@ The anaerobic digestion and wood
liquefaction processes are not
promising routes to low cost syn-
thetic fuels in view of the superior
HYGAS® and H-Coal® process
economics.

@ In certain localities, power
generation from wood may be
economically competitive with
power generation from coal if the
coal/wood price ratio is high
enough.

@ The small biomass conversion
plants do not appear to have an
overall environmental advantage
over their coal conversion plant
counterparts on a relative basis;
however, more and better quanti-
tative emission data need to be
developed in order to better assess
the probable impacts of both the
biomass and coal conversion
technologies.

@ Managed properly, biomass
residue collection should have
less severe environmental
impacts than coal mining, even
though much more land area
would be affected by residue col-
lection.

From these comparisons, it is evident
tiat the coal conversion processes are
more likely to become major routes to
clean fuels than these biomass conver-
sion processes, primarily because of
better economics. Other biomass feed-
stock/conversion process/energy
product scenarios could prove to be
more favorable in this type of biomass-
coal comparison. A combination of
three factors is desirable:

@ a relatively low-priced biomass
feed material,

@ aprocess that has a relatively high
conversion efficiency, and

@ a higher-priced product than fuel
oil or fuel gas.

Steam and power production from
low-cost residues and co-firing of wood
and fossil fuels appear to be promising
ways of using biomass resources in a
number of localities in the U.S. Biomass
conversion into more valuable products
(chemicals, fertilizers, animal feeds)
should also be a promising area of
study.

Both biomass and coal conversion
would have adverse environmental
impacts, and there is continuing need to
better define the likely impacts of
resource collection, conversion, and
product usage.

The coal conversion plants need to be
large in order to produce competitively
priced clean energy. If the coal conver-
sion plants could be scaled-down to the
same low capacities as their biomass
plant counterparts, it is likely that the
coal-derived energy products would be
more costly than the respective
biomass-derived products. In some
localized scenarios, biomass conversion
could have an economic advantage over
coal conversion on a small scale.

US GOVERNMENT PRINTING OFFICE, 1981 — 757-012/7313

San Francisco, CA 94119.

only from:
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Telephone: 703-487-4650

Cincinnati, OH 45268

R. A. Stenzel, B. T. Kown, M. C. Weekes, J. D. Ruby, B. R. Gilbert, C. M. Harper,
Y. J. Yim, and R. T. Milligan are with Bechtel National, Inc., P.O. Box 3965,

Thomas J. Powers is the EPA Project Officer (see below).

The complete report, entitled “Environmental and Economic Comparison of
Advanced Processes for Conversion of Coal and Biomass into Clean Energy,”
(Order No. PB 81-234 239; Cost: $29.00, subject to change) will be available

National Technical Information Service

The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency

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oe


SEPA

United States
Environmental Protection
Agency

Industrial Environmental Research
Laboratory
Cincinnati OH 45268

Research and Development

EPA-600/S7-81-133 Sept. 1981

Project Summary

Environmental and Economic
Comparison of Advanced
Processes for Conversion of
Coal and Biomass into

Clean Energy

. Stenzel, B. T. Kown, M. C. Weekes, J. D. Ruby, B. R. Gilbert, C. M. Harper,

Yim, and R. T. Milligan

Biomass and coal conversion into
clean energy is compared on an econ-
omic and environmental basis in three
regional scenarios: (1) electric power
from direct combustion of wood
versus conventional coal combustion
in the south central U.S., (2) synthetic
pipeline gas from anaerobic digestion
of wheat straw and manure versus
high-Btu gasification of coal
{HYGAS®) in the midwest, and (3)
synthetic fuel oil from wood liquefac-
tion versus coal liquefaction (H-Coal®)
in the northeast. Conceptual commer-
cial-scale plants are described. Capital
and operating costs are presented for
each of the six plants, and the biomass
versus coal economics are compared.
General environmental impacts of bio-
mass and coal resource collection are
assessed and compared in the
scenario contexts. Plant environmen-
tal emissions were estimated where
possible, and relative environmental
impacts are discussed. Conclusions
are given about the conversion con-
cepts which seem the more promising
routes to clean energy, and areas
needing further study are identified.

This Project Summary was develop-
ed by EPA’s Industrial Environmental
Research Laboratory, Cincinnati, OH,
to announce key findings of the

research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).

