STATEMENT OF JAY RATAFIA-BROWN

SENIOR ENGINEER

SCIENCE APPLICATIONS INTERNATIONAL CORPORATION

BEFORE THE UNITED STATES SENATE

COMMITTEE ON ENERGY AND NATURAL RESOURCES

MAY 24, 2007

Good Morning Mr. Chairman, Senator Domenici and Members of the
Committee. Thank you for the opportunity to appear this morning to
discuss the technical feasibility of co-converting coal and biomass to
gaseous and liquid fuels via gasification and Fischer-Tropsch synthesis
technologies. My testimony is based on over 30 years of broad experience
conducting technical and environmental assessment and systems analysis
for large-scale energy conversion methods, including recent project
work.

Co-gasification of combined 'coal + biomass' feedstock is being
advocated by researchers as a potential means of producing significant
quantities of transportation fuels while yielding very low levels of
pollutant discharges, as well reduced or near-zero release of carbon
dioxide (CO~2~), a greenhouse gas (GHG) forcing agent. To achieve these
goals both rapidly and cost-effectively, this concept likely needs to
utilize the technological strengths of large-scale, commercial coal
gasification technology, which enables co-conversion of *renewable*
*crop-based* *biomass* feedstock with coal, generation of suitably
"clean" syngas at required pressure/temperature conditions, and the
capability to efficiently capture carbon dioxide (CO~2~) for
sequestration. Since the addition of biomass into a coal-based
conversion system introduces unique technical requirements and
challenges, my goal in this testimony is to discuss the potential for
successfully engineering of such a hybrid energy conversion system.

**DRIVERS FOR 'BIOMASS + COAL' CO-CONVERSION**

The primary motivation for converting our substantial domestic coal and
biomass resources to transportation fuels and chemicals is to displace
the use of imported oil and, thereby, help mitigate its high price and
supply security concerns. Inclusion of biomass in this endeavor also
represents a potential means of reducing the environmental footprint of
this transformation on a sustainable basis. In this regard, ambitious
national and international goals, like *the U.S. Biomass Research and
Development Act of 2000* and the *Biofuel Directive of the European
Union*, call for large biomass-based energy conversion capacity in order
to diversify the resource base for transportation fuels, chemicals, and
power/heat generation. The ***U.S. Vision*** recommends that *biomass
supply 5% of the nation's power, 20% of its transportation fuels, and
25% of its chemicals by 2030*. The ***EU Vision*** (as of March 2007)
sets a goal of 10% biofuels use for transportation by 2020.

Key roadblocks to this resource conversion are associated with: 1)
environmental consequences of greatly increasing coal consumption,
particularly related to amplified release of greenhouse gas emissions
(GHG); 2) small-scale, high specific-cost and relatively poor
performance of available biomass conversion technologies; 3)
availability of sufficient biomass feedstock (locally) for an economic
plant size; and 4) shut-off risk or curtailment of operations if there
is a biomass supply shortage or reduction in supply.

A very promising approach to resolution of most of these roadblocks is
to combine conversion of coal and biomass in a large-scale facility that
incorporates *gasification technology* to convert solid feedstock to
syngas (primarily H~2~, CO, CO~2~, H~2~O, and CH~4~); *syngas
processing* to remove unwanted contaminants such as sulfur, potassium,
and mercury; *Fischer-Tropsch (F-T) synthesis technology* to convert
syngas to clean liquid fuels (naphtha and diesel); *carbon capture and
storage (CCS)* technologies technology to allow efficient and safe
sequestration of CO~2~; and *power generation technology* to both supply
internal requirements and electricity for sale. Individual plants would
have to be very large to capture required economies-of-scale:
**Transportation Sector** ─ 25,000 to 50,000 barrels/day; and **Chemical
Sector** ─ 5,000 barrels/day equivalent. I will refer to this as the
coal/biomass-to-liquids (CBTL) concept.

The environmental consequences of this approach, particularly as related
to the net release of CO~2~, have been investigated by researchers from
the Princeton Environmental Institute.[^1] Their findings indicate that
a plant that combines co-gasification of biomass (switchgrass) and coal
could potentially achieve a near-zero net CO~2~ emission rate by
exploiting the negative emissions of storing photosynthetic CO~2~ in
roots and soils. By comparison, the CO~2~ emission rate for coal-only
F-T liquids production, with CCS, could be reduced to about the same
rate as crude oil-derived fuels. This approach could also require
considerably less net biomass input to realize near-zero emissions than
conventional biofuels conversion, such as cellulosic ethanol.

