Biodiesel: Fuel Composition, Vehicle

Emissions, and Potential Research

By: Jack Reed

April 29, 2016

CEE Graduate Seminar

Overview • Background

• Biofuels: What are they? • Biodiesel: A liquid transportation fuel, alternative to diesel

• FAME Composition and General Chemical Properties • Compositional effect on emissions

• Biodiesel Oxidative Instability of Biodiesel • Previous studies

• Research Hypothesis and proposed methods

Global Greenhouse Gas Emissions by Economic Sector

• Transportation plays a fairly major role in global total GHG emissions

• Vehicles directly emit: – CO2

– CH4

– Nitrogen oxides + hydrocarbons= O3

International Plant Protection Convention, 2014

Potential Solutions to Lower Production of GHG in the Transportation Sector?

1. Improve engine/vehicle technology Electric/hybrid vehicles

2. Decrease vehicle miles traveled (VMT)

3. Redesign city roadways to be less vehicle-dominated Bike paths, walking paths

4. More readily available public transportation Lower the number of cars on the road

5. Change the composition of the fuel

-fuels with a net GHG benefit that are alternatives to fossil fuels

Biofuels: What are they?

• Biofuels- biomass is converted directly into liquid fuel – Gasoline cars:

• Ethanol (starches and sugar from corn are converted to ethanol) – E85

– E10

– Heavy Duty Diesel trucks • Biodiesel

– Cellulosic ethanol- ethanol produced from leftover inedible parts of plants to be used as a liquid fuel source • Wood

• Stocks and leaves of the corn[1]

• Potential for the future

Background

Biodiesel: Liquid Transportation Fuel

Biodiesel: derived from Vegetable oils, animal fats, or waste vegetable oils (cooking grease)

– Specific type of biofuel

– Alternative to petroleum based diesel fuel (No.1 and No.2)

– Renewable fuel (declared by Dept. of Energy)

– Required Volumes of production

Completely miscible with diesel • Fatty Acid Methyl Esters

– FAMES provide similar characteristics of diesel fuel

– Ex: Methyl Linolenate – Shorthand: (C18:3)*

2-D

Image source: www.chemspider.com

Transesterification of Oils into Biodiesel

Figure 2. Transesterification of vegetable oils

Reagents 1.) Oils or fats containing triglycerides 2.) Methanol

• Stoichiometry: 1 mol of Triglyceride and 3 mol Methanol

1 mol 3 mol 1 mol 3 mol

Products 1.) Glycerin (by-product) 2.) FAMEs

• Stoichiometry: 1 mol of glycerin is produced, and 3 mol of FAME

(Barnard, et. al. [2])

Biodiesel Terminology Terms

– Feedstock- the source of which biodiesel is produced from (plants, animal fats, cooking grease) • Plants: soybean, rapeseed, jatropha, sunflower, ALGAE

– Blend (Bxx)- biodiesel is typically mixed on a volumetric basic with petrodiesel • Ex: B20- denotes 20% biodiesel in 80% ULSD (v/v) • B20 is the most commonly used blend [3]

– Unsaturation • Compound has double bonds

Acronyms WVO- Waste Vegetable Oil FAME- Fatty Acid Methyl Ester

• i.e. BIODIESEL • Most abundant are typically these [4] and :

– Palmitic acid (16:0) [4]

– Stearic Acid (18:0) [4]

(http://www.dieselnet.com)

Biodiesel is a complex mixture of multiple FAME species

• Vehicle emissions are heavily influenced by fuel composition • “What goes in must come out”

• Conservation of mass

Effect of Biodiesel Feedstock on NOx Emission Levels

Figure 5. Biodiesel feedstock effect on NOX emissions (EPA, 2002)[8]

What are the pollutants and associated health risks of vehicle emissions?[7]

• CO – Reduces flow of oxygen in the bloodstream

(increased risk for heart disease patients)

• NO2 – (NO+NO2) – Precursor of ozone

– O3 : Causes Eye irritation, Lung and respiratory damage

• SO2 – Damage to respiratory system

• Particulate Matter – Microscopic particles – *PM2.5- particles with diameter less than 2.5

micrometers – PM10- particles with diameter less than 10

micrometers

%Change in Emissions for biodiesel relative to Diesel

A closer look at EPA Particulate Matter results:

Studies were with

older vehicles

~1990 M.Y.

