Sustainability: Humanity Perspective - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 761

TABLE 15.4 Recycle Times and Productivities of Chemical/Energy Feedstock (Liu SJ, Woody Biomass: Niche
Position as a Source of Sustainable Renewable Chemicals and Energy and Kinetics of Hot-Water
Extraction/Hydrolysis. J. Biotech. Adv. 2010; 28: 563e582.)

Standing biomass,
tons/ha
or 10 L 1 kg/m 2

Biomass production,
tons/(ha year)
or 10 L 1 kg/m 2 /year Feed stock Recycle time

Algae 1 month 0.9 11.25

Agricultural crops 3 months e 1 year 4.5 2.93

Temperate grasses 1 year 7.2 2.70

Savanna 1 year 18.0 4.05

Shrubs 1 e 5 years 27.0 3.15

Tropical forest 5 e 25 years 202.5 9.90

Tropical season forest 5 e 25 years 157.5 7.20

Boreal forest 25 e 80 years 90.0 3.60

Temperate deciduous 10 e 50 years 135.0 5.40

Temperate evergreen 10 e 80 years 157.5 5.85

10 21 J) Oil, gas, and coal 280 million years (38.4 (0.1371 PJ/year)

occurs on the Earth, preserving a large amount of organic matter. Given the advanced forms
of life existing now, the chances of such an event occurring are unlikely. Nevertheless, the 280
million years rotation is far too long and the amount of possible reserves is negligible
compared to the recharge duration from a human use (or need) standpoint, even if mankind
could survive a fossil replenishment era. If fossil replenishment was possible without inter-
rupting the continuity of humanity, it would be renewable only if the utilization rate was no
greater than 0.1371 PJ/year or 4.348 MW, which was six or seven orders of magnitude too
small as compared to the current human needs. Thus, fossil resources in general are deemed
nonrenewable. Societal awareness of environmental impact as well as problems in the
stability and sustainability of the energy supply have made the development and implemen-
tation of bio-based chemicals and energy urgent and in the same time, more questions were
raised. Regional energy security and rural economies both benefit from a plant biomass-
derived chemical/energy economic base. Reverting to reliance on biomass as chemical and
energy source is thus our destiny.
Woody biomass is the most abundant organic source on Earth, with an annual production in
the biosphere of about 5.64

10 10 Mg-C (Field CB, BehrenfeldMJ, Randerson JTand Falkowski
P. Primary production of the Biosphere: Integrating Terrestrial and Oceanic Components.
Science. 1998; 281: 237 e 240). Of the 5.64 10 10 Mg-C biomass production each year, only 4.8%

10 9 Mg-C/year was utilized by mankind, including food (1.7 10 9 Mg-C), pulp,

or 2.7

10 9 Mg-C), and the rest as
clothing and chemicals (Thoen J. and Busch R. Industrial chemicals from biomass e industrial

paper, energy, furniture and construction materials (0.9