Solid state anaerobic digestion of mixed organic waste: the synergistic effect of food waste addition on the destruction of paper and cardboard

Full-scale anaerobic digestion processes for organic solid waste are common in Europe but are generally unaffordable in Canada and the United States because of inadequate regulations to restrict cheaper forms of disposal, particularly landfill. We investigated the viability of solid-state anaerobic digestion (SS-AD) as an alternative that reduces the costs of waste pretreatment and subsequent wastewater treatment. A laboratory SS-AD digester, comprising six 10 L leach beds and an upflow anaerobic sludge blanket reactor treating the leachate, was operated continuously for 88 weeks, with a mass balance based on chemical oxygen demand (COD) of 100 ± 2% (CODout/CODin). The feed was a mixture of fibers (cardboard, boxboard, newsprint, and fine paper) with varying amounts of food waste added. The process remained stable throughout. The addition of food waste caused a synergistic effect, raising methane production from the fiber mixture from a low of 52.7 L kg–1 COD fibersadded at no food waste, to 152 L kg–1 CO...