1. Environmental Mathematics & Economics of Sustainability
The purpose of this study is to understand the
analysis of biomass options in the bio-refinery
industry. This industry, of international relevance, uses
plant matter to produce bio-fuel, feedstock, and
proteins. In a world that is searching for ways to
minimize the use of fossil fuels, there is a great sense
of importance in researching and developing new
methods in this field. To assess the biomass sources,
comparative units are derived using quantitative data
points. The conclusion from this study illustrates the
sources that are the most efficient and cost-effective to
be considered as primary sources of biomass.
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63,
• This study focuses on the bio-refinery
process; this is the process of extraction from
grasses and other biomasses in order to
provide alternative protein sources, while
allowing leftover residues to be used for
ethanol production. (4)
• So there is a decision to be made for any
company in the bio-refining industry: What
crop should be used as a source of biomass?
• A good choice crop as a source of biomass
would maximize profits and have the
following qualities: high yield, cold tolerance,
low environmental impact, resistance to pests
and diseases, ease of harvesting and handling,
and non-invasiveness. (5)
• In the procedure section of the display, data
on 4 different crops is analyzed in order to
determine which would potentially be the best
choice as a biomass source.
• More specifically, the computed Energy Use
Efficiency (EUE) values (or the ratio of
energy output : energy input) will be
compared, and the meaning of these
numerical values are discussed in the results
section.
Below are data points from a field experiment in Belgium
(using average values at the low fertilizer level) (6) :
Annul dry matter yield (DMY) [t/ha/yr]
Maize monoculture 17.0
Switchgrass 9.0
M x giganteus 21.1
Willow 12.5
Projected energy content (EC) [MJ*kg/DM]
Maize monoculture 17.105
Switchgrass 16.805
M x giganteus 18.21
Willow 17.985
Energy Input (EI) [GJ/ha/yr]
Maize monoculture 8.3
Switchgrass 1.7
M x giganteus 8.5
Willow 1.5
Primary Energy Yield (PEY) = DMY * EC
P. Net Energy Yield (PNEY) = PEY – EI
EUE = PNEY /EI
Computed values using above equations:
PEY [GJ/ha/yr]
Maize monoculture 290.785
Switchgrass 151.245
M x giganteus 384.231
Willow 224.8125
PNEY[GJ/ha/yr]
Maize monoculture 282.485
Switchgrass 149.545
M x giganteus 375.731
Willow 223.313
EUE [/]
Maize monoculture 34.03
Switchgrass 87.96
M x giganteus 44.20
Willow 148.875
• It is often difficult to compare how one resource
compares with another in an economic/business
perspective due to the many different variables at
any given time.
• There do, in fact, exist tools to help assess the
sustainability and economic value of products.
For example, the Life Cycle Analysis assessment
determines the overall environmental and
economic effects of a product “from cradle to
grave.” (1)
• Two additional tools that compute a
sustainability rating are the internationally
accepted Ecological Footprint, and the emerging
Waste Absorption Footprint. These tools,
however are not effective for influencing
business decisions from an economic
standpoint.(2)
• Still, the LCA is not standardized, therefore it is
difficult to compare information on different
products as results from separate studies. (3)
• Different decisions at different points in time
need to be influenced by an assessment of the
subjects that are relevant to that time period
In terms of energy use efficiency, it
is clear that willow has the highest; in
other words, willow provides the most bio-
energy with the least amount of energy
input. However, willow is only harvested
every 3 years, so that could be problematic
in keeping up with biomass demand. (4)
Switchgrass has a similar problem; while
its EUE looks quite high, its annual DMY
is significantly low. Miscanthus is
regarded to be a very promising candidate
for primary biomass supply for a few
reasons: it outperforms maize in DMY and
EUE (as well as many other crops from the
study that are not listed), and it would not
influence price change on food crops (as
over-cultivation of maize would). In the
future, the selection of crops for biomass
sources will definitely take into
consideration the rate of demand for bio-
refinery products as well as the amount of
energy that a company is willing to put
into growing said crop.
The College of Saint Rose
Department of Mathematics
Study by: Anthony Sauve
Supervisor: Dr. Amina Eladdadi