Pretreatment methods to enhance anaerobic digestion of organic solid waste

•Pretreating organic solid wastes leads to an enhanced anaerobic digestion process.•Pretreatments may also reduce the cost for post treatment of digestates.•Efficiency of pretreatment methods depends on the substrates’ characteristics.•Only few pretreatment methods are successfully applied at full-scale to date. This paper reviews pretreatment techniques to enhance the anaerobic digestion of organic solid waste, including mechanical, thermal, chemical and biological methods. The effects of various pretreatment methods are discussed independently and in combination. Pretreatment methods are compared in terms of their efficiency, energy balance, environmental sustainability as well as capital, operational and maintenance costs. Based on the comparison, thermal pretreatment at low (