Press release
Presse-Information  Information de presse
Trend Report No. 1 : Plant engineering for biomass processing
Contact/Kontakt:
Dr. Kathrin Rübberdt
Tel. ++49 (0) 69 / 75 64 - 2 77
Fax ++49 (0) 69 / 75 64 - 2 72
e-Mail: presse@dechema.de
October 2011
Biomass creates a new set of challenges for equipment manufacturers

Bio-based processes provide a sustainable, expanding raw material base

Standard technologies will have to be modified
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Purification/downstreaming will present a challenge
Biomass is more than just an input material for power generation (either directly in
cogeneration plants or indirectly via the biogas/syngas route). Biomass is also being
used to produce an increasing number of chemical intermediates and finished products. Government policies are supportive, creating enormous growth potential. All
of the players in the industry including equipment manufacturers and companies in
the supply base can exploit the new opportunities, but there are also challenges
which extend throughout the value-added chain. At ACHEMA 2012 on June 18th-22nd
in Frankfurt am Main, Germany, exhibitors will present techniques for further optimization of biomass conversion.
When asked during an interview with EFCE whether bio-based technologies can replace
conventional oil-based technologies, Steen Riisgaard, President and CEO of the Danish
firm Novozymes A/S, replied that there is no limit to the possibilities. He said that he does
not expect to see an economy totally based on biotechnology any time soon, but he is
confident that the chemical industry will take full advantage of the available opportunities.
Biomass and the related markets are in the ascendency, and that is reflected in the investment levels. The Biomass Markets and Technologies study published by Pike Research at
the end of 2010 provided data to support this view, and it made the prediction that worldwide investment in the biomass market will continue to grow at a stable rate over the next
five years. According to the study, investment will increase from $28.2 billion in 2010 to
$33.7 billion in 2015.
Biomass is mankind's oldest source of energy. Wood has kept people warm since time
immemorial. The exploitation of biomass as a raw material base is a more recent development. According to the German Chemical Federation (VCI), annual consumption of bio1/7
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mass in the German chemical industry is roughly 2.7 million MT which is about 13 % of the
raw material base in the industry. The fossil resources coal, oil and gas used to be cheap,
but the attitude in the industry has changed dramatically.
Biomass covers a broad spectrum both in terms of the source of materials and the end
products. The European Biomass Industry Association (EUBIA) has defined four categories
of biomass conversion: direct combustion, thermochemical conversion processes (pyrolysis
and gasification), biochemical processes (anaerobic digestion, fermentation) and physicochemical (the route to biodiesel). The choice of technology depends on the chemical composition of the raw materials and the target product.
Making chemical products from biomass
Similar to a petrochemical refinery, biorefineries convert biomass to produce a series of
chemical raw materials and fuel products.
Integrated biorefinery concepts are still in their infancy for the most part, and as a result
biorefineries in Germany and the rest of Europe are few and far between. Most are demonstration or pilot plants. Biorefineries operating on a commercial basis tend to be the exception. As of 2010, there were seven biorefineries in Germany. The number is 121 for all of
Europe. The US is playing a leading role in the construction and operation of biorefineries
and in providing support to the industry. The Department of Energy’s Biomass Program
alone is providing support for 29 biorefineries.
The question of who will operate biorefineries in the future is a major issue in Germany. The
chemical industry is reluctant to take on this responsibility. As a result, chemical parks and
the agribusiness are the most likely candidates.
The VDI (Association of German Engineers) Technology Center has conducted a study to
assess the extent to which biomass and its maximum utilization in biorefineries will replace
conventional oil-based production techniques. The study provides information on bio-based
production methodologies for 26 precursors (platform chemicals). There are strong indications that production is being migrated to bio-based techniques on eleven of these precursors. To take one example, production capacity for succinic acid and polylactic acid (PLA)
made exclusively of biomass is expanding worldwide.
Biotransformation of biomass in living cells or biocatalysis using isolated enzymes or enzyme systems is widespread in the white biotech industry. A very wide range of microorganisms are used for biotransformation, the most common ones being yeast, Escherichia
coli and Corynebacterium glutamicum. A variety of hexoses (C6 sugar) such as glucose
and fructose serve as precursors which can for example be isolated from the biomass
through hydrolytic pretreatment. A different methodology is needed for lignocellulose, however, to separate the non-fermentable lignin from the sugar. Currently, lignocellulosic bio2/7
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mass passes through a mechanical or chemical pretreatment process using acids, phenol
derivatives or hot steam and, to an increasing extent, hydrolytic-catalytic pretreatment with
cellulases. Hemicellulose recovered from the lignocellulose has a high pentose content (C5
sugar), for example xylose, and particular microorganisms are needed to break these substances down.
Technical hurdles and solutions
To roll out competitive, cost-effective bio-based production on an industrial scale, a number
of technical hurdles will have to be overcome.
