Biosynthesis of alkanes/alkenes from fatty acids or derivatives (triacylglycerols or fatty aldehydes).

This review summarizes the most relevant advances in the biological transformation of fatty acids (or derivatives) into hydrocarbons to be used as biofuels (biogasoline, green diesel and jet biofuel). Among the used enzymes, the fatty acid decarboxylase from Jeotgalicoccus sp. ATCC 8456 (OleTJE) stands out as a promising enzyme. OleTJE may be coupled in cascade reactions with metalloenzymes or reductases from the Old Yellow Enzymes (OYE) family to perform the hydrogenation of α-olefins into paraffins. The photodecarboxylase from Chlorella variabilis NC64A (CvFAP) is an example of coupling biocatalysis and photocatalysis to produce alkanes. Besides the (photo)decarboxylation of free fatty acids and/or triacyclglycerols to produce alkanes/alkenes, by enzymes has also been employed. The cyanobacterial aldehyde decarbonylase (cAD) from Nostoc punctiforme is an outstanding example of this kind of enzymes used to produce alkanes. Overall, these kinds of enzymes open up new possibilities to the production of biofuels from renewable sources, even if they have many limitations on the current situation. The possibilities of improving enzymes features via immobilization or coimmobilization, as well as the utilization of whole cells haves been also reviewed.

Screening biorefinery pathways to biodiesel, green-diesel and propylene-glycol: A hierarchical sustainability assessment of process.

Plant design implies the best choice among a set of feedstock-to-product process pathways. Multiple sustainability performance indicators can blur the decision, and existing sustainability assessment methods usually focus only on environmental life-cycle performance and corporate metrics or solely on the gate-to-gate process. It is relevant to incorporate integrated system analysis to address sustainability comprehensively. To this end, the Sustainable Process Systems Engineering (S-PSE) method was previously introduced to select the most sustainable feedstock-process-product configuration via four-dimensional indicators (environment, efficiency, health-&-safety, and economic), and then pinpoint the sustainability hotspots of the best design to unveil possible improvements. This work expands S-PSE by adding new features: (i) cradle-to-gate environmental assessment; (ii) composition of flowsheets; (iii) new indicators; (iv) statistical screening of indicators; and (v) 2030 Agenda compliance. A biorefinery case-study demonstrates S-PSE: to select the best pathway from soybean-oil, palm-oil, and microalgae-oil to biodiesel, green-diesel, and propylene-glycol. Firstly, statistical screening reduces the indicator set by 62%. Results evince all routes from microalgae-oil as economically unfeasible due to oil cost, despite superior environmental performance. S-PSE evinces palm-oil-to-biodiesel as the most sustainable due to lower cradle-to-gate emissions and manufacturing cost, with sustainability hotspots associated to hazardous methanol input and energy-intensive distillations. 2030 Agenda analysis also outlines palm-oil-to-biodiesel as best for 5 out of 10 Sustainable Development Goals linked to the reduced indicator set.

Genotoxicity of organic material extracted from particulate matter of alternative fuels.

Global demand for energy is rapidly increasing, and resources for the production of petroleum-based fuels are running out. For this, renewable fuels like biodiesel and hydrotreated vegetable oil biofuel are considered important alternatives to replace such fuels. In this study, we evaluated the in vitro genotoxicity effect on HepG2 cells of organic material extracted from particulate matter emissions of an engine fueled with conventional diesel or mixtures of diesel with 10% of biomass. The emissions were collected in two operational modes, 2410 rpm (slope simulation) and 1890 rpm (plane). Genotoxicity was evaluated through two methods, chromosomal aberration test and the alkaline comet assay. The former did not show any genotoxic effect, but the latter exhibited a statistically significant effect despite the operational mode of the engine and the concentration organic material extracted. In conclusion, regardless of the concentration of organic material extracted from particulate matter, the operational mode of the engine, or the fuel used, a significant damage of the DNA was found. In general, at the physicochemical level, a decrease in the amount of emissions of the used fuels is not directly related to a decrease in the genotoxicity potential.