on full electric power, because water is withdrawn for many other purposes AND if all miles (2.7 trillion) in 2005 were driven on electricity, that would amount to about 900 billion kWh, when the entire nation generated 3,883 billion kWh without any measurable amount of PHEV/EVs. Thus, all light duty vehicle travel by electric miles would be only 23% more electricity (and associated consumption and withdrawal), NOT 17 times more. See misleading quote from article:

"Though most of this water is returned to the source (albeit at a higher temperature), a 17-fold increase in demand would pose a real problem for water-stressed regions, making power plants more vulnerable to shut down during times of drought. "

New Scientist

Chemistry World

- The following quote is completely incorrect. The nation's water consumption (which includes that for irrigation, municipal use, mining, and thermoelectric generation) will NOT triple if we switch to PHEV/EVs. See above comment on the Popular Mechanics article, same argument goes for not tripling nation's water consumption with all electric light duty vehicle travel. See misleading quote from article:

"Michael Webber and Carey King, from the University of Texas at Austin, suggest that powering America's cars with electricity, rather than gasoline (petrol), could triple the nation's water consumption."


Have a good day.

Another article about my PHEV/EV and water usage - unneccesarily alarmist

Another article, this time in New Scientist, has been written about my paper on "water of the plugged-in automotive economy". See a recent post on water used while driving on electric miles for my basic take on how to interpret the analysis.

Phil McKenna, the journalist and writer of the article, chose the title " 'Thirsty' electric cars threaten water resources". This is an unfortunately alarmist title. The article prompted some to blog on the New Scientist page that I was against plug-in hybrid electric vehicles (PHEV) or electric vehicles (EV). This is certainly not true. Some suggested I must be paid or work for some petroleum or natural gas company. This is also certainly not true.

I gave Phil information to present the scope and scale of electric driving upon the electricity grid and water resources, but he didn't mention this.

For example:
1 million PHEV40s (PHEVs that have a 40 mile range) would drive about 7.3 billion miles per year. This is about 0.3% of miles driven by light duty vehicles.

The resulting water consumption is 1.7 billion gallons, or ONLY 0.13% of water consumption already associated with power generation.

The resulting water withdrawal is 76 billion gallons, or ONLY 0.11% of water withdrawal already associated with power generation.


I, and my coauthor, chose to independently look at link between energy and water. This work is a first foray into this area, and we have also analyzed other fuels (biofuels, hydrogen, coal to liquids, etc.) that is in the review process for publishing.


So ... NO ALARM. We have time to plan for 10s of millions of PHEVs, let's get them on the road!

Water for Transportation - publication on "electric miles"

A paper of mine has been published online today in the journal Environmental Science and Technology. The paper describes how much water is used, that means consumed and withdrawn (which are two different concepts) for driving a vehicle on electricity as "fuel". This pertains to electric vehicles (EV) or plug-in hybrid electric vehicles (PHEV) while they travel on battery power alone.

First, two basic definitions:

water withdrawal is that water which is taken from a source, run through a process, and returned to the source or some other source.

water consumption is water that is withdrawn but not returned to the source due to evaporation (for example - in cooling processes for steam power plants) or evapotranspiration (evaporation from through plants).

Due to water consumed and withdrawn for cooling steam electric power plants (coal, nuclear, geothermal, solar concentrated power, and most natural gas), we can associate that water usage with the electricity generated from the plant. Assuming that an EV or PHEV is charged with electricity from the generic U.S. grid, each mile driven by a average light duty vehicle (a car, pickup truck, or SUV) will consume 0.2-0.3 gallons of water and withdraw 8 gallons of water. This is approximately 2-3X more water consumption and 12X more water withdrawal than when driving a light duty vehicle on petroleum gasoline.

Does this mean we should not pursue EV and PHEV technology? ABSOLUTELY NOT.

There are many benefits to the integration of EV/PHEV vehicles which include the ability to use a diversity of fuels sources - anything that can end up generating electricity (burning stuff to produce steam, nuclear power, wind power, photovoltaic solar, etc.). The ability to use a variety of transportation fuels by way of the electric grid is very powerful and important.

While the water consumption and withdrawal is higher than using petroleum gasoline, we can easily plan and accommodate for the increase in water usage per mile. The use of EV/PHEVs will occur gradually, and water resources will not be the limiting factor for their adoption. Full speed ahead for electric cars.

Deregulated vs. Regulated Energy Prices

In Texas in 1999, Senate Bill 7 created a deregulated electricity market within the Electric Reliability Council of Texas (ERCOT). Some areas opted not to join into the fun of a deregulated market, where consumers could choose their retail electricity provider of choice. Examples of these ares are the city of Austin (Austin Energy) and the city of San Antonio (CPS).

So since 1999, I wondered: if the economic 'free' market is supposed to be optimal and drive prices lower for the consumer, why aren't prices in the deregulated market lower than those at Austin Energy and CPS Energy?

Today, the winter charge for electricity within the Austin Energy domain is near 8.5 cents/kWh if using 1000 kWh per month. The summer rate this year was near 9.4 cents/kWh. If I look on the Texas Public Utility Commission's website for finding a retail electric provider (Power To Choose) in Round Rock, Texas (just north of Austin) in the Oncor region, I notice for the fixed rates (I will not consider variable rate electricity) the price varies between 10.2 - 14.1 cents/kWh. This is approximately 1.5 cents/kWh more than Austin Energy averaged over the year. Note that the price a consumer pays is due to costs for (1) electricity generation, (2) transmission, and (3) retail electric providers (REP) who administer the service. The ERCOT deregulated market makes it such that no one company can perform more than one of those functions.

One major reason for this discrepancy is how electricity is priced in the deregulated market.

Assume the following:
1. Company A is in the deregulated market in ERCOT, and Company B is a city municipality within ERCOT but not engaged in the deregulated market (like Austin Energy).

2. Both Company A and B have identical power generation capacity and mix at: 33% natural gas combined cycle, 33% pulverized coal, and 33% nuclear.

The deregulated market prices electricity at the 'marginal price' (i.e. the cost to generate the last bit of electricity). Also, all coal and nuclear power runs almost continuously with the natural gas units cranking up and down to follow the rise and fall of electric demand. Assume the case now with high natural gas prices, it is the most expensive.

Say nuclear power costs 1.7 cents/kWh, coal costs 3.5 cents/kWh, and natural gas generation costs 5.0 cents/kWh.

For 1000 kWh of generation the deregulated cost of energy is:

= (nuclear electricity)*price + (coal electricity)*price + (natural gas electricity)*price
= 333 kWh*5.0 cents/kWh +333 kWh*5.0 cents/kWh + 333 kWh*5.0 cents/kWh
= $50.00

For 1000 kWh of generation the municipality cost of energy is:

= (nuclear electricity)*price + (coal electricity)*price + (natural gas electricity)*price
= 333 kWh*1.7 cents/kWh +333 kWh*3.5 cents/kWh + 333 kWh*5.0 cents/kWh
= $34.00

So using THE EXACT SAME GENERATION units, the municipality is inherently cheaper. Of course, municipalities can be less efficient running their organization than competitive companies and end up charging more. But, competitive REPs also need to pay for marketing their product, which incurs costs. Thus, municipalities can afford to be less efficient in their general operation and organization up to the point that they make up for marginal price differences and marketing costs from REPs. There are also other factors, but the basic price structure for charging for generated electricity is perhaps the most influential.

Of course, since the deregulated market was created after lots of infrastructure existed already, it is not truly a 'free' market system since some companies started with a tremendous amount of assets. But that is a discussion for another day ...