Biofuels, fossil energy ratio, and the future of energy production

Two hundred years ago, much of humanity’s energy came from burning wood. As energy needs outstripped supplies, we began to burn fossil fuels. This transition allowed our civilization to modernize rapidly, but it came with heavy costs including climate change. Today, scientists and engineers are taking another look at

Life Cycle Analysis on Fossil Energy Ratio of Algal Biodiesel: Effects of Nitrogen Deficiency and Oil Extraction Technology

Life cycle assessment (LCA) has been widely used to analyze various pathways of biofuel preparation from “cradle to grave.” Effects of nitrogen supply for algae cultivation and technology of algal oil extraction on life cycle fossil energy ratio of biodiesel are assessed in this study. Life cycle fossil energy ratio ofChlorella vulgarisbased biodiesel is improved by growing algae under nitrogen-limited conditions, while the life cycle fossil energy ratio of biodiesel production fromPhaeodactylum tricornutumgrown with nitrogen deprivation decreases. Compared to extraction of oil from dried algae, extraction of lipid from wet algae with subcritical cosolvents achieves a 43.83% improvement in fossil energy ratio of algal biodiesel when oilcake drying is not considered. The outcome for sensitivity analysis indicates that the algal oil conversion rate and energy content of algae are found to have the greatest effects on the LCA results of algal biodiesel production, followed by utilization ratio of algal residue, energy demand for algae drying, capacity of water mixing, and productivity of algae.

OPPORTUNITIES FOR REDUCTION OF ENERGY CONSUMPTION IN THE LIFE CYCLE OF BIODIESEL OBTAINED FROM MICROALGAE SCENEDESMUS SP.

The article considers the opportunities for reduction of energy consumption in the life cycle of biodiesel obtained from microalgae oil. Results show that by introducing technical glycerol and substrate leftover after production of biogas into the microalgae growth media energy consumption can be significantly reduced. Production of biogas from de-oiled microalgae improves the energy balance of the life cycle of biodiesel obtained from microalgae oil. It is impossible to obtain fuel containing more energy than would be used in the process of production if microalgae for biodiesel production are cultivated in conventional growth media. Only by subjecting microalgal biomass for production of gaseous and liquid biofuel (biodiesel and biogas) the total energy consumption is lower and equals to 65802.03 MJt-1 than energy value of biofuel, i.e. 79083.32 MJt-1. In this case the fossil energy ratio (FER) for biodiesel reaches 1.2.

Sustainability study of biodiesel from Acrocomia totai

<p>The aim of this work is to quantify the life-cycle emissions in terms of CO₂ equivalent grams per megajoule of biodiesel produced from Acrocomia totai, a native oily seed from Paraguay, according to Directive 2009/28/EC. The other key point is to calculate the amount of energy invested to get a megajoule of biodiesel, by means of two different ratios: the EROI (Energy Return On Investment) and the FER (Fossil Energy Ratio).</p> <p>The LCA (Life Cycle Assessment) performed considers the following steps: harvesting, transportation, oil extraction from the fruits, transportation of the vegetable oil, oil conversion to biodiesel, distribution and combustion of the biodiesel. In this case, two different scenarios have been considered: Scenario 1: full distribution in Paraguay; Scenario 2: exportation to European countries, such as Spain.</p> <div> <p>The first set of results is the emissions in each step of the LC (Life Cycle) as well as the total emissions. The second set of results is the energy ratios. The GHG emission saving is 86.69 % with respect to the LC greenhouse emissions from Diesel EN-590 (with a default emissions value of 83.8 g CO_2e MJ_diesel-1) for Scenario 1 and 74.24 % for Scenario 2.</p> </div> <p>&nbsp;</p>