In recent decades, the concern over depletion of the world׳s petroleum reserves and environmental pollution has increased the demand to develop a renewable and environmental friendly fuel. Biodiesel, which mainly consists of Fatty Acid Methyl Esters (FAME) is one of the best substitutes for diesel fuel. Currently, vegetable oils, edible or non-edible, are the main resources of biodiesel. This review aims at providing comprehensive information and analyzes on biodiesel produced from edible and non-edible vegetable oils, their composition and specifications. Accordingly, the Fatty Acid (FA) profiles of 28 edible vegetable oils and 40 non-edible vegetable oils were collected. Their main specifications including sulfur content, density, viscosity, flash point, cloud point, pour point, cold filter plugging point, cetane number, iodine number, heating value, acid value and carbon residual before and after transesterification (vegetable oil and biodiesel, respectively) were analyzed in detail. Many researchers have developed prediction models to quantify biodiesel specifications to optimize its manufacturing and obtain biodiesel with the best specifications. Three factors that are especially influential are the fatty acids profiles, the degree of unsaturation within the FA structures and molecular weight. Accordingly, many models have been constructed on these features. There are also models that quantify the relationship between the biodiesel specifications and its thermodynamic properties or other specifications. Accordingly, the second part of this work was conducted on the existing prediction models. All the models were discussed along with their deviation in prediction.

A comprehensive review on properties of edible and non-edible vegetable oil-based biodiesel: Composition, specifications and prediction models

The increasing demand for energy and diminishing sources of fossil fuels have called for the discovery of new energy sources. The effective energy conversion process of biomass is able to fulfill energy needs. Among the advanced biomass conversion technologies, thermochemical processes hold considerable potential approaches and needed for optimization. Thus, this study presents a comprehensive review of the research and development on the effects of catalysts on the thermochemical conversion of biomass to determine the progress of catalytic thermochemical conversion processes. The effects of catalysts on torrefaction, pyrolysis, hydrothermal liquefaction, and gasification are highlighted. Aspects related to reaction conditions, reactor types, and products are discussed comprehensively with the reaction mechanisms involved in the catalytic effects. Hydrogenation and hydrodeoxygenation can occur in the presence of zeolite catalysts during fast pyrolysis while producing highly aromatic bio-oil. A heterogeneous catalyst in liquefaction increases the hydrocarbon content and decreases viscosity, acid value, and oxygenated compounds in the bio-oil. Thus, expanding and enhancing knowledge about catalyst utilization in the thermochemical conversion technologies of biomass will play an important role in the generation of renewable and carbon-neutral fuels.

Catalytic thermochemical conversion of biomass for biofuel production: A comprehensive review

Chemical compositions, properties, and standards for different generation biodiesels: A review

Camelina uses, genetics, genomics, production, and management

Review on transesterification of non-edible sources for biodiesel production with a focus on economic aspects, fuel properties and by-product applications

A review on hydrothermal co-liquefaction of biomass

An overview on performance characteristics of bio-jet fuels

A rapid growth in biodiesel production has naturally led to a surplus of crude glycerol generated. Due to the impurities present in the crude glycerol, expensive refining processes are often necessary in order for the crude glycerol to be used in the same applications as pure glycerol. As a result, the demand for crude glycerol is quite low, and biodiesel producers must find ways to dispose it. Disposal can be costly, detrimental to the environment, and wasteful. Exploration of crude glycerol utilization is of significance for not only reducing the negative impact on the environment but also for increasing the economic benefits of biodiesel production. This paper reviewed a number of valuable and practical applications of crude glycerol in the sector of renewable energy generation through processes such as fermentation, digestion, gasification, pyrolysis, liquefaction, combustion, and steam reforming. Studies indicated that an integration of crude glycerol to other systems for energy production is a promising option despite the impurities in crude glycerol, and some processes even benefit from their presence.

Jie Yang

Papers

A review on hydrothermal co-liquefaction of biomass

An overview on performance characteristics of bio-jet fuels

Utilization of the residual glycerol from biodiesel production for renewable energy generation

Hydrothermal liquefaction of biomass model components for product yield prediction and reaction pathways exploration

An evaluation of biodiesel production from Camelina sativa grown in Nova Scotia.