BIOMETHANE DIGESTATE FROM HORSE MANURE, A NEW WASTE USABLE IN COMPOST FOR GROWING THE BUTTON MUSHROOM, AGARICUS BISPORUS ?

Mushroom cultivation is a direct utilization of their ecological role of organic matter degradation in the bioconversion of solid wastes generated from industry and agriculture into edible biomass, which could also be regarded as a functional food or as a source of drugs and pharmaceuticals. Significant changes are expected in the integrated management of wastes streams in the future due to the use of plant biomass for biofuel and energy production and other non-food crops. On the one hand these activities may use the same wastes than those allowing mushroom cultivation today and problem of competition for supplying may occur. On the other hand these new activities will generate new wastes to be treated and valorise by the mushroom industry. Horse manure is a component of the compost used to grow the button mushroom, Agaricus bisporus and other Agaricus species. We studied the methanisation of horse manure and utilisation of the digestate produced by the biogas reactor as waste for growing A. bisporus. Methanisation was efficient and the compost obtained from the digestate in mixture with wheat straw and low quantities of mushroom compost as source of aerobic and thermophilic microflora allowed to grow A. bisporus, but with lower yields than in conventional mushroom composts. Horse manure methanisation digestate was also used without composting by incorporation into the compost at spawning compared to a proteinic supplementation and in the preparation of casing soil in substitution of a part of peat moss. No beneficial effect was observed and with increasing rate of digestate incorporated, negative effect appeared (unproductive area).