Pretreatment of Organic Solid Substrates for Bioenergy and Biofuel Recovery

Pretreatment of organic solid substrates (OSS) for bioenergy and biofuel recovery practices has been viewed as one of the most expensive processing steps in the past decades. But, in recent years more cost-effective integrated pretreatment technologies have been researched and are the focus of this review. In particular, this review compiles the various physical, mechanical, thermal, chemical, and biological pretreatment methods used for OSS treatments and their end-user applications are discussed. From the overall assessment, acid/alkali pretreatment technologies, along with mechanical size reduction of OSS, are found to be best suitable for the energy/fuel recovery process. Also, thermal pretreatment technologies like steam explosion are found to be more advantageous than other methods, but not economically attractive, whereas the biological pretreatment methods are less exploited and require more research studies. Also, a few research gaps are identified and summarized for future research and development.