Biodiesel from algae: challenges and prospects

Energy technologies emit greenhouse gases with differing radiative efficiencies and atmospheric lifetimes [1][2][3]. Standard practice for evaluating technologies, which uses the global warming potential (GWP) to compare the integrated radiative forcing of emitted gases over a fixed time horizon [4], does not acknowledge the importance of a changing background climate relative to climate change mitigation targets [5,6]. Here we demonstrate that the GWP misvalues the impact of CH 4 -emitting technologies as mid-century approaches, and we propose a new class of metrics to evaluate technologies based on their time of use. The instantaneous climate impact (ICI) compares gases in an expected radiative forcing stabilization year, and the cumulative climate impact (CCI) compares their integrated radiative forcing up to a stabilization year. Using these dynamic metrics, we quantify the climate impacts of technologies and show that high-CH 4 -emitting energy sources become less advantageous over time. The impact of natural gas for transportation, with CH 4 leakage, exceeds that of gasoline within 1-2 decades for a commonly-cited 3 W/m 2 stabilization target. The impact of algae biodiesel overtakes that of corn ethanol within 2-3 decades, where algae co-products are used to produce biogas and corn co-products are used for animal feed. The proposed metrics capture the changing importance of CH 4 emissions as a climate threshold is approached, thereby addressing a major shortcoming of the GWP for technology evaluation [7,8].Comparing the climate impacts of energy technologies is challenging because they emit differing types and quantities of greenhouse gases, most notably CH 4 and CO 2 , and these gases have dissimilar properties (Fig. 1a,b). Present approaches to technology evaluation use an equivalency metric to convert emissions to their CO 2 -equivalent value [1][2][3]9]. The most common metric is the global warming potential (GWP(τ )), which takes the ratio of the time-integrated radiative forcing of pulse non-CO 2 and CO 2 emissions over a fixed time horizon (τ ), typically 100 years. The GWP(100) was initially intended as a placeholder [10], in large part because of its sensitivity to the arbitrarily selected time horizon [7] (Fig. 1c,d), but it remains the standard metric for technology evaluation.

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“…8). These results suggest the importance of developing alternative low-CH 4 co-product processing techniques [26].…”

Section: Gasoline"mentioning

confidence: 99%

Climate impacts of energy technologies depend on emissions timing

Edwards

Trancik

2014

Nature Clim Change

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“…Algae biomass as its primary source of feedstock for biofuel conversion technologies has seen as flip side of fossil fuel (Scott et al, 2010). Microalgae, unlike fossil fuel, the CO 2 is taken out of the atmosphere and release oxygen in the environment by the algae cultivation (IEA, 2013;Koller et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of autotrophic and mixotrophic regimen Chlorella pyrenoidosa cells in various wastes water for its biochemical composition and biomass production

Dhull

Soni²,

Rahi

et al. 2014

Preprint

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The present study investigates the possibility of integrating an existing industrial large scale biomass production with the treatment of waste water in which a mixture of organic and inorganic rich pollutants was used as a medium. This study suggests that the replacement of a defined medium with a complete mixotrophic medium gives a significant statistical difference in terms of growth parameters i.e. biomass production and specific growth rate.The green microalga C. pyrenoidosa was cultivated under different mixotrophic conditions for evaluation of biomass production. Inorganic defined fog's medium supplemented, with raw dairy wastewater led to 1.37g/L biomass production in comparison to 1.2g/L obtained with pure glucose revealing 14.16% increase. The study also involves the supplementation of raw dairy wastewater as an organic carbon source in an inorganic medium comprising municipal treated water and reverse osmosis (RO) treated wastewater and attained 2.4g/L and 1.6g/L of biomass respectively, as compared to 0.3g/L and 0.16g/L obtained in the wastewaters alone revealing 700% and 900% increase respectively. Mixotrophic regimen cells as analyzed by a 2D Fourier transform infrared (FTIR) spectroscopy for its biochemical content revealed that fog's blended raw dairy waste (RDW) regimen cells had maximum

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“…Rising fossil fuel prices and dwindling reserves have led to renewed interest in developing alternative fuel sources (1)(2)(3)(4)(5)(6)(7). Although biomass from terrestrial plants can be processed and used as a feedstock for generating alcohols and other fuels (8) oil from photoautotrophically grown algae or seeds represents another fuel source, with algae offering distinct advantages over traditional oil crops (9,10).…”

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confidence: 99%

Three Acyltransferases and Nitrogen-responsive Regulator Are Implicated in Nitrogen Starvation-induced Triacylglycerol Accumulation in Chlamydomonas

Boyle

Page

Liu

et al. 2012

Journal of Biological Chemistry

377

422

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Background: Nitrogen-starvation and other stresses induce triacylglycerol (TAG) accumulation in algae, but the relevant enzymes and corresponding signal transduction pathways are unknown. Results: RNA-Seq and genetic analysis revealed three acyltransferases that contribute to TAG accumulation. Conclusion: TAG synthesis results from recycling of membrane lipids and also by acylation of DAG. Significance: The genes are potential targets for manipulating TAG hyperaccumulation.

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Biodiesel from algae: challenges and prospects

Cited by 999 publications

References 42 publications

Climate impacts of energy technologies depend on emissions timing

Climate impacts of energy technologies depend on emissions timing

Evaluation of autotrophic and mixotrophic regimen Chlorella pyrenoidosa cells in various wastes water for its biochemical composition and biomass production

Three Acyltransferases and Nitrogen-responsive Regulator Are Implicated in Nitrogen Starvation-induced Triacylglycerol Accumulation in Chlamydomonas

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