Biosorbents for grass silage effluent retention

Abstract

Silage effluent, or liquor, is the by-product of anaerobic crop preservation to provide winter feed in the form of silage. Virtually all of the silage produced in Europe and in other parts of the world is made from grass which is usually cut at an early stage of growth when its nutrient and moisture content are high. The production of effluent depends mainly on the moisture content of the ensiled crop, the volume being either very large, from 500 litres per tonne for grass ensiled at 12% dry matter (DM) content to relatively small, 50 litres at 25% DM. Above 25% DM, production of liquor is virtually nonexistent. From this it can be recognised therefore that those parts of the world with low rainfall do not experience severe pollution problems arising from silage effluent whilst those with wetter climates have an enormous environmental problem. It is the latter therefore which have to address the need to prevent effluent entering watercourses and to technically assess the means by which such effluent can be retained at source. This paper assesses several new, untried natural biopolymeric materials to act as biosorbents for silage effluent, namely cellulosic ethers and commercially available gums.