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4. Parreira Almond Processing Company N-1082706, N-1337-1-6,2x7,6-1,7-0, 8-0 As shown in Section VIII.A.1 of this document, BACT Is triggered for NOx and VOC emissions from the engine. Top-Down SACT AMhols for NOs EmissigU2 Step 1 —Identify All Possible Control Technologies: 1. 9 ppmvd NO,@ 15% 02, rich bum syngas-fueled IC engine with air-to-fuel ratio . controller and 3-way catalyst—ApplicarWs Proposal 2. 5 ppmvd NOx C 15 % 02, rich bum syngas-fueled IC engine with air-to-fuel ration controller and i-way catalyst—Technologically Feasible (based on BACT Guideline 3.3.12) The District has determined that NOx emissions of 9 ppmvd are achieved in practice for full-time IC engines whether fossil-fueled or waste gas-fueled. Therefore, a syngas-fueled Rall-time IC engine will also be required to meet the same NOx emissions standard. Available data, including the manufacturer's guarantee and the source test data obtained for YSAQMD for a similar rich-bum engine burning a similar syngas, support an emission limit no greater than 9 ppmvd at 15%02, but do not justify setting a limit lower than 9 ppmvd. BACT Guideline 3.3.12 lists a NOx emission limit of 5 ppmvd at 15% 02 as being technologically feasible for fossil-fueled IC engines. This emission level can be achieved by either using a larger three-way catalyst for a rich bum engine, or by using a suitably sized selective catalytic reduction system for a lean-bum engine, this level of NOx control will be listed as technologically feasible for this engine application as well. Step 2—Eliminate Technologically'lnfeasible Options: The first control option listed in step 1 is achieved in practice for fossil-fueled and waste gas- fueled engines, and is technologically feasible for IC engines,using other fuels such as syngas because the applicant has supplied testing data and a manufacturer's guarantee for a catalyst to reduce NOx emissions to 9 ppmvd at 15% 02. Since the District has determined that the lower uncontrolled NOx emissions from syngas combustion are likely to make it technologically feasible for a lean-bum syngas-fueled engine to comply with an even lower limit, 5 ppmvd NOx emissions at 15% Oz will be considered technologically feasible as well. However, according to the manufacturer of the proposed three-way catalyst, the reduction of NOx in a three-way catalyst is driven*by the oxidation of excess hydrocarbons In the exhaust stream. If the concentration of hydrocarbons falls too low, then the control efficiency for NO, reduction will fall. The applicant has provided a syngas analysis showing that only 3% (by volume) of the syngas is methane, the only hydrocarbon present, compared to natural gas{� 100°x6 hydrocarbons) or waste gas (30-70% hydrocarbons).The catalyst manufacturer stated that, given the shortage of testing data, they cannot guarantee compliance with a NO, emissions limitation of 5 ppmvd with a catalyst of any size. Therefore, a NOx emissions limit of 5 ppmvd at `16%02 is not technologically feasible for a rich-burn engine fueled with syngas, and will be removed from consideration at this time.