Biodiesel from Low-Grade Animal Fats: Diesel Engine Performance

Energy & Fuels 2009, 23, 121–129

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Biodiesel from Low-Grade Animal Fats: Diesel Engine Performance and Emissions Magı´n Lapuerta,*,† Jose´ Rodrı´guez-Ferna´ndez,† Fermı´n Oliva,† and Laureano Canoira‡ Escuela Te´cnica Superior de Ingenieros Industriales, UniVersidad de Castilla-La Mancha, AVda. Camilo Jose´ Cela s/n, 13071 Ciudad Real, Spain, and Escuela Te´cnica Superior de Ingenieros de Minas, UniVersidad Polite´cnica de Madrid, Rı´os Rosas 21, 28003 Madrid, Spain ReceiVed June 19, 2008. ReVised Manuscript ReceiVed October 17, 2008

With the aim to evaluate the biodiesel performance and emissions of a feedstock with promising economic and sustainability perspectives, such as waste animal fat, two biodiesel fuels, one obtained from 100% animal fat and the other from 50% soybean oil/50% animal fat, were tested in a DI common-rail diesel engine. Blends [30 and 70% (v/v)] of these two biodiesel fuels with reference diesel fuel were also tested. The pressure drop across the fuel filter was measured, and for the pure animal fat biodiesel fuel, a large increase in pressure over 5 h was recorded, indicating a clogged filter. This poor filterability should be considered by biodiesel fuel manufacturers to decide about combinations of different feedstock or additivation. Brake thermal efficiency was not affected by the use of biodiesel fuels, for both pure and blended cases. A slight increase in fuel consumption was measured for all biodiesel fuels, and it was proportional to the heating value of the fuels. Biodiesel fuels reduced hydrocarbon emissions, smoke opacity, particulate matter, particle mean diameter, and total particle concentration, with the magnitude of these decreases depending upon the biodiesel fuel origin. NOx emissions were increased with the 50:50 animal fat and soybean oil compared to the reference diesel fuel but decreased with the pure animal fats, and combustion was advanced as the percentage of biodiesel fuel in the blend was increased.

1. Introduction Nowadays, renewable biodiesel fuels are the most promising alternative to partly replace fossil diesel fuel consumption. The use of alternative biodiesel fuels is being strongly promoted by the European Parliament, which established a biofuels market share target of 5.75% in 2010 and 10% in 2020.1 This promotion is mainly justified by the renewable character and the environmental advantages in terms of reduction in pollutant and CO2 emissions of biodiesel fuels, which has been extensively proven.2-5 Consequently, the production and use of biodiesel fuels is expected to noticeably increase in the next few years. However, in the case that these increasing quantities of biodiesel fuels come from non-used vegetable oils, it has been recently claimed that the biofuels promotion could derive in a shortage of raw materials for feed purposes and a steep rise of * To whom correspondence should be addressed: Escuela Te´cnica Superior de Ingenieros Industriales, Universidad de Castilla La-Mancha, Avda. Camilo Jose´ Cela s/n, 13071 Ciudad Real, Spain. Telephone: +(34) 926295431. Fax: +(34) 926295361. E-mail: [email protected]. † Universidad de Castilla-La Mancha. ‡ Universidad Polite ´ cnica de Madrid. (1) European Commission. Communication from the Commission to the European Council and the European Parliament: An Energy Policy for Europe, 2007 (available on-line at http://eur-lex.europa.eu/LexUriServ/site/ en/com/2007/com2007_0001en01.pdf). (2) Lapuerta, M.; Armas, O.; Rodrı´guez-Ferna´ndez, J. Prog. Energy Combust. Sci. 2008, 34, 198–223. (3) Graboski, M. S.; McCormick, R. L. Prog. Energy Combust. Sci. 1998, 24, 125–164. (4) Lapuerta, M.; Rodrı´guez-Ferna´ndez, J.; Agudelo, J. R. Bioresour. Technol. 2008, 99, 731–740. (5) Agarwal, A. K. Prog. Energy Combust. Sci. 2007, 33, 233–271.

