Sustainability: Humanity Perspective - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 777

the dangers associated with uranium mining, nor nuclear leaks. Unlike uranium, hydroelec-
tricity is also a renewable energy source.
While both hydroelectricity and wind electricity are renewable and sustainable, hydro-
electricity power plants have a more predictable load factor. If the project has a storage reser-
voir, it can be dispatched to generate power when needed. Hydroelectric plants can be easily
regulated to follow variations in power demand. The water storage reservoirs can have
a stabilizing effect on the “local climate”, improving biomass cycles in otherwise arid areas.
Unlike fossil-fueled combustion turbines, construction of a hydroelectric plant requires
a long lead time for site studies, hydrological studies, and environmental impact assessment.
Hydrological data up to 50 years or more are usually required to determine the best sites and
operating regimes for a large hydroelectric plant. Unlike plants operated by fuel, such as
fossil or nuclear energy, the number of sites that can be economically developed for hydro-
electric production is limited; in many areas, the most cost effective sites have already
been exploited. New hydro sites tend to be far from population centers and require extensive
transmission lines. Hydroelectric generation depends on rainfall in the watershed and may
be significantly reduced in years of low rainfall or snowmelt. Long-term energy yield may be
affected by climate change. Utilities that primarily use hydroelectric power may spend addi-
tional capital to build extra capacity to ensure sufficient power is available in low water
years. The most serious industrial accidents of all are also the water storage reservoirs or
the failure of the dams that forming the water storage reservoirs.
Biomass utilization also brings sustainable state change. Biomass has lower energy density
than fossils. Switching from fossil energy use to biomass use will see an increase in carbon
dioxide emission into the atmosphere. The increase in CO 2 emission is permanent. However,
there is a new sustainable state (or CO 2 level) that is reachable with biomass use. This is in
direct contrast to fossil energy use, where CO 2 emission is monotonous or a one-way traffic
from ground to atmosphere. There is no sustainable state in sight if fossil was continuously
been used. Apart from the sustainability impact, the depletion of fossil has made it impera-
tive to move away from its utilization.
Wood or forest biomass has the highest saturation standing biomass, while algae have the
highest production rate. Biomass production can be maximized by

X max X 0
t max

P X max ¼ r X j t¼t max ¼ (15.12)

i.e. the line originated from the initial point of standing biomass pinch at the accumulative
biomass growth (or standing biomass) curve. The maximum biomass production (harvest-
able) rate is at a much lower standing biomass level than saturation biomass. Biomass utili-
zation requires the gathering of biomass for processing. Denser or higher biomass capacity
at harvesting provides more opportunities and easier access to commercial processing facil-
ities. Therefore, high saturation biomass speciesaremoreadvantageousthanlowsatura-
tion biomass species due to the collection and transportation restrictions. The lower
standing biomass than saturation biomass also leads to more CO 2 staying in the atmo-
sphere when biomass is managed for utilization. Utilization of biomass does lead to
a sustainable state change.
Depending on the life span of the final product, the effect of forest biomass management
on the carbon storage can be either positive or negative as compared with an unmanaged