-Sulfur still in diesel

at this time

Summary: Why Biodiesel over Petrodiesel?

1. Renewable, nontoxic, eco-friendly and sustainable alternative to a traditional fossil fuel source

2. Completely miscible with petrodiesel- no vehicle modifications required

3. Reduces CO, HC, and PM emissions with the exception of Nox (EPA, 2002)

Most importantly: • Emissions can differ depending on composition of the fuel (feedstock

type used, etc.) – Assuming same vehicle operating conditions, engine type, fuel

injection system, road gradient, engine load, and drive cycle*

Biodiesel’s Main “Pitfall”: Oxidation Stability Index (OSI)

Air can enter tank through station refilling and biodiesel vapors do not

saturate the existing headspace

• Engine Performance Issues

• Degree of unsaturation is a factor (i.e, number of double bonds)

• Antioxidant additives improve stability, but are not mandated and only used when B100 doesn’t pass OSI by ASTM or EN standard test methods • a-Tocopherol is a natural antioxidant found

in biodiesel

Reactive Site

O2

+ +

ASTM65741 B100 Parameter Requirements

ASTM

American Society for Testing and Materials

Biodiesel, FAME Tests EN 14214-03 Biodiesel Test Comments ASTM D6751-07b

Density EN ISO 3675 or 12185 Hydrometer, Densitometer N/A

API Gravity or density N/A Not a specification requirement D1298 or D4052

Kinematic Viscosity @ 40OC EN ISO 3104 Methods are equivalent D445

Flash Point EN ISO 3679 Rapid equilibrium closed cup N/A

Flash Point N/A PM Closed cup D93

Sulphur content EN ISO 20846 or 20884 UV fluorescence, WDXRF N/A

Sulfur content N/A UV Fluorescence D5453

Carbon residue (on 10% Bottoms) EN ISO 10370 MCRT N/A

Carbon residue (whole sample) N/A MCRT D4530

Cetane number EN ISO 5165 Cetane Engine, Methods are equivalent D613

Derived Cetane Number N/A IQT, Alternative for D6751 D6890

Sulphated ash ISO 3987 Methods are equivalent D874

Water content EN ISO 12937 Coulometric Karl Fischer N/A

Water & sediment content N/A By Centrifuge D2709

Total contamination EN 12662 By Filtration N/A

Copper strip corrosion EN ISO 2160 Methods are equivalent D130

Oxidation stability EN 14112 Rancimat, 6 hour requirement N/A

Oxidation stability N/A Rancimat, 3 hour EN 14112

Acid value EN 14104 PP Colorimetric Titration N/A

Acid number N/A Potentiometric Titration D664

Iodine value EN14111 By Titration N/A

Linolenic acid methyl ester EN 14103 By GC. N/A

Polyunsaturated methyl esters EN 14103 By GC. N/A

Ester content EN 14103 By GC. N/A

Methanol content EN 141110 By GC. EN14110

Monoglyceride content EN 14105 / 6 By GC. N/A

Diglyceride content EN 14105 / 6 By GC. N/A

Triglyceride content EN 14105 / 6 By GC. N/A

Free glycerol EN 14105 / 6 By GC. N/A

Total glycerol EN 14105 / 6 By GC. N/A

Free & total Glycerin N/A By GC. D6584

Group I (alkali) metals Na, K EN 14108 Na, 14109 K AAS N/A

Group I (alkali) metals Na, K N/A ICP EN14538

Group II (alkali) metals Ca, Mg EN 14538 ICP EN14538

Phosphorus content EN 14107 ICP N/A

Phosphorus content N/A ICP D4951 Mod.

Cold Filter Plugging Point, OC EN 116 Cold Flow Test N/A

Cloud Point N/A Wax Appearance Temp. D2500

90% Recovered Distillation N/A Vaccum Distillation D1160

http://www.intertek.com/biofuels/en-astm-specs/

Does the fuel stay “In Spec” until it is used?

Biodiesel is produced in SPEC, but does it maintain oxidative stability while in the storage tanks?

