Digested fiber solids : methods for adding value

Abstract

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. Unfortunately, costs can be sizable. 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. These lower electrical revenues have threatened profitability for both existing and planned dairy digester projects, leading AD project developers to focus on increasing value from all of the other digester revenue streams. These can include tipping fees (as well as increased biogas or power) from accepting off-farm organics to be digested, various environmental credits, and sales from the digested fibrous solids or its value-added products. 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.