Why BioDiesel and Not Hydrogen Cars...

From: Michael Foster (PostNoSpam_at_recoverybydiscovery.com)
Date: 07/30/04 

Date: Fri, 30 Jul 2004 17:44:42 -0400

http://www.unh.edu/p2/biodiesel/article_alge.html

Widescale Biodiesel Production from Algae
Michael Briggs, University of New Hampshire, Physics Department

As more evidence comes out daily of the ties between the leaders of
petroleum producing countries and terrorists (not to mention the human
rights abuses in their own countries), the incentive for finding an
alternative to petroleum rises higher and higher. The environmental problems
of petroleum have finally been surpassed by the strategic weakness of being
dependent on a fuel that can only be purchased from tyrants.

In the United States, oil is primarily used for transportation - roughly
two-thirds of all oil use, in fact. So, developing an alternative means of
powering our cars, trucks, and buses would go a long way towards weaning us,
and the world, off of oil. The best alternative at present is clearly
biodiesel, a fuel that can be used in existing diesel engines with no
changes, and is made from vegetable oils or animal fats rather than
petroleum.

In this report, we will first examine the possibilities of producing
biodiesel on the scale necessary to replace all petroleum transportation
fuels in the U.S.

I. How much biodiesel?

First, we need to understand exactly how much biodiesel would be needed to
replace all petroleum transportation fuels. So, we need to start with how
much petroleum is currently used for that purpose. Per the Department of
Energy's statistics, each year the US consumes roughly 60 billion gallons of
petroleum diesel and 120 billion gallons of gasoline. First, we need to
realize that spark-ignition engines that run on gasoline are generally about
40% less efficient than diesel engines. So, if all spark-ignition engines
are gradually replaced with compression-ignition (Diesel) engines for
running biodiesel, we wouldn't need 120 billion gallons of biodiesel to
replace that 120 billion gallons of gasoline. To be conservative, we will
assume that the average gasoline engine is 35% less efficient, so we'd need
35% less diesel fuel to replace that gasoline. That would work out to 78
billion gallons of diesel fuel. Combine that with the 60 billion gallons of
diesel already used, for a total of 138 billion gallons. Now, biodiesel is
about 5-8% less energy dense than petroleum diesel, but its greater
lubricity and more complete combustion offset that somewhat, leading to an
overall fuel efficiency about 2% less than petroleum diesel. So, we'd need
about 2% more than that 138 billion gallons, or 140.8 billion gallons of
biodiesel. So, this figure is based on vehicles equivalent to those in use
today, but with compression-ignition (Diesel) engines running on biodiesel,
rather than a mix of petroleum diesel and gasoline. Combined diesel-electric
hybrids in wide use would of course bring this number down considerably, but
for now we'll just stick with this figure.

One of the biggest advantages of biodiesel compared to other alternative
transportation fuels is that it can be used in existing diesel engines. This
completely eliminates the "chicken-and-egg" dilemma that other alternatives
have, such as hydrogen powered fuel cells. For fuel cells, even when (and
if) vehicle manufacturers eventually have production stage vehicles ready,
nobody would buy them unless there was already a wide scale hydrogen fuel
production and distribution system in place. But, no companies would be
interested in building that wide scale hydrogen fuel production and
distribution system until a significant number of fuel cell vehicles are on
the road, so that consumers are ready to start using it.

However, with biodiesel, since the same engines can run on conventional
petroleum diesel, manufacturers can comfortably produce diesel vehicles
before biodiesel is available on a wide scale. As biodiesel production
continues to ramp up, it can just go into the same fuel distribution
infrastructure, just replacing petroleum diesel. Not only does this
eliminate the chicken-and-egg problem, making biodiesel a much more feasible
alternative than fuel cells, but also eliminates the huge cost of revamping
the nationwide fuel distribution infrastructure.

II. Large scale production

There are two steps that would need to be taken for producing biodiesel on a
large scale - growing the feedstocks, and processing them into biodiesel.
The latter step would perhaps be best accomplished by existing oil
refineries within the US being converted to biodiesel refineries, but could
also be accomplished by new companies building new plants. The main issue
that is often contested is whether or not we would be able to grow enough
crops to provide the oil for producing the amount of biodiesel that would be
required to completely replace petroleum as a transportation fuel. So, that
is the main issue that will be addressed here.

