Biorefineries using waste – production of energy and chemicals from biomasses by micro-organisms - Biomass as Energy Source: Resources, Systems and Applications - page 253

indicated by the wide experimentation with the PMEU units, to develop further applications on
the basis of the volatiles. In the refinement of biogas, for example, the gaseous compounds may
also cause problems, since upgrading the biogas includes removing carbon dioxide to increase
the content of methane and to remove hydrogen sulfide and water, which can cause damage in the
gas utilization system (Weiland, 2010). Other possible impurities are nitrogen, oxygen, ammonia,
siloxanes, and particles (Petersson and Wellinger, 2009).
Many alternative ways in designing the reactors could be accomplished. One experimental
semi-industrial plant has been built in the northern Finland (planned and designed by Finnoflag
Oy for Biometa Finland Oy, built by subcontractorsYTT Oy and Kaitek Oy). This plant has been
constructed in such a way that various sequential runs could be performed simultaneously.
13.11 DIFFERENCES BETWEEN CHEMICAL TECHNOLOGIES AND
BIOTECHNICAL PROCESS SOLUTIONS
Several companies are exploiting bioprocesses in their chemical and materials production. Many
biotechnological processes are cheaper than traditional chemistry, have higher yields or produce
a cleaner product (Venter, 2004). Amino-acid supplements, vitamin supplements, antibiotics,
anti-influenza drugs, substances of creams for cosmetics and even the solid rocket-fuel that
is used in air-to-air missiles. Several polymeric product applications have been established.
Metabolic Explorer Inc., for example, turns glucose into acrylate, a feedstock for the plastics
industry. Cargill Inc., a large agricultural company, produces a glucose-derived substance called
3-hydroxypropionic acid. This can be manufactured with modified microbes. Further strains can
then produce a dozen chemicals that are precursors for plastics. John Frost of Michigan State
University (and the inventor of biotech rocket-fuel) has even worked out how to use bacterial
enzymes to make a form of nylon. Cargill-Dow Inc., a joint-venture between Cargill Inc. and
Dow Chemicals Inc., produces a cost-effective polymer made from lactic acid that has been pro-
duced from maize-derived glucose. DuPont Inc. has Sorona®, a plastic that is half biotech and
half-traditional. These are only a few of numerous applications.
The main source of industrial glucose in North America is maize starch, which is relatively
costly. However, most of the dry weight of a plant is composed of cellulose. If cellulose residues
were used to make glucose, much agricultural waste, such as straw and the leftovers from maize
farming, could be turned to account. It can be broken down biologically, and the enzymes to
do such a job are found in many bacteria and fungi. The search is now on for the best enzymes
and ways of upgrading these into industrial products. Novozyme Inc.'s target chemical is ethanol,
which is fermented from glucose. The firm has improved the process of hydrolyzing cellulose into
glucose, and then fermenting glucose into ethanol, in ways that have reduced the cost ten-fold. In
our own process development, we have found out that such savings are achievable by new planning
principles of the biotechnological production. This still means that the enzyme processing for an
American gallon of cellulose-derived ethanol costs 50 cents. However, Novozyme hopes to bring
that cost down another ten-fold over the next few years, to a point where ethanol derived from
cellulose might be cost-competitive with petroleum-derived products. In addition, if ethanol can
be made cheaply from cellulose, then this can be achieved with many other bulk chemicals.
In principle, biotechnical industries must often rely on the use hydrolytic enzymes for the
pretreatments, which make an additional step into the process when compared with the chemical
industries. In the actual process, the biological substances act in a less predictable manner due to
the vast amount of parameters controlling their function.
13.12 BIOREFINERY CONCEPT EVALUATION
13.12.1 New ideas on materials: all process wastes serve as raw materials in nature
In nature, all organic matter circulates. Besides this network, or multidirectional flow of sub-
stances, we have learnt to recognize the importance of water cycle, and carbon, nitrogen, sulfur