img

FIGURE G-1 Chart showing the general power law dependence of a materials cost with production scale.
NOTES: As scale increases, price generally decreases. This is true both for fuel components and coproducts. The dotted line shows Szmant’s original curve and the solid line is inflation corrected to 2010.

Adapted from Szmant (1989). Reprinted with permission from Elsevier

Coproduct production is also a function of the lipid fraction (Eq. G-2):

img

where ρ is the density of the lipid fuel and ƒ is the lipid fraction, by weight, on a dry basis.

Extraction of the residual biomass has two major costs: one from electrical power and where one from nutrient loss. Biogas is commonly quoted as having a heating value of 650 BTU per cubic foot (DOE-EERE, 2011) or approximately 20 megajoule per kilogram. Electrical energy production is assumed to be 33 percent efficient (Davis et al., 2011) and 85 percent of the potential is captured. This means that the energy potential in the residual biomass from anaerobic digestion may be approximated as (Eq. G-3):

img

where α is the efficiency of electricity generation from biomass and β is a loss term, entered as 0.85. This is a coarse approximation and neglects the effect of excess power generation for sale. It assumes that all the power produced by the anaerobic digester system needs to



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement