Abstract
Different types of agro-industrial wastes including lignocellulosic wastes, carbohydrate and protein-rich wastes, syrup wastes and glycerol wastes were explored as biodiesel feedstocks. This strategy not only can partially replace fossil fuel but also simultaneously decrease the environmental impact. This is the first report on the techno-economic analysis and CO2 emissions of biovalorization of these wastes for biodiesel production by potential oleaginous yeasts. These evaluations could help to identify potential bottlenecks and suggest suitable implementations. Process models include steps of waste preparation, yeast cultivation, harvesting and biodiesel production through direct transesterification. The evaluation results reveal that the energy intensive steps which also have high CO2 emissions are the heating steps during waste preparation and sterilization prior to yeast cultivation. The most practical and cost-effective scenario was the recycling of glycerol waste from biodiesel industry as renewable feedstocks. This process not only reduces the production cost of biodiesel but also leads to a zero-waste discharge process with low CO2 emissions.
Highlights
Microbial oils produced by oleaginous microorganisms, are considered as potential feedstocks for biodiesel production due to their similar fatty acid compositions to those of plant oils
(1) Waste preparation Among four wastes, expired soft drinks (ES) could be directly used without treatment while crude glycerol (CG) needed pH adjustment prior to yeast cultivation
The optimal acid concentration used for acid hydrolysis process was in the range of 1–10% and at the temperature between 100 and 150 °C [24,25,26,27]
Summary
Microbial oils produced by oleaginous microorganisms, are considered as potential feedstocks for biodiesel production due to their similar fatty acid compositions to those of plant oils. The cultivation of oleaginous microorganisms as oil sources, has advantages over the production of plant oils because they have shorter life cycle, are affected neither by seasons nor climates, and much easier in scaling up [1]. The suitability of the wastes as nutrient sources for the yeasts depends on the availability of carbon source and high carbon-to-nitrogen (C/N) ratio [4]. There are a number of agro-industrial wastes having high fermentable carbon source and high C/N ratio. These include expired soft drinks (ES) from the carbonated soft drinks industry, solid wastes from brewing industry. As ES contains high amounts of sugars including glucose, fructose and sucrose, when left unsold and expired they cannot
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
