Biomedical Engineering Reference
In-Depth Information
TABLE 15.5 Emission Specifications of Some Power Plants in the State of Massachusetts, USA
Particulate
matter, kg/GJ
Power plant
Fuel type
CO 2 , kg/GJ NO x , kg/GJ
Boardman (PGE)
Coal
287.5
0.107
0.019
Mount Tom Power Plant
Coal
227.3
0.189
0.025
Pioneer Valley Energy Center
Natural gas
99.3
0.007
0.004
Russell
Biomass wood
400.9
0.124
0.054
Pioneer Renewable Energy
Biomass wood
358.7
0.110
0.034
Palmer Renewable Energy (planned but
dropped for greenwood instead)
Construction
and demolition
debris
393.7
0.112
0.022
bio-products. The net effect is that solar energy and atmospheric carbon dioxide are con-
verted to energy and materials that are utilized by humans.
Utilization of forest materials imparts a price or impact on the environment. A change
in sustainable state is expected. CO 2 is CO 2 , whether it is from fossil or biogenic. Fossil
energy sources are dense in energy content. Tabl e 15. 5 shows some environmental factors
of energy production (electricity generation by burning fuel) from fossil source and
woody biomass. Both the higher efficiency and denser energy content of the raw materials
have contributed to much lower CO 2 emission of fossil than wood. There is the appear-
ance of much higher carbon dioxide emission from woody biomass (nominally C H 2 O )
use due in part to the H 2 O generationwithoutheatgainbutwithaheatdrainforH 2 O
evaporation and heating to the operating temperature. In addition to the clear impact
of woody biomass use on CO 2 emission, there are hidden effects as well. Trees need to
be harvested for energy. Harvesting trees, in particular above ground biomass, affect
the forest ecosystem. Old-growth forest continues to sequestrate CO 2 from atmosphere,
decaying sending mineralized carbon into soil. For forests between 15 and 800 years of
age, net ecosystem productivity (the net carbon balance of the forest including soils) is
usually positive. The mineralization of carbon and storage in soil is very slow and carbon
saturation limit below ground takes a longer time to occur. Old-growth forests accumulate
carbon for centuries and contain large quantities of it. However, that much of this carbon,
even soil carbon, will move back to the atmosphere if these forests are disturbed
(Luyssaert S., Schulze E-D., B ¨ rner A., Knohl A., Hessenm ¨ ller D., Law B.E., Ciais P.,
Grace J. Old-growth forests as global carbon sinks. Nature, 2008; 455:213 e 215). The
world's soils store more carbon than is present in biomass and in the atmosphere. Little
is known, however, about the factors controlling the stability of soil organic carbon stocks
and the response of the soil carbon pool to climate change remains uncertain. The supply
of fresh plant-derived carbon to the subsoil (0.6 e 0.8 m/depth) stimulates the microbial
mineralization of 2567
226 year-old carbon. In the absence of fresh organic carbon, an
essential source of energy for soil microbes, the stability of organic carbon in deep soil
Search WWH ::




Custom Search