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Self-generated renewable fuels can be a valuable asset to an agricultural operation. For many farms, energy represents a large fraction of their variable costs of production. Dairy operations, in particular, are large consumers of energy for lighting, milk chilling, pasteurization and equipment sanitation. To mitigate the risk of over-reliance on fossil-fuel energy sources agricultural operations are seeking alternative energy solutions to meet on-farm energy needs and to improve the overall environmental quality on the farm.

This project evaluates a hybrid on-farm energy system that can produce multiple types of bioenergy from both oilseed crops (biodiesel) and agricultural waste (biogas). Figure 1 shows a schematic of the system. On-farm generation of energy allows farmers to decrease the amount of fossil fuels purchased for farm use, thereby improving their economic sustainability. In addition, the proposed system offers substantial environmental improvements via improved on-farm water quality and enhanced crop management on the farm.

This is an innovative strategy for on-farm bioenergy production, yet has less technical risk than other new energy generation approaches since it is based on the proven technologies of biodiesel-from-oilseeds and biogas from anaerobic digestion. The especially positive (and innovative) feature of this project is the enhanced energy production efficiency achieved by combining two parallel energy production processes. Enhanced efficiency is critical if the farmer is to cost-effectively replace purchased fossil-fuels that are used on-farm.

Growing bioenergy crops is an appealing idea as farmers seek to increase overall productivity from their land. Some bioenergy crops can be grown in rotation with existing crops or can be grown on land that is otherwise unfit for conventional crop production. Some states have evaluated bioenergy crop production on highway right-of-ways, airport property, and other non-traditional cropland1. Planting oilseeds can be a good way to extract additional economic value from farm acreage.

The key to our approach is to use biodiesel by-products effectively, particularly the use of oilseed meal. This oilseed meal is an excellent co-feedstock for an anaerobic digester, and will increase biogas production when mixed with other feedstocks2. Our initial calculations show that biogas production can increase significantly.

The ultimate metric of success will be to determine the increase in overall energy production (both biodiesel and biogas) using a hybrid system.  The purpose of the proposed CIG effort is to demonstrate an effective bioenergy production system. Our goal is to show that, by maximizing efficiency of the overall production process, we can ultimately achieve cost-competitiveness of biodiesel for on-farm uses. This approach is innovative in the sense that it takes advantage of the synergy between biodiesel and biogas production to maximize the overall production efficiency of biofuels.


Figure 1: Hybrid Biodiesel-Biogas Production System


Figure 1: Hybrid Biodiesel-Biogas Production System  

1 Utah and Michigan have both done preliminary assessments of the Freesways2Fuel concept.

2 Keymer, U. 2004. Biogasausbeuten Verschiedener Substrate (Biogas Yields from Various Substrate). Institut fu Landliche Strukturentwicklung.