Pipeline transport and simultaneous saccharification of corn stover

Abstract

Pipeline transport of corn stover delivered by truck from the field is evaluated against a range of truck transport costs. Corn stover transported by pipeline at 20% solids concentration (wet basis) or higher could directly enter an ethanol fermentation plant, and hence the investment in the pipeline inlet end processing facilities displaces comparable investment in the plant. At 20% solids, pipeline transport of corn stover costs less than trucking at capacities in excess of 1.4 M dry tonnes/yr when compared to a mid range of truck transport cost (excluding any credit for economies of scale achieved in the ethanol fermentation plant from larger scale due to multiple pipelines). Pipelining of corn stover gives the opportunity to conduct simultaneous transport and saccharification (STS). If current enzymes are used, this would require elevated temperature. Heating of the slurry for STS, which in a fermentation plant is achieved from waste heat, is a significant cost element (more than 5 cents/l of ethanol) if done at the pipeline inlet unless waste heat is available, for example from an electric power plant located adjacent to the pipeline inlet. Heat loss in a 1.26 m pipeline carrying 2 M dry tonnes/yr is about 5 °C at a distance of 400 km in typical prairie clay soils, and would not likely require insulation; smaller pipelines or different soil conditions might require insulation for STS. Saccharification in the pipeline would reduce the need for investment in the fermentation plant, saving about 0.2 cents/l of ethanol. Transport of corn stover in multiple pipelines offers the opportunity to develop a large ethanol fermentation plant, avoiding some of the diseconomies of scale that arise from smaller plants whose capacities are limited by issues of truck congestion.