Abstract
The current management practice of digestate from biogas plants involves its use for land application as a fertilizer. Nevertheless, the inadequate handling of digestate may cause environmental risks due to losses of ammonia, methane and nitrous oxide. Therefore, the key goals of digestate management are to maximize its value by developing new digestate products, reducing its dependency on soil application and the consequent air pollution. The high nitrogen and lignin content in solid digestate make it a suitable substrate for edible and medicinal mushroom cultivation. To this aim, the mycelial growth rate and degradation capacity of the lignocellulosic component from corn silage digestate, undigested wheat straw and their mixture were investigated on Cyclocybe aegerita, Coprinus comatus, Morchella importuna, Pleurotus cornucopiae and Pleurotus ostreatus. The structural modification of the substrates was performed by using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Preliminary in vitro results demonstrated the ability of P. ostreatus, P. cornucopiae and M. importuna to grow and decay hemicellulose and lignin of digestate. Cultivation trials were carried out on C. aegerita, P. cornucopiae and P. ostreatus. Pleurotus ostreatus showed the highest biological efficiency and fruiting body production in the presence of the digestate; moreover, P. ostreatus and P. cornucopiae were able to degrade the lignin. These results provide attractive perspectives both for more sustainable digestate management and for the improvement of mushroom cultivation efficiency.
Highlights
Managing organic waste streams is a major challenge for the agricultural industry
Coprinus comatus was included, because, recently, a substrate containing biogas residues has been patented for its cultivation [21]
The anaerobic digestate from biogas plants has considerable operational and environmental drawbacks caused by the releasing greenhouse gases (NH3, CO2 and N2 O) and by the presence of nondigested organic compounds [37,38,39]
Summary
Managing organic waste streams is a major challenge for the agricultural industry. Anaerobic digestion (AD) treatment process is considered the most suitable bioenergy technology to treat wastes for biogas production from agriculture, industry and household food wastes [1]. Public policies of several EU Member States have promoted the use of AD to treat organic wastes and to generate renewable energy. Digestate is a heterogeneous material produced in large amounts during the AD process [3]. The physicochemical characteristics of digestate depend on the nature and composition of feedstocks, as well as on the operational parameters of the process. Agricultural wastes typically have a high content of lignocellulose. In this rigid structure, lignin coats cellulose and hemicellulose while blocking
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