The Office of Fuels Development, a division of the Department of Energy,
funded a program from 1978 through 1996 under the National Renewable Energy
Laboratory known as the "Aquatic Species Program". The focus of this program
was to investigate high oil yield algaes that could be grown specifically
for the purpose of wide scale biodiesel production1. Some species of algae
are ideally suited to biodiesel production due to their high oil content
(some as much as 50% oil), and extremely fast growth rates. From the results
of the Aquatic Species Program2, algae farms would let us supply enough
biodiesel to completely replace petroleum as a transportation fuel in the US
(as well as its other main use - home heating oil).

One of the important concerns about wide scale development of biodiesel is
if it would displace croplands currently used for food crops. With algae,
that concern is completely eliminated, as algae grows ideally in either hot
desert climates or off of waste streams. NREL's research focused on the
development of algae farms in desert regions, using shallow salt water pools
for growing the algae. Another nice benefit of using algae as a food stock
is that in addition to using considerably less water than traditional
oilseed crops, algae also grows best in salt water, so farms could be built
near the ocean with no need to desalinate the seawater as it is used to fill
the ponds.

NREL's research showed that one quad (ten billion gallons) of biodiesel
could be produced from 200,000 hectares of desert land (200,000 hectares is
equivalent to 780 square miles). In the previous section, we found that to
replace all transportation fuels in the US, we would need 140.8 billion
gallons of biodiesel, or roughly 14 quads. To produce that amount would
require a land mass of almost 11,000 square miles. To put that in
perspective, consider that the Sonora desert in the southwestern US
comprises 120,000 square miles. As can be seen in Figure 1 below, the Sonora
desert is located along the Pacific ocean, making it an ideal location for
algae farms. The arid climate of the desert is very supportive of algae
growth, and the nearby ocean could supply saltwater for the algae ponds.
Enough biodiesel to replace all petroleum transportation fuels could be
grown in 11,000 square miles, or roughly nine percent of the area of the
Sonora desert.

The algae farms would not all need to be built in the same location, of
course. In fact, it would be preferable to spread them around throughout the
country, to lessen the cost and energy used in transporting the feedstocks.
Algae farms could also be constructed to use waste streams (either human
waste or animal waste from animal farms) as a food source, which would
provide a beautiful way of spreading algae production around the country.
The algae farms also yield recoverable methane (commonly referred to as
"biomethane" when it comes from biomass). This methane could then be turned
into methanol, to provide a biomass derived source of alcohol for turning
the algal oils into biodiesel. The left-over sludge remaining makes an ideal
fertilizer, high in nitrogen and phosphorous. Such algae farms could also
use the waste-streams from agriculture to aid algae growth.

III. Cost

In "The Controlled Eutrophication process: Using Microalgae for CO2
Utilization and Agircultural Fertilizer Recycling"3, the authors estimated a
cost per hectare of $40,000 for algal ponds. In their model, the algal ponds
would be built around the Salton Sea (in the Sonora desert) feeding off of
the agircultural waste streams that normally pollute the Salton Sea with
over 10,000 tons of nitrogen and phosphate fertilizers each year. The
estimate is based on fairly large scale ponds, 8 hectares in size each. To
be conservative (since their estimate is fairly optimistic), we'll
arbitrarily increase the cost per hectare by 50% as a margin of safety. That
brings the cost per hectare to $60,000. Ponds equivalent to their design
could be built around the country, using wastewater streams (human, animal,
and agricultural) as feed sources. We found that at NREL's yield rates,
11,000 square miles (2.82 million hectares) of algae ponds would be needed
to replace all petroleum transportation fuels with biodiesel. At the cost of
$60,000 per hectare, that would work out to roughly $169 billion, to build
the farms.

The operating costs (including power consumption, labor, chemicals, and
fixed capital costs (taxes, maintenance, insurance, depreciation, and return
on investment) worked out to $12,000 per hectare. That would equate to $33.8
billion per year for all the algae farms, to yield all the oil feedstock
necessary for the entire country. Compare that to the more than $100 billion
the US spends each year just on purchasing crude oil from foreign countries.

