Scale-up economics for cultured meat.

This analysis examines the potential of "cultured meat" products made from edible animal cell culture to measurably displace the global consumption of conventional meat. Recognizing that the scalability of such products must in turn depend on the scale and process intensity of animal cell production, this study draws on technoeconomic analysis perspectives in industrial fermentation and upstream biopharmaceuticals to assess the extent to which animal cell culture could be scaled like a fermentation process. Low growth rate, metabolic inefficiency, catabolite inhibition, and shear-induced cell damage will all limit practical bioreactor volume and attainable cell density. Equipment and facilities with adequate microbial contamination safeguards have high capital costs. The projected costs of suitably pure amino acids and protein growth factors are also high. The replacement of amino-acid media with plant protein hydrolysates is discussed and requires further study. Capital- and operating-cost analyses of conceptual cell-mass production facilities indicate economics that would likely preclude the affordability of their products as food. The analysis concludes that metabolic efficiency enhancements and the development of low-cost media from plant hydrolysates are both necessary but insufficient conditions for displacement of conventional meat by cultured meat.

Effect of corn stover compositional variability on minimum ethanol selling price (MESP).

A techno-economic sensitivity analysis was performed using a National Renewable Energy Laboratory (NREL) 2011 biochemical conversion design model varying feedstock compositions. A total of 496 feedstock near infrared (NIR) compositions from 47 locations in eight US Corn Belt states were used as the inputs to calculate minimum ethanol selling price (MESP), ethanol yield (gallons per dry ton biomass feedstock), ethanol annual production, as well as total installed project cost for each composition. From this study, the calculated MESP is $2.20 ± 0.21 (average ± 3 SD) per gallon ethanol.

Uncertainty in techno-economic estimates of cellulosic ethanol production due to experimental measurement uncertainty.

BACKGROUND: Cost-effective production of lignocellulosic biofuels remains a major financial and technical challenge at the industrial scale. A critical tool in biofuels process development is the techno-economic (TE) model, which calculates biofuel production costs using a process model and an economic model. The process model solves mass and energy balances for each unit, and the economic model estimates capital and operating costs from the process model based on economic assumptions. The process model inputs include experimental data on the feedstock composition and intermediate product yields for each unit. These experimental yield data are calculated from primary measurements. Uncertainty in these primary measurements is propagated to the calculated yields, to the process model, and ultimately to the economic model. Thus, outputs of the TE model have a minimum uncertainty associated with the uncertainty in the primary measurements. RESULTS: We calculate the uncertainty in the Minimum Ethanol Selling Price (MESP) estimate for lignocellulosic ethanol production via a biochemical conversion process: dilute sulfuric acid pretreatment of corn stover followed by enzymatic hydrolysis and co-fermentation of the resulting sugars to ethanol. We perform a sensitivity analysis on the TE model and identify the feedstock composition and conversion yields from three unit operations (xylose from pretreatment, glucose from enzymatic hydrolysis, and ethanol from fermentation) as the most important variables. The uncertainty in the pretreatment xylose yield arises from multiple measurements, whereas the glucose and ethanol yields from enzymatic hydrolysis and fermentation, respectively, are dominated by a single measurement: the fraction of insoluble solids (fIS) in the biomass slurries. CONCLUSIONS: We calculate a $0.15/gal uncertainty in MESP from the TE model due to uncertainties in primary measurements. This result sets a lower bound on the error bars of the TE model predictions. This analysis highlights the primary measurements that merit further development to reduce the uncertainty associated with their use in TE models. While we develop and apply this mathematical framework to a specific biorefinery scenario here, this analysis can be readily adapted to other types of biorefining processes and provides a general framework for propagating uncertainty due to analytical measurements through a TE model.

Economic impact of total solids loading on enzymatic hydrolysis of dilute acid pretreated corn stover.

In process integration studies of the biomass-to-ethanol conversion process, it is necessary to understand how cellulose conversion yields vary as a function of solids and enzyme loading and other key operating variables. The impact of solids loading on enzymatic cellulose hydrolysis of dilute acid pretreated corn stover slurry was determined using an experimental response surface design methodology. From the experimental work, an empirical correlation was obtained that expresses monomeric glucose yield from enzymatic cellulose hydrolysis as a function of solids loading, enzyme loading, and temperature. This correlation was used in a technoeconomic model to study the impact of solids loading on ethanol production economics. The empirical correlation was used to provide a more realistic assessment of process cost by accounting for changes in cellulose conversion yields at different solids and enzyme loadings as well as enzyme cost. As long as enzymatic cellulose conversion drops off at higher total solids loading (due to end-product inhibition or other factors), there is an optimum value for the total solids loading that minimizes the ethanol production cost. The optimum total solids loading shifts to higher values as enzyme cost decreases.

Improved interatomic potentials for silicon-fluorine and silicon-chlorine.

Improved sets of empirical interatomic potentials for silicon-fluorine and silicon-chlorine are presented. The Tersoff-Brenner potential form has been reparameterized using the density-functional theory (DFT) cluster calculations of Walch. Halogenated silicon cluster energetics computed with DFT are, on average, within several tenths of an eV of the energies of the corresponding clusters with the reparameterized empirical potential for both Si-F and Si-Cl. Using the reparameterized Tersoff-Brenner potentials, molecular-dynamics simulations of F and Cl atom exposure to undoped silicon surfaces are in excellent agreement with published data on etch probability, halogen coverage at steady state, and etch product distributions.