NOx emissions for the SoCAB and future NOx emissions for CA and North America are estimated to be 2 g/bhp-hr, which is equivalent to a controlled lean-burn engine. Future NOx emissions for engines located in the SoCAB are estimate to 0.48 g/bhp-hr, based on SCAQMD Rule 1110.2 (Emissions from Stationary Internal Combustion Engines).
Current CO and HC emissions for all engine prime movers in the U.S. are based on a population profile of the gas turbine prime movers (Huey 1993) and emissions data (Urban 1980 and Fanick 1988) for uncontrolled engines and are consistent with AP-42 factors. Future CO and HC emissions for all engines in the U.S. should increase slightly due to the greater use of NOx control technologies. Generally CO and HC emissions increase as NOx emission decreases. Similar to gas turbines, the emissions data also show that methane emissions makes up over 90 percent of the VOC emissions from an engine.
4.1.2 Biomass Collection Equipment
Fuels and feedstocks are transported and distributed by a variety of equipment including trucks, trains, and marine vessels. Emissions from fuel or material transport were determined from emission rates and equipment usage factors that take into account distance traveled and cargo load. The emissions and use factors for the relevant fuels are discussed for each transportation mode. Several types of biomass are potential feedstocks for fuel production. Such feedstocks include agricultural wastes, wood waste, and purpose grown energy crops. Potential energy crops include poplar and euclyptus. feedstock transportation requirements for a combustion of agricultural material and forest residue were used to estimate fuel usage in this study.
Emission factors from an ARB study on farming equipment are shown in Table 4-4 (Kreebe 1992). The study considered a range of equipment power that did not vary substantially (for the overall emission factor) in NOx. The most prominent size range for agricultural equipment is used in this study. Typical energy consumption values are assumed for diesel equipment and increased by 20 percent for gasoline.
Evaporative emissions were estimated from ARB’s study on off-road emissions. For the 40 to 100 hp category of agricultural equipment, evaporative emissions were 550 lb/unit per year of which 98 percent were running losses. Running losses in the ARB study were based on the EMFAC emission factor for uncontrolled automobiles. The study indicates 5248 operating hours per year and 32,906 gallons per year of fuel use for 70‑hp equipment. The evaporative emissions are then 7.6 g/gal. An additional 4.6 g/gal was added for uncontrolled fueling emissions from Section 4.2. Evaporative emissions for RFG- and diesel-fueled equipment were adjusted for the vapor pressure in proportion to the mass emissions in Section 4.2.
Usage rates for farming equipment in Table 4-5 are combined with fuel production yields in Table 4-6. The study shows diesel energy as a proxy for petroleum fuels and other energy inputs. Table 4-5 shows the energy components for diesel in greater detail. ARB's off-road emission study (Kreebe) indicates that 10 percent of agricultural