Emissions From Various Biodiesel Sources Compared to a Range of Diesel Fuels in DPF Equipped Diesel Engines

Abstract

The purpose of this study was to measure the impact of various sources of petroleum-based and bio-based diesel fuels on regulated emissions and fuel economy in diesel particulate filter (DPF) equipped diesel engines. Two model year 2008 diesel engines were tested with nine fuels including a certification ultra-low sulfur diesel (ULSD), local ULSD, high aromatic ULSD, low aromatic ULSD, and twenty percent blends of biodiesel derived from algae, camelina, soy, tallow, and yellow grease. Regulated emissions were measured over the heavy duty diesel transient test cycle. Measurements were also made of DPF-out particle size distribution and total particle count from a 13-mode steady state test using a fast mobility particle sizer. Test engines were a 2008 Cummins ISB and a 2008 International Maxx Force 10, both equipped with actively regenerated DPFs. Fuel consumption was roughly 2% greater over the transient test cycle for the B20 blends versus certification ULSD in both engines, consistent with the slightly lower energy content of biodiesel. Unlike studies conducted on older model engines, these engines equipped with diesel oxidation catalysts and DPFs showed small or no measurable fuel effect on the tailpipe emissions of total hydrocarbons (THC), carbon monoxide (CO) and particulate matter (PM). No differences in particle size distribution or total particle count were seen in a comparison of certification ULSD and B20 soy, with the exception of engine idling conditions where B20 produced a small reduction in the number of nucleation mode particles. In the Cummins engine, B20 prepared from algae, camelina, soy, and tallow resulted in an approximately 2.5% increase in nitrogen oxides (NOx) compared to the base fuel. The International engine demonstrated a higher degree of variability for NOx emissions, and fuel effects could not be resolved (p > 0.05). The group of petroleum diesel test fuels produced a range of NOx emissions very similar to that caused by blending of biodiesel. Test cycles where an active regeneration of the DPF occurred resulted in a nearly threefold increase in NOx emissions and a 15% increase in fuel consumption. The full quantification of DPF regeneration events further complicates the accurate calculation of fuel impacts on emissions and fuel consumption.

Properties and Performance of Levulinate Esters as Diesel Blend Components

“…Increasing the cetane number can reduce or eliminate the NO x increase from oxygenates in some cases. , This is because of the reduced ignition delay, which reduces the degree of premixed ignition/combustion and the size of the standing premixed autoignition zone, thereby reducing the effect of changing stoichiometry during these phases of combustion. In another study conducted on this engine, a higher cetane number fuel typically reduced NO x emissions, although the effect was not significant for cetane number differences of roughly 2 or lower …”

Use of the microalga Monoraphidium sp. grown in wastewater as a feedstock for biodiesel: Cultivation and fuel characteristics

“…Their data indicated little difference in NO emission with values of 970 ppm and 994 ppm at 1500 rpm for petrodiesel and B20, respectively. Another study saw NOx values increase 2.6% and 4.4% for algal B20 operated in sixcylinder, heavy-duty 250-kW and 246-kW engines, respectively, along with a corresponding 2% reduction in fuel efficiency [42]. It is possible that the variable NOx emissions measured for biodiesel from several feedstocks may also be related to engine test procedures, and can be ameliorated by adjusting fuel injection timing [43].…”

Evaluation of the Impacts of Biodiesel and Second Generation Biofuels on NOx Emissions for CARB Diesel Fuels

“…It should be noted that while the elimination of regenerations from the test matrix creates some limitations in extrapolating the results to in-use emissions, the complexity of designing a study to characterize fuel effects under regeneration conditions was beyond the scope of this study. 37 In general, the soy-based, animal-based and renewable diesel fuels were tested over UDDS, FTP, and 50 mph Cruise cycles, while the GTL fuel was only tested on the FTP. 38,39 Standard emissions measurements of NO x emissions were measured using a chemiluminescent analyzer.…”

“…In their study at a B20 level, they suggested the NO x increases for biodiesel with the 2008 Cummins ISB 340 were greater than those found in the broader literature, but they found no significant increases in biodiesel NO x emissions for the International MaxxForce engine. 37 Further study may be needed to see how prevalent or consistent these trends would be over a wider range of engine technologies.…”