## 2 Materials and Methods
### Methods
#### 2.2.2 Co\({}_{2}\) Pollution  
CO\({}_{2}\) emission results from diesel fuel usage were determined for the harvesting and transporting of banagrass feedstock from production sites to the ethanol processing plant and transporting ethanol from the processing plant to Kawaihae port. The optimal transporting routes are determined through the route analysis in the ArcGIS network analyst toolbox using the Hawaii road network database. Determination of CO\({}_{2}\) emission is based on the studies by [29; 30]. The amount of CO\({}_{2}\) emission depends on the level of fuel consumption (FC) and the carbon content (CC) released from fuel combustion during truck operations. Figure 3 shows the mathematical equation for quantifying CO\({}_{2}\) emission.  
Figure 3: Flowchart for estimating spatial distribution of CO\({}_{2}\) emission.  
The carbon content of diesel fuel was estimated at 2.778 kg/gallon [29]. The number 0.99 is the oxidation factor which indicates that 99% of the carbon is oxidized in the fuel. The ratio (44/12) is the ratio of the molecular weight of CO\({}_{2}\) to the molecular weight of carbon [29].  
The banagrass harvesting system used in Hawaii is the same as the sugarcane harvesting system [4]. The harvesting component includes operations of harvesters and trucks/trailers for in-field feedstock transport. The harvesting operation uses a Claas CC 1400 harvester which has a fuel consumption rate of 8 gallons/hour [25]. Given the adjusted biomass harvest rate of 0.26 ha/hour (see Table 1), total estimated fuel consumed by eight harvesters over an area of 16.64 ha per day (see Table 1) is about 512.00 gallons/day. The fuel consumption rate of trucks/trailers was estimated at 7 gallons/hour for 1 ha of in-field transport [25]. This results in total daily consumption of 116.48 gallons/day for in-field trucks/trailers operations.  
An average empty 45 cubic yard (yd\({}^{3}\)) truck/trailer's weight was estimated at 37,300 lbs or 18.65 tons [31]. Chopped banagrass has a bulk density of about 8 pounds per cubic foot (lbs/ft\({}^{3}\)) or 216 pounds per cubic yard (lbs/yd\({}^{3}\)) (1 ft\({}^{3}\) = 0.03703704 yd\({}^{3}\)). As a result, a truck/trailer can carry approximately 4.86 tons of wet banagrass (see Table 1). The average weight of a loaded truck/trailer is estimated at 23.65 tons. This results in an estimated 217 truckloads daily to meet the daily requirement of 1056 tons of feedstock for ethanol processing. For the transport of ethanol fuel, assuming that ethanol is transported using tanker trucks with a capacity up to 9000 gallons. This would require three roundtrips to transport 24,657 gallons of ethanol daily. The average weights of an empty and loaded truck tanker are respectively estimated at about 20,000 and 80,000 lbs.  
Truck/trailers and tanker trucks are categorized as class 8 - heavy duty vehicles [32; 33]. These vehicles have a gross loaded weight range from 33,001 to 80,000 lbs. Fuel consumption ranges from 4 to 7.5 mpg for this class [32; 33]. Therefore, the average fuel consumption rates for an empty and loaded tanker truck are respectively 7.5 and 4 mpg. The adjusted fuel consumption rates of 6.5 and 5 mpg were also estimated for an empty and loaded truck/trailer.  
The information on fuel consumption is used in Equation (F2) (Figure 3) to estimate CO\({}_{2}\) emission and its spatial distribution from harvesting and transporting banagrass feedstock and ethanol fuel. Spatial results were generated based on ArcGIS version 10.3.1 (ESRI, Redlands, CA, USA) which shows the spatial distribution of dust and CO\({}_{2}\) emissions within the study area.