Environ. Sci. Technol. 2002, 36, 4656-4662
Brassica carinata as an Alternative Oil Crop for the Production of Biodiesel in Italy: Engine Performance and Regulated and Unregulated Exhaust Emissions MASSIMO CARDONE,† MARIA VITTORIA PRATI,‡ VITTORIO ROCCO,§ MAURIZIA SEGGIANI,| ADOLFO SENATORE,† AND S A N D R A V I T O L O * ,| Dipartimento di Ingegneria Meccanica per l’Energetica, Universita` Federico II di Napoli, Via Claudio, 21 80125 Napoli, Italy, Istituto Motori CNR, Viale Marconi, 8 80125 Napoli, Italy, Dipartimento di Ingegneria Meccanica, Universita` di Roma “Tor Vergata”, Via di Tor Vergata, 00100 Roma, Italy, and Dipartimento di Ingegneria Chimica, Chimica Industriale e Scienza dei Materiali, Universita` di Pisa, Via Diotisalvi, 2 56126 Pisa, Italy
A comparison of the performance of Brassica carinata oil-derived biodiesel with a commercial rapeseed oilderived biodiesel and petroleum diesel fuel is discussed as regards engine performance and regulated and unregulated exhaust emissions. B. carinata is an oil crop that can be cultivated in coastal areas of central-southern Italy, where it is more difficult to achieve the productivity potentials of Brassica napus (by far the most common rapeseed cultivated in continental Europe). Experimental tests were carried out on a turbocharged direct injection passenger car diesel engine fueled with 100% biodiesel. The unregulated exhaust emissions were characterized by determining the SOOT and soluble organic fraction content in the particulate matter, together with analysis of the content and speciation of polycyclic aromatic hydrocarbons, some of which are potentially carcinogenic, and of carbonyl compounds (aldehydes, ketones) that act as ozone precursors. B. carinata and commercial biodiesel behaved similarly as far as engine performance and regulated and unregulated emissions were concerned. When compared with petroleum diesel fuel, the engine test bench analysis did not show any appreciable variation of output engine torque values, while there was a significant difference in specific fuel consumption data at the lowest loads for the biofuels and petroleum diesel fuel. The biofuels were observed to produce higher levels of NOx concentrations and lower levels of PM with respect to the diesel fuel. The engine heat release analysis conducted shows that there is a potential for increased thermal NOx generation when firing biodiesel with no prior modification to the injection timing. It seems that, for both the biofuels, this * Corresponding author. Tel: +39 050511278. Fax: +39 050511266. E-mail:
[email protected]. † Universita ` Federico II di Napoli. ‡ Istituto Motori CNR. § Universita ` di Roma “Tor Vergata”. | Universita ` di Pisa. 4656
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 21, 2002
behavior is caused by an advanced combustion evolution, which is particularly apparent at the higher loads. When compared with petroleum diesel fuel, biodiesel emissions contain less SOOT, and a greater fraction of the particulate was soluble. The analysis and speciation of the soluble organic fraction of biodiesel particulate suggest that the carcinogenic potential of the biodiesel emissions is probably lower than that of petroleum diesel. Its better adaptivity and productivity in clay and sandy-type soils and in semiarid temperate climate and the fact that the performance of its derived biodiesel is quite similar to commercial biodiesel make B. carinata a promising oil crop that could offer the possibility of exploiting the Mediterranean marginal areas for energetic purposes.
Introduction Oxygenated fuels, in particular methyl tert-buthyl ether (MTBE) and ethanol, are well known to produce reduced exhaust emissions from motor vehicles. They are also of special interest since they are a potential source of renewable energy. Biodiesel is an oxygenated diesel fuel made from vegetable oils and animals fats by conversion of the triglyceride fats to esters via transesterification. In recent years, many studies have looked at the potential of biodiesel as an alternative fuel for diesel engines, and these works have been reviewed by Wang et al. (1). Initially, environmentally related research concentrated on regulated exhaust gas emissions (carbon monoxide, NOx, and particulate matter), and it was recognized that there was a substantial reduction in these emissions, with the exception of NOx sometimes, when compared with the use of petroleum diesel fuel with no real penalties in terms of fuel consumption or engine performance (2-10). For conventional petroleum diesel fuel, the tradeoff between PM and NOx emissions is well known. Normally, a decrease in particulate emissions produces an increase in NOx emissions and vice versa. For a given injection system, a balance between NOx and particulate emissions can be achieved by controlling the fuel’s start of injection. By moving the start of injection to later in the engine cycle or retarding the start of injection, both the amount of premixed burning and the peak in-cylinder combustion temperatures are reduced, thereby reducing the NOx emissions; however, this method tends to increase particulate emissions by slowing soot oxidation rates. The reason for increased NOx emissions for biodiesel with respect to petroleum diesel has been the object of recent studies. A number of biodiesel properties, such as density, cetane number, iodine number, composition, and boiling point have been shown to affect emissions of NOx (11-14), as well as the changes in fuel injection timing observed with biodiesel compared to petroleum diesel (15, 16). Recently, additional information on exhaust emissions with potential environmental and health importance has been studied by the characterization of unregulated exhaust emissions (1731). In the study described in this paper, we examined a biodiesel made from the oil of Brassica carinata. The crop was cultivated in two areas typical of coastal central-southern Italy in the Tuscan district of Livorno. It was then transformed into biodiesel by transesterification at a pilot plant in the Cereol Research Centre in Budapest, Hungary. A commercial biodiesel made from rapeseed oil (Diesel-Bi supplied by Novaol S.r.l.) and a commercial petroleum diesel were also used as comparison. 10.1021/es011078y CCC: $22.00
2002 American Chemical Society Published on Web 10/04/2002
TABLE 1. Comparative Analysis of B. carinata Biodiesel, Commercial Diesel-Bi Biodiesel, and Italian Standards for Biodiesel properties acid number (mg of KOH/g) water (mg/kg) sulfated ash (wt %) distillation initial boiling point (°C) distillate at 95% volume (°C) density (kg/m3) at 15 °C phosphorus (mg/kg) bound glycerine monoglycerides (wt %) diglycerides (wt %) triglicerydes (wt %) free glycerine (wt %) methanol (wt %) methyl ester (wt %) flammable point (°C) pour point (°C) Conradson carbonaceous residue (wt %) viscosity (mm2/s at 40 °C) sulfur (wt %) a
6 March-15 November.
b
B. carinata biodiesel
commercial biodiesel
UNI 10635 standards
analysis standard method
0.08 465
