Removal of hardly fermentable ballast from the maize silage to accelerate biogas production

The removal of hardly fermentable ballast from the maize silage was investigated on a commercial scale to reduce the retention times, volumes of fermentors and associated heating requirements. The technology consisted of the under-hot-water maceration followed by decantation and the double-screw-press to separate the most labile pools of carbon from the ballast organic matter. This procedure minimized the inhibitor formations in the subsequent steam-explosion followed by enzymatic hydrolysis. The hydrolysis products were squeezed out from the lignocellulose ballast by the rotary dewatering press, fused with liquids previously obtained and anaerobically fermented providing 316.7 m3 CH4 VS t−1 in 200 h. The rigid briquettes from the ballast at the rotary dewatering press were charcoaled (27.506 MJ kg−1). All the technology was designed to run on the waste heat from the flue gases (490 °C) at the cogeneration unit linked to the 1 MWep biogas station.

► Recalcitrance pools of carbon act as ballast in biogas production from lignocellulose phytomass.
► Maceration, press, steam explosion, hydrolysis and dewatering reduced the amounts of ballast.
► Removal of the ballast minimized the inhibitor formations in steam explosion.
► Removal of the ballast lowered reactor volumes and pumping and heat requirements.