Over 75% of our waste consists of organic by-products from the brewing process including spent grains, waste yeast and trub (a residual sludge from the process). The remainder is made up of broken glass from packaging, paper and labels, cartons and cardboard, kieselguhr (a filtration medium), broken crates and other plastic waste, metal bindings and bottle caps, effluent sludge from waste water reatment and boiler ash from the combustion of coal. For more information please see the Sustainable Development Report 2008