The challenges begin with handling aspects that are closely related to the very nature of
biomass. Large quantities have to be harvested, transported and processed. The sheer
volumes are not the only challenge for industry. Diversity is another issue which needs to
be addressed. The term biomass extends beyond dry bulk solids such as corn and wood
chips to include high-viscosity liquids like sewage sludge and liquid manure. Given this level
of diversity, different techniques are needed to move the biomass to the intended destination.
Logistics is not the only area where special solutions are needed. Biomass has to be stored
between delivery and industrial processing. Spontaneous ignition has been a recurring
problem with wood chips. The problem is caused by microbial decomposition in the wood.
Poor heat conductivity in the bulk materials tends to catalyze the process, often producing
smoldering or even open flames.
Besides chemical oxidation reactions which are the largest exothermic factor in the overall
process, the German Materials Research and Testing Agency (BAM) has pointed out that
physical and microbiological processes play a part in bulk biomass heat management. The
information has been published in the Agency's biomass storage fire prevention guidelines.
For example, water adsorption on the surface of relatively dry solids also raises the temperature when adsorption heat is released.
The need to be very careful is not limited to dry biomass. Building and water management
regulations apply to the storage of commercial liquid manure to ensure that overflowing or
escaping liquid manure is not released into the sewage system or, even worse, into the
ground water.
Following conversion, the products are normally highly diluted, often in the form of complex
product mixtures which contain constituents that are very similar to each other. The products also contain various residues and waste products. Fermentation solutions, cell cultures
and plant extracts are typical examples.
Product purification/downstreaming to meet chemical standards are a big challenge. Large
amounts of aqueous solution are normally involved, and the product often still has to be
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isolated from the organism. Extracting the product from a fermentation broth can often
account for 80 % of production costs, making it a major cost factor in biotech production.
The list of additional technological hurdles includes the development of new specific catalysts and biocatalysts.
Product inhibition during fermentation can be another problem if high product concentrations are not conducive to the organisms involved. Innovative approaches such as in-situ
product isolation or low pH process design can provide the answer.
Upscaling from the lab environment can also cause problems. Bio-based processing needs
to be combined with conventional chemical techniques. Hybrid chemical production is
essential particularly during the early stages of development. Intensive work is underway in
the US and China on polybutylene succinate. The process combines biological fermentation
with chemical hydrogenation.
Biogas plants: watching out for trouble spots
The natural metabolism of microorganisms is exploited in anaerobic fermentation of waste
and other biomass to convert substrates into biogas.
The makeup of the solid substrates has a major influence on the fermentation process at
biogas plants. To an increasing extent, standard input materials such as corn silage are
being replaced by alternative substrates like manure, grass, straw or, more recently, sugar
beets. The targeted breakup of agglomerates and shredding of solids increases the surface
area, so that process bacteria can act faster on the nutrients. Also, a faster and more homogeneous distribution can be achieved in the liquid phase if the substrates have been
shredded. This has crucial advantages for the entire process:
 Higher gas yields/reduction of the average residence time in the fermenter
 Reduced load on agitators and pumps
 Improved composition of the fermentation residue
Deficiencies were discovered at 80 % of the biogas plants which were assessed by the
chemical industry employer’s liability insurance association (BG Chemie). The fact that
biogas plants produce flammable, explosive methane was a major source of concern. Other
potentially critical intermediates and end products such as carbon dioxide and hydrogen
sulfide are also produced.
Design errors and material defects can cause accidents when structural parts fail to withstand biomass or gas pressure.
Cogeneration plants, and the gas motors in particular, are one of the potential trouble spots.
The introduction of solids by the pumps is another source of problems.
Biogas: the dream of foam management
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Biogas plants often operate at the margin of commercial viability. Technical problems and
process interruptions resulting in extended downtime or high repair costs can have serious
economic consequences at biogas plants. The uncontrolled buildup of foam is one of the
most frequent causes of operational problems at biogas plants. Foam can lead to stoppages and cause defects in biogas reactors. The list of foam-related problems includes
crust formation on reactor walls, gate failure, contamination and blockage of gas lines,
condensate lines and recirculation pumps, excessive foam buildup and complete production
stoppages. Gas yields decline and so does the profit margin.
Development of an early warning system to predict and avoid impending foam events is
being explored at the Helmholtz environmental research center. Substrate samples from
several biogas plants are being examined to reach a better understanding of the foam
which forms at biogas plants. Samples from plants that maintain a stable operating state
and do not produce foam are being analyzed to provide a reference. All of the data is entered into a database. This information will be used later on to determine causalities and
make predictions based on the patterns that are detected.
Natural gas grade biogas
A totally new process is being developed at the University of Hohenheim for the production
of natural gas grade biogas. What sets this method apart is the fact that the methane bacteria which are responsible for biogas production are themselves being used to maintain the
pressure and purity levels which are needed for natural gas grade biogas. The university
researchers are developing a special instrumentation and control system for that purpose.
Downstream compression and purification of the gas is no longer necessary, and that
reduces energy costs by up to 40 %. The next step will be to build a prototype of the new
system in Hohenheim.
