Bioenergy co-products derived from microalgae biomass via thermochemical conversion – Life cycle energy balances and CO2 emissions

Thermochemical conversion of microalgal biomass into biofuels: A review

“…In conventional gasification, dry microalgae react with oxidizer, such as air, oxygen, and water or steam, in a partial oxidation environment at temperature range of 800-1000°C and pressure range of 1-10 bar (Khoo et al, 2013). In the entire reaction process, microalgae undergo several different reactions in a gasifier, including dehydration or drying, devolatilization or pyrolysis, combustion or oxidation, and gasification or reduction; the homogeneous water gas shift and methanation reactions as well as heterogeneous water gas and Boudouard reactions are also involved .…”

“…The carbon conversion of the microalga increased from 93% at 850°C to nearly 100% at 1000°C. Khoo et al (2013) carried out the gasification of Nannochloropsis sp. in a fixed-bed reactor at 850°C.…”

Life cycle cost optimization of biofuel supply chains under uncertainties based on interval linear programming

“…corn and wheat, and the performance is usually assessed by life cycle tools, such as life cycle energy and CO 2 analysis (Khoo et al, 2013;Khoo et al, 2011), life cycle energy efficiency and environment impact (Wang et al, 2013), life cycle assessment (Singh et al, 2010), and life cycle cost analysis (Luo et al, 2010;Resurreccion et al, 2012;Stoeglehner and Narodoslawsky, 2009). In other words, the total cost of biofuel is usually assessed in life cycle perspective, form the cultivation of grain, grain transport to bioethanol factory, biofuel production, and biofuel distribution to market.…”

Microalgae Oil: Algae Cultivation and Harvest, Algae Residue Torrefaction and Diesel Engine Emissions Tests

“…Previously (Khoo et al, 2013) reported a 78.82%, 18.44%, 6.74% solid, bio-oil and gas yields at 330°C while (Rizzo et al, 2013) pyrolized Chlorella spp and performed non isothermal TGA and reported a solid (char) yield of 29 wt%, liquid yield (34%) and 37% wt gas yield at 450°C. Khoo et al, (2013) reports higher solid yields even at higher temperatures principally because unlike this study. They evaluated the product yields on the basis of dry weight while this study did not factor the contribution of moisture content in the original microalgae residue.…”

“…These various processes include thermochemical processes such as pyrolysis, gasification (Rizzo et al, 2013) and torrefaction. The process of torrefaction primarily results in solid products while pyrolysis gives off liquids containing acids, alcohols, aldehydes, esters, ketones sugars phenols, furans and gasification produces gases such as CO, CO 2 , H 2 and CH 4 (Khoo et al, 2013). In addition to biodiesel production the algae residue can be treated via torrefaction and used as a source of energy.…”