Despite all of the positive environmental benefits of anaerobic digestion, the economics are not sufficient for widespread adoption by US farmers when selling surplus power to the grid. Often farms are only paid the wholesale price (2 to 3 cents/kWh) for electricity, making it difficult to justify generating it in the first place. In addition, typically in the Northeast, approximately 40% of the energy from a digester goes unused (excess heat). Therefore, promising value-added technology/business partnerships need to be evaluated and demonstrated, such as partnering anaerobic digestion with commercial greenhouses.
Greenhouses are an ideal end user of the waste heat and surplus electricity produced by a digester. In the Northeast and other similar climates, heat and electricity represent a major expense for greenhouse growers. Greenhouses can make use of excess heat to provide the necessary growing conditions for year-round production and excess electricity can be used to run supplemental lighting to keep production constant year-round.
To facilitate the adoption of digester/greenhouse unions, we are developing a comprehensive computer model of both the energy output of farm-based digesters, the energy requirements of the associated farm, and the energy required by greenhouses, in terms of timing and magnitude. We will use existing and project-developed data collected from five Northeast digesters and three greenhouse operations to aid in developing and validating the model. The model will be complex enough to handle varying biomass inputs and required outputs, and the economics of operation. We will use the model to run several real-world “what ifs” and use the outputs for making recommendations to existing anaerobic digesters considering coupling with greenhouses. System economics are also going to be included.
Curt Gooch, Cornell PRO-DAIRY email@example.com
Tim Shelford, Cornell PRO-DAIRY
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