Ammonia is an important input into agriculture and is used widely as base chemical for the chemical industry. It has recently been proposed as a sustainable transportation fuel and convenient one-way hydrogen carrier. Employing typical meteorological data for Palmdale, CA, solar energy is considered here as an inexpensive and renewable energy alternative in the synthesis of NH 3 at ambient pressure and without natural gas. Thermodynamic process analysis shows that a molybdenum-based solar thermochemical NH 3 production cycle, conducted at or below 1500 K, combined with solar thermochemical H 2 production from water may operate at a net-efficiency ranging from 23-30% (lower heating value of NH 3 relative to the total energy input). Net present value optimization indicates ecologically and economically sustainable NH 3 synthesis at above about 160 tons NH 3 per day, dependent primarily on heliostat costs (varied between 90 and 164 dollars/m 2 ), NH 3 yields (ranging from 13.9 mol% to stoichiometric conversion of fixed and reduced nitrogen to NH 3 ), and the NH 3 sales price. Economically feasible production at an optimum plant capacity near 900 tons NH 3 per day is shown at relative conservative technical assumptions and at a reasonable NH 3 sales price of about 534 ± 28 dollars per ton NH 3 .

This article examines the empirical performance of alternative frontier estimators' ability to replicate a known underlying technology and economic measures such as multi-product and product-specific economies of scale, and economies of scope. A cross sectional Monte Carlo procedure to simulate data is used to evaluate a two-sided error system, an OLS system restricting errors to be above the cost frontier, the stochastic frontier method, and data envelopment analysis (DEA). The data are generated assuming a half-normal distribution, and a uniform distribution. Data were also simulated with single and two output firms. The DEA estimator was most robust in estimating the "true" cost frontier and associated economic measures including data sets without single output firms and less effected by distributional assumptions.

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Nonparametric cost frontier estimation and subsequent analysis of the relative efficiency of firms has historically been conducted without critically examining the shape of the cost frontier. The shape of the cost frontier has been examined using additional parametric estimation methods to recover potential cost savings from multiproduct and product-specific economies of scale. This paper presents and tests an approach to estimate multiproduct and product-specific economies of scale using data envelopment analysis. Data for the study are simulated assuming an underlying production technology. Nonparametric estimates of efficiency, multiproduct scale, product specific scale, and scope economies are compared to those of the assumed production technology. Results show that the nonparametric approach accurately estimates multiproduct economies of scale and product-specific economies of scale under alternative inefficiency distributional assumptions.JEL classifications: C13, C14, D20

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