Introduction and Summary

This report presents the results of
three environmental and economic
comparisons of biomass and coal con-
version into clean energy. The study
was initiated to help develop priorities
for assessing conversion technologies
capable of producing clean energy from
biomass and coal resources. Electric
power, synthetic pipeline gas (SPG), and
synthetic fuel oil were chosen as repre-
sentative clean energy products which
can be produced from both biomass and
coal. Representative coal conversion
technologies were to serve as base
cases to which biomass conversion
technologies were to be compared.
Three regional scenarios, each with a
biomass-coal plant pair, were selected
from a number of possible candidates.
Conceptual designs of commercial-
scale plants were compared in these
regional scenarios:

@ A50MWewood-fired power plant
versus a 500 MWe coal-fired
power plant in the south central
U.S.


@ A7MMSCFD(6.7 billion Btu/day)
biogas plant (anaerobic digestion
of wheat straw and manure)
versus a 274 MM SCFD (250
billion Btu/ day) high-Btu
gasification plant (steam-oxygen
HYGAS®) in the midwest.

@ A 1764 BPD wood-oil liquefac-
tion plant versus a 66,856 BPD
coal liquefaction plant (H-Coal®)
in the northeast.

In the scenarios, biomass residue is
collected locally from forestland
(chipped forest residue), from farmland
(wheat straw), and from feedlots (cattle
manure). Coal is strip-mined in the first
two scenarios and deep-mined in the
third. As plant feedstocks, the biomass
materials have lower sulfur and ash
contents, lower heating values, and
lower bulk densities (except manure)
than coal.

The plant capacities chosen are
representative of commercial scales
being proposed for biomass residue and
coal conversion. The disparity in
biomass-coal plant capacities is almost
inherent; hence, the higher capacity
coal conversion plants have a distinct
economy-of-scale advantage. The direct
combustion and the liquefaction pro-
cesses for biomass conversion are
similar to their coal conversion counter-
parts. A biological conversion process,
anaerobic digestion, is compared with a
thermal conversion process, steam-
oxygen gasification. Estimated plant
thermal efficiencies (based on net prod-
uct output) are compared below:

Fuel
Power SPG Oil
Biomass
Conversion 21.6% 31.9% 42.1%
Coal
Conversion 35.1% 69.1% 65.5%

It 1s apparent that these three bio-
mass processes have relatively low con-
version efficiencies. In the wood
conversion processes, the feedstock
properties are a disadvantage—low
heating values (high moisture and
oxygen contents) and low bulk densities
mean that more material must be
handled per unit of energy content than
for coal. Energy consumption and losses
are high. The anaerobic digestion
process suffers from a low methane
production rate and incomplete biomass
conversion. This process does yield a

2

digester residue that may be a valuable
byproduct if it can be used as an animal
feed.

Improvements in conversion effi-
ciencies are important if these particu-
lar biomass processes are to be
competitive with the coal processes.
Worthwhile ideas for improving feed-
stock properties (preprocessing of
biomass) should be given attention, as
such ideas could lead to increased
Process conversion efficiencies.

Economic comparisons of the
biomass and coal conversion concepts
are presented in Figures 1, 2, and 3 for
utility and private financial methods,
using the ERDA-AGA Cost Guidelines.
These figures illustrate that the bio-
mass-derived energy products are
about 50 percent (power) to 300 percent
(SPG) more expensive to produce than
the corresponding coal-derived pro-
ducts from much larger conversion
plants, Synthetic fuel oil from wood
liquefaction is about 2.5 times more
costly than oil from the H-Coal® process.
In these scenarios at least, the
economic disparities result from a
combination of less desirable feedstock
properties, smaller biomass plant
capacities, and lower process conver-
sion efficiencies. In many economic

would produce electric power more
cheaply than it could be produced in
conventional power plants firing any of
the four synthetic fuels.

Figure 1 shows that the cost of elec-
tricity from a wood-fired plant is not
competitive with that from a large coal-
fired generating station if wood and coal
prices are about the same on a $/MM
Btu basis. For a high coal cost/low wood
cost scenario, a small wood-fired plant
could be economic as evidenced by
existing power boilers burning wood
wastes in many pulp and paper mills in
the northeast.

The biomass-derived synthetic gas
and oil are just not close to being
competitive with the coal derived syn-
thetic fuels, as Figures 2 and 3 illustrate.