Let me summarize the key drivers for CBTL concept as I see them: **1**)
Reduction of imported crude oil; **2**) Continued use of our abundant
coal resources in an environmentally acceptable manner; **3**) Greater
utilization of our abundant biomass resources in accordance with our
national goals; **4**) Efficient and cost-effective utilization of
biomass resources; **5**) Coal acts as a "flywheel" to keep a facility
operating even if biomass is not sufficiently available; **6**) Within a
strict carbon-constrained framework, such as McCain-Lieberman, this
approach should become cost-effective, **7**) Use of reliable coal in
concert with more environmentally acceptable renewable feedstock may
reduce project financial risk for large-scale energy conversion plants;
and **8**) Gasification-based projects could benefit significantly from
the more positive public attitude displayed towards co-utilization of
renewable feedstock, as well as development of a reliable multi-source
fuel supply network for such projects.

Successful technical and cost-effective implementation of CBTL
particularly depends on adoption of *suitable gasification technolog*y,
addressing *biomass handling challenges*, satisfying *syngas "cleanup"
constraints*, and effectively *integrating CCS*. My intent in the
remainder of this testimony is to focus on the challenges that each
represent and their potential for enabling this concept to function
effectively.

**GASIFICATION TECHNOLOGY CAPABILITY AND EXPERIENCE**

First, I want to convey that gasification technology is in widespread
use today. The 2004 World Gasification Survey, sponsored by DOE, shows
that in 2004 existing world gasification capacity had grown to 45,000
MWth of syngas output at 117 operating plants with a total of 385
gasifiers. Coal (49% of capacity), petroleum products (37%) and natural
gas (9%) currently dominate the gasification market as the primary
feedstocks for production of F-T liquids, chemicals, and power. Note,
however, that biomass gasification only accounts for about 2% of the
total syngas production. Figure 1 presents a summary of large-scale
gasification experience.

The gasification technology represents the most critical component that
impacts system design and operation of a CBTL facility. The desirable
design characteristics for co-gasification technology for F-T liquids
applications (using high rank coals) are: *large individual gasifier
throughput* (\>1000 MWth); *high temperature* (\> 2,300^o^ F to
eliminate tars/oil contaminants in the syngas); *high pressure* to
increase syngas throughput and reduce process component sizes;
*oxygen-blown* (as opposed to air-blown) to eliminate nitrogen as a
syngas diluent; *slagging* (a consequence of high temperature operation)
to render most of the feedstock ash as a benign byproduct for
utilization purposes; *dry feed* of biomass since it is difficult to
handle as a slurry, and use of a relatively *large particle size* to
reduce feedstock preparation.

**Exhibit 1. Summary of Large-Scale Gasification Experience**

**(2004 DOE World Gasification Survey)**

![](media/image1.wmf){width="5.821527777777778in"
height="3.3291666666666666in"}

Fortunately, these design characteristics are generally met with the
widely used *entrained-flow gasification* technology, which currently
dominates the large-scale gasification market with 85% of the installed
units. (Note that this technology also continues to benefit from a
variety of related R&D efforts sponsored by DOE to further improve
performance and cost, including development of a compact transport-type
gasifier technology.) While these gasifiers are quite flexible with
regard to feedstock characteristics, their high reaction rates demand
very small feedstock input size (e.g., \< 100 micron or 0.004 inches)
that is easily achievable for friable materials like coal, but more
challenging and energy-consuming for biomass feedstock. Compounding this
important issue is the high pressure injection requirement for the
entrained-flow technology, which may present a challenge to biomass
injection into the gasifier. Also, the chemical make-up of biomass ash
will cause it to behave differently that coal ash, which must be
accounted for in design and operation. Several large-scale
demonstrations of entrained-flow co-gasification of coal and biomass
have already been performed here and in Europe.

