Nutrient Flows and Quality of Bio-crude Oil Produced via Catalytic Hydrothermal Liquefaction of Low-Lipid Microalgae
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Nutrient Flows and Quality of Bio-crude Oil Produced via Catalytic Hydrothermal Liquefaction of LowLipid Microalgae Guo Yu & Yuanhui Zhang & Bin Guo & Ted Funk & Lance Schideman
# Springer Science+Business Media New York 2014
Abstract Five heterogeneous and two alkaline catalysts were applied into the hydrothermal liquefaction (HTL) of Chlorella pyrenoidosa, a low-lipid microalgal species. The effects of catalysts on the bio-crude oil yield were more substantial at 280ºC (bio-crude oil yield was increased by 10 %) than at 240ºC although bio-crude oil formation had already occurred at the low temperature. At 240ºC, additions of catalyst could improve the boiling point distribution of bio-crude oil. At 280ºC, addition of alkaline catalysts increased the fractions of compounds with high boiling points due to the formation of nitrogen and oxygen heterocyclic compounds. The majority of nitrogen (59∼68 %) and phosphorus (52∼86 %) content in the feedstock remained in the aqueous phase after the HTL process, implying the possible feasibility to reuse the nutrients in the post-HTL water. Carbon deposition and mineral mixing were found on the surface of metal catalysts after HTL. Keywords Hydrothermal liquefaction . Catalyst . Low-lipid microalgae . Environment-enhancing energy . Bio-crude oil
Introduction As a petroleum substitute, biofuel development has now been realized not only can help nations pursue energy independence but also mitigate the impact of human activities on G. Yu : Y. Zhang (*) : T. Funk : L. Schideman Department of Agricultural and Biological Engineering, Agricultural and Engineering Science Building, University of Illinois at Urbana-Champaign, 1304 West Pennsylvania Ave., Urbana, IL 61801, USA e-mail: [email protected] B. Guo Newmark Lab, Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 205 N. Mathews Ave., Urbana, IL 61801, USA
environment, such as reducing greenhouse gas emission. However, with high oil price, the goal to provide sufficient and cost-competitive feedstocks for the biofuel production without government subsidy has not been achieved yet [1]. Microalgae are considered as suitable feedstocks to produce the next-generation biofuel because of their fast growth rates and prolific yields. Additionally, growing algae have less impact on land use for food production compared with grain and other lignocellulosic biomass [2]. However, current lipidto-biodiesel technology primarily focuses on utilizing highlipid algae, which usually has lower biomass productivities than low-lipid algal strains [3, 4]. Due to the high production cost, algal cultivation for biofuel production alone is difficult to achieve a positive energy balance as well as cost effectiveness. One possible solution to decrease the production cost of algae is to combine the algal cultivation with current wastewater treatment process to reduce the energy cost [5]. On the other hand, algal species grown in wastewater usually have low lipid content; thus, they are not desirable to be
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