Biofuels, Solar and Wind as Renewable Energy Systems_Benefits and Risks Episode 2 Part 1 pot

10 Biomass Fuel Cycle Boundaries and Parameters 237

The second parameter type is the individual parameters (pk’s and k’s discussed in

Section 10.2.2.2) unique to a given module Sub-activity. In the BFCM treatment,

Ycrop and Ybfp variability relationships are examined separately from the pk values.

10.2.2.1 Biomass Yield Parameters

For a given BFC:

Ncrop to bfp = Ycrop A Ybfp

Here Ncrop to bfp is the BFC net fuel production, Ycrop is the agriculture stage

biomass crop yield, A is the planted land area, and Ybfp is the biofuel production

stage yield. Another BFC general yield and biofuel energy relationship is:

Ebiofuel = Ncorn to bfp UEfuel e

Here Ebiofuel is the BFC created biofuel energy and UEfuel e is the biofuel useable

energy (see Section 10.3). Combining and rearranging these two equations:

Ebiofuel/A = Ycrop Ybfp UEbiofuel (10.1)

Ebiofuel/A is a measure of the BFC crop and biomass fuel production effi￾ciency in creating the biofuel. This equation enables biofuel yield evaluation (see

Section 10.4.1) at both the local/regional and national fuel cycle production lev￾els. Clearly gains in crop and process yields mean higher biofuel energy per acre

planted.

10.2.2.2 Template Parameters

For each template Activity, there is an assigned k value. This k value is used to index

the pk value assigned to that Activity and it’s associated Sub-activities. The pk value

and it’s uncertainty k are specific numerical values used in the analysis. Consider,

for example, in Template 1 (Table 10.1) under the Facilities Phase there is the Seed

Plant Sub-phase. It’s assigned Activity and associated Sub-activities index value is

k = 5. Therefore it’s numerical values used in an analysis are assigned to the p5

and 5 parameter in the BFCM equations discussed here (see also Section 10.4.2

for specific illustration) The pk’s are used to calculate the Smodule j value of interest:

Smodule j = fj(pk)

and the k’s are used to quantify the uncertainty (j) associated with that Smodule j

(see Section 10.2.4). The fj(pk) equations are typically simple summations for the

BFC’s but can be any mathematical relationship. The detail for a given Smodule j is

determined by the BFC scenario and associated module. Both the Smodule j value and

its’ j are used to quantifying and characterizing the BFC.

238 T. Gangwer

The general relationship applicable to each module is:

SBFC = m

j=1

Smodule j Uj Fj (10.2)

Here SBFC is the total value (e.g., energy, mass, volume) for the given BFC mod￾eled scenario made up of m modules; Uj is the land area planted, Biorefinery pro￾cessed biomass, or biofuel volume; and Fj is the scenario specified decimal fraction

factor used to evaluate a Uj variation (Fj = 1 if Uj held constant). Sections 10.4.2

and 10.4.3 present the application of this equation to energy and environmental

treatments respectively.

BFC yields, pk’s, and k’s values, which are annual numbers, are reported in vari￾ous units in the literature. In order to sum the Smodule j ‘s, the data must be normalize

to a common unit. In the current treatment the numerical values are normalized

to Btu/Acre. The conversion factors used were: 948.452 Btu/MJ, 0.2520 Kcal/Btu,

3.7854 L/Gal, and 2.471 Acre/Ha. The Biorefinery pk values were normalized to

Btu/Acre using each specific study crop and biofuel yields. The resultant Smodule 3

values are thus a function of these specific yields which introduces two sources of

variability into the analysis.

10.2.3 BFC Boundaries

A fundamental consideration is the establishment of the given BFC boundaries. As

is evident from the results shown in Fig. 10.1, the choice of boundaries can dra￾matically change results. It is important to clearly and concisely disposition what is

included in and excluded from the BFC.

The boundaries for a given BFC are established by using Templates 1, 2, and 3

(see Tables 10.1, 10.2, and 10.3 respectively) as the starting point. The three tem￾plates cover a broader range of BFC aspects than typically addressed. Their level

of Sub-activity breakout focuses on aspects needing explicate dispositioning. The

Sub-activities encompass materials, components, and facilities starting from natural

resources through fabrication and usage to disposal. The pk’s quantify aspects such

as raw material extraction (e.g., mining of coal and minerals, petroleum drilling),

materials fabrication (e.g., steel, fuel, fertilizer, farm equipment), construction (e.g.,

facilities, roads), operation (e.g., farming, storage, processing, transporting), and

waste management (e.g., discharges, emissions, equipment and facility replaced or

decommissioned).

The dispositioning (i.e., inclusion or exclusion) of a pk is a boundary decision.

The BFC modules enable capturing the justification, including quantification of the

impact, of Sub-activity exclusion. However, as evidenced in Fig. 10.1, Sub-activity

exclusion can result in important differences between models. Inclusion has the ad￾vantages of simplifying the description, facilitating cross model comparison and

evaluation, and minimizing the potential for underestimating (which is inherent to

BFC’s as a result of their cumulative parameter property).