Commercial feasibility of an integrated closed-loop ethanol-feedlot-biodigester system based on triticale feedstock in Canadian Prairies

Xue Li and Edmund Mupondwa

Renewable and Sustainable Energy Reviews, 2018, vol. 97, issue C, 401-413

Abstract: This paper presents techno-economic assessment of a closed-loop integrated system combining ethanol plant, feedlot, and biodigester in the Canadian Prairies. Triticale is the primary feedstock for ethanol production. Wet distiller's grains (WDG) and thin stillage from the ethanol plant is used as feed for feedlot beef cattle. Feedlot manure is used to produce methane via anaerobic digestion (AD), for subsequent conversion to electricity and heat through a combined heat and power generation facility. Three scenarios and two system scales were investigated. Total investment in the integrated system was $38–54 (small scale) and $132–237 million (large scale). The results showed that only one scenario in a large scale case has potential to generate profit; in this case, only the feedlot generated positive net present value (NPV) due to savings in feed cost of feeding WDG. Both the ethanol plant and biodigester generated negative returns under the integrated system. Co-locating a feedlot with an ethanol plant enhances ethanol plant profitability along with generation of extra revenue from feedlot operations. Compared to the non-integrated feedlot, the integrated feedlot saves $71.51 in feed cost per cow when cattle are fed 25% WDG. Electricity and heat from the biodigester could only supply 7–20% and 46–71% of the demand of the ethanol plant respectively. Sensitivity analysis tested key factors affecting the profitability of the subsystems. The ethanol plant generates profit under higher ethanol prices. However, NPV for all biodigesters is negative, even under favourable changes in investment and electricity prices. The study also showed that incorporating straw into ethanol fermentation and biogas production was not economically profitable in comparison with single triticale grain fermentation and manure digestion. Overall results suggest need for more policy support to improve economics of anaerobic digesters under current conditions, in the context of clean technology strategies.

Keywords: Integrated system; On-farm biodigester; Ethanol plant; Feedlot; Triticale; Techno-economic analysis (search for similar items in EconPapers)
Date: 2018
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DOI: 10.1016/j.rser.2018.08.051

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