Environmental implications of crude glycerin used in special products for the metalworking industry and in biodegradable mulching films

Industrial Crops and Products 75 (2015) 29–35

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Environmental implications of crude glycerin used in special products for the metalworking industry and in biodegradable mulching films Lorenzo D’Avino a,∗ , Gianni Rizzuto b , Sara Guerrini c , Marco Sciaccaluga b , Eleonora Pagnotta d , Luca Lazzeri d a Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di ricerca per l’agrobiologia e la pedologia (CRA-ABP), via di Lanciola 12/A, Cascine del Riccio 50125, Firenze, Italy b Foundry Alfe Chem S.r.L. – Via Alessandria, 55, 10152 Torino, Italy c Novamont S.p.A. – Via G. Fauser 8, 28100 Novara, Italy d Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di ricerca per le colture industriali (CRA-CIN) – Via di Corticella 133, 40128 Bologna, Italy

a r t i c l e

i n f o

Article history: Received 11 July 2014 Received in revised form 5 February 2015 Accepted 20 February 2015 Available online 23 March 2015 Keywords: Glycerol Metal working fluids Biodegradable mulching films Biodegradation Bio-based product formulation

a b s t r a c t Crude glycerin from biodiesel supply chain can replace synthetic glycerol or other chemicals in industrial applications. To improve sustainability according to the biorefinery perspective, a purification phase will be carried out only if it is really necessary to reach standards for industrial processes or final products. In metal working, the use of crude glycerin-based hydraulic fluids, replacing mineral oil-based and glycolbased ones, has fulfilled industrial requirements and made it possible to increase (i) worker safety because of its non-flammability; (ii) biodegradability and (iii) time-life of the product due to anti-wear properties; in addition, post-use waste management will be simplified, due to the possibility to declassify fluids as special waste. In biodegradable mulching films, the replacement of synthetic glycerol was successful because it made it possible both to maintain the same compounding conditions and to obtain the same yields and film biodegradation in an agronomic trial on muskmelon. The benefits compared with conventional polyethylene films are the same as conventional readily biodegradable films. The key parameters in the analytical composition of glycerin concerning specific industrial applications are discussed; the environmental benefits in metal working fluid formulation and in mulching film compounding are then assessed. © 2015 Elsevier B.V. All rights reserved.

1. Introduction Crude glycerin (CG) is a byproduct of the biodiesel chain, every ton of methyl-ester produced generating approximately 0.1 tons of CG. According to the International Renewable Energy Agency, total biodiesel production in 2012 was more than 2 million tons of CG. 1,2,3-propanetriol (aka glycerol) is the main component of CG. Synthetic glycerol, which the carbon is generally fossil-based, is a high-value and commercial chemical with thousands of different applications; global demand was 1.99 mega tons in 2011 and this is expected to reach 3.06 mega tons by 2018 (Transparency Market Research, 2014). For these reasons, the industrial valorization of CG from biodiesel production is gaining interest in order to recoup part of the production cost of biodiesel and therefore to promote biodiesel industrialization on a large scale (Yang et al., 2012).

∗ Corresponding author. Tel.: +39 055 2492226; fax: +39 055 209177. E-mail address: [email protected] (L. D’Avino). http://dx.doi.org/10.1016/j.indcrop.2015.02.043 0926-6690/© 2015 Elsevier B.V. All rights reserved.

CG composition varies with the type of catalyst used to produce biodiesel, the transesterification efficiency, the recovery efficiency of the biodiesel, the presence of other impurities in the feedstock, and the recovery processes, if any. Hansen et al. (2009) studied the chemical compositions of 11CG collected from seven Australian biodiesel producers and indicated that the glycerol content ranged between 38% and 96%, with some samples including more than 14% methanol and 29% ash. Salt content in CG obtained with homogeneous alkaline catalyst generally ranged from 5 to 7% (Lancrenon and Fedders, 2008), and also in heterogeneous transesterification processes, impurities existing in the natural raw feedstock tend to accumulate in the CG phase. Pure glycerol is an extremely reactive molecule and for this characteristic is widely applied in many different applications, as confirmed by around three thousand patent applications, but CG has also been proposed as an excellent source of carbon in different fields starting from feed, i.e. calories for broilers, laying hens and pigs, although glycerol in excess may affect metabolism (Yang et al., 2012). In addition, fermentative industrial applications of CG

