Advanced bioconversion of biowaste for production of a peat substitute and renewable energy.

Traditional composting systems for biowaste generally produce low quality composts that may endanger recycling. A pilot-scale bioconversion process yielding quality compost and renewable energy was designed and tested. The process consisted of a set of wet physical separation units, composting and anaerobic digestion. Biowaste was divided in four streams by physical separation: (1) organic fraction >2 mm, (2) inorganic fraction 0.05-2 mm, (3) residual fraction composed of organics 0.05-2 mm and the fraction <0.05 mm and (4) a fraction solubilised in the washing water. The organic fraction >2 mm was composted and the compost, high in organic matter and low in EC and heavy metals, aimed at replacing peat in horticulture. The inorganic fraction 0.05-2 mm was completely made up of sand and can be used as a construction material. Solubilised organic matter in the washing water was converted to CH(4) by anaerobic digestion. The residual fraction can be used as landfill cover material.