Fourth generation biofuel (FGB) uses genetically modified (GM) algae to enhance biofuel production. Although GM algae biofuel is a well-known alternative to fossil fuels, the potential environmental and health-related risks are still of great concern. An evaluation of these concerns and accordingly devising appropriate mitigation strategies to deal with them are important to a successful commercialized production of FGB. While extensive research has been carried out on genetic modification and other technologies that aim to increase the productivity of algae strains, only a handful of them deal with the legislative limitations imposed on exploiting and processing GM algae. This paper examines this legislation and the mitigation strategies to meet potential risks associated with the exploitation and processing of FGB. Open-pond system is an economic solution for large-scale cultivation of microalgae; however, the concern regarding the health and environmental risk of cultivating GM algae and the associated stringent regulations is considered as the main barrier of FGB production. Disposal of the residue is another important issue that should be considered in FGB production. The byproducts obtained from energy extraction step and residual water from the harvesting process may contain plasmid or chromosomal DNA that may cause the risk of lateral gene transfer. Hence an appropriate mitigation practices should be used for replacement of the hazardous water residue and by-products with more environmentally friendly alternatives. The results obtained from several field testing projects for open-environment exploitation of GM algae show that under the various conditions used, there was no apparent proof to support possible horizontal gene transfer in release of GM algae.

Fourth generation biofuel: a review on risks and mitigation strategies

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

Application of nanoparticles in biofuels: an overview

Potential of fat, oil and grease (FOG) for biodiesel production: A critical review on the recent progress and future perspectives

Sustainability of the four generations of biofuels – A review

An algal feedstock or biomass may contain a very high oil fraction, and thus could be used for the production of advanced biofuels via different conversion processes. Its major advantage apart from its large oil fraction is the ability to convert almost all the energy from the feedstock into different varieties of useful products. In the research to displace fossil fuels, algae feedstock has emerged as a suitable candidate not only because of its renewable and sustainable features but also for its economic credibility based on the potential to match up with the global demand for transportation fuels. Cultivating this feedstock is very easy and could be developed with little or even no supervision, with the aid of wastewater not suitable for human consumption while absorbing CO2 from the atmosphere. The overall potential for algae applications generally shows that this feedstock is still an untapped resource, and it could be of huge commercial benefits to the global economy at large because algae exist in millions compared to terrestrial plants. Algae applications are evident for everyday consumption via foods products, non-foods products, fuel, and energy. Biofuels derived from algae have no impact on the environment and the food supply unlike biofuels produced from crops. However, any cultivation method employed could control the operating cost and the technicalities involved, which will also influence the production rate and strain. The scope of this paper is to review the current status of algae as a potential feedstock with diverse benefit for the resolution of the global energy demand, and environmental pollution control of GHG.

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Algae biofuel: Current status and future applications

This paper analyses the current trends in application of biomass-based fuels as a valid option for heavy-duty transport and discusses their technology readiness levels, cost and emphasizes on these fuels to be applied as drop-in fuels in heavy-duty engines to minimize potential green-house and toxic gas emissions. Through the extended analysis, this study has identified that ethanol could be the best candidate for application in heavy-duty transport in terms of sustainability, cost, and emission reduction. Ethanol can be used in high concentrations as an additive or blended with the conventional diesel, which still remains a main type of fuel for heavy-duty transport. However, in order to completely adapt ethanol-diesel fuel blends to heavy-duty transport, a few challenges have to be resolved. The first challenge is the phase separation when high-concentration ethanol is blended with neat diesel. This can be fairly resolved by using certain types of surfactants, which will not negatively affect, but on the contrary, result in engine performance improvements as well as emission reductions. The second challenge is the ignition quality of the blends, as the cetane number of an ethanol-diesel blend decreases when high-concentration ethanol is blended with neat diesel. This can be resolved by using certain types of cetane improvers, as highlighted in this paper. The third challenge is the sustainable production and supply of ethanol without competing with food producers and minor impact on the indirect land use. This challenge can be resolved by producing ethanol from different types of organic waste, wastewater and biomass. 

Biomass-based fuel blends as an alternative for the future heavy-duty transport: A review

Today, due to increased efficiency of heavy-duty diesel engines in the global industry, discussion of the performance of these motors, including higher efficiency and lower emissions, is very important. Several methods exist to meet these demands by the diesel engine. Piston bowl geometry deformation strategy is a reliable method for achieving pollutants of lower nitrogen oxides (Nox) and soot and higher yield. This paper has used Converge software to model the CFD for the performance of a Caterpillar 3401 engine with three different piston bowl geometries and various depths and chamfers for one of the geometries. The compression, inlet temperature, and pressure ratio are assumed to be constant. The results of efficiency and pollution of the engine are presented at all stages for analysis, comparisons, and conclusions. The results show that the cylindrical piston bowl geometry has a proper performance in terms of efficiency and the pollutions produced.

https://www.maptapublishing.com/index.php/mjmie/article/download/114/85

Oladapo Martins Adeniyi

Papers

Algae biofuel: Current status and future applications

Biomass-based fuel blends as an alternative for the future heavy-duty transport: A review

Numerical Investigation on the Effect of Piston Bowl Geometry on Combustion Characteristics of a Heavy-Duty Diesel Engine