CRC Report E112 (2015)

• Surveyed retail biodiesel samples (B06-B20 blend levels) from stations in Minnesota and Illinois

• Tested various parameters using ASTMD7467

• All met specification, except for one station where OSI failed below the 6hr requirement

In some instances, biodiesel does not stay “in spec”

• Alleman et. al (2011): took 40 samples that were gathered from all over the U.S (cold and warmer states)

– Results concluded that 18% of cold weather state samples (10th percentile minimum ambient temperature below 12oC) failed OSI

– As well, 57% of the warm state samples failed the ASTM OSI

Tang et. al (2008) • Sampled biodiesel blends sold at 24 retail stations (Detroit, MI)

– OSI failed for 45% of the samples

– B20, the most commonly used blend in the US, seems to be the blend with the greatest number of samples that near or actually do fail OSI

What are the emission effects of oxidized biodiesel?

• Knowing that composition of biodiesel changes emissions, and that there has been evidence of oxidized biodiesel at pumps… • And, although antioxidants can improve storage stability, it has been

documented that they can cause negative emission effects • Increased HC and CO emissions (Fattah et al. 2014)

• Karavakalis (2010): • European Diesel Passenger Car • observed an increase in OXY- and NITRO-PAHs • Used an oxidized blend that was naturally aged, and used two

different feedstocks for comparison

There are a limited number of studies on oxidized biodiesel emissions, and we currently do not know the exact condition the fuel is in when it is dispensed into fuel tank

PM Hypothesis • Since biodiesel inherently has more %oxygen (compared

to diesel), better combustion is experienced; hence decrease in PM

• I hypothesize that, with an oxidized blend, PM will

decrease as well – Reason 1: More oxygen containing species, better combustion

– COUPLED WITH -

– Reason 2: Fuel composition changes to lower molecular weight compounds (aldehydes, acids, ketones), that have higher vapor pressures, and would stay in gas phase

• PAH hypothesis- lower total PAH (due to more complete combustion), but OXY and NITRO-PAH species could increase in overall PAH composition

Experimental Methods (in the works)

• Obtain Fuel Samples – Contacted local ASTM B100

producer/distributor

• Analyze fuel samples by GCMS for detailed composition

• Perform controlled oxidation of fuel samples by Standard methods to varying OSI ranges that fail ASTM requirements • EN Rancimat instrument to

measure OSI • Test Acid Value and Peroxide

value parameters by AOCS titration methods for additional information about the quality of the fuel

• Identify oxidation products

“DIY” 893 Biodiesel Rancimat

Conductivity Cell

measurement

Volatiles

Enter DI

water

sltn

Metrohm 893 Rancimat Instrument

Heated fuel

sample

Air in

Experimental Methods • Run controlled oxidized and unoxidized samples

in the LDD engine in the TAQ lab

• Quantify PM results by GCMS

– Agilent 6890N/5973 GC-MS

• Relate particulate matter (PM) emission differences to the detailed chemical composition of the original biodiesel FAMEs and oxidation byproducts of the starting fuel.

Acknowledgements

• Advisor: Dr. Britt A. Holmén

• The University of Vermont Transportation Research Center

References

• [1] NREL. “Learning about Renewable Energy”. Web. 22 April 2016. <http://www.nrel.gov/learning/re_biofuels.html>

• [2] Didem Ozcimen and Sevil Yucel (2011). Novel Methods in Biodiesel Production, Biofuel's Engineering Process Technology, Dr. Marco Aurelio Dos Santos Bernardes (Ed.), InTech, DOI: 10.5772/18750.

• [3] US Department of Energy. Alternative Fuels Data Center. Web. 21 April 2016. <http://www.afdc.energy.gov/fuels/biodiesel_blends.html>

• [4] Hoekman et al. (2012) “Review of Biodiesel Composition, properties, and specifications.” ScienceDirect.

• [5] Shair et al. (2015). “Comparative Study of Diesel and Biodiesel on CI engine with Emphasis to Emissions- A Review.” Science Direct.

• [6] Environmental Protection Agency. “Criteria Air Pollutants.” Web. 20 April 16. <https://www.epa.gov/criteria-air-pollutants>

• [8] Environmental Protection Agency. “A comprehensive analysis of biodiesel impacts on exhaust emissions.” EPA420-P-02-001. October, 2002.

Happy to take any questions!

Biodiesel Degradation Monitoring System?