Biomedical Engineering Reference
In-Depth Information
The fermentation industry takes starch as the basic raw material and annually
consumes hundreds of millions of tons of grain, with development limited because
of competition with humans and livestock for grain.
Cellulose and hemicellulose in natural lignocellulose are polysaccharide poly-
mers that can be generated into glucose, xylose, and other sugars after hydrolysis.
By microbial fermentation, these sugars can be converted into ethanol, acetone,
butanol, acetic acid, butanediol, and other liquid fuels and chemical raw materials.
They also can be taken as the fermentation raw material for antibiotics, organic
acids, single-cell protein, and enzyme preparations. Phenylpropanoid derivatives as
the monomers of lignin can be transformed into other chemical products and further
used as basic raw materials for the organic chemical industry.
In the 1990s, developed countries successfully exploited renewable chemicals
to replace the oil feedstock and further accelerated the development of nonfood
renewable resources, such as agricultural stalks and urban fiber waste. The U.S.
Department of Energy proposed that by 2020 at least 10 % of the chemical-
based products should be produced from lignocellulose, with that value increased
to 50 % in 2050. In 2030, biomass should provide 5 % of the electricity, 20 %
of transportation fuels, and 25 % of chemicals, equivalent to 30 % of current oil
consumption in the United States. In order to realize this target, a billion tons of dry
biomass feedstock would be consumed annually, five times the current consumption
[
30
,
31
]. This indicates the transition of fuel and chemical industries from the
nonrenewable hydrocarbon era to the renewable carbohydrate era [
32
]. From an
environmental perspective, the large biomass upconversion process has a slight
effect on the balance between the various nature systems because that biomass can
constitute an active basic element of Earth's ecosystem. In the growth of biomass,
it absorbs CO
2
through photosynthesis, and the production and utilization process
constitutes closed circulation of CO
2
[
33
]. Therefore, the biomass-based industrial
structure is sustainable.
In recent years, with energy shortages and environmental problems, China has
come up with several policies to support and protect the development of biomass
energy and the biochemical industry. The
Twenty-First Centenary Agenda of China:
White Paper on the Population, Environment and Development of Twenty-First
t
Century China
clearly pointed out that to achieve rapid economic development, it is
necessary to put development and utilization of new energy and renewable resources
into the national energy development strategy preferentially and strengthen the
development and utilization technologies of biomass-based energy, especially
clean liquid fuels from biomass. China's Renewable Energy Law was formally
implemented in January 1, 2006, and prescribed in a legal form that 5 % of
primary energy in 2010 should be generated from renewable energy, and that this
proportion would reach 10 % in 2020. The government not only arranged the overall
industrial development of biomass but also provided tax support policies [
34
,
35
].
It is not difficult to understand that, in the evolution of human material, natural
lignocellulose will become the common substitute for the chemical and fermentation
industries. The comprehensive utilization of natural lignocellulose in biotechnology
will reconstruct the traditional industries relying on grains as a raw material and
promote the strategic transfer of the chemical industry.