Pollution control costs will be high for
the large coal conversion plants,
probably 5 to 10 percent of the total
plant capital costs. These large expendi-
tures, however, do not shift the
economic advantage to biomass
conversion, as the foregoing figures
show.

Environmental impacts of plant con-
struction and operation were consid-
ered separately from impacts of
resource collection. Resources
consumed by the plants and emissions

situations, both direct-fired plants of conventional pollutants were esti-
Wood Cost, $/MMBTU
0 0.50 1.00 1.50 2.00 2.50 3.00
1 1 1 1 i 1
125 T T T T T T 1
5 10 15 20 25 30
Wood Cost, $/Ton
100), Som deme a Private -

nme Utility

Cost of Electricity, Mills/K' WH

Coal Cost, $/Ton

10 20 30 40 50 60 70 80
0 1 1 rt f rn n L L
T TT —T T T T
t) 0.50 1.00 1.50 2.00 2.50 3.00

Coal Cost, $/MMBTU

Figure 1.

Economic comparisons of wood and coal to power.


Straw or Manure Cost, $/MMBTU

0.50 1.00 1.50 2.00 2.50 3.00
n 1 i n 1 ia
Straw 10 20 30, 40 = Straw
_4 ‘_ n 1
Manure 2 4 6 8 Manure
20 Straw and Manure Cost, $/Ton 4
>
3 oe
3 -
= 15 5 4
3
a
s
io}
S
® 10] 4
3
is)
— -_
5| Dh J omnes wee ® Private 4
eee (/t//it
Coal Cost, $/Ton Utility
10 20 30 40 50 60
i) 1 1 n 1 1 n
ts) T T T T T T
0.50 1.00 1.50 2.00 2.50 3.00
Coal Cost, $/MMBTU
Figure 2. Economic comparison of straw/manure and coal to SPG.
Wood Cost, $/MMBTU
0.50 1.00 1.50 2.00 2.50 3.00
100 2 n L 1 i i n
T T T T T
5 10 15 20 25 30
Wood Cost, $/Ton -
—_
80- ae 4
-_
-_ ~~ BPD)
oi (17
60 7
g
~
oN
S$ 40 - 4
3 —a—T
g 5 a eee en Private
© 20 mcmmmeenmess (tility  _|
Coal Cost, $/Ton
40 50 70 80
0 ? 20 2 i 1 a n
T T T T T T
0 0.50 1.00 1.50 2.00 2.50 3.00
Coal Cost, $/MMBTU
“igure 3. Economic comparison of wood and coal to fuel oil.

mated for each biomass and coal
conversion plant, and then comparisons
were made ona relative (energy output)
basis. None of the three biomass
conversion plants appears to have an
overall environmental advantage over
its coal conversion plant counterpart on
the relative comparison basis. This
environmental standoff is partly due to
the extensive pollution controls used in
the coal conversion plants which reduce
conventional pollutant emissions to
about the same overall levels as those
from biomass conversion. The potential
for generation and release of toxic or
hazardous substances (priority pollu-
tants) cannot be assessed adequately at
this time because much of the informa-
tion has not been developed yet.
Biomass residue collection should
entail considerably fewer adverse con-
sequences on the environment than
deep-mining or strip-mining coal
resources. Forest residue or wheat
straw collection activities will affect
much more land area than coal mining,
but little environmental damage should
occur if collection activities are man-
aged properly. Unlike coal, the biomass
resources are renewable and some
environmental credit is deserved for
their utilization. If the plant impacts and
the collection impacts are considered
together, biomass conversion in these
scenarios may be preferable from an

overall environmental impact view-
point.
Major conclusions reached from

these three biomass-coal comparisons
are:

@ The coal conversion plants have
considerably higher thermal effi-
ciencies than their biomass
counterparts.

@ The biomass residues have the
advantage of Jow sulfur and ash
contents, but their low bulk densi-
ties and low energy contents are
distinct disadvantages with
respect to coal as a plant feedstock.

@ Biomass-derived electric power,
SPG, and synthetic fuel oi are
more expensive to produce than
the corresponding coai-derived
clean energy products from the
large-scale conversion plants.

® Pollution control costs for the
conversion plants are high, but
have little impact on the relative
economics of coal versus biomass
conversion.