IV. Other issues

To make biodiesel, you need not only the vegetable oil, but an alcohol as
well (either ethanol or methanol). The alcohol only constitutes about 20-25%
of the volume of the biodiesel, so the volume of alcohol needed is only
about 1/4 the volume of oil. One of the most land-efficient and
energy-efficient way of producing methanol is using pyrolysis on biomass.
One of the additional benefits of this method is that the process produces
both methanol as well as charcoal, which can be burned for energy production
(replacing coal, and producing no net CO2 emissions or sulfate emissions).
In the early days of the automobile, most vehicles ran on biofuels, with
Henry Ford himself being a big advocate of methanol produced from industrial
hemp (not to be confused with marijuana, which is significantly different).
The Department of Energy's "Mustard Project" has focused on the prospect of
growing mustard for the dual purposes of biodiesel and organic pesticide
production. Their process focused on alternating mustard crops with wheat.
One nice effect of this is that the wheat could be used as the cellulose
feedstock for producing alcohol through pyrolysis for biodiesel production.

V. Hydrogen?

Hydrogen as a fuel has received widespread attention in the media of late,
particularly ever since the Bush administration proclaimed that developing a
hydrogen economy would clean our air, and free us of oil dependence. There
are many problems with using hydrogen as a fuel. The first, and most
obvious, is that hydrogen gas is extremely explosive. To store hydrogen at
high pressures for as a transportation fuel, it is essential to have tanks
that are constructed of rust-proof materials, so that as they age they won't
rust and spring leaks. Hydrogen has to be stored at very high pressures to
try to make up for its low energy density. Diesel fuel has an energy density
of 1,058 Btu/cu.ft. Biodiesel has an energy density of 950 Btu/cu.ft, and
hydrogen stored at 3,626 psi (250 times atmospheric pressure) only has an
energy density of 68 Btu/cu.ft.4 Hydrogen's energy density is only 7.2% of
that of biodiesel. Even if the hydrogen fuel cell is twice as efficient as a
diesel engine, running on hydrogen stored at 250 atmospheres would yield an
equivalent vehicle only 14% of the range of a vehicle running on biodiesel,
with equivalent space set aside for fuel storage. To get a 1,000 mile range,
a tractor trailer running on diesel needs to store 168 gallons of diesel
fuel. When the greater efficiency of the engine running on biodiesel is
taken into account, it would need roughly 175 gallons of biodiesel for the
same range. But, to run on hydrogen stored at 250 atmospheres, to get the
same range would require 2,360 gallons of hydrogen. Dedicating that much
space to fuel storage would drastically reduce how much cargo trucks could
carry. Additionally, the cost of the high pressure, corrosion resistant
storage tanks to carry that much fuel is astronomical.

There are two options for using hydrogen in a fuel cell - using compressed
hydrogen produced by electrolyzing water, and extracting hydrogen from other
fuels. I will look at each individually, and then analyze the use of
hydrogen as a fuel in general. Currently, most hydrogen used industrially is
extracted from natural gas. At current usage rates, the United States will
deplete its natural gas reserves in 46 years. If the use of natural gas for
transportation (whether directly, or as hydrogen extracted from natural gas)
increases dramatically, the time it will take before we use up all of our
reserves will decrease correspondingly. One of the primary reasons for
looking for alternatives to petroleum is to decrease our dependence on
foreign fuels. If we spend trillions of dollars converting to using natural
gas, only to use up our own reserves in a decade or two, we would find
ourselves back in the exact same position of being dependent on foreign
sources.

Thus, the focus needs to be on renewable fuels. For hydrogen, it is only
renewable when it is extracted from biofuels, or when the hydrogen is
produced by electrolyzing water using renewable energies (wind, solar,
etc.). The most logical biofuel to use in fuel cells would be biodiesel, due
to its high energy balance and energy density. But, let's consider the
option of producing hydrogen through electrolysis.

VI. Hydrogen electrolyzed from water

The first way to look at a potential transportation fuel is to examine the
overall energy balance. The energy balance tells you how much energy you get
back for each unit of energy you put into developing the fuel. The higher
the energy balance, the better the fuel source. The lower the energy
balance, the more energy that has to be put into producing the fuel per
amount of energy yielded when using the fuel.

