Current progress in lipid-based biofuels: Feedstocks and production technologies.

The expanding use of fossil fuels has caused concern in terms of both energy security and environmental issues. Therefore, attempts have been made worldwide to promote the development of renewable energy sources, among which biofuel is especially attractive. Compared to other biofuels, lipid-derived biofuels have a higher energy density and better compatibility with existing infrastructure, and their performance can be readily improved by adjusting the chemical composition of lipid feedstocks. This review thus addresses the intrinsic interactions between lipid feedstocks and lipid-based biofuels, including biodiesel, and renewable equivalents to conventional gasoline, diesel, and jet fuel. Advancements in lipid-associated biofuel technology, as well as the properties and applicability of various lipid sources in terms of biofuel production, are also discussed. Furthermore, current progress in lipid production and profile optimization in the context of plant lipids, microbial lipids, and animal fats are presented to provide a wider context of lipid-based biofuel technology.

Incorporation of Biosolids as Water Replacement in a Two-Step Renewable Hydrocarbon Process: Hydrolysis of Brown Grease with Biosolids.

ABSTRACT: The accumulating volumes of biosolids in lagoons worldwide have intensified the need to develop innovative wastewater treatment strategies. Here, we provide proof-of-concept for the incorporation of biosolids into the hydrolysis step of a two-step thermal conversion of lipids for production of renewable hydrocarbons, which can be utilized as renewable fuels. Brown grease was hydrolysed with biosolids or water at 260-280 °C for 60 min at a mass ratio of 1:1 feed to water or biosolids. The feedstock and products were characterized using various analytical techniques to compare the performance of biosolids to water. The results indicated that there was no significant difference in the degree of hydrolysis of brown grease when biosolids was used as water replacement. The fatty acids composition after hydrolysis when biosolids was used as a water replacement also remained largely unchanged. Hydrolysis of brown grease with biosolids could be achieved at pH ranging from 3.3 to 8.9, and at a lower than previously established temperature. Significantly, the rapid settling of solid material in biosolids observed after thermal hydrolysis of brown grease may reduce the necessity of biosolids settling lagoons. Thus, incorporation of biosolids into a lipid hydrolysis-pyrolysis process may simultaneously benefit the biofuel and waste management sectors.

Pyrolysis of fatty acids derived from hydrolysis of brown grease with biosolids.

The escalating generation of biosolids and increasing regulations regarding their safe handling and disposal have created a great environmental challenge. Recently, biosolids have been incorporated into the hydrolysis step of a two-step thermal lipid conversion process to act as water replacement in the production of renewable chemicals and fuels. Here, the hexane extract recovered from hydrolysis of biosolids, lipids from brown grease hydrolyzed using either water (control) or biosolids as a water replacement, was pyrolyzed at 410-450 °C for 2 h. The product distribution and composition were not significantly different when biosolids were used to hydrolyze brown grease instead of water. The liquid product consisted mainly of alkanes, alkenes, aromatics, and cyclic compounds similar to those in petroleum-derived liquid fuels. However, the use of biosolids as a water substitute resulted in a significant increase in sulphur content of the pyrolysate, which will necessitate processes to reduce the sulphur content before or after pyrolysis. Nevertheless, the pathways proposed in this paper are considered as potentially economically viable approaches to not only resolve the issues associated with disposal of biosolids but also to produce renewable hydrocarbons for fuel and chemical applications. Graphical abstract.

Enzymatic modification of egg lecithin to improve properties.

This research studied the enzymatic modification of egg yolk phospholipids and its effect on physicochemical properties. Egg yolk lipids were extracted with food grade ethanol and egg phospholipids (ePL) produced by deoiling with acetone. Vegetable oils were used to interesterify ePL utilizing Lipozyme®: sn-1,3 specific lipase. The enzymatic interesterification resulted in a single phase liquid product, whereas simple blending of the ePL and vegetable oil resulted in a product with two phases. In addition solid fat content decreased by 50% at -10°C and 94% at 35°C when compared with egg yolk lipids extract. A decrease in melting temperature resulted from the interesterification process. Interesterification improved emulsion stability index when used as an emulsifier in oil-in-water emulsion and compared to the native and soy lecithin. Enzyme reusability test showed retention of 63% activity after 10 cycles. Overall, the properties of native egg phospholipids were significantly enhanced in a potentially useful manner through interesterification.

Two-stage thermal conversion of inedible lipid feedstocks to renewable chemicals and fuels.

The aim of this work was to study the conversion of inedible, low cost lipid feedstocks to renewable hydrocarbons using a two stage thermal hydrolysis-pyrolysis method. Beef tallow, yellow grease, brown grease and cold pressed camelina oil were first hydrolyzed and the fatty acids produced were recovered and pyrolyzed in batch reactors. The pyrolysis products were identified and quantified using gas chromatography and mass spectrometry. The pyrolysis product yields were similar for all the feedstock used with the organic liquid fraction (OLF) accounting for 76-80% of the product. The OLF consisted predominantly of n-alkanes. Approximately 30% OLF constituted a gasoline-equivalent fraction and 50% a diesel fraction. Other fuel property test showed that the OLF met the specifications set out by the Canadian general standards board. This research demonstrated a novel two-stage thermal hydrolysis-pyrolysis conversion method for producing OLF from inedible and low-value lipids.

Two-step thermal conversion of oleaginous microalgae into renewable hydrocarbons.

The aim of this study was to evaluate the conversion of microalgal biomass to renewable chemicals and fuels through a two-step reaction and separation process. High density Chlorella protothecoides culture with 40% lipid accumulation (dwb) was produced in 10 L bioreactors and hydrolyzed in batch stainless steel reactors under subcritical conditions. After hydrolysis, fatty acids free of sulfur and low in nitrogen and salts, were recovered by hexane extraction. The fatty acids were pyrolyzed at 410°C for 2h under N2 yielding n-alkanes, α-olefins and internal olefins and low molecular weight fatty acids. This study demonstrated the direct conversion of microalgal biomass into valuable platform chemicals and fuels compatible with the existing industrial hydrocarbon infrastructure.