The new process could give a real boost to biogas production. Most of the current energy
costs would be eliminated, and in contrast to the conventional process small plants would
be economically viable. Total investment is substantially lower because there is no need for
gas upgrading.
Biogas plants: optical analysis enhances efficiency
Siemens is working on instrumentation and control systems which are designed to enhance
process management and plant efficiency in the biogas industry. Acids are produced when
biomass ferments to make methane. If the acid concentration is too high, the process
reaches a critical point. The system then has to be cleaned and restarted. Currently, operators periodically take samples from the tank for lab analysis.
As they do not know the actual acid content in the fermenter at any given time, many users
leave a wide safety margin which means that they have to accept high losses.
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Infrared spectroscopy can solve this problem. Molecules emit characteristic light spectra
when they are exposed to infrared light. The spectra provide information about the chemical
bonds, and that information can then be used to determine the presence of specific elements or chemical groups. Instrumentation developed by Siemens emits infrared light into
the fermenter through a glass window in order to detect the acid content. This eliminates
the risk of excessive acid levels, and users can utilize the full potential of their production
systems. Experts estimate that the energy yields will increase by 5 % to 10 %.
Bio corrosion: the importance of removing sulfur
Stephan Prechtl and Martin Faulstich (ATZ Development Center) have published a study
which highlights another very real challenge for equipment manufacturers. Biofilms colonize
metal, natural stone, concrete and plastic surfaces in equipment which is used for industrial-scale biomass processing or power generation.
Many agricultural biogas systems are made of concrete, and mechanical agitators are used
for mixing. The hydrogen sulfide and its by-products (sulfurous acids and sulfuric acid)
which form during anaerobic microbiological decomposition of the substrate often cause
corrosion to the structure and equipment such as agitators, heat exchangers and cogeneration systems. Biological desulfurization directly in the fermenter is the most common technique for reducing the hydrogen sulfide content in the biogas. Microbiological desulfurization is a very simple process. Capital investment and operating costs are low, and the
technique is used in the majority of systems. Under optimal conditions, the desulfurization
rate can be as high as 95 %.
Deposits of elemental sulfur can cause blockage problems in pipes. Fluctuating crude gas
concentrations have a negative effect on microbiological desulfurization directly in the
fermenter gas chamber.
Corrosion damage can often be avoided by selecting a more suitable method of biogas
desulfurization. The following techniques are used in practical application. However, the
technical suitability as well as the capital investment and operating costs of the various
options have to be evaluated for the specific application.
 Precipitation by directly adding ferric salt
 Caustic rinse
 Adsorption on iron-rich bodies
 Adsorption on activated carbon
 External biological desulfurization in a separate reactor
There are an estimated 7,000 biogas plants in Germany, and many of them have been
operating for years without interruption. Most of the equipment at these plants is no longer
state-of-the-art. Susceptible parts are wearing out, and experts predict massive repowering,
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for example with advanced instrumentation and control systems to facilitate process management. Susceptible parts which are subjected to high stress (e.g. agitators, feed units
and cogeneration plants) will be replaced.
Syngas plants: preventing deposits
Tar formation is a problem associated with the production of syngas from biomass. The
main difficulties are the trouble-free supply of biomass, high coke and tar content in the
product mixture and the cost and effort of gas upgrading.
The main problem associated with the use of biomass for Stirling engine applications is the
efficient transfer of heat from the biomass combustion flue gas to the working gas in the
Stirling engine.
The hot gas heat exchanger provides the interface between the flue gas and the working
gas. To ensure high electrical efficiency, the temperature of the flue gas at the inlet to the
hot gas heat exchanger should be as high as possible, but this can cause problems resulting from ash deposits in this part of the system. A computer program to calculate heat
transfer at the flue gas end of the hot gas heat exchanger has been developed to address
the problem. Following extensive engineering and development work, the efficiency of
these system components has been improved significantly. An automated gas scrubber for
the hot gas heat exchanger is now also available.
Using a nanotechnology-based coating technique, the Nanostir Project is taking a different
approach to the problem. The objective is to eliminate or greatly reduce slag formation at
the hot gas head over a long period of time.
Summary: the chemical industry is already working intensively on the development of biobased sources of energy and raw materials. As is the case with conventional technology,
not every technique developed in the lab can be scaled up for industrial use. At ACHEMA
2012 which will be held on June 18th-22nd in Frankfurt am Main, Germany, exhibitors will
showcase new process strategies, better catalysts and innovative products which further
improve the cost and efficiency aspects of biomass conversion for the production of energy
and raw materials.
www.achema.de
(The trend reports are compiled by specialized international journalists. DECHEMA is not
liable for incomplete or inaccurate information.)
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Theodor-Heuss-Allee 25  60486 Frankfurt am Main  Germany  T + 49(0)69 75 64-0  F +49(0)69 75 64-201  presse@dechema.de
www.dechema.de