Commercial scale co-gasification of biomass with coal has been
demonstrated at the 253 MWe Nuon IGCC power plant in Buggenum, The
Netherlands (using the dry-feed Shell entrained-flow technology), as
well as at Tampa Electric's 250 MWe Polk IGCC power plant (using GE
entrained-flow technology). (The latter was built in the 1990s as part
DOE's Clean Coal Demonstration Program.) The Nuon plant recently tested
biomass content up to 30% by weight (17% of total energy input), which
requires up to 205,000 tons/year of biomass feedstock and coal feed is
about 435,000 tons/year. Besides gasification of *demolition wood*,
tests were also conducted with *chicken litter* and *sewage sludge*. The
co-gasification tests conducted at the Polk plant used up to 1.5% by
weight of woody biomass harvested from a 5-year-old, locally-grown
Eucalyptus grove. Since the plant uses 2,200 tons/day of coal, the
biomass co-gasification basis was 33 tons/day (about 10,000 tons/yr).

Not only did these plants operate normally, but we can generally
conclude that biomass feed size can be on the order of 1 mm (0.04
inches) due to biomass' high reactivity relative to coal. The importance
of this lies in the capability to minimize biomass milling power
consumption and possibly avoid other efficiency-reducing pre-treatment
processes. The Nuon experience has also shown that a relatively high
throughput of biomass is possible in an entrained-flow unit that is
co-gasifying coal. Pilot-scale tests were also tests were also conducted
at the National Energy Technology Laboratory (NETL)/Morgantown some
years ago with coal and up to 35% biomass.

**COAL+BIOMAS CO-GASIFICATION CHALLENGES**

Below, I provide a brief overview on key challenges associated with
oxygen-blown, entrained-flow gasification of coal and biomass.

**Oxygen feed to the gasifier --** standard cryogenic method of oxygen
production is both costly and energy intensive; however, DOE is well
into development of so-called ion transport membrane (ITM) technology,
which promises significant cost reductions and efficiency gains.

**Biomass and coal injection** **--** Feedstock injection into high
pressure gasifiers is challenging. Conventional dry-feed methods employ
a series of complex lock hoppers. Due to the low energy density of
biomass, lock hoppers have two major disadvantages: (1) large amounts of
inert gas are required and must be compressed, and (2) gasification
efficiencies drop due to the dilution of the syngas. Fortunately, DOE's
gasification program has been developing a rotary dry-feed coal pump
that, when fully tested, should allow the feedstock to be "pushed"
directly into the gasifier.

**Biomass particle size** **--** While entrained-flow gasifiers require
very small coal particle sizes (\< 0.004 inches), recent commercial
'coal + biomass' tests suggest a much larger size (0.04 inches) is
likely feasible due to the high reactivity of biomass due to its high
O~2~ and volatiles content

**Biomass ash slagging behavior** **--** While the slagging performance
of the biomass ash may be an issue, testing has shown that "flux"
material (aluminum-silicates) can be added to the gasifier to
re-establish acceptable ash slagging performance.

The bottom-line is that the practical limit of biomass co-processing
with high rank coals (bituminous and subbituminous coals) is probably
associated more with biomass preparation and feed issues and desired
syngas production level, than the capabilities of the entrained-flow
gasification process.

**BIOMASS HANDLING CHALLENGES**

Our work has primarily focused on crop-based biomass, particularly
prairie grass/switchgrass and short rotation woody crops (SRWC), such as
Poplar and Eucalyptus. These are defined as fast-growing, genetically
improved trees and grasses grown under sustainable conditions for
harvest at 1 to 10 years of age. In general, their biomass heating
values \[MJ/kg\] and particle densities are about half of that of coal,
whereas bulk raw densities \[kg/m^3^\] are about 20% of that of coal,
resulting in overall biomass energy density \[MJ/m^3^\] approximately
10% of coal (see Exhibit 2). As a consequence, when co-gasifying raw
biomass at a 10% heat input rate with coal, the volume of coal and
biomass can actually be similar; therefore, *biomass requirements with
regard to transport, storage and handling are very high in comparison to
its heat contribution.*

**Exhibit 2. Energy Density Comparison of Different Biomass Physical
Forms with Coal**

![](media/image2.wmf){width="6.152777777777778in"
height="3.1465277777777776in"}

Biomass either has to be located very close to a conversion facility and
processed immediately, or some form of "densification" needs to be
implemented to mitigate handling issues. Since this is a well-recognized
issue for biomass, especially for conversion processes that can consume
very large quantities, a number of methods have been developed, albeit
currently at small-scale, that are applicable. These are
*pelletization*, which is a drying/compression method that increases
energy density of switchgrass pellets by a factor of eight.
*Torrefaction* is a "roasting" treatment that operates within a
temperature range of 200 to 300 °C and is carried out under atmospheric
conditions in the absence of oxygen. This process not only increases the
energy density of wood by about 25%, but also greatly reduces the
milling energy consumption to reduce size. Combined torrefaction and
pelletization can increase the energy density of wood by about five
times. *Pyrolysis* is an option to produce a liquid product (pyrolysis
oil) from biomass, via its thermal decomposition, at temperatures of
450-550° C. Yield efficiency of pyrolysis oil production averages about
70%, and volumetric energy content of pyrolysis oil is 19 68,300 Btu/gal
compared with \# 6 Oil at 144,000 Btu/gal.

***SYNGAS "CLEANUP" CONSTRAINTS***

The CBTL concept requires strict limits on various contaminants in the
syngas, most of which come from coal, but biomass co-contributes certain
elements and related compounds such as calcium (Ca), phosphorous (P),
chlorine (Cl), sodium (Na) and potassium (K). The limits are intended to
prevent poisoning of the F-T catalysts and fouling/corrosion of
downstream system components, such as heat exchangers and gas turbine
blades. As an example, constraints on alkali metals (Na + K) are less
than 10 part per billion by volume (ppbv) and halides (HCL + HBr + HF)
are also less than 10 ppbv. These and other limits are controlled via
the integration of a group of processes that sequentially treat the
syngas once it exits the gasifier. These include dry particulate
removal, wet syngas scrubbing for fine particulate and gases, mercury
removal, and acid gas (H~2~S and CO~2~) removal. Experience with
commercial IGCC power plants, such as the Polk IGCC plant and the Wabash
River plant (another DOE Clean Coal Technology Program investment), as
well as refinery gasifiers, have established that the CBTL syngas limits
can be met with appropriate system design.

**CARBON CAPTURE AND STORAGE CHALLENGE**

Operation of a CBTL facility will reduce CO~2~ emissions relative to a
more conventional coal-to-liquids (CTL) design, even without integration
of CCS technology. The extent of the reduction depends on the relative
level of biomass energy input. For example, the 30% (by weight) biomass
feed to the Nuon plant that I discussed previously, resulted in an
effective CO~2~ reduction of about 17% or 220,000 tons/yr (excluding GHG
emissions related to biomass collection and treatment). On the other
hand, integration of CCS technology will reduce the GHG footprint of
CBTL to a much greater extent. However, while CO~2~ capture technology
is commercially available and well-proven for gasification-type
applications, it increases capital expenditure and operating costs; DOE
is currently developing advanced membrane technologies to lower this
impact. More importantly, the actual sequestration of CO~2~ is far from
commercially available and acceptable. As stated by DOE, key challenges
are to demonstrate the ability to store CO~2~ in underground geologic
formations with long-term stability (permanence), to develop the ability
to monitor and verify the fate of CO~2~, and to gain public and
regulatory acceptance. DOE's seven Regional Carbon Sequestration
Partnerships are engaged in an effort to develop and validate CCS
technology in different geologies across the Nation. This is vital to
sequestration's future and use with the CBTL technology.

**CONCLUSION**

Even without considering currently favorable government programs to
encourage investment in CTL and CBTL technology, I've endeavored to
convey that that there are considerable drivers that strongly support
continued development. *Importantly, it takes advantage of the
significant investment and progress that the country has made with
gasification and related technologies over the past twenty-five years.*
Commercial entrained-flow gasification technology has been proven to be
capable of co-gasifying coal and biomass, which at the minimum would
permit reduced GHG emissions from future CTL facilities. Incorporation
of CCS technology, when sequestration is technically available and
appropriate to regulatory conditions, can have a major impact on the
sustained use of our abundant coal resources and greater use of our
biomass resources. Although, I've reported on some successful tests of
coal and biomass co-gasification, I've also attempted to convey that R&D
is needed to deal with significant challenges related to biomass
handling and feeding issues that are important to plant operability and
cost-effectiveness. Also, longer-term, large-scale tests of the CBTL
concept are required to better understand how a well-integrated design
will perform and function. Overall, I strongly believe this is a
technology that has great potential to improve our energy security while
also being a good steward of the environment.

I will be happy to answer any questions.

[^1]: Williams, R., "Synthetic Liquid Fuels From Coal + Biomass with
    Near-Zero GHG Emissions," Princeton Environmental Institute,
    Princeton University, January 12, 2005.