food prices, which could lead to poverty in some regions.6,7 This situation could be avoided by the use of second-generation biodiesel fuels,8-10 but their associated technology is currently being developed. Therefore, different less-valuable feedstock should be considered, such as waste cooking oils/fats (known in the literature as yellow and brown greases11,12) and animal fats collected from supermarkets, slaughterhouses, etc. Both greases and animal fats represent a large share of the total oil and fat production, and their potential is increasing continuously.13 With regard to the animal fats, these are classified into three categories, according to their risk level, by the Regulation 1774/ 2002.14 Most of the animal fats used by different industries fall into category number 3, which is free of risk and has the wider (6) Trostle, R. Economic Research Service of the USDA. USDA’s World Agricultural Outlook Board, 2008; pp 1-29 (available on-line at www. ers.usda.gov). (7) International Fund for Agricultural Development (IFAD). Biofuel Expansion: Challenges, Risks and Opportunities for Rural Poor People (available on-line at http://www.ifad.org/events/gc/31/roundtable/biofuels. pdf). (8) Zabaniotou, A.; Ioannidou, O.; Skoulou, V. Fuel 2008, 87, 1492– 1502. (9) Abu-Jrai, A.; Tsolakis, A.; Theinnoi, K.; Cracknell, R.; Megaritis, A.; Wyszynski, M. L.; Golunski, S. E. Energy Fuels 2006, 20, 2377–2384. (10) Szybist, J. P.; Kirby, S. R.; Boehman, A. L. Energy Fuels 2005, 19, 1484–1492. (11) Goodrum, J. W.; Geller, D. P.; Adams, T. T. Biomass Bioenergy 2003, 24, 249–256. (12) Kinast, J. A. National Renewable Energy Laboratory, 2003; NREL/ SR-510-31460. (13) Canakci, M. Bioresour. Technol. 2007, 98, 183–190. (14) Regulation (EC) Number 1774/2002 of European Parliament and of the Council laying down health rules concerning animal byproduct not intended for human consumption. Available on line: http://eur-lex.europa.eu/ LexUriServ/site/en/consleg/2002/R/02002R1774-20070724-en.pdf

10.1021/ef800481q CCC: $40.75  2009 American Chemical Society Published on Web 12/03/2008

