Water, and supercritical carbon dioxide – are these solvents really green? C. Turner1, P. Börjesson2, M. Co3, A. Ekman2, S. Khan1, J. Samuelsson4, S. Lindahl1, L. Mijangos Trevino1, A. Mustafa1, E. Nordberg Karlsson1 1Lund University, Department of Chemistry; 2Lund University, Environmental and Energy System Studies; 3Uppsala University, Analytical Chemistry; 4Karlstad University, Chemistry www.kilu.lu.se/cas, [email protected] Aim Case 2 – Betulin in bark • To enhance the value of byproducts from agricultural and Betulin is an anti-inflammatory compound constituting 10-20 forestry industry by isolating high-value compounds. weight% of the . An extraction method using liquid

• To develop environmentally sustainable processes using CO2 mixed with ethanol was used to extract betulin [3] “green” solvents – pressurized hot water, ethanol and (“developed method” in Fig. 2). Life cycle assessment (LCA) supercritical CO2 (scCO2). was applied to compare the developed method with a • To evaluate if the developed processes are really green! conventional one based on leaching into ethanol (Fig. 2, [3]). Background There are large amounts of byproducts from agricultural and forestry industry, that is currently recycled for its energy value, or used as animal feed or for soil improvement. These materials contain valuable compounds, for instance pigments and antioxidants, which potentially could be isolated from the biomass before any final usage. Figure 2. Energy consumption (left) and global warming potential (right) for the extraction of 150 g betulin from birch bark. Developed

method: CO2/ethanol (8:2, w/w) at 50 bar and 16 °C, 2-3 h extraction. Conventional: leaching into ethanol for 3-7 days. Three times more ethanol was used in the conventional method. Case 3 – Quercetin in onion Quercetin is an antioxidant present in onion (2 mg/g, f.w.). Figure 1. Carrots, birch bark and onions – voluminous byproducts. Pressurised hot water extraction (PHWE) with β-glucosidase- catalysed hydrolysis was used to isolate quercetin from onion Water is undoubtedly the most environmentally sustainable waste and compared to a conventional method using LCA solvent, and when used at higher temperature and pressure, [4], see Fig. 3. fast extraction can be obtained. For nonpolar compounds, 160 600 140 scCO is a more suitable solvent, while for “medium-polar” 500 2 120 Enzyme Enzyme Energy for extraction 400 Energy for extraction 100 compounds, a better alternative could be ethanol. HCl HCl 80 Methanol 300 Methanol

60 200

Case 1 – in carrots MJ/10 g quercetin 40

GWP (kg CO2-eq./10 g Q) (kg CO2-eq./10 GWP 100 Carotenoids are antioxidants and pigments, traditionally 20 0 0 extracted using an organic solvent such as hexane, petroleum Methanol + HCl PHWE + enzyme Methanol + HCl PHWE + enzyme ether or tetrahydrofuran. In an effort to establish “greener” Figure 3. Energy consumption (left) and global warming potential (right) for the extraction of quercetin from onion byproducts [5]. methods, hot ethanol was tested as extraction solvent [1], as Developed method: water at 120 °C and 50 bar, 15 min, enzymatic well as scCO2 mixed with vegetable oil. reaction at 85 °C and 10 min. Conventional method: methanol with Table 1. Environmental performance of extraction methods, with the HCl, 80 °C and 2 h. functional unit 1 g of β-carotene. For the scCO2-method, the carotenoids were recovered in vegetable oil. Carrots extracted Conclusions contained around 28 mg β-carotene/100 g f.w. carrot [1]. Choosing a solvent for extraction should include both consideration of of the compound to be extracted Parameter Convenonal Ethanol scCO2/oil and “greenness” of the solvent. As demonstrated for β- method* method** method*** carotene in Table 1, it is not certain which of the three Solvent amount 0.09 / 1.1 1.4 0 (kg) methods is to prefer. Our study further shows that LCA is a Extracon me per - 40 20 useful tool to compare the environmental impact of different sample (min) extraction methods, as demonstrated for betulin in birch bark *Based on solubility data for tetrahydrofuran respectively hexane, 20 °C [2] and quercetin in onion byproducts. **Ethanol at 60 °C, 50 bar, using an ASE-200 (Thermo) system. Sample: 2 g References of fresh carrot mixed with Hydromatrix. 1. Mustafa, A. et al., Molecules, 2012, 17, 1809. ***scCO /vegetable oil (86/14, v/v), 400 bar, 40 °C (0.99 g/mL), 5 mL/min. 2 2. Craft, N.E. & Soares, J.H., J. Agric. Food Chem., 1992, 40, 431. Total usage of recyclable compressed CO2 for 1 g of β-carotene was 341 kg. Sample: 1 g of freeze dried carrot. 3. Ekman, A. et al., subm. to J. Cleaner Prod., 2012. pdf available 4. Lindahl, S. et al, Green Chem., 2010, 1, 159. Research Poster pdf: SuReTech Research is funded by the Swedish Research Council Formas homepage: group – Sustainable Resource Technology (www.suretech.lu.se) homepage: