Table 8 Primary and secondary inputs needed for the ethanol and biomass procedure

Plant capacity

This value represents the maximum amount of biofuel that could be produced by the plant considered. This value should be reported in million liters per year for ethanol plants and megawatts electrical (MWe) for wind farms.

Yearly growth factor

If the plant is expected to increase its capacity in the future, the designer may add a reasonable growth factor. However, it is uncommon for a plant to be built and have its capacity increased later on in its service life. The default value is 0%.

Capacity factor for biomass plants

Biomass plants produce power but are not exclusively consistent in doing so. The capacity factor is a percentage that represents the average power output of a plant. It ranges from 15% to 100%. When this value is unknown, an average value of 67% is assumed.

Ethanol plant products and raw materials

Amount of corn hauled to the plant by trucks, as opposed to be transported by another means, or grown within the plants' grounds, thus not using any local roads. Therefore, the default value assigned is 100%.

Ethanol hauled from the plant by trucks, as opposed to stored or sold locally. Most ethanol plants are located close to rail freight tracks. For this reason, most (if not all) of the ethanol production will be shipped by rail. The assigned default value is conservatively set to 20%.

DDGS hauled from the plant by trucks. This has a default value of 20%.

Design period

The amount of time the road is expected to remain in service without major rehabilitation. This value is typically 20 years; however, for county roads, it can be lower.

Biomass fuel type

Biomass fuel can be produced using various components and ratios of these components. Different component raw materials have different weights. It is important to determine the different percentages of each raw material to avoid underestimating the weight of incoming trucks. The four typical components are corn stover, wood chips, saw dust, and baled straw. Each is set at a default value of 25%.

California bearing ratio (CBR)

This value reflects the strength of the underlying soil. To get the actual field CBR of the soil, soil bores need to be drilled in the construction location. However, the value can be closely estimated by knowing the type of soil in the area. Highway supervisors can resort to previous experience or soil maps to determine the soil type in the area.

Reliability (R%)

The designer should choose the level of reliability of the design. For local county roads, the reliability is typically low. This value ranges from 50% to 99%; 75% is the default value.

Terminal serviceability index (Pt)

This is the value that reflects the condition of the pavement at the end of its service life. This value ranges from 3 (for major highways) to 1.5 (minimum). The default value is 2, as recommended for county roads by the AASHTO design guide [49].

Overall standard deviation

This number reflects the variability within the pavements' materials. It typically ranges from 0.3 to 0.5. A value of 0.5 is recommended by the AASHTO design guide [49] and is set as the default value.