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produce propylene glycol, 1,3-propanediol (Mu et al., 2008), citric acid from Yarrowia lipolytica (Papanikolaou and Aggelis, 2009), poly(3-hydroxybutyrate) (PHB) (Ibrahim and Steinbüchel, 2009), docosahexaenoic and eicosapentaenoic acid from algae or fungi as ingredients for fortified foods or feeds (Athalye et al., 2009; Ethier et al., 2011), lipids with a high concentration of monounsaturated fatty acids (Liang et al., 2010), and succinic acid (Vlysidis et al., 2011). CG (without any purification) could also be used directly to produce methane by anaerobic digestion (López et al., 2009), acrolein by vaporization (Sereshki et al., 2010), and as a green solvent for some organic reactions (Wolfson et al., 2009). This work focused on the environmental implications of CG applications in two industrial fields which exemplify the potential of the industrial use of CG as a replacement for polluting chemicals or synthetic glycerol: in metal working fluids (MWFs) as safety hydraulic fluids and as a component of biodegradable mulching films (BMFs). MWFs, also called suds, coolants or slurry, are widely used in various manufacturing processes viz during the machining of metals to reduce friction and cooling and to help carry away debris such as swarf and fine metal particles. Over the last 10–15 years, globalization and the current economic and financial crisis have strongly changed the global lubricants industry structure. A majority of the MWFs used worldwide are based on non-renewable mineral oils. In 2010, about 5.3% of the worldwide lubricant consumption was used to formulate MWFs, which are about 197 million tons (Gosalia, 2010). The potential hazard towards human health and the environmental impact is a critical factor in the use of mineral oil-based MWFs (Dettmer, 2004). The application of CG as a main MWF component can be advantageous: since CG is produced from renewable resources, and it turns by- and surplus products into an innovative raw material for mineral oil replacement, also making it possible to achieve environmental certification as a biolubricant, e.g. European “ecolabel” or American “USDA biobased”. However, the possibility of using a lubricant from renewable carbon sources becomes interesting for the industry only when its technical performances are similar (or better) if compared to conventional mineral oils. In particular, not only lubrication, but also hydrolysis stability and oxidation stability via transesterification should be taken into account. A biolubricant containing natural source components (such as vegetal oil and/or CG), viz biobased lubricant, could ensure better lubrication and at the same time it could increase workers’ health and safety and reduce the environmental impact due to potentially better biodegradability (Lazzeri et al., 2006). For these reasons, it can be more easily disposed of than a product based on mineral oil, or after its disposal it could be a source of organic acids, useful as a domestic cleaning product or in the paint industry (Mannan, 2012). The second industrial application of CG investigated in this paper is mulching films; traditionally made of low density polyethylene (LDPE), these accounted for 25% of the 2.9 million tons of agricultural plastic films consumed worldwide in 2011, and in Europe alone 545,000 tons of plastic mulches per year (AMI, 2011). Conventional plastic mulching films are commodity products and therefore produced by the main converters active in the plastic agro-market. BMFs, excluding oxo-photo or other fragmentable mulches, are estimated to be applied several thousand tons per year in Europe, mainly in the horticultural areas. Biodegradable mulches can be laid on the same crops as traditional plastic mulches, but also on other crops where the harvesting requirements, the lack of herbicides or the agronomical techniques in general require a material with different performances in terms of end of life (e.g. raspberry and blueberry, processing tomato or vine). A BMF has mechanical properties and characteristics similar to traditional plastic mulches: good soil coverage until the end of the crop cycle with proper weed control, using the same laying machines and irrigation system, and guaranteeing similar crop

yield and quality (Scarascia-Mugnozza et al., 2006; Briassoulis, 2006, 2007). Differences mainly regard lower thickness (BMF is generally 12–15 ␮m depending on crop and climate condition), that allows a lower consumption of material per square meter and full biodegradability in soil, which is the key characteristic of these materials. In fact, they do not need to be removed from the field after their use and can be incorporated in the soil at the end of their life cycle and degraded by soil microorganisms, significantly reducing post-harvest plastic waste. On the contrary, in Europe, according to EC Directive n◦ 31 (1999)EC (1999) and EC Directive n◦ 76 (2000)EC (2000), conventional plastic mulch films must be removed from the field at the end of their use and properly disposed of, involving high costs due to contamination and degradation characteristics, including the contamination of the films with pesticides (Briassoulis et al., 2012, 2013). These difficulties can explain the low percentage of recovery of traditional plastic films and the illegal practices for disposal (burning in the field, uncontrolled landfilling, film incorporation in the soil at the end of the crop cycle) that involve environmental concerns (Garthe, 2004). These procedures, in fact, cause the release of dangerous substances in the soil, with a negative environmental impact (Kyricou and Briassoulis, 2007), but also in the air, through the burning that releases air pollutants, such as polycyclic aromatic hydrocarbons (Font et al., 2004). A valuable solution to this problem is provided by BMF. A mulching film can be considered “biodegradable” if it complies with the requirements of the norms on biodegradability (e.g. ISO 17556, 2012; ISO 14855-1, 2012; CEN 13432, 2005). There are different national standards that indicate how to assess the biodegradability in soil of a mulching film, e.g. NF U52-001 (2005) in France or UNI 11495 (2013) in Italy. In general, it is possible to summarize the various standards in a few main points: (i) absence of eco-toxicity effects on the soil and on the crops; (ii) no release of hazardous substances (i.e. heavy metals above certain thresholds) both in composting conditions and in soil; (iii) disintegration of the film; (iv) biodegradation (90% at soil temperature within 12 or 24 months) in standard condition and in comparison with a reference (crystalline cellulose). In this paper, the investigations and results covering the functional and chemical aspects of a new MWF based on CG derived from the biodiesel chain are presented, together with a systematic analysis of the performance of a new CG-based BMF. The type of formulation of the new products has to be considered as confidential information and it will not be reported in detail. The aims of this paper were to identify the environmental key issues in the use of CG in industrial applications in which the environmental cost of purification is not necessary and environmental benefits could be optimized. 2. Materials and methods 2.1. Materials CG derived from a biodiesel chain was purchased from Cerealdoks S.p.A. (Vicenza, Italy). Pure industrial glycerin, oil derived and used as a reference, was kindly provided by Foundry Chem (Torino, Italy). 2.2. Characterization of crude glycerin Glycerin density was measured by gravimetric analysis. Water, methanol and glycerol contents were determined by using, Karl Fischer colorimetric titration, UNI, (1996), GLC analysis, and HPLC determination, respectively. An HP1100 (Hewlett Packard, Waldbronn, Germany) system equipped with a HP1047A refractive index detector and an Aminex HPX-87H column (7.8 mm × 300 mm, Bio-

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Rad Richmond, USA) was used. The mobile phase used was 0.01 N sulfuric acid at a flow rate of 0.8 mL min−1 . The column and RID temperatures were maintained at 65 ◦ C and 35 ◦ C, respectively. The injection volume was 20 ␮L. An external six point calibration curve was constructed by analyzing standard dilutions of 99.5% glycerin from 10 to 25 mg mL−1 . Acidity and unsaponifiable fractions were determined applying NGD (1976) method C10 and C12, respectively; waxes were analyzed by gas chromatography following EC 2568 (1991); organic–halogenated compounds were determined by gas chromatography–mass spectrometry using a quadrupole detector. A capillary column Supelco SPB 624 60 m, 0.25 mm, 1.4 ␮m was used. A carrier gas at constant flow rate of 2 mL min−1 was used. Samples were injected at 40 ◦ C; the oven was then heated to 175 ◦ C at a rate of 27 ◦ C min−1 and from 175 ◦ C to 235 ◦ C at a rate of 4 ◦ C min−1 . Determination of ash content was performed according to BS-EN 14775 (2009); aldehydes and esters were analyzed according to AOAC 969.09 (2000); Cd, Cr, Cu and Pb were assayed by inductively coupled plasma spectrometry; samples were prepared according to AOAC 922.02 (1990) and the analysis according to AOAC 985.01 (1988).

