Page 2 of 4

Additional testing was performed using biodiesel produced from soybeans, the leading source of feedstock for biodiesel production in the United States. Because the gelling temperature of soybean-derived biodiesel is much lower than that of tallow-based biodiesel, storage temperatures of 50˚F or higher generally are sufficient.

Burner performance also was examined. Ignition on B100 biodiesel, even from a cold starting condition, was smooth and identical to that observed with traditional No. 2 heating oil. Carbon-monoxide (CO) emissions and smoke-number readings essentially were zero during steady-state operation at a normal excess-air level of 25 percent. Following the test runs on the tallow- and soybean-derived biodiesels, the burner head was inspected for coke deposits. No significant deposits were found.

Boiler-emissions testing showed a measurable reduction in nitrogen-oxide (NOx), sulfur-dioxide (SO2), CO, and soot emissions during operation, while energy efficiency basically remained unchanged. SO2 emissions, in particular, were reduced to almost zero.

Figure 3 shows carbon-dioxide (CO2), NOx, and SO2 flue-gas readings during a switchover from No. 2 heating oil to B100 operation. Measurable and repeatable improvements in emissions performance were observed.

During laboratory testing, smaller volumes of condensate were produced during B100-fired operation than during natural-gas- or heating-oil-fired operation. B100 flue gas has a lower moisture-saturation temperature curve than traditional natural-gas and heating-oil fuels, resulting in lower theoretical condensate formation.

Table 1 shows pH values and acidic concentrations in condensate produced by the boiler during operation with natural gas, B100 biodiesel, and traditional No. 2 heating oil. The samples were collected at a condenser temperature of 71˚F, well below the flue-gas water dew point for all of the fuels tested. Under these conditions, the concentration of acid components and pH, both of which impact corrosivity, are favorable for B100 firing and much closer to natural-gas characteristics than No.-2-heating-oil combustion.