Feasibility study of a pilot scale integrated biowaste to biofuel system fed with waste frying oil, organic waste and algal biomass

Nowadays, the importance of recycle and energy savings is increasing due to the current economic and environmental situation. A lot of different technologies were developed in order to utilize biowaste to produce biofuels but they are not always easily available and economically advantageous, especially at small scale. A possible solution could be to couple them in a synergic cooperation. In this paper we discuss the best layout of a pilot plant producing biofuels from waste frying oil, solid organic wastes and algal biomass. The crucial point of this work is to the find best layout and operative conditions in order to use organic wastes and by-products in a closed-loop process. The study is carried out through a complete experimental campaign on the integrated pilot process, consisting of three parts, so defined: i) biodiesel and glycerol production by transesterification of waste frying oil added with oil extracted from algal biomass; ii) syngas production by gasification of biowaste, added with glycerol to increase the total LCV; iii) algal biomass production in airlift photo-bioreactors, fed by the recycled process wastewater rich in glycerol, and capable to capture carbon dioxide from flue gases and to produce valuable material to be reintroduced in the process cycle. Waste oil and organic waste were provided by the University Campus canteen and wood pellets were collected in the Campus park. Quality levels of biodiesel cetane number ranged from 47.7 to 58.4 and LHVs ranged from about 36080 kJ/kg to 36992 kJ/kg. A better syngas quality was found by adding glycerol, and flue gas composition was suitable to partially feed the airlift reactors. On the basis of this first step of experimentation, the technological feasibility of the proposed closed loop integrated system is verified.