Performance and Environmental Impact of Biodegradable Films in Agriculture: A Field Study on Protected Cultivation

The performance, the degradability in soil and the environmental impact of biodegradable starch-based soil mulching and low tunnel films were assessed by means of field and laboratory tests. The lifetime of the biodegradable mulches was 9 months and of the biodegradable low-tunnel films 6 months. The radiometric properties of the biodegradable films influenced positively the microclimate: air temperature under the biodegradable low tunnel films was 2 °C higher than under the low density polyethylene films, resulting in an up to 20% higher yield of strawberries. At the end of the cultivation period, the biodegradable mulches were broken up and buried in the field soil together with the plant residues. One year after burial, less than 4% of the initial weight of the biodegradable film was found in the soil. According to ecotoxicity tests, the kinetic luminescent bacteria test with Vibrio fischeri and the Enchytraeus albidus ISO/CD 16387 reproduction potential, there was no evidence of ecotoxicity in the soil during the biodegradation process. Furthermore, there was no change in the diversity of ammonia-oxidizing bacteria in the soil determined on the basis of the appearance of amoA gene diversity in denaturing gradient gel electrophoresis.     

Influence for Soil Environment by Continuing use of Biodegradable Plastic

The influence on soil environment by continuing use of the biodegradable plastic films (biodegradable mulching films) in farmland was investigated. The difference was not seen in the amount of soil bacteria between mulching film plowing sections and non-plowing sections. The total bacteria amount did not increase by the effect of plowing the biodegradable mulching film. Poly-(butylene succinate and adipate) (PBSA) and poly-(ε-caprolactone) (PCL) decomposing bacteria did not increase in PBSA and PCL mulching film plowing sections comparing polyethylene covering section (PE) and no-film section. Polylactic acid (PLA) decomposing bacteria were not detected in all sections. Total denaturing gradient gel electrophoresis (DGGE) band patterns did not show a clear transition of the bacterial community structure in both the cultivating and promoting sections. In usual usage condition of the biodegradable plastic films, it was hardly influence to the soil environment such as bacterial community structure in farmland.     

Biodegradation of Epoxy and MF Modified Polyurethane Films Derived from a Sustainable Resource

Mesua ferrea L. seed oil (MFLSO) modified polyurethanes blends with epoxy and melamine formaldehyde (MF) resins have been studied for biodegradation with two techniques, namely microbial degradation (broth culture technique) and natural soil burial degradation. In the former technique, rate of increase in bacterial growth in polymer matrix was monitored for 12 days via a visible spectrophotometer at the wavelength of 600 nm using McFarland turbidity as the standard. The soil burial method was performed using three different soils under ambient conditions over a period of 6 months to correlate with natural degradation. Microorganism attack after the soil burial biodegradation of 180 days was realized by the measurement of loss of weight and mechanical properties. Biodegradation of the films was also evidenced by SEM, TGA and FTIR spectroscopic studies. The loss in intensity of the bands at ca. 1735 cm⁻¹ and ca. 1050 cm⁻¹ for ester linkages indicates biodegradation of the blends through degradation of ester group. Both microbial and soil burial studies showed polyurethane/epoxy blends to be more biodegradable than polyurethane/MF blends. Further almost one step degradation in TG analysis suggests degradation for both the blends to occur by breakage of ester links. The biodegradation of the blends were further confirmed by SEM analyses. The study reveals that the modified MFLSO based polyurethane blends deserve the potential to be applicable as “green binders” for polymer composite and surface coating applications.     

Action of soil microorganisms on PCL and PHBV blend and films

Poly(hydroxybutyrate-co-valerate) (PHBV) and poly(ε-caprolactone) (PCL) PCL/PHBV (4:1) blend films were prepared by melt-pressing. The biodegradation of the films in response to burial in soil for 30 days was investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG). The PHBV film was the most susceptible to microbial attack, since it was rapidly biodegraded via surface erosion in 15 days and completely degraded in 30 days. The PCL film also degraded but more slowly than PHBV. The degradation of the PCL/PHBV blend occurred in the PHBV phase, inducing changes in the PCL phases (interphase) and resulting in an increase of its crystalline fraction.     