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availability. Other commonly used classification is based on the free fatty acids (FFAs) content of the animal fats, distinguishing low-, medium-, and high-grade (or quality) fat. High-grade animal fats, with a very low FFA content (below 2%), are used for the human and animal (mainly livestock) food and cosmetics industry. Their high prices (above 750 euros/ton) prevent them from being used as biodiesel fuel feedstock. Medium-grade fats have 3-5% FFA content and a sell price of 625 euros/ton, approximately, and they are mainly used for poultry fodder production. Finally, low-grade animal fats, with a FFA content above 5% and a sell price of 600 euros/ton, approximately, are used in both the fodder and biofuel industry. Sometimes, biodiesel fuel manufacturers also use blends of medium- and low-grade animal fats as feedstock to reduce their FFA content. It should be noticed that, during the production process of rendered animal fats, composed by several stages, such as crushing, cooking, draining, filtering, and depuration, the sulfur content of the animal fat product is progressively reduced. However, only after the final depuration stage, the sulfur content is low enough for biodiesel fuel production, because this element is limited in fuel quality normative. Moreover, the current high prices of most vegetable oils have encouraged the use of low-priced waste sources in biodiesel fuel plants. In fact, in the last few months, most of the Spanish plants that used vegetable oils as their raw material had no choice than to stop their production as a consequence of the high market prices.15 Only those plants that use waste cooking oils and/or animal fats, apart from those others that purchased large quantities of vegetable oils when prices were lower, are currently able to produce biodiesel fuels in Spain with a final sell price similar to that of fossil diesel fuel. With regard to sustainability, the new Draft Directive for the promotion of the use of energy from renewable sources,16 approved by the European Commission, establishes a mandatory minimum reduction of greenhouse gas emissions of 35% with respect to petroleum diesel fuel. The default value initially considered for this relative saving is 77% in the case of both waste cooking oil and animal fat biodiesel fuels, while the typical value (obtained in the Directive by reducing in 40% the CO2 emissions of the production processes) rises up to 83%. These values are the highest among all of the raw materials contemplated in the Directive, which constitutes a considerable advantage for both waste cooking oils and animal fats. Several advantages and disadvantages of the production and use of biodiesel fuels from animal fats have been pointed out in the literature. Biodiesel fuels from animal fats are typically more saturated than those from vegetable oils,3,17 thus having (1) a higher cetane number that reduces the amount of fuel burnt in the premixed fraction of the combustion process, the combustion noise, and the NOx formation and (2) a better oxidation stability improvement when additives are added to meet biodiesel fuel quality requirements. On the contrary, animal fats have commonly (3) a high content of FFAs; therefore, a previous esterification process is usually needed to reduce it before entering the trasesterification reactor. (4) In addition, animal fats have poor cold-flow properties that could prevent them from being used in cold climates. To overcome the (15) Miralles, R. Info APPA 2008, 26, 16–18 (in Spanish). (16) European Commission. Draft Directive of the European Parliament and of the Council on the Promotion of the Use of Energy from Renewable Sources, 2008 (available on-line at http://ec.europa.eu/energy/climate_actions/doc/2008_res_directive_en.pdf). (17) Aranda Moraes, M. S.; Krause, L. C.; da Cunha, M. E.; Faccini, C. S.; de Menezes, E. W.; Veses, R. C.; Rodrigues, M. R. A.; Carama˜o, E. B. Energy Fuels 2008, 22, 1949–1954.

