BackgroundLignin is a highly abundant biopolymer synthesized by plants as a complex component of plant secondary cell walls. Efforts to utilize lignin-based bioproducts are needed.ResultsHerein we identify and characterize the composition and pyrolytic deconstruction characteristics of high-lignin feedstocks. Feedstocks displaying the highest levels of lignin were identified as drupe endocarp biomass arising as agricultural waste from horticultural crops. By performing pyrolysis coupled to gas chromatography-mass spectrometry, we characterized lignin-derived deconstruction products from endocarp biomass and compared these with switchgrass. By comparing individual pyrolytic products, we document higher amounts of acetic acid, 1-hydroxy-2-propanone, acetone and furfural in switchgrass compared to endocarp tissue, which is consistent with high holocellulose relative to lignin. By contrast, greater yields of lignin-based pyrolytic products such as phenol, 2-methoxyphenol, 2-methylphenol, 2-methoxy-4-methylphenol and 4-ethyl-2-methoxyphenol arising from drupe endocarp tissue are documented.ConclusionsDifferences in product yield, thermal decomposition rates and molecular species distribution among the feedstocks illustrate the potential of high-lignin endocarp feedstocks to generate valuable chemicals by thermochemical deconstruction.

CO 2 capture and recycle using microalgae was demonstrated at a coal-fired power plant (Duke Energy's East Bend Station, Kentucky). Using an in-house designed closed loop, vertical tube photobioreactor, Scenedesmus acutus was cultured using flue gas as the CO 2 source. Algae productivity of 39 g/(m 2 day) in June-July was achieved at significant scale (18,000 L), while average daily productivity slightly in excess of 10 g/(m 2 day) was demonstrated in the month of December. A protocol for low-cost algae harvesting and dewatering was developed, and the conversion of algal lipids-extracted from the harvested biomassto diesel-range hydrocarbons via catalytic deoxygenation was demonstrated. Assuming an amortization period of 10 years, calculations suggest that the current cost of capturing and recycling CO 2 using this approach will fall close to $1,600/ton CO 2 , the main expense corresponding to the capital cost of the photobioreactor system and the associated installation cost. From this it follows that future cost reduction measures should focus on the design of a culturing system which is less expensive to build and install. In even the most optimistic scenario, the cost of algae-based CO 2 capture is unlikely to fall below $225/ton, corresponding to a production cost of *$400/ton biomass. Hence, the value of the algal biomass produced will be critical in determining the overall economics of CO 2 capture and recycle.

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Effective removal of oil from metal surfaces utilizing aqueous solutions depends on the appropriate selection of surfactant(s) and pH conditions. In the experiments described in this paper, the detachment of oil droplets from a solid surface in aqueous surfactant solutions was studied and the variation in droplet shape, particularly contact angle, and the time required for droplet detachment were measured. In parallel, tests of oil removal from solid surfaces in an industrial ultrasonic bath were conducted under conditions similar to drop-detachment tests. Consistent trends were found in both types of tests; that is, conditions for which droplets detach more quickly correspond to conditions of greater oil removal in an ultrasonic bath. At high pH, faster drop-detachment (and oil removal) kinetics were observed when the oil-water interface was negatively charged (per -potential measurements). In contrast, at low-pH conditions, faster kinetics were observed when the solid-liquid interface was positively charged. The pH effect is consistent with a mechanistic model in which electrostatic interactions and solid-surface hydrophobicity changes due to surfactant adsorption onto solid surfaces under various pH conditions are considered. This study also demonstrated that single-drop-detachment tests and/ or -potential measurements are useful as simple, timesaving screening methods for selecting promising conditions for specific cleaning applications.

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