Research Article Received: 2 November 2015 Revised: 30 March 2016 Accepted article published: 15 April 2016 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/jctb.5002 Potential use of vegetable waste for biofuel production Sérgio S de Jesus, a* Aline Santana, a,b Gustavo HSF Ponce a and Rubens Maciel Filho a Abstract BACKGROUND: In this study, the use of vegetable waste as a potential source of raw material for biofuel production was investigated. The microalga Chlorella vulgaris was used to maximize the production of lipids and carbohydrates. The culture medium was prepared with vegetable waste and diluted in the following proportions of medium:water: 1:0, 1:1, 1:2 and 1:3; the resulting solutions were adjusted for three different pH values (5.5, 7.2, 8.5). For a comparative analysis, modified CHU-10 medium was used. RESULTS: The initial concentration of carbon in the medium was 279.6 ± 3.5 mg L -1 , while nitrogen was 11.22 ± 1.32 mg L -1 . The growth in heterotrophic conditions was performed for 21 days, during which it was observed that higher concentrations of biomass and higher productivity of lipids and carbohydrates were obtained in cultures performed in medium without dilution (1:0) and pH 5.5; however, higher yields of lipids and carbohydrates were obtained when the medium was diluted in the proportion 1:3 and with alkaline pH. CONCLUSION: The results of this study should encourage the use of vegetable waste as raw material for the production of microalgae rich in lipids and carbohydrates for the production of environmentally friendly fuels. © 2016 Society of Chemical Industry Keywords: algae; biofuel; biomass; biotransformation; waste treatment INTRODUCTION Approximately 1.3 billion tonnes of food produced worldwide is wasted. A study released by the United Kingdom points out that up to 50% of the food that is produced every year is never ingested and is destined to the trash. The impact of food waste is not just financial; food waste also causes the overuse of other resources that are already in crisis, such as water and energy. According to a United Nations report, currently, approximately 550 billion cubic meters of water are wasted every year in the production of food that goes to waste. ‘Environmentally, food waste leads to wasteful use of chemicals such as fertilizers and pesticides; more fuel used for transportation; and more rotting food, creating more methane – one of the most harmful greenhouse gases that contributes to climate change’. 1 – 4 The residue of the food waste generated is also little reused, being destined to landfills, in which decomposition is one of the main components in the formation of leachate, which, if not treated properly, can reach groundwater, rivers and streams, lead- ing to the contamination of these water resources. In this case, fish may be contaminated and, if the water is used in agricultural irri- gation, the contamination can enter the food chain, thus restart- ing the cycle. This waste is considered a potential raw material to obtain energy (biogas, bioelectricity and biofuels) because its composition presents a high organic composition that is easily biodegradable, and it can simply be collected from markets or cen- tral supplies. These wastes have in their composition high protein, vitamins and minerals content, among other elements, which is ideal for fermentation processes or simply for microbial growth. 5,6 Studies conducted with vegetable waste for the production of biogas and bioelectricity have demonstrated an economically viable alternative for it. 5 – 8 Recently, studies on the production of biodiesel were performed with the use of acid catalysis of vegetable waste oil, and these studies showed great potential for biodiesel production; however, the catalyst used had com- pounds that were harmful to the environment, which is a typi- cal environmental problem at large scale. Studies conducted with microalgae show it to be a potential source of substrate for bio- fuel production. 4,9 – 11 Biofuel (biodiesel and bioethanol) produc- tion by microalgae using vegetable waste, for the automotive and aircraft industries, has received little attention; the residue gen- erated is a true source of clean energy generation, from which we can reach 100% reuse, which would comprise the production of biodiesel, bioethanol, biogas, bioelectricity, protein for animal feed and some high value-added products such as carotenoids. 9,12 ∗ Correspondence to: SS de Jesus, Laboratory of Optimization, Design and Advanced Control, Bioenergy Research Program, School of Chemical Engineer- ing, University of Campinas, P.O. 6066, Zip: 13083–852 Campinas/SP, Brazil. Email: ssjesus@gmail.com a Laboratory of Optimization, Design and Advanced Control, Bioenergy Research Program, School of Chemical Engineering, University of Campinas, P.O. 6066, Zip: 13083-852 Campinas/SP, Brazil b Laboratory of High Pressure Process, Department of Chemical Engineering and Environmental Technology, University of Valladolid, Zip 47011, Valladolid, Spain J Chem Technol Biotechnol (2016) www.soci.org © 2016 Society of Chemical Industry