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disadvantages mentioned, blending animal fats with vegetable oils is an alternative. The above-mentioned advantages/drawbacks, related to the production process and the fuel properties, are well-known from the literature of the past few years. However, much less is reported about the effect of animal fat biodiesel fuels on the performance and emissions in diesel engines. Equal thermal efficiency and increased fuel consumption is reported when comparing animal fat biodiesel fuels to petroleum diesel fuel,17,18 similarly as for all types of biodiesel fuels, as a consequence of their lower heating value.2,3,18 The United States Environmental Protection Agency (EPA)19 and Wyatt et al.20 reported lower NOx emissions from animal fat biodiesel fuels compared to vegetable oil ones, although the latter only measured for B20 blends; therefore, their conclusions are restricted to this lowcontent blend. Particle mass (PM) emissions are typically reduced when biodiesel fuels are used in substitution of diesel fuels, regardless of the origin of the biofuel, because the oxygen content is the main reason for such reduction.2,3,18 Only Kado21 found larger reductions with animal fat biodiesel fuels. However, no less important than total mass are particle size distributions, because particles are more dangerous as they become smaller22,23 and the particle number will be limited by future legislation. After we studied the production process and the properties of biodiesel fuels produced with both animal fats and blends of animal fats with vegetable oils in a former paper,24 this paper presents the performance and emissions of these biodiesel fuels in a 2.2 L, common-rail injection diesel engine. Special attention has been paid to particle number emissions, because this was found to be an increasingly important matter not sufficiently considered in the literature yet. 2. Experimental Section 2.1. Experimental Equipment. A scheme of the installation used, which has been previously presented in other works of this research group,4,25,26 is shown in Figure 1. The experimental tests were carried out in a four-cylinder, four-stroke, turbocharged, intercooled, direct-injection, 2.2 L Nissan diesel engine connected to an asynchronous electric brake Schenck Dynas III LI 250. The main technical specifications of this engine are given in Table 1. The engine exhaust gas recirculation (EGR) valve was driven by a stepper motor, which allows the user to set, for each operation mode, the same EGR ratio regardless of the fuel tested. This is necessary when comparing different fuels, because emissions are dependent upon the EGR ratio. Several temperature and pressure sensors installed in the engine were used to monitor and control the engine operation. Additionally, two absolute pressure sensors were located up- and downstream of the fuel filter to monitor the pressure drop across the filter. This pressure drop was expected to increase as a (18) Graboski, M. S.; McCormick, R. L.; Alleman, T. L.; Herring, A. M. National Renewable Energy Laboratory, 2003; NREL/SR-510-31461. 2003. (19) Assessment and Standards Division, Office of Transportation and Air Quality of the U.S. Environmental Protection Agency (EPA), 2002; EPA420-P-02-001. (20) Wyatt, V. T.; Hess, M. A.; Dunn, R. O.; Foglia, T.; Hass, M. J.; Marmer, W. N. J. Am. Oil Chem. Soc. 2007, 82, 585–591. (21) Kado, N. Y.; Kuzmicky, P. A. National Renewable Energy Laboratory, 2003; NREL/SR-510-31463. (22) Kittelson, D. B. J. Aerosol Sci. 1998, 29 (5/6), 575–588. (23) Environmental Protection Agency (EPA). Health Assessment Document for Diesel Engine Exhaust, 2002 (available on-line at http:// cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid)29060). (24) Canoira, L.; Rodrı´guez-Gamero, M.; Querol, E.; Alca´ntara, R.; Lapuerta, M.; Oliva, F. Ind. Eng. Chem. Res. 2008, 47, 7997–8004. (25) Lapuerta, M.; Armas, O.; Rodrı´guez-Ferna´ndez, J. SAE Tech. Pap. 2008-01-1676, 2008. (26) Lapuerta, M.; Herreros, J. M.; Garcı´a-Contreras, R.; Lyons, L. L.; Bricen˜o, Y. Fuel 2008, doi: 10.1016/j.fuel.2008.05.013.

Biodiesel from Low-Grade Animal Fats

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Figure 1. Scheme of experimental facilities. Table 1. Engine Characteristics fuel injection maximum power maximum torque cylinder arrangement bore (mm) stroke (mm) displacement (L) compression ratio

common rail, with pilot injection 82 kW at 4000 rpm 248 N m at 2000 rpm 4 cylinders, in line 86.5 94 2.2 18:1

consequence of the high saturation level of the biodiesel fuels used. Fuel consumption was measured with a gravimetric fuel balance AVL 733-S (maximum error of 1%), and air consumption was measured with a hot-wire sensor Siemens 5WK9628. Particulate matter was collected using a partial flow dilution minitunnel (Nova Microtroll) equipped with mass flow controllers to achieve the dilution ratio specified by the operator. This minitunnel as well as the filters, electronic balance, and climatic chamber used in the present work are described in ref 4. The collection and conditioning procedure was optimized as described in ref 27. Finally, the filters were subjected to a thermal extraction method to calculate the volatile organic fraction (VOF) of the particulate matter by means of a thermogravimetric analyzer with an uncertainty of 0.1% and resolution of 0.1 µg. This method is fully presented in a former work of the group.28 A smoke meter AVL 439 (0.1% resolution) was used to determine the smoke opacity (expressed here in percentage of the light absorbed or dispersed with respect to the intensity of the emitted beam). Particle size distributions were measured using a scanning mobility particle sizer (SMPS) TSI 3080. Particles were sampled from the dilution minitunnel, where the exhaust gas was diluted previously before entering the SMPS. Once classified according to their mobility diameter, the particles were counted in a condensation particle counter (CPC), with a resolution of 1 particle/cm3. With regard to gaseous emissions, nitrogen oxides (NOx) were recorded with a chemioluminiscence analyzer Topaze 3020 and total hydrocarbon (THC) emissions were measured with a flame ionization detector Graphite 52M-D (minimum detectable ) 0.05 ppm). Carbon monoxide emission was determined in a nondispersive infrared analyzer MIR. The three gas analyzers have an uncertainty of 1%. (27) Lapuerta, M.; Armas, O.; Ballesteros, R.; Dura´n, A. SAE Tech. Pap. 99-01-3531, 1999. (28) Lapuerta, M.; Ballesteros, R.; Rodrı´guez-Ferna´ndez, J. Meas. Sci. Technol. 2007, 18, 650–658.