Comparison of the weight-loss degradability of various biodegradable plastics under laboratory composting conditions

Eight kinds of biodegradable plastics were compared for their degradability in controlled laboratory composting conditions. A thin film of each plastic was mixed into the composting material, and weight-loss degradability was calculated from the weight changes of the film during composting. It was found that weight-loss degradability strongly depended on the specific kind of biodegradable plastic; two were very high, four moderate, and the remaining two very slight. The most easily degradable plastic degraded by as much as 81.4% over 8 days of composting. By comparing the weight-loss degradability with ultimate degradability, which is defined as a molar ratio of carbon loss as CO₂ to the carbon contained in the biodegradable plastic, the order of the ease of degradation of the biodegradable plastics differed. Received: February 7, 2000 / Accepted April 14, 2000     

Physical and Thermal Analysis of the Degradation of Poly(3-Hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-4-Hydroxybutyrate) Coated Paper in a Constructed Soil Medium

The degradation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) coated brown Kraft paper and its components in a constructed soil environment was investigated. Soil burial tests were carried out over 8 weeks. Weight loss measurements, photographic analysis, environmental scanning electron microscopy (ESEM), dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) were conducted to assess the physical, structural, mechanical and thermal behavior before and after the soil burial test. Paper showed the highest physical degradation and weight loss. With respect to the control samples, the stiffness of the partially degraded samples decreased. The overall crystallinity of the biopolymer and the coated paper was affected significantly by burial. The pure biopolymer’s weight loss was substantially enhanced when coated on paper. This result reveals a possible increased microbial population in the coated paper relative to the pure biopolymer.     

Preparation and Characterization of Gamma Irradiated Sugar Containing Starch/Poly (Vinyl Alcohol)-Based Blend Films

Blends based on different ratios of starch (35–20%) and plasticizer (sugar; 0–15%) keeping the amount of poly(vinyl alcohol) (PVA) constant, were prepared in the form of thin films by casting solutions. The effects of gamma-irradiation on thermal, mechanical, and morphological properties were investigated. The studies of mechanical properties showed improved tensile strength (TS) (9.61 MPa) and elongation at break (EB) (409%) of the starch-PVA-sugar blend film containing 10% sugar. The mechanical testing of the irradiated film (irradiated at 200 Krad radiation dose) showed higher TS but lower EB than that of the non-radiated film. FTIR spectroscopy studies supported the molecular interactions among starch, PVA, and sugar in the blend films, that was improved by irradiation. Thermal properties of the film were also improved due to irradiation and confirmed by thermo-mechanical analysis (TMA), differential thermo-gravimetric analysis (DTG), differential thermal analysis (DTA), and thermo-gravimetric analysis (TGA). Surface of the films were examined by scanning electron microscope (SEM) image that supported the evidence of crosslinking obtained after gamma irradiation on the film. The water up-take and degradation test in soil of the film were also evaluated. In this study, sugar acted as a good plasticizing agent in starch/PVA blend films, which was significantly improved by gamma radiation and the prepared starch-PVA-sugar blend film could be used as biodegradable packaging materials.     

Preparation and Characterization of Compatible and Degradable Thermoplastic Starch/Polyethylene Film

The degradability of the compatible thermoplastic starch/polyethylene film was investigated by weight loss percent (WLP), Fourier Transform Infrared (FT-IR) Spectroscopy, and Scanning Electron Microscope (SEM). The compatible film was prepared by using the particles of thermoplastic starch/polyethylene blends that were produced by one-step reactive extrusion. The weight of the film after degradation reduced more than 3% for 30 days and 4% for 60 days. The FTIR results revealed that both starch and polyethylene in the film exhibited varying degrees of degradation. SEM photographs of the films after degradation showed that starch particles in the film disintegrated into smaller particles or separated out of the film surface. Degradation studies demonstrated that the compatible thermoplastic starch/polyethylene film had increased degradability at the given degradable environment. The information implies that this film could be utilized as a degradable plastic.     

Biodegradability of Chemically Modified Starch (RS4)/PVA Blend Films: Part 2

Biodegradable films were successfully prepared by using cornstarch (CS), chemically modified starch (RS4), polyvinyl alcohol (PVA), glycerol (GL), and citric acid (CA). The physical properties and biodegradability of the films using CS, RS4, and additives were investigated. The results of the investigation revealed that the RS4-added film was better than the CS-added film in tensile strength (TS), elongation at break (%E), swelling behavior (SB) and solubility (S). Especially, the RS4/PVA blend film with CA as an additive showed physical properties superior to other films. Furthermore, when the film was dried at low temperature, the properties of the films clearly improved because the hydrogen bonding was activated at low temperature. The biodegradation of films was carried out using the enzymatic, microbiological and soil burial test. The enzyme used in this study was amyloglucosidase (AMG), α-amylase (α-AM) and β-amylase (β-AM). At the enzymatic degradation test, the GL-added films had an approximately 60% degradation, while the CA-added films were degraded about 25%. The low degradation value on CA-added film is attributed to low pH of film added CA that deactivated the enzymatic reaction. The microbiological degradation teat was performed by using Bacillus subtilis and Aspergillus niger.     

