Orange wastes are an example of a raw material, which pose a problem when used in biological processes. This is mainly due to the content of poorly biodegradable lignin, phenols, and essential oils, mainly d-limonene. For this reason, a new techniques are constantly being sought to enable their further utilisation, e.g. in the anaerobic digestion process. This study evaluated the effectiveness of microwave irradiation as a pre-treatment method allowing for improving biodegradability of orange wastes. The experiment was conducted at a temperature of T = 50°C and input power of P = 900 W. The following time intervals were evaluated: 0, 3, 5, 10, 20 and 30 min. Among various analyses cases, the most beneficial results were found at the time of 5 min. Therein, the major growth of biodegradability index of 16.36% and higher solubilisation yield of 23.9% was achieved with moderate release of inhibitors. These operating conditions allowed for an increase in biogas and methane production by 8.9 and 10.4%, respectively, compared to untreated orange wastes.