Investigating the potential use of composted grape marc in the production of Agaricus bisporus

Mushroom production is gradually spreading in Lebanon and becoming more modernized, however, the high cost of substrates remains one major constraint facing this industry. The large number of wineries in Lebanon produces huge amounts of winery wastes which in general are not reused. Therefore, an experiment was carried out in May 2017 where a mushroom production room was installed providing traditional conditions of production. The general aim was to assess the potential use of composted grape marc on mushroom production seeking to valorize local winery wastes. This was achieved by comparing the effect of five different substrates on yield and quality of Agaricus bisporus; 100% conventional compost based on horse manure (S1), 30% conventional compost + 70% composted grape marc (S2), 50% conventional compost + 50% composted grape marc (S3), 30% composted grape marc + 70% conventional compost (S4) and 100% composted grape marc (S5). Results showed that the substrate S3 induced the earliest and highest yield compared to other substrates. However, yields were not affected with less than 50% composted grape marc in the substrate. Fruit characteristics such as average individual fruit weight, mushroom length, cap diameter and stipe diameter were not significantly different between S3 and S1, while in S3 productivity was increased by 32% and nutritional composition was enhanced; higher protein, crude fibers, ash, fat, and carbohydrates compared to S1. Mushroom shelf-life was increased with increasing proportions of conventional compost while production costs were reduced by higher proportions of composted grape marc. Finally, using composted grape marc could provide an economic benefit to the Lebanese mushroom sector by lowering the cost of production while maintaining mushroom quality.