Transfer of Graphene CVD to Surface of Low Density Polyethylene (LDPE) and Poly(butylene adipate-co-terephthalate) (PBAT) Films: Effect on Biodegradation Process

Here, the influence of graphene as a coating on the biodegradation process for two different polymers is investigated, poly(butylene adipate-co-terephthalate) (PBAT) (biodegradable) and low-density polyethylene (LDPE) (non-biodegradable). Chemical vapor deposition graphene was transferred to the surface of two types of polymers using the Direct Dry Transfer technique. Polymer films, coated and uncoated with graphene, were buried in a maturated soil for up to 180 days. The films were analyzed before and after exposure to microorganisms in order to obtain information about the integrity of the graphene (Raman Spectroscopy), the biodegradation mechanism of the polymer (molecular weight and loss of weight), and surface changes of the films (atomic force microscopy and contact angle). The results prove that the graphene coating acted as a material to control the biodegradation process the PBAT underwent, while the LDPE covered by graphene only had changes in the surface properties of the film due to the accumulation of solid particles. Polymer films coated with graphene may allow the production of a material that can control the microbiological degradation, opening new possibilities in biodegradable polymer packaging. Regarding the possibility of graphene functionalization, the coating can also be selective for specific microorganisms attached to the surface.     

New biodegradable polyester-copolymers from commodity chemicals with favorable use properties

Copolyesters composed of aliphatic and aromatic compounds were synthesized by the polycondensation of 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, sebacic acid, adipic acid, and terephthalic acid. By applying an appropriate ratio of aliphatic to aromatic acids, the synthesized materials proved to be biodegradable, as was verified by several degradation test methods such as aqueous polymer suspension inoculated by a soil eluate (Sturm test), a soil burial test (at ambient temperature), and a composting simulation test at 60°C. The degradability of the polyester-copolymers (measured as weight loss) was investigated with respect to the aliphatic monomer components and the fraction of terephthalic acid. Excellent biodegradability was observed even for copolymers with a content of terephthalic acid up to 56 mol% (of the acid fraction) and melting points in the range up to 140°C. Degradation by chemical hydrolysis of the polyesters was determined independently and was found to facilitate microbial attack significantly only at higher temperatures. The findings demonstrate that biodegradable polymers with advantageous usage properties can easily be manufactured by conventional techniques from commodity chemicals (adipic acid, terephthalic acid, and ethylene glycol or 1,4-butanediol).Dedicated to Prof. J. Klein's 60th birthday.     

Biodegradability of chitin- and chitosan-containing films in soil environment

The biodegradation of polyethylene-chitin (PE-chitin) and polyethylene-chitosan (PE-chitosan) films, containing 10% by weight chitin or chitosan, by pure microbial cultures and in a soil environment was studied. Three soil-inhabited organsims,Serratia marcescens, Pseudomonas aeruginosa, andBeauveria bassiana were able to utilize chitin and chitosan in prepared PE-chitin and PE-chitosan films after eight weeks of incubation at 25°C in a basal medium containing no source of carbon or nitrogen. In a soil environment, the biodegradation of those films was studied and compared with a commercial biodegradable film containing 6% by the weight of corn starch. In soil placed in the lab, 73.4% of the chitosan and 84.7% of the chitin in the films were degraded, while 46.5% of the starch in the commercial film was degraded after six months of incubation. In an open field, 100% of the chitin and 100% of the chitosan in the films were degraded, but only 85% of the starch in the commercial film was degraded after six months of incubation. The weight of controls, (polyethylene films), remained mainly stable during the incubation period. Both PE-chitin and PE-chitosan films degraded at a higher rate than the commercial starch-based film in a soil environment indicating the potential use of chitin-based films for the manufacturing of biodegradable packaging materials.     

