Anaerobic digestion (AD) of dairy manure and other organic residuals produces biogas, a source of renewable power and fuel, while also benefitting the environment by capturing and converting methane, destroying pathogens and odors, and stabilizing organic matter (Informa Economics 2013; EPA 2008). Unfortunately, costs can be sizable, with capital costs estimated to be $2,000 per cow in 2011 for combined heat and power (CHP) projects in Washington State (David Paul Rosen and Associates 2011). While revenue generated from the sale of electricity from biogas can offset these costs, the value of electricity has decreased in many parts of the US. In some places, it has been valued so low that electricity sales do not even cover operation and maintenance costs (Costa and Voell 2012).
This publication describes the composition and separation process for fibrous solids that result from the digestion of dairy manures. It also reviews both current and future potential uses of fiber.