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, ph:970-491-4770 Microalgae represents a promising feedstock due to inherent advantages such as high solar energy efficiencies, large lipid fractions, and utilization of various waste streams including industrial flue gas. This study directly evaluates and compares the economic viability of biomass production from two different open cultivation platforms, 1) algal turf scrubbers and 2) open raceway ponds. Modular sub-process models were developed and leveraged for the economic comparison of the systems on the metrics of harvested biomass. The system boundary was expanded to include downstream processing for the production of renewable diesel through thermochemical conversion for a comparison of the production platforms on a cost per gallon of fuel. Economic results of the two production pathways show a biomass production cost for the algal turf scrubber of $510 tonne-1 and $8.34 per gallon for fuel. Open raceway pond results give a biomass cost of $673 tonne-1 and a fuel cost of $6.27 per gallon. Sensitivity analysis show productivity and culture stability to be critical factors in the economic viability. Multiple scenarios are presented with baseline results directly compared to literature and highlight the need for robust growth modelling.

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.

This article reports on a simulation and scenario analysis of Chinese passenger vehicle growth and resulting energy demand and CO 2 emissions. The model includes provincial level logistic growth functions with saturation levels representative of neighboring Asian economies, income growth measured in international dollars, and both estimated and literature-based income elasticities. Scenarios explore variation in key parameters, including income and population growth rates, elasticity income ranges, fuel economy, and vehicle saturation. Countrywide base case results estimate growth from 4.22 to 54.33 passenger vehicles per thousand people from 1995 to 2025. Resulting passenger vehicle oil demands and CO 2 emissions increase nearly 17-fold. (JEL R40, Q40, N70) * This is a revision of a paper presented at