Sustainability of biodiesel production in Malaysia by production of bio-oil from crude glycerol using microwave pyrolysis: a review

Biodiesel being one of the most promising renewable biofuels has seen rapid increase in production capacity due to high demand for diesel replacement; along with oversupply of its by-product, crude glycerol. Developing new industrial usage for glycerol is essential to defray the cost and sustainability of biodiesel industry and to promote the biodiesel industrialization. One of the approaches is by the transformation of glycerol into a liquid, referred as bio-oil through pyrolysis technology. Bio-oils produced by pyrolysis processes can be upgraded to produce transportation fuels or for power generation. However, current state of pyrolysis technologies are still major hurdles their development with respect to its commercial applications. Recently, microwave technology has attracted considerable attention as effective method for significantly reducing reaction time, improving the yields and selectivity of target products. Hence, this review strives extensively towards addressing the application of microwave-assisted technology applied to the pyrolysis process as a way of cost-effective and operationally feasible processes to directly utilize crude glycerol. The present review will focus on the pyrolyzed liquid product (bio-oil) derived by employing the microwave-assisted pyrolysis method. This review concludes that microwave-assisted glycerol conversion technology is a promising option as an alternative method to conventional glycerol conversion technology