Bio-oil from mico algae

Micro algae
Microphytes or micro algae are microscopic algae, typically found in freshwater and marine systems. They are unicellular species which exist individually, or in chains or groups. Depending on the species, their sizes can range from a few micrometers (µm) to a few hundreds of micrometers. Unlike higher plants, micro algae do not have roots, stems and leaves. Micro algae, capable of performing photosynthesis, are important for life on earth; they produce approximately half of the atmospheric oxygen and use simultaneously the greenhouse gas carbon dioxide to grow photoautotrophically. Micro algae have higher photosynthetic efficiency, larger biomass, faster growth and higher content of components preferable for pyrolysis compared to those lignocellulosic materials and been suggested as very good candidates for fuel production.
Pyrolysis
Pyrolysis is a most efficient process for biomass conversion and it can compete and replace nonrenewable fossil fuels. Pyrolysis process can be tuned to yield char, liquid or gas as products. Liquid bio-oil obtained from pyrolysis can be readily stored or transported and has lower nitrogen and sulfur contents which favor its use as transportation fuel. In recent years fast pyrolysis process for biomass has attracted a great attention for maximizing liquid yields compared to slow pyrolysis as almost no flowing bio-oil products were directly produced from slow pyrolytic process.
Fast pyrolysis
Fast pyrolysis is a high temperature process in which biomass is rapidly heated in the absence of oxygen. The essential features of a fast pyrolysis process are very high heating and heat transfer rates, carefully controlled pyrolysis reaction temperature of around 500◦C, short vapor residence times of less than 2 s and rapid cooling of the pyrolysis vapor. Further a greater amount of high quality bio-oil can be continuously produced.
Mico algae bio-oil
Bio oil can be produced using fast pyrolysis from mico algae at temperature of 500◦C with a heating rate of 600◦Cs−1 and the sweep gas (N2) flow rate of 0.4m3/h and a vapor residence time of 2–3 s. The bio-oil yields vary from 17.5 to 23.7%. By continuously processing micro algae by the fast pyrolytic process high-quality bio oil can be obtained. The process is time saving and requires a lower energy input compared to the slow pyrolytic process. The contents of carbon and hydrogen of bio-oils from micro algae are higher than those of oil from wood. The bio-oils of micro algae are characterized by low oxygen contents with higher H/C ratios than the bio-oil from wood, sunflower bagasse and cotton straw and stalk. The decrease in the oxygen contents of bio-oils from micro algae compared to the bio-oil from higher plants such as wood is important because the high oxygen content is not attractive for the production of transport fuels Low oxygen content of mico algae bio-oils makes it more stable than the bio-oil from wood. Compared with the bio-oil from wood, the bio-oil from micro algae has higher heating value (about 1.4 times of that of wood), lower viscosity and lower density. These physical properties of bio-oil of micro algae make it more suitable for fuel oil use than pyrolysis oils from lignocellulosic materials.