When discussing hydrogen as a fuel, people usually take a very simplified
approach. When used in a fuel cell, the only by-product of using hydrogen as
a fuel is water. However, that completely ignores the issue of where the
hydrogen came from in the first place. It is tempting to think that this
hydrogen would be produced by electrolyzing water using renewable energy
sources, such as wind. To see how realistic this approach is, it is
important to analyze the overall energy balance, and henceforth the amount
of energy that would need to be produced for the fuel to be used on a wide
scale.

The place to start with hydrogen is electrolysis (directly separating the
hydrogen and oxygen atoms in water molecules, using electricity). While
biodiesel is produced by growing crops and transesterifying the oils,
hydrogen as a fuel could be produced by electrolyzing water. Electrolysis
systems are around 60% efficient. That means that for each unit of energy
you put in, the amount of recoverable energy in the hydrogen produced is
equal to 0.6 units. The hydrogen then needs to be compressed to high
pressures for storage in fuel tanks (due to the low energy density, hydrogen
has to be stored at high pressures so that vehicles can have a reasonable
range). Compressing the hydrogen takes energy, but for the moment we will
ignore this energy cost, as well as the cost of transporting hydrogen
(likewise, we will ignore the cost of transporting biodiesel. Transporting
biodiesel should be more efficient, since hydrogen needs to be stored and
shipped in high pressure stable metal containers (which are very heavy),
whereas biodiesel can be shipped in the same fuel trucks used today. The
mass of the fuel tanks for transporting hydrogen is a greater percentage of
the energy yield in the fuel than for biodiesel)).

So, the hydrogen fuel can be produced with an energy balance of 0.6:1 (0.6
units produced per unit of energy input, a 60% efficiency). Current
generation fuel cells are 50-60% efficient. Assuming a 60% efficiency, that
reduces the overall energy yield from 0.6:1 down to 0.36:1. That means that
for each unit of energy that goes into producing the fuel (hydrogen), 0.36
units of energy gets used for moving a vehicle.

The limited range of hydrogen powered vehicles makes them comparable to
electric vehicles. The energy balance, however, is completely different.
While a hydrogen vehicle would use electricity to electrolyze water to get
hydrogen for fuel, an electric vehicle uses electricity to charge batteries.
Battery charging systems are around 90% efficient, compared to the 60%
efficiency for electrolysis. Using the charged batteries to propel a car has
an efficiency in the upper 90% range, giving electric cars an overall energy
efficiency of around 85%, or 0.85:1. The energy balance of electric vehicles
is more than twice as efficient as a car powered with hydrogen produced
through electrolysis.

Now let us consider biodiesel. Based on a report by the US DOE and USDA
entitled "Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in
an Urban Bus"5, biodiesel produced from soy has an energy balance of 3.2:1.
That means that for each unit of energy put into growing the soybeans and
turning the soy oil into biodiesel, we get back 3.2 units of energy in the
form of biodiesel. That works out to an energy efficiency of 320%. The
reason for the energy efficiency being greater than 100% is that the growing
soybeans turn energy from the sun into chemical energy (oil). Current
generation diesel engines are 43% efficient (HCCI diesel engines under
development, and heavy duty diesel engines have higher efficiencies, but for
the moment we'll just use current car-sized diesel engine technology). That
brings the overall energy balance down to 1.38:1, roughly three times better
than the 0.36:1 of the hydrogen fuel cell car. This figure means that for
each unit of energy that goes into growing the crops and producing the
biodiesel, 1.38 units of energy are available to be used for moving the
vehicle, a net gain of 38%, compared to a net loss of 64% for hydrogen. With
the improved energy balances of other crops such as mustard and algae
compared to the 3.2:1 of soy, this energy balance would be even better.

---------------------------------------------------------------------------- 

----
The UNH Biodiesel Group is working on improving the technology for growing
algae on waste streams for biodiesel production. UNH has filed a provisional
patent application and is seeking partners to develop the technology. For
more information contact:
Michael Briggs 603-862-2828;
email michael.briggs@unh.edu
  1.. http://www.nrel.gov/docs/legosti/fy98/24190.pdf
  2.. http://www.nrel.gov/docs/legosti/fy98/24190.pdf
  3.. http://www.unh.edu/p2/biodiesel/pdf/algae_salton_sea.pdf
  4.. http://www.osti.gov/fcvt/deer2002/eberhardt.pdf
  5.. http://www.nrel.gov/docs/legosti/fy98/24089.pdf

Relevant Pages

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