Christopher J. Chuck

Oxidative Stability of Biodiesel Fuel

Biodiesel, the fatty acid alkyl esters derived from vegetable oils, animal fats, or waste cooking oils, is an alternative to diesel fuel. One of the major technical issues with the use of biodiesel is its susceptibility to oxidation. Oxidation of biodiesel is a complex process which involves a number of mechanisms producing an array of chemical components such as aldehydes, acids, ketones, and oligomeric compounds. These components in turn increase the viscosity and deposits in the fuel beyond acceptable levels. A variety of factors affect the level of these decomposition products as well as the rate of formation and decay. These factors include the temperature, presence of light, catalytic metals in the fuel system, sump oil, or storage containers, type of biodiesel, fatty acid profile, blend level, other contaminants, and presence of antioxidants. This paper examines the relevant factors influencing the biodiesel oxidative stability, the methods used to analyse and test biodiesel oxidation, as well as the effect that oxidation has on the fuels properties.

Co-production of bio-oil and propylene through the hydrothermal liquefaction of polyhydroxybutyrate producing cyanobacteria.

A polyhydroxybutyrate (PHB) producing cyanobacteria was converted through hydrothermal liquefaction (HTL) into propylene and a bio-oil suitable for advanced biofuel production. HTL of model compounds demonstrated that in contrast to proteins and carbohydrates, no synergistic effects were detected when converting PHB in the presence of algae. Subsequently, Synechocystis cf. salina, which had accumulated 7.5wt% PHB was converted via HTL (15% dry weight loading, 340°C). The reaction gave an overall propylene yield of 2.6%, higher than that obtained from the model compounds, in addition to a bio-oil with a low nitrogen content of 4.6%. No propylene was recovered from the alternative non-PHB producing cyanobacterial strains screened, suggesting that PHB is the source of propylene. PHB producing microorganisms could therefore be used as a feedstock for a biorefinery to produce polypropylene and advanced biofuels, with the level of propylene being proportional to the accumulated amount of PHB.

The impact of biodiesel blend ratio on vehicle performance and emissions

Abstract Biodiesel is synthesized via the transesterification of triglycerides contained within vegetable, animal, or waste oils. First-generation biofuels are not the solution to global transport energy needs; however, biodiesel does have a role to play in reducing greenhouse gas emissions from the transport sector, so long as necessary production can be achieved in a sustainable manner without negative impact on plant and animal biodiversity. The biodiesel content within diesel sold to consumers is set to increase in the future, with implications on vehicle fuel consumption, emissions, and base engine durability. This study examines the effects of increasing the biodiesel blend ratio on the performance and emissions of a production vehicle equipped with a common-rail direct-injection diesel engine, evaluated on a chassis rolls dynamometer, at various ambient temperatures. Results obtained show that reductions in engine-out carbon monoxide and hydrocarbon emissions do not always translate to lower tailpipe emissions as reduced exhaust gas temperatures at higher blend ratios lead to reduced catalyst conversion efficiencies and higher total cycle emissions. Catalyst conversion efficiencies for carbon monoxide and hydrocarbons over the New European Drive Cycle (NEDC) are reduced by 9–19 per cent (depending on the ambient temperature) for a 50:50 blend (B50) compared with the petroleum diesel (B0) baseline. Increasing the blend ratio caused a linear decrease in the vehicles maximum tractive force. This reduction was of the order of 5 per cent for a B50 blend at low vehicle speeds and 6–10 per cent at higher speeds, which is greater than would be expected on the basis of the differences in calorific values. Over the NEDC, the fuel consumption was found to increase with increasing blend ratio.

Renewable biofuel additives from the ozonolysis of lignin

In this investigation ozonolysis in the presence of ethanol was used to depolymerise lignin, resulting in a low conversion of oxygenated aromatics over short reaction times, or a range of saturated esters over 24 h. Short chain oxygenates can be used as fuel additives, displacing a percentage of a hydrocarbon fuel while leading to improvement in some of the fuel properties. The utility of the resulting bio-oils was therefore assessed by blending with a range of fuels. Guaiacol, a potential antioxidant, was formed over short reaction times and was found to be completely miscible with low-sulphur petrol (ULSP), diesel, aviation kerosene and rapeseed methyl ester. The mainly aliphatic proportion of the bio-oil produced over 24 h could be blended with the fuels replacing a maximum of 12-17 wt.% of the hydrocarbon fuel.

The effect of functional groups in bio-derived fuel candidates

Interest in developing renewable fuels is continuing to grow and biomass represents a viable source of renewable carbon with which to replace fossil-based components in transportation fuels. During our own work, we noticed that chemists think in terms of functional groups whereas fuel engineers think in terms of physical fuel properties. In this Concept article, we discuss the effect of carbon and oxygen functional groups on potential fuel properties. This serves as a way of informing our own thinking and provides us with a basis with which to design and synthesize molecules from biomass that could provide useful transportation fuels.

Bioprospecting the thermal waters of the Roman baths: isolation of oleaginous species and analysis of the FAME profile for biodiesel production

The extensive diversity of microalgae provides an opportunity to undertake bioprospecting for species possessing features suited to commercial scale cultivation. The outdoor cultivation of microalgae is subject to extreme temperature fluctuations; temperature tolerant microalgae would help mitigate this problem. The waters of the Roman Baths, which have a temperature range between 39°C and 46°C, were sampled for microalgae. A total of 3 green algae, 1 diatom and 4 cyanobacterial species were successfully isolated into ‘unialgal’ culture. Four isolates were filamentous, which could prove advantageous for low energy dewatering of cultures using filtration.Lipid content, profiles and growth rates of the isolates were examined at temperatures of 20, 30, 40°C, with and without nitrogen starvation and compared against the oil producing green algal species, Chlorella emersonii. Some isolates synthesized high levels of lipids, however, all were most productive at temperatures lower than those of the Roman Baths. The eukaryotic algae accumulated a range of saturated and polyunsaturated FAMEs and all isolates generally showed higher lipid accumulation under nitrogen deficient conditions (Klebsormidium sp. increasing from 1.9% to 16.0% and Hantzschia sp. from 31.9 to 40.5%). The cyanobacteria typically accumulated a narrower range of FAMEs that were mostly saturated, but were capable of accumulating a larger quantity of lipid as a proportion of dry weight (M. laminosus, 37.8% fully saturated FAMEs). The maximum productivity of all the isolates was not determined in the current work and will require further effort to optimise key variables such as light intensity and media composition.

Upgrading biogenic furans : blended C10–C12 platform chemicals via lyase-catalyzed carboligations and formation of novel C12 – choline chloride-based deep-eutectic-solvents

Benzaldehyde lyase (BAL) results in an efficient biocatalyst for the umpolung carboligation of furfural, HMF, and mixtures of them, leading to blended C10–C12 platform chemicals. Subsequently, the mixing and gentle heating (<100 °C) of the formed hydroxy-ketone with choline chloride leads to the formation of a novel biomass-derived deep-eutectic-solvent.

Optimizing the lipid profile, to produce either a palm oil or biodiesel substitute, by manipulation of the culture conditions for Rhodotorula glutinis.

Background: Lipids are an increasingly important chemical feedstock for the manufacture of biofuels, bioplastics, care products and as a food source. Developing sustainable sources of lipids, derived from oleaginous microbes, is therefore a key scientific challenge. Methodology: Design of Experiments was used to optimize the lipid production and lipid profile. Results: Here we successfully apply Design of Experiments to optimize the lipid profile in Rhodotorula glutinis to tailor the fatty acid profile. A high culture temperature and high nitrogen ratio yielded a mainly monounsaturated oil, while low temperatures and high glucose loadings gave a more saturated profile. Conclusions: On transesterification, the oil high in monounsaturated esters yielded biodiesel with fuel properties akin to rapeseed methyl ester, whereas the oil high in saturates was found to be suitable as a substitute for palm oil.

Quantifying the Effects of Biodiesel Blend Ratio, at Varying Ambient Temperatures, on Vehicle Performance and Emissions

A number of studies have been carried out examining the impact of biodiesel blend ratio on vehicle performance and emissions, however there is relatively little data available on the interaction between blend ratio and reduced ambient temperatures over the New European Drive Cycle (NEDC). This study examines the effects of increasing the blend ratio of Rapeseed Methyl Ester (RME) on the NEDC fuel consumption and tailpipe emissions of a vehicle equipped with a 2.0 litre common rail diesel engine, tested on a chassis dynamometer at ambient temperatures of 25, 10 & -5°C. This study found that under low temperature ambient conditions increasing blend ratios had a significant detrimental effect on vehicle particulate emissions reversing the benefits observed at higher ambient temperatures. Blend ratio was found to have minimal impact on hydrocarbon emissions regardless of ambient temperature while carbon monoxide and NOx emissions were found to increase by up to 20% and 5.5% respectively. Fuel consumption rose by 5% for a B50 blend - a larger than expected increase when considering differences in calorific values alone.

Liquid transport fuels from microbial yeasts – current and future perspectives

Global transportation is one of the major contributors to GHG emissions. It is essential, therefore, that renewable, carbon neutral fuels are developed to reduce the impact of this sector on the environment. Yeasts, especially Saccharomyces cerevisiae, are key to transforming renewable bioresources to fuels that can be used with little adaption to the current transport infrastructure. Yeasts demonstrate a large diversity that produces a great metabolic plasticity; as such, yeasts are able to produce a range of fuel-like molecules including alcohols, lipids and hydrocarbons. In this article the current and potential fuels produced through fermentation, the latest advances in metabolic engineering and the production of lipids suitable for biodiesel production are all reviewed.