Methane Gas from High Solids Digestion of Poultry Manure and Wheat Straw

Abstract

An investigation was conducted for 15 months to assess the potential for methane production from high solids slurries consisting of manure from laying chickens combined with 0, 20, 40, and 60% by volatile solids (VS) weight chopped wheat straw. Two pilot scale digesters, each with an operating volume of 100 liters, were fed on alternate days at loading rates of 6 kg VS/m3·day. Retention times were held constant at 15 days, and the temperatures were maintained at 35 C. The methanogenic bacteria appeared to acclimate successfully to high concentrations of ammonia nitrogen (4.5 g/liter). Greatest gas production and volatile solids breakdown were observed for the digester fed 100% chicken manure (2.95 v/v gas/digester per day and 57.4%, respectively). Although addition of wheat straw provided a more stable environment for the methanogenic bacteria, gas production decreased with increasing amounts of straw (1.75 v/v gas/digester per day for 40% manure plus 60% straw).