David D. McLean

Bio: David D. McLean is an academic researcher from University of Ottawa. The author has contributed to research in topics: Biodiesel & Biodiesel production. The author has an hindex of 11, co-authored 17 publications receiving 3452 citations.

Acid-catalyzed production of biodiesel from waste frying oil

Abstract: The reaction kinetics of acid-catalyzed transesterification of waste frying oil in excess methanol to form fatty acid methyl esters (FAME), for possible use as biodiesel, was studied. Rate of mixing, feed composition (molar ratio oil:methanol:acid) and temperature were independent variables. There was no significant difference in the yield of FAME when the rate of mixing was in the turbulent range 100 to 600 rpm. The oil:methanol:acid molar ratios and the temperature were the most significant factors affecting the yield of FAME. At 70 °C with oil:methanol:acid molar ratios of 1:245:3.8, and at 80 °C with oil:methanol:acid molar ratios in the range 1:74:1.9–1:245:3.8, the transesterification was essentially a pseudo-first-order reaction as a result of the large excess of methanol which drove the reaction to completion (99±1% at 4 h). In the presence of the large excess of methanol, free fatty acids present in the waste oil were very rapidly converted to methyl esters in the first few minutes under the above conditions. Little or no monoglycerides were detected during the course of the reaction, and diglycerides present in the initial waste oil were rapidly converted to FAME.

A comparison of attenuated total reflectance-FTIR spectroscopy and GPC for monitoring biodiesel production

Abstract: Gel permeation chromatography (GPC) and attenuated total reflectance (ATR)-FTIR spectroscopy were used to monitor the products of transesterification of waste frying oil in methanol to FAME or biodiesel. To evaluate the reliability and reproducibility of each method, quantitative analyses of mixtures of standards (TG, DG, MG, FAME, and glycerol) as well as lipid products of transesterification were carried out. The reproducibility of each method was found to be within ±1–5%. The differences between the results of the two methods were less than ±2%. The GPC method showed good separation of the intermediate products MG and glycerol from the TG starting material and FAME, but DG were not completely separated from TG, GPC gave good quantitative results for MG and FAME, but the TG and DG analyses required correction, depending on the mole ratio of TG/DG. In contrast, ATR-FTIR spectroscopy could only give quantitative data for the sum of TG+DG+MG.

Carbon-Negative Biofuels from Low-Input High-Diversity Grassland Biomass

Abstract: Biofuels derived from low-input high-diversity (LIHD) mixtures of native grassland perennials can provide more usable energy, greater greenhouse gas reductions, and less agrichemical pollution per hectare than can corn grain ethanol or soybean biodiesel. High-diversity grasslands had increasingly higher bioenergy yields that were 238% greater than monoculture yields after a decade. LIHD biofuels are carbon negative because net ecosystem carbon dioxide sequestration (4.4 megagram hectare(-1) year(-1) of carbon dioxide in soil and roots) exceeds fossil carbon dioxide release during biofuel production (0.32 megagram hectare(-1) year(-1)). Moreover, LIHD biofuels can be produced on agriculturally degraded lands and thus need to neither displace food production nor cause loss of biodiversity via habitat destruction.