Chemical properties of biocrude oil from the hydrothermal liquefaction of Spirulina algae, swine manure, and digested anaerobic sludge

Life cycle comparison of hydrothermal liquefaction and lipid extraction pathways to renewable diesel from algae

“…Hydrothermal liquefaction (HTL) is a thermal process that converts biomass to several products including an oil portion with high heating value (Alba et al 2012;Biller and Ross 2011;Brown et al 2010;Duan and Savage 2011;Minowa et al 1995;Vardon et al 2011;Yu et al 2011). HTL offers several advantages compared to other approaches.…”

“…Many aspects of HTL have been studied including reaction temperature, pressure, retention time, feedstock species, influence of solvents, effects of catalysts, elemental distribution in products, and energy recovery. That work indicates that high temperatures (250°C to 350°C) and high pressures (approximately 10 to 20 MPa) are required and that the HTL oil can contain substantial amounts of nitrogen incorporated from the algal biomass (Alba et al 2012;Biller and Ross 2011;Brown et al 2010;Duan and Savage 2011;Minowa et al 1995;Valdez et al 2011;Vardon et al 2011;Yu et al 2011). From a life cycle perspective considering total energy demand and total emissions, these aspects suggest net energy demand may be higher than for lipid-extracted pathways because heat will be needed to establish the process conditions.…”

“…The HTL yield is defined here to be the mass of HTL oil recovered per dry mass of algae processed, sometimes written as a percentage. Numerous studies are reported in the literature and each reports different yields for the various fractions (Table 1) and different distributions of solids between oil and aqueous phases (Alba et al 2012;Biller and Ross 2011;Brown et al 2010;Duan and Savage 2011;Minowa et al 1995;Valdez et al 2011;Vardon et al 2011;Yu et al 2011). The product distribution may be influenced by many factors, including chemical composition of the algae, reaction temperature, retention time, feedstock solid content, and catalyst usage.…”

“…Their gas values do not include gases still dissolved in the product liquids and thus likely underestimate the gas yield. Vardon et al (2011) measured dissolved solids in the aqueous phase by filtration and evaporation and subtracted this from the feed to estimate gas yields. If the aqueous phase had light volatile compounds, they would have been lost from the aqueous phase when heated causing overestimation of gas yields, which may be why the Vardon yields are so much higher than the others in Table 1.…”

Gasification of Phycoremediation Algal Biomass

“…Combustion, gasification, pyrolysis, and hydrothermal liquefaction processes have been rigorously investigated on a wide variety of feedstocks ranging from wood and crop residues (Scott et al 1985;Van der Drift et al 2001;Sadaka 2013) to industrial and municipal wastes (Xu and Antal 1998;Larson et al 2000) and livestock manures (He et al 2000;Young and Pian 2003;Priyadarsan et al 2004). Bio-crude produced from the hydrothermal liquefaction of Spirulina algae has been characterized and compared with bio-crude produced from swine manure and digested sludge (Vardon et al 2011). Few investigations, however, have been carried out to examine atmospheric pyrolysis, gasification, and combustion of microalgae feedstocks.…”