The Effects of Additives on the Biodegradation of Polycaprolactone Composites

Because environmental pollution caused by plastic waste is a major problem investigations concerning biodegradable packaging are important and required. In this study, the biodegradation of PCL composite films with organic (glycerol monooleate and oleic acid) and inorganic additives (organo nano clay) was investigated to understand which additive and the amount of additive was more effective for biodegradation. The relationship between the degree of crystallinity and the effect of additives on the biodegradability of polycaprolactone (PCL) was examined. PCL composite films were prepared using organo nano clay (0.1–0.4–1–3 wt%) and oleic acid (1–3–5 wt%) or GMO (1–3–5 wt%). The 35 films prepared with PCL (P), clay (C), oleic acid (O), or glycerol monooleate (G) are coded as P_C#wt%_O (or G)#wt%. The composite films, P_C0.4_O5 contains 0.4 wt% clay and 5 wt% oleic acid and the P_C3_G1 contains 3 wt% clay and 1 wt% glycerol monooleate. The biodegradation of PCL films in simulated soil was studied for 36 months. The films were periodically removed from the simulated soil and film thicknesses, weight losses, visual changes, crystal structures, and a functional group analyses were performed. PCL composite films are separated into three groups, depending on degradation time, (1) films that degraded before 8 months (fast degradation), (2) films that degraded around 24 months (similar to neat PCL), and (3) films that take longer to degrade (slow degradation). The films in the first group are PCL films with 1 and 3 wt% clay additive and they begin to biodegrade at the 5th month. However, a composite film of PCL with only 0.4 wt% clay and 5 wt% GMO addition has the shortest degradation time and degraded in 5 months. The films in the last group are; P_G3, P_G5, P_C0.1, P_C0.1_O1, and P_C0.1_O5 and they took around 30 months for biodegradation. It was observed that increasing the organo nanoclay additive increases the biodegradability by disrupting the crystal structure and causing a defective crystal formation. The addition of GMO with organo nano clay also accelerates biodegradation. The addition of organo nano clay in an amount as small as 0.1 wt% acts as the nucleating agent, increases the degree of crystallinity of the PCL composites, and slows the biodegradation period by increasing the time.     

Study on the Thermo-Mechanical and Biodegradable Properties of Shellac Films Grafted with Acrylic Monomers by Gamma Radiation

Shellac (SL) films were prepared by casting and were grafted with various acrylic monomers of different functionalities using gamma radiation. Different formulations of shellac with varying concentrations (3, 5 and 7%) of these acrylic monomers such as 2-hydroxyethyl methacrylate (HEMA), 2-ethylhexyl acrylate (EHA) and 1,4-butanediol diacrylate (BDDA) in methanol were prepared. The pure shellac and other treated films were then irradiated under gamma radiation (Co-60) at different doses (0.5–5 kGy) at a dose rate of 3.5 kGy/h where 1 Gy = 1 J/kg = 100 rads. The mechanical properties like tensile strength (TS) and elongation at break (Eb) of the prepared films were studied. The mechanical properties of the irradiated shellac films demonstrated superior values. Among the formulations, shellac grafted with BDDA (SL-g-BDDA) showed the highest TS and Eb values which were 543 and 168% higher than those of raw shellac films, respectively. The water uptake behavior of raw and treated films was also studied. The raw film showed 11% water uptake but HEMA containing film showed 67%. In the soil burial test, HEMA containing shellac film was rapidly degraded than other raw, EHA and BDDA grafted films. Thermal properties indicated that grafting of acrylic monomers decreased the melting temperature of the pure shellac films.     

Biodegradation of Polylactide and Gelatinized Starch Blend Films Under Controlled Soil Burial Conditions

The biodegradability of polylactide (PLA) and gelatinized starches (GS) blend films in the presence of compatibilizer was investigated under controlled soil burial conditions. Various contents (0–40 wt%) of corn and tapioca starches were added as fillers; whereas, different amounts of methylenediphenyl diisocyanate (MDI) (0–2.5 wt%) and 10 wt% based on PLA content of polyethylene glycol 400 (PEG400) were used as a compatibilizer and a plasticizer, respectively. The biodegradation process was followed by measuring changes in the physical appearance, weight loss, morphological studies, and tensile properties of the blend films. The results showed that the presence of small amount of MDI significantly increased the tensile properties of the blends compared with the uncompatibilized blends. This is attributed to an improvement of the interfacial interaction between PLA and GS phases, as evidenced by the morphological results. For soil burial testing, PLA/GS films with lower levels (1.25 wt%) of MDI had less degradation; in contrast, at high level of MDI, their changes of physical appearance and weight loss tended to increase. These effects are in agreement with their water absorption results. Furthermore, biodegradation rates of the films were enhanced with increasing starch contents, while mechanical performances were decreased.     

