Introduction - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 6

Sustainable state 2

Quantity

Undisturbed state

Sustainable state 1

Human Interruption

low

Time

FIGURE 1.2 Change of sustainable state owing to human interruption.

1.4. BIOREFINERY

On a grand scale, sustainability is the basis of nature. Enforcing sustainability at the time-
scale of humanity is an insurance of our way of life to continue. Prior to the 1900s, agriculture
and forestry were the predominant sources of raw materials for energy, food and a wide
range of everyday commodities, and the human civilization depended almost entirely on
renewable materials. Humanity was restricted by the sustainable supply inefficiently har-
vested from the biomass, which drew energy from the sun. The industrial revolution has
brought a leap in the human civilization. Mass production of goods by machines dominates
our daily life. The industrial revolution was brought to mature by the development of
combustion engines and subsequent development of fossil energy and chemical industry.
Besides the more than doubling of useful biomass production/harvest, mankind has increas-
ingly taped into the large fossil energy reserves. At first the fossil chemicals were regarded as
waste and thus any use was welcomed. It soon became the cheapest chemical and energy
sources for the industrial revolution. As a result, our living standards have seen a leap. There
is no turning back to the primitive way of life in the past. However, fossil energy and chem-
ical sources are depleting. There is a critical need to change the current industry and human
civilization to a sustainable manner, assuring that our way of life today continues on the path
of improvement after the depletion of fossil sources. Our way of life exists only if sustain-
ability is maintained on a timescale no longer than our life span.
Biorefinery is a concept in analogous to a petroleum refinery whereby a raw material feed
(in this case, plant lignocellulosic biomass instead of petroleum) is refined to a potpourri of
products (on demand). In a biorefinery, lignocellulosic biomass is converted to chemicals,
materials, and energy that runs on the human civilization, replacing the needs of petroleum,
coal, natural gas, and other nonrenewable energy and chemical sources. Lignocellulosic
biomass is renewable as shown in Fig. 1.1 , in that plant synthesizes chemicals by drawing
energy from the sun, and carbon dioxide and water from the environment, while releasing
oxygen. Combustion of biomass releases energy, carbon dioxide, and water. Therefore,