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Table 1 Average conditions of compounding. Compounding conditions and parameters Revolution speed (rpm) Temperature profile (◦ C) Output (kg h−1 ) Energy motor (A) Venting pressure (Pa) Venting condensation (%) Die melt temperature (◦ C) Die pressure (MPa)

180–220 60–150–180–210 (4 times)–150 (2 times) 45–50 55–68 0 4.5–5.0 150–160 1–1.8

duration 60 ± 1 min. A Brugger test according to DIN 51347 (2000) was also carried out. 2.3.5. Metal working fluids anti-wear performances The resistance to chemical changes over time was evaluated according to ASTM D-2882 (2000) by using a Vickers V104C vane pump under the following conditions: 600 h test duration, 13.8 MPa discharge pressure, 38–42 ◦ C lubricant temperature, 1200 rpm speed, 3 L min−1 output volume.

2.3. Crude glycerin in metal working fluids 2.4. Processing parameters in manufacturing mulching films Several sectors of metal manufacturing were assessed to introduce biobased lubricant in formulation, in particular applications including CG in MWF formulation. CG-based MWF was characterized for stability in the cold following ASTM D-97 (2012b), viscosity at 40 ◦ C in line with the ISO 46 (1973) conditions laid down by DIN 51519 (1998), and cloud point according to ASTM D-5773 (2010). The new product was subjected to various tests in order to evaluate its properties. Non-flammability, biodegradability, compatibility with elastomers, and tribological properties were evaluated. 2.3.1. Metal working fluids non-flammability The product containing CG and the one containing pure glycerol were heated at T > 100 ◦ C and at a pressure of 70 kg cm−2 . They were then sprayed on an oxyacetylenic flame or on a steel plate heated at 650 ◦ C. 2.3.2. Metal working fluids biodegradability The biodegradability of the product containing CG and the one containing ethylene glycol was evaluated in fresh and demineralized water, according to OECD 310 (2006), using sodium benzoate as a reference substance, 106 cells density inoculum and determining the course of biodegradation by CO2 evolution. Triplicate bottles were analyzed after 28 days. A product could be classified as readily biodegradable under aerobic conditions if biodegradation rates of >60% were obtained in OECD test. 2.3.3. Metal working fluids compatibility with elastomers The product containing CG was tested on elastomers commonly used in “o-rings” according to the compatibility of the polymers by ASTM D-471 (2012a) which is an immersion test carried out in the absence of direct light, aimed to assess the effect of CGbased MWF on elastomers under defined conditions of time and temperature. The elastomers were immersed for 166 h in fluids at 80 ◦ C (since under normal conditions the hydraulic MWF can reach 70 ◦ C), assessing the variation in elastomer mass, shore hardness, volume and density. 2.3.4. Metal working fluids tribological tests The product containing CG was subjected to the four ball test in order to evaluate the tribological characteristics of lubricants. Tests were conducted according to ASTM D-4172 (2010) method under the following conditions: load 392 ± 2 N, speed 1200 ± 60 revolutions per minute (rpm), lubricant temperature 75 ± 2 ◦ C, test

CG granules were obtained by compounding the same dilution and quantities as for the oil-based glycerol and then built-into mulching film via blowing extrusion, adding compostable black masterbatch (7%). Table 1 reports the average conditions employed in the compounding process. The granules obtained were compared by melt flow rate (rpm) index at 160 ◦ C (5 kg) and melt density. The film was produced by film blowing, at the standard blowing conditions employed for biodegradable materials, as reported in Table 2. The BMFs obtained with these conditions were compared to the commercial mulch film Mater-Bi® (Novamont, Novara, Italy) by draw down ratio and blow up ratio and then analyzed in terms of mechanical properties. Young modulus (E), elongation at break (b ), tensile stress at break (␴b ), and energy at break (Enb ) were measured according to ASTM D-882 (1991). 2.5. Open field test on innovative mulching film The optimized mulch film containing CG was laid and checked for its agronomical characteristics at open field trial carried out at the Experimental Center for Horticulture “Po di Tramontana” in the Veneto Region, North East Italy, 3 km from Adriatic see (45◦ 04 N, 12◦ 14 E). The main characteristics of the trial are summarized in Table 3. The trial comprised the following treatments: (a) bare soil; (b) soil mulched by a 15 ␮m commercial black biodegradable Table 2 Film blowing average conditions. Conditions and parameters

Values

Revolution speed (rpm) Temperature profile (◦ C)

62–65 120–135–145 (2 times)/150–145 (2times)/145 (2 times) 35 10 2050 150–155 15.5–16.0 150–155 18.3–18.8 140–145 8.8–9.5

Energy motor (A) Air temperature at ring (◦ C) Fan speed (rpm) Melt temperature before filter (◦ C) Pressure before filter (MPa) Melt temperature after filter (◦ C) Pressure after filter (MPa) Die melt temperature (◦ C) Die pressure (Mpa)

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Table 3 Characteristics of the trial at Po di Tramontana, on muskmelon (2013). Crop and cultivar

Muskmelon (Cucumis melo L.); cv Macigno (Clause Italia S.p.A.)

Experimental design Seeding Laying of mulch films Transplanting and small tunnel covering Type of covering

Randomized blocks, 4 repetitions 1st March 2nd May 3rd May single row, 2.1 m inter-row, 0.75 on the row, 0.6 plant m−2 Small tunnel 0.8 m wide and 0.6 m high, with non-woven covering material; from the beginning of the test until 28th May Pelleted barn manure (3.5–3.5–3.5) 2 t ha−1 ; ternary fertilizer (12–17–17) 0.4 t ha−1 ; weekly fertirrigation, with a nutritive solution including macro and micro nutrients From 10th to 19th July

Fertilization

Harvesting

and rancidity, respectively. So, the key requirements reached by CG were: appearance, clear colorless liquid, low water content, low total acidity in oleic acid. Regarding BMF two specific key parameters were assessed: the content of water (in accordance with the Karl Fischer method) and the presence of impurities (e.g. methanol) and/or heavy metals, in order to avoid technical problems in the compounding processes and to be in line with the norms concerning biodegradation and environmental impact of the final products, i.e. EN13432, Annex A (CEN, 2005). Both for MWF and BMFs water content, methanol and impurities were considered compatible with the planned industrial processes.

3.2. New formulation for metalworking: opportunity and test results mulching from Novamont S.p.A. produced using pure glycerol; (c) soil mulched by a 15 ␮m experimental black biodegradable mulching from Novamont S.p.A. and produced using CG; (d) soil mulched by a conventional black LDPE mulching film. Commercial yields were subjected to analysis of variance by Statistica 8.0 (Statsoft, Inc.). Significant differences among treatments were determined by Tukey’s multiple range test (P ≤ 0.05). Soil temperature (weekly average soil temperature measured at 10 cm of depth in the soil during the crop cycle) was assessed comparing means ± standard error. Quality of the crop (thickness of the peal, hardness, sugar content, uniformity of fruit dimension, color of flesh), influence of the mulch film on the plant growth and production and visual assessment on the mulch film biodegradation was observed. 3. Results and discussion 3.1. CG characteristics The specifications of pure glycerol versus CG are reported in Table 4. CG showed a relatively lower content in glycerol due to the higher content in water and to the small content of ashes and methanol as a residue of the transesterification process. These changes determined a slight reduction in density. Impurities, including heavy metal content, organic halogenated compounds, aldehydes and esters were often close to the limit of detection and, anyway, did not represent a restriction for industrial non-food uses. The analytical weaknesses that limit the use of CG in the MWF formulation regarded mainly cleanliness properties and pour point; purification from natural waxes (contained in vegetable oil) and phospholipids by winterization was needed to prevent precipitate

Analyzing the MWF sector, the use of a formulation based on renewable materials in high steel rolling gave longer emulsion life and better cleanliness performances on sheets surface and in the area around the mill, compared to traditional products based on mineral oil (data not shown). Another interesting MWF sector was neat cutting oil, using a “full ester” formulation based on biobased lubricants and a polymeric ester tested successfully in denting operation, instead of a traditional cutting fluid with high content of chlorinated paraffin. Biobased lubricant chain oil in MWFs could also improve the environmental benefit due to improved biodegradability; as a matter of fact, the first application for biolubricants was in chainsaw oils, where lubricants are directly released into the environment. Among all the MWF sectors, however, the most promising application for CG was deemed hydraulic MWF, where CG makes it possible to formulate a water-based hydraulic fluid, replacing flammable fossil-based oil, reducing the risk of accidents in the workplace and also replacing ethylene glycol, which has important environmental and clinical consequences (Center for the Evaluation of Risks to Human Reproduction, 2004; Devlin and Schwartz, 2014). Anyway, in this application worker risks are limited to accidental loss, because hydraulic MWFs are generally locked into the industrial machinery. By using CG-based MWF, on the other hand, waste lubricant management could be definitely simplified compared to glycol-based and, even more, mineral oil-based MWFs, assuming, as a discriminant feature, the use of non-hazardous component in the rest of the formulation. The hydraulic MWF based on CG showed good stability with pour point <−20 ◦ C, viscosity within the ISO 46 requirements and a cloud point >70 ◦ C, analogous to the pure glycerol. The product passed the flammability test positively, and risk situations at the

Table 4 Specifications of tested crude glycerin versus pure industrial glycerol. Means ± standard deviation (when available).

Density at 20 ◦ C Glycerol content Water content Methyl alcohol Acidity in oleic acid Waxes Unsaponifiable Ashes Cadmium (Cd) Total Chromium (Cr) Lead (Pb) Copper (Cu) Organic–halogenated compounds Aldehydes expressed in acetic aldehyde Esters expressed in ethyl acetate n/a: not applicable.

Unit

Pure industrial glycerol

Crude biodiesel glycerin

g cm−3 % w/w % w/w % w/w % w/w mg kg−1 % w/w % w/w mg kg−1 mg kg−1 mg kg−1 mg kg−1 mg kg−1 mg kg−1 mg kg−1

1.26 ± 0.02 98.5 ± 0.7 1.5 <0.01 <0.1 n/a n/a <0.01 <0.05 0.05 ± 0.01 <0.05 0.16 ± 0.01 <0.01 <0.1 <1

1.23 ± 0.03 80.2 ± 0.6 14.7 1.34 0.41 ± 0.02 12 0.48 ± 0.02 4.21 ± 0.19 <0.05 0.02 ± 0.00 0.054 ± 0.003 0.58 ± 0.03 0.07 ± 0.01 0.76 ± 0.08 <1

L. D’Avino et al. / Industrial Crops and Products 75 (2015) 29–35 Table 5 Wear behavior in the Vickers vane pump test. Results are expressed as weight difference in grams.

Conventional product CG-based product

Rotor

Vanes

Stator

Total weight loss

0.402 0.050

0.045 0.104

4.159 1.523

4.606 1.677

workplace in the event of any contact with sources of heat loss, due to accidental causes, are therefore avoided. The formulation containing CG showed an ultimate biodegradability in fresh water of 63.4 ± 3.9% in 28 days, so it is classifiable as readily biodegradable, while conventional water/glycol MWF did not exceed 50%. In general, according to Stolte et al. (2012), biodegradability is a key parameter in the hazard assessment of lubricants and chemicals, affecting the tendency to bioaccumulate or to persist in the environment. In this application the biodegradation in fresh water is particularly important, due to the management in biological waste water treatment units of tramp oil or hydraulic fluid at the end of its life. Therefore the increase in biodegradability is an important benefit of this new product as it combines work safety with eco-compatibility of fluids used in industrial processes. During their time-life, lubricants come into contact with some polymeric items such as joints and seals in a continuous or intermittent mode, and following exposure to such fluids, the properties of polymeric materials can deteriorate, mainly affecting their physical-chemical, mechanical or dimensional characteristics. The new product based on CG proved compatible with useful elastomers; in particular, it showed compatibility with red and white silicon, polyurethane, nitrile butadiene rubber, ethylene-propylene diene monomer, Viton® , Teflon® and Vulkollan® . Specifically, none of the cases showed dimensional variation; mass variation was lower than 4% (and lower than 1% in most cases), a slight softening was observed (but without variation between 22 and 166 h) and also variation in density and volume was not significant. These results are extremely promising, taking into account (i) that the softening increase and the mass or volume variation of o-rings or seals lead up to the elastomers break, causing fluid losses and (ii) that a weakness of conventional MWFs is just the wear of some polymers. Indeed, industrial experiences carried out by Foundry Alfe Chem with glycol and fossil-based hydraulic fluids highlighted that fluids affected some seals in nitrile (buna-N) rubber. Regarding tribological tests, the product based on CG was similar to conventional products in use in the four ball test and the load capacity in the Brugger test was about double that of conventional water/glycol MWF (79 vs 39 N mm−2 ), showing a comparatively better lubrication and, consequently, a lower wear of pump elements and valves. Finally, CG-based MWF showed higher resistance to chemical alteration by wear behavior in the Vickers vane pump test. As reported in Table 5, the total wear was about 35% lower than conventional glycol-based hydraulic MWF. In particular, the rotor weight loss was negligible and stator weight loss was significantly less in CG-based MWF. Consequently, the risk in pipe deposition and lodgement markedly decreases, prolonging the life cycle of the

Table 6 The blowing process parameters to produce mulching films containing crude glycerin and oil-based glycerol. The resulting melt flow rate was for both materials into the range values reported in the table and required by technical specification. Common characteristics Draw down ratio Blow up ratio Melt density (g cm−3 ) Melt flow rate (g 10 s−1 )

Table 7 Common characteristics of biodegradable mulching films (BMF) containing crude glycerin (CG) and oil-based glycerol. All parameters were measured according to standard methods cited in the text. Material Synthetic glycerol BMF CG BMF

CG: crude glycerin.

18.9 3.18 1.13–1.18 4.5–5.0

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␴b (MPa)

b (%)

E (MPa)

Enb (kJ m−2 )

TP (N mm−1 )

33 31

239 293

393 382

2759 3318

89 80

␴b : tensile stress at break; b : elongation at break; E: young’s modulus; Enb : energy at break; TP: tear propagation.

product, provided that external contamination is removed by an effective filtration system. 3.3. Crude glycerine in biodegradable mulching films: test results and opportunity CG was substituted for the oil-based one in the preparation of the raw materials (reactive extrusion and compounding). The granules obtained with CG were tested for the melt flow rate, which is one of the most important parameters for the optimal transformation via extrusion blowing into a film. Also for this parameter no differences were observed between the pure glycerol and CG-based materials. The granules were then extrusion blown using the same parameters as for the oil-based glycerol raw material, obtaining a mulch film to which compostable black masterbatch was added. The films were produced at a nominal thickness of 15 ␮m, which is the normal thickness of BMFs. As reported in Table 6, process parameters were the same for both materials, the resulting melt flow rate was into the range value required in the technical specification, no differences were observed between the two types of materials and no water was detected in BMFs. Mechanical property values (i.e. young modulus, elongation at break, tear propagation, tensile stress at break) are reported in Table 7. These values were, for both BMFs, higher than the thresholds set by some standards (e.g. UNI 11495, 2013) and therefore did not affect the minimum level of mulch mechanization, as confirmed in the open field test. For all tested materials, tear propagation was classified as strong, following ASTM D-1922 (2009). Finally, the compounding process with CG-based BMFs did not present any critical point, and did not differ from the pure glycerolbased BMFs. Similarly, the process of film blowing did not show any critical point compared to the commercial raw materials, leading to the production of good quality CG-based BMF. 3.4. Open field test on innovative biodegradable mulching film During the first cultivation phases (3rd–31st May, 2013) the highest temperatures in the soil were recorded, as expected, under LDPE mulch film and the lowest under bare soil. Compared with CG containing BMF, in soil mulched with LDPE the temperature was Table 8 Main influence of different mulching treatments on marketable muskmelon yield. Earliness is marketable yield (kg m−2 ) at the first 10 days of harvesting. Treatment

Total yield (kg m−2 )

Earliness (kg m−2 )

Average fruit weight (kg)

Bare soil LDPE mulching film Synthetic glycerol BMF Crude glycerin BMF Significance

1.1b 4.6a 4.4a 3.9a **

0.2b 1.8a 1.8a 1.6a ***

1.2b 1.6a 1.5ab 1.6a *

*Significant at the P ≤ 0.05 level; **significant at the P ≤ 0.01 level; ***significant at the P ≤ 0.001 level; in the same column the values without common letters are significantly different for P ≤ 0.05% in accordance with Tukey’s test; LDPE: low density polyethylene; BMF: biodegradable mulching film.

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higher (+1.2 ◦ C ± 0.4), while in bare soil it was lower (−0.8 ± 0.4). After 31st May when the weather conditions became more stable, the plants in all mulched treatment almost completely covered the mulch film and the temperatures recorded under all the biodegradable mulch films were similar to those under LDPE mulched soil. At harvesting time, the data showed no statistical difference in yield and earliness on the fruits obtained by the conventional plastic films and those obtained using BMF produced both using pure glycerol and CG, while yields were statistically improved when compared with bare soil (Table 8). The fruits obtained from BMF showed an average fruit weight ranging from 1553 g for BMW with pure glycerol to 1635 obtained with CG-based BMW, although this difference was within the experimental error. Mulching was confirmed as a fundamental technique for melon weight improvement, considering that all three mulched film test results were significantly higher than those with bare soil, that reached a mean weight of 1191 g. In further observations (data not shown) concerning (i) peal thickness (ii) hardness and (iii) sugar content, no statistical differences were obtained among the different treatments; (iv) the bare soil treatment showed a higher degree of discrepancy in terms of fruit dimensions, together with (v) a lower chromatic intensity; (vi) concerning the development of vegetation, the non-mulched plants showed a reduced growth with a lower leaf coverage and uniformity that on non-mulched soil determined a higher manual weeding requirement; (vii) at harvesting time, the exposed parts of both biodegradable and conventional mulched films showed sufficient performances in terms of degradation, considering that the biodegradable films showed a slight degradation only after 75 days, three days before the end of harvest (Table 3). These results are promising taking into account the environmental implications of BMFs. An Italian study carried out in 2009 analyzed the environmental impact of biodegradable mulches in comparison with conventional plastic ones, the savings by BMFs were estimated at over 500 kg of CO2 equivalent per hectare of mulch. These data were obtained considering the typical end-oflife scenario for all conventional plastic materials utilized in Italian agriculture, where 10% is recycled, 14% is incinerated and 78% is sent to landfill after use (Razza et al., 2010).

4. Conclusion The inclusion of CG in industrial processes could increase the renewable content in product formulation, when replaces synthetic glycerol. In terms of global warming potential, the production of synthetic glycerol was estimated at 9.6 kg of CO2 equivalent per kg (Van Dam et al., 2009); these emissions could be reduced or saved using CG, obtained as a byproduct from the biodiesel chain, but only if the replacement feasibility exceeds the industrial performance requirements. Also in BMF the substitution was successful, increasing the renewable carbon. The biodegradable mulch films’ performance in the field confirmed that, compared to those with synthetic glycerol, biodegradable mulches with CG showed no significant differences for yield quality and quantity; no differences among the biodegradable mulches and LDPE mulch were evident. These results therefore showed that BMFs represent a real alternative for crop management in order to reduce the production of plastic waste that can be generated by agricultural production. Furthermore, the substitution of CG in the industrial formulation was shown to be successful at all levels and the innovative mulch film obtained can therefore increase its value in terms of reduction of environmental impact. In addition, pure glycerol and CG, both characterized by low environmental and human toxicity (UNEP, 2002; EFSA, 2010), could replace pollutant components such as mineral oil or ethylene glycol in special products for metal working. Furthermore, the use of CG

could also limit the addition of biocide in MWF formulations due to the good biostatic effect of glycerol (Winter et al., 2012). In all these cases, replacement increases the safety of workers and reduces environmental impact. In addition, the possibility (i) to reduce the time-life of the product due to the increase in wear resistance and (ii) to avoid the special waste code (generally associated with waste with hazardous properties, which may render it harmful to human health or the environment) could simplify and markedly reduce lubricant management costs. This new formulation of hydraulic MWF won the innovation award in a international biennial expo of customized technology for the aluminium & innovative metals (Metef) in June 2014. Finally, the increase of the biobased carbon content by CG, potentially enables the achievement of several current environmental certifications, e.g. Environmental Product Declaration, ecolabel or Vinc¸otte in Europe, biobased USDA in the American biopreferred program, or those which are likely to be finalized in the near future. Acknowledgements The trials were performed as a part of the activities of the Project “Sistema Integrato di Tecnologie per la valorizzazione dei sottoprodotti della filiera del Biodiesel (VALSO) financed by Italian Ministry of Agricultural, Food and Forestry Policies (MiPAAF D.M. 17533/7303/10 del 29/04/2010) and coordinated by CRA-CIN of Bologna. Characterization of CG and pure glycerol was carried out by INNOVHUB-SSI (Divisione Stazione Sperimentale Industrie Oli e Grassi) Milano, Italy and by Istituto di Ricerche Agrindustria srl (Research Institute for Agro-industry, Modena, Italy). We thank Laura Righetti, Susanna Cinti and Onofrio Leoni for cooperation in paper revision. References AOAC (Association of Analytical Communities) 985.01, 1988. Official Methods of Analysis. Metals and Other Elements in Plants and Pet Foods, 16th ed. AOAC International Official Methods of analysis, Washington, USA. AOAC (Association of Analytical Communities) 922.02, 1990. Official Methods of Analysis. Plants, 15th ed. AOAC International Official Methods of analysis, Washington, USA. AOAC (Association of Analytical Communities) 969.09, 2000. Official Methods of Analysis. Alcohols (Higher) and Ethyl Acetate in Distilled Liquors, 17th ed. AOAC International Official methods and analysis, Gaithersburg, USA. AMI (Applied Market Information), 2011. Agricultural Film Proceedings. Applied Market Information Ltd., Bristol, United Kingdom. ASTM (American Society for Testing and Materials), D-882, 1991. Standard Test Method for Tensile Properties of Thin Plastic Sheeting. American Society for Testing and Materials International, West Conshohocken, PA, USA. ASTM (American Society for Testing and Materials), D-2882, 2000. Standard Test Method for Indicating the Wear Characteristics of Petroleum and Non-petroleum Hydraulic Fluids in Constant Volume Vane Pump. American Society for Testing and Materials International, West Conshohocken, PA, USA. ASTM (American Society for Testing and Materials), D-1922, 2009. Standard Test Method for Propagation Tear Resistance of Plastic Film and Thin Sheeting by Pendulum Method. American Society for Testing and Materials International, West Conshohocken, PA, USA. ASTM, (American Society for Testing and Materials), D-4172, 2010. Standard Test Method for Wear Preventive Characteristics of Lubricating Fluid (Four-Ball Method). American Society for Testing and Materials International, West Conshohocken, PA, USA. ASTM (American Society for Testing and Materials D-5773, 2010. Standard Test Method for Cloud Point of Petroleum Products (Constant Cooling Rate Method). American Society for Testing and Materials International, West Conshohocken, PA, USA. ASTM (American Society for Testing and Materials), D-471, 2012a. Standard Test Method for Rubber Property—Effect of Liquids. American Society for Testing and Materials International, West Conshohocken, PA, USA. ASTM (American Society for Testing and Materials), D-97, 2012b. Standard Test Method for Pour Point of Petroleum Products. American Society for Testing and Materials International, West Conshohocken, PA, USA. Athalye, S.K., Garcia, R.A., Wen, Z.Y., 2009. Use of biodiesel-derived crude glycerol for producing eicosapentaenoic acid (EPA) by the fungus Pythium irregular. J. Agric. Food Chem. 57, 2739–2744.

L. D’Avino et al. / Industrial Crops and Products 75 (2015) 29–35 Briassoulis, D., 2006. Mechanical behavior of biodegradable agricultural films under real field conditions. Polym. Degrad. Stab. 18, 1256–1272, ISSN 0141-3910 http://dx.doi.org/10.1016/j.polymdegradstab.2005.09.016 Briassoulis, D., 2007. Analysis of the mechanical and degradation performances of optimised agricultural biodegradable films. Polym. Degrad. Stab. 92, 1115–1132 http://dx.doi.org/10.1016/j.polymdegradstab.2007.01.024 Briassoulis, D., Hiskakis, M., Babou, E., Antiohos, S.K., Papadi, C., 2012. Experimental investigation of the quality characteristics of agricultural plastic wastes regarding their recycling and energy recovery potential. Waste Manage. 32, 1075–1090 http://dx.doi.org/10.1016/j.wasman.2012.01.018 Briassoulis, D., Hiskakis, M., Babou, E., 2013. Technical specifications for mechanical recycling of agricultural plastic waste. Waste Manage. 33, 1516–1530 http://dx.doi.org/10.1016/j.wasman.2013.03.004 BS-EN (British-Adopted European Standard) 14775, 2009. Solid Biofuels. Determination of Ash Content. British Standard Institution1. CEN (Comité Européen de Normalisation) 13432, 2005. Packaging – Requirements for Packaging Recoverable Through Composting and Biodegradation–Test Scheme and Evaluation Criteria for the Final Acceptance of Packaging. European Committee for Standardization, Brussels, Belgium. Center for the Evaluation of Risks to Human Reproduction, 2004. NTP-CERHR expert panel report on the reproductive and developmental toxicity of ethylene glycol. Reprod. Toxicol. 18 (4), 457–532, http://dx.doi.org/10.1016/j.reprotox.2004.01.003. DIN (Deutsches Institut Fur Normung), 51347, 2000. Lubricants – Testing of Lubricants – Testing Under Boundary Lubricating Conditions with the Brugger Lubricant Tester. Deutsches Institut Fur Normung E.V., German National Standard). DIN (Deutsches Institut Fur Normung), 51519, 1998. Lubricants – ISO Viscosity Classification for Industrial Liquid Lubricants. Deutsches Institut Fur Normung E.V., German National Standard). Dettmer, T., 2004. Not Water Miscible Metalworking Fluids on the Basis of Renewable Raw Materials. Dr. -Ing. Diss. TU Braunschweig, Vulkan Verlag, Essen, Germany (In German). Devlin, J.J., Schwartz, M., 2014. Ethylene Glycol, In Encyclopedia of Toxicology. In: Wexler, Philip (Ed.), 3rd ed. Academic Press, Oxford, pp. 525–527, http://dx.doi.org/10.1016/B978-0-12-386454-3.728-4, ISBN 9780123864550. EC (European Union) Regulation n(2568), 1991. Regulation of the European commission on the characteristics of olive oils and olive-pomace oils as well as their relevant methods of analysis. Off. J. Eur. Communities L248, 1–83. EC (European Union) Directive n(31), 1999. The landfill of waste. Off. J. Eur. Communities L182, 1–19. EC (European Union) Directive n(76), 2000. The incineration of waste. Off. J. Eur. Communities L332, 91–111. EFSA (European Food Safety Authority), 2010. Scientific opinion on the abiotic risks for public and animal health of glycerine as co-product from the biodiesel production from category 1 animal by-products (ABP) and vegetable oils. EFSA J. 8 (accessed 07.10.14.) www.efsa.europa.eu/it/efsajournal/pub/1934.htm. Ethier, S., Woisard, K., Vaughan, D., Wen, Z.Y., 2011. Continuous culture of the microalgae schizochytrium limacinu on biodiesel-derived crude glycerol for producing docosahexaenoic acid. Bioresour. Technol. 102, 88–93. Font, R., Aracil, I., Fullana, A., Conesa, J.A., 2004. Semivolatile and volatile compounds in combustion of polyethylene. Chemosphere 57 (7), 615–627, http://dx.doi.org/10.1016/j.chemosphere.2004.06.020. Garthe, J., 2004. Managing Used Agricultural Plastics. In: Lamont, W. (Ed.), Production of Vegetables, Strawberries, and Cut Flowers Using Plasticulture. Natural Resource, Agriculture, and Engineering Service (NRAES), Ithaca. Gosalia, A., 2010. The European base oils and lubricants industry: trends in a global context. Lube Mag. 95, 8–16. Hansen, C.F., Hernandez, A., Mullan, B.P., Moore, K., Trezona-Murray, M., King, R.H., Pluske, J.R., 2009. A chemical analysis of samples of crude glycerol from the production of biodiesel in Australia, and the effects of feeding crude glycerol to growing-finishing pigs on performance plasma metabolites and meat quality at slaughter. Anim. Prod. Sci. 49, 154–161. Ibrahim, M.H.A., Steinbüchel, A., 2009. Poly(3-hydroxybutyrate) production from glycerol by Zobellella denitrifican MW1 via high-cell-density fed-batch fermentation and simplified solvent extraction. Appl. Environ. Microbiol 75, 6222–6231. ISO (International Organization for Standardization) 46, 1973. Aircraft – Fuel Nozzle Grounding Plugs and Sockets. International Organization for Standardization, Geneva. ISO (International Organization for Standardization) 17556, 2012. Plastics – Determination of the Ultimate Aerobic Biodegradability of Plastic Materials in Soil by Measuring the Oxygen Demand in a Respirometer or the Amount of Carbon Dioxide Evolved. International Organization for Standardization, Geneva. ISO (International Organization for Standardization) 14855-1, 2012. Determination of the Ultimate Aerobic Biodegradability of Plastic Materials under Controlled Composting Conditions – Method by Analysis of Evolved Carbon Dioxide – Part 1: General Method. International Organization for Standardization, Geneva.

35

Kyricou, I., Briassoulis, D., 2007. Biodegradation of agricultural plastic films. A critical review. J. Polym. Environ. 15, 125–150. Lancrenon, X., Fedders, J., 2008. An innovation in glycerin purification. Biodiesel Mag. 2008 (May (14th)) (accessed 07.10.14.) http://www.biodieselmagazine.com/articles/2388/an-innovation-in-glycerin -purification Lazzeri, L., Mazzoncini, M., Rossi, A., Balducci, E., Bartolini, G., Giovannelli, L., Pedriali, R., Petroselli, R., Patalano, G., Agnoletti, G., Borgioli, A., Croce, G., D’Avino, L., 2006. Biolubricants for the textile and tannery industries as an alternative to conventional mineral oils: an application experience in the Tuscany province. Ind. Crops Prod. 24, 280–291. Liang, Y.N., Sarkany, N., Cui, Y., Blackburn, J.W., 2010. Batch stage study of lipid production from crude glycerol derived from yellow grease or animal fats through microalgal fermentation. Bioresour. Technol. 101, 6745–6750. López, J.Á.S., Santos, M.D.M., Pérez, A.F.C., Martín, A.M., 2009. Anaerobic digestion of glycerol derived from biodiesel manufacturing. Bioresour. Technol. 100, 5609–5615. Mannan, S., 2012. Lees’ Loss Prevention in the Process Industries. Hazard Identification, Assessment and Control, 4th ed. Butterworth-Heinemann, United Kingdom. Mu, Y., Xiu, Z.L., Zhang, D.J., 2008. A combined bioprocess of biodiesel production by lipase with microbial production of 1:3-propanediol by Klebsiella pneumonia. Biochem. Eng. J. 40, 537–541. NF (Norme Franc¸aise) U52-001, 2005. Matériaux Biodégradables Pour L’agriculture Et L’horticulture - Produits De Paillage - Exigences Et Méthodes D’essai, Afnor Ed. La Plaine Saint-Denis, France. NGD (Norme Grassi e Derivati), 1976. Method C10-1976 and C12-1976,c10- and C12-1976. Stazione Sperimentale per le industrie degli oli e grassi, Milano, Italy. OCED (Organisation for Economic Cooperation and Development), 310, 2006. Ready Biodegradability – CO2 in Sealed Vessels (Headspace Test), Oecd Guidelines for the Testing of Chemicals, Section 3. OECD Publishing, http://dx.doi.org/10.1787/9789264016316-en. Papanikolaou, S., Aggelis, G., 2009. Biotechnological valorization of biodiesel derived glycerol waste through production of single cell oil and citric acid by Yarrowia lipolytic. Lipid Technol. 21, 83–87. Razza, F., Farachi, F., Degli Innocenti, F., 2010. Assessing the environmental performance and eco-toxicity effects of biodegradable mulch film, published in the conference proceedings of: LCA food 2010 VII. Bari (Italy) September 22-24 2010 In: International Conference on Life Cycle Assessment in the Agri-food Sector, vol. 2, pp. 378–383. Scarascia-Mugnozza, G., Schettini, E., Vox, G., Malinconico, M., Immirzi, B., Pagliara, S., 2006. Mechanical properties decay and morphological behavior of biodegradable films for agricultural mulching in real scale experiment. Polym. Degrad. Stab. 91, 2801–2808. Sereshki, B.R., Balan, S.J., Patience, G.S., Dubois, J.L., 2010. Reactive vaporization of crude glycerol in a fluidized bed reactor. Ind. Eng. Chem. Res. 49, 1050–1056. Stolte, S., Steudte, S., Areitioaurtena, O., Pagano, F., Thöming, J., Stepnowski, P., Igartua, A., 2012. Ionic liquids as lubricants or lubrication additives: an ecotoxicity and biodegradability assessment. Chemosphere 89 (9), 1135–1141, http://dx.doi.org/10.1016/j.chemosphere.2012.05.102. Transparency Market Research, 2014. Report: glycerol market expected to reach $2.1 billion in 2018. Biodiesel Mag. (March (14)) (accessed 07.10.14.) http://www.biodieselmagazine.com/articles/9004/report-glycerol-market -expected-to-reach-2-1-billion-in-2018 UNI (Ente Italiano di Normazione) N(22048), 1996. Oli E Grassi Vegetali Ed Animali E Derivati. Biodiesel. Determinazione Del Contenuto in Alcole Metilico. Ente Italiano di Normazione, Milano, Italy. (UNI (Ente Italiano di Normazione) N(11495), 2013. Materiali Termoplastici Biodegradabili per Uso in Agricoltura E Orticoltura – Film per Pacciamatura – Requisiti E Metodi Di Prova. Ente Italiano di Normazione, Milano, Italy. UNEP (United Nations Environment Programme), 2002. Glycerol, CAS N(56-81-5) (accessed 07.10.14.) http://www.chem.unep.ch/irptc/sids/OECDSIDS/56815.pdf Van Dam, J., Faaij, A.P.C., Hilbert, J., Petruzzi, H., Turkenburg, W.C., 2009. Large-scale bioenergy production from soybeans and switchgrass in Argentina part B. Environmental and socio-economic impacts on a regional level. Renew. Sustainable Energy Rev. 03, 012. Vlysidis, A., Binns, M., Webb, C., Theodoropoulos, C., 2011. A techno-economic analysis of biodiesel biorefineries: assessment of integrated designs for the co-production of fuels and chemicals. Energy 36, 4671–4683. Winter, M., Bocka, R., Herrmanna, C., Stache, H., Wichmannb, H., Bahadir, M., 2012. Technological evaluation of a novel glycerol based biocide-free metalworking fluid. J. Cleaner Prod. 35, 176–182. Wolfson, A., Litvak, G., Dlugy, C., Shotland, Y., Tavor, D., 2009. Employing crude glycerol from biodiesel production as an alternative green reaction medium. Ind. Crops Prod. 30, 78–81. Yang, F., Hanna, M.A., Sun, R., 2012. Value-added uses for crude glycerol-a byproduct of biodiesel production. Biotechnol. Biofuels 5 (13), http://dx.doi.org/10.1186/1754-6834-5-13.