Finally, a zero-dimensional thermodynamic model, described in refs 29 and 30, was used to determine the main parameters of the combustion process, such as the start of combustion (SOC) and the heat release law (HRL). The cylinder pressure signal was determined by averaging 20 pressure cycles obtained with a piezoelectric transducer Kistler Z17090 (with a sensibility of 25 pC/bar). 2.2. Selected Fuels. A conventional diesel winter fuel following EN590 standards, similar to those available in Spanish petrol stations, was supplied by Repsol-YPF and used as the reference fuel (REF) in this work. Two biodiesel fuels produced from animal fats (AF_100) and a blend (AF-S_100) of 50% (v/v) animal fats and 50% (v/v) soybean oil were also tested. Both biodiesel fuels were produced and supplied by CIDAUT and Combustibles Ecolo´gicos Biotel, respectively, and the animal fats were supplied to them by Valgrasa. The process used to synthesize both biodiesel fuels, along with a discussion of its industrial feasibility, was fully presented in a former work.24 Additionally, blends of reference diesel fuel with biodiesel fuels in percentages of 30% (v/v) (AF_30 and AF-S_30) and 70% (v/v) (AF_70 and AF-S_70) were tested too. The main characteristics of the pure and blended fuels are presented in Table 2, while the speciation of the pure fuels is shown in Table 3.

3. Methodology The five operating modes tested were selected among the collection of steady stages, which reproduce the transient cycle that light vehicles must follow for certification according to the European Emission Directive 70/220, amendment 2001/C 240 E/01. Four of the five modes (named as C′, F, G′, and H) were chosen based on their highest contribution to the total PM emissions, with the selection process being described in other works published by the group.4,32 The fifth mode (U10) was selected because it was the mode with the highest THC emissions and also one of those with the highest CO emissions. The engine speed, (29) Lapuerta, M.; Armas, O.; Herna´ndez, J. J. Appl. Therm. Eng. 1999, 19 (5), 513–529. (30) Lapuerta, M.; Armas, O.; Bermudez, V. Appl. Therm. Eng. 2000, 20 (9), 843–861. (31) Murphy, M. J.; Taylor, J. D.; McCormick, R. L. National Renewable Energy Laboratory, 2004; NREL/SR-540-36805. (32) Lapuerta, M.; Armas, O.; Ballesteros, R.; Ferna´ndez, J. Fuel 2005, 84, 773–780.

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Table 2. Fuel Properties AFREF AF_30 AF_70 AF_100 S_30 F (kg/m3)a 834 υ (cSt)b 2.72 LHV (MJ/kg)c 42.49 C (wt %) 86.13 H (wt %) 13.87 O (wt %) ∼0 S (wt ppm) 34e MWg 211.7h AFRsti 14.67 cetane number 52 IV (g of I2/100 g ∼0 k of sample) -19 CFPP (°C)l

AFS_70

846 3.24 41.09 83.11 13.41 3.47

864 4.17 38.63 79.25 12.82 7.93

877 5.23 37.20 76.46d 12.40d 11.14 47.5f 230.58d 260.35d 287.09d 14.02 13.18 12.57 57j 65j 70j 17.12 39.05 54.88

848 3.09 41.06 83.24 13.33 3.43

866 3.76 38.78 79.54 12.63 7.83

-4

4

-8

-1

10

AFS_100

882 4.78 37.14 76.87d 12.13d 11.00