Experimental Processing of Biodegradable Drip Irrigation Systems—Possibilities and Limitations

The increased cost associated with the waste removal and disposal of conventional agricultural plastic in contact with the soil combined with the gradually decreasing cost of the biodegradable plastics allowed the commercialization of biodegradable mulching films. Since the conventional thin wall or tape drip irrigation system lies under the mulching film and is used for one season only, it would be desirable to replace it with a biodegradable one. This paper presents the results of a research work investigating the possibilities and limitations in developing biodegradable drip irrigation thin wall pipes and pipes. The first ever experimental biodegradable drip irrigation thin wall pipes were produced. Rigid pipes were also produced for experimental purposes. Manufacturing problems were encountered in the processing of the biodegradable drippers and irrigation thin wall pipes with the experimental materials due to the complex formulation of the raw materials and the fact that the machinery used was specifically designed for PE processing. Experimental biodegradable thin wall pipes made of Bioflex with embedded drippers made of Mater-Bi were produced. The processing problems encountered with the production of thin wall pipes were surpassed during the experimental production of rigid type irrigation pipes. A biodegradable rigid irrigation pipe made of a grade of Mater-Bi, with embedded cylindrical drippers made of another grade of Mater-Bi was produced successfully. A better understanding of the thermal profile of the biodegradable raw materials and the use of processing equipment adapted to this profile might allow in the future the manufacturing of thin wall drip irrigation pipes for agricultural applications, and the use of alternative biodegradable materials.     

Effect of environmental parameters on the degradability of polymer films in laboratory-scale composting reactors

Previous research in our laboratory reported a convenient laboratory-scale composting test method to study the weight loss of polymer films in aerobic thermophilic (53°C) reactors maintained at a 60% moisture content. The laboratory-scale compost reactors contained the following synthetic compost mixture (percentage on dry-weight basis): tree leaves (45.0), shredded paper (16.5), food (6.7), meat (5.8), cow manure (17.5), sawdust (1.9), aluminum and steel shavings (2.4), glass beads (1.3), urea (1.9), and a compost seed (1.0) which is designated Mix-1 in this work. To simplify the laboratory-scale compost weight loss test method and better understand how compost mixture compositions and environmental parameters affect the rate of plastic degradation, a systematic variation of the synthetic mixture composition as well as the moisture content was carried out. Cellulose acetate (CA) with a degree of substitution (DS) value of 1.7 and cellophane films were chosen as test polymer substrates for this work. The extent of CA DS-1.7 and cellophane weight loss as a function of the exposure time remained unchanged when the metal and glass components of the mixture were excluded in Mix-2. Further study showed that large variations in the mixture composition such as the replacement of tree leaves, food, meat, and sawdust with steam-exploded wood and alfalfa (forming Mix-C) could be made with little or no change in the time dependence of CA DS-1.7 film weight loss. In contrast, substituting tree leaves, food, meat, cow manure, and sawdust with steam-exploded wood in combination with either Rabbit Choice (Mix-D) or starch and urea (Mix-E) resulted in a significant time increase (from 7 to 12 days) for the complete disappearance of CA DS-1.7 films. Interestingly, in this work no direct correlation was observed between the C/N ratio (which ranged from 13.9 to 61.4) and the CA DS-1.7 film weight loss. Decreasing moisture contents of the compost Mix-2 from 60 and 50 and 40% resulted in dramatic changes in polymer degradation such that CA DS-1.7 showed an increase in the time period for a complete disappearance of polymer films from 6 to 16 and 30 days, respectively.Guest Editor: Dr. Graham Swift, Rohm & Haas.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.     

Degradation Study of Biobased Polyester–Polyurethane and its Nanocomposite Under Natural Soil Burial,UV Radiation and Hydrolytic-Salt Water Circumstances

The current study focuses on the development of a formulation of polyester polyurethane (PEPU) samples using castor oil (CO) modified polyester polyol and partially biobased aliphatic isocyanate. The CO modified polyester polyol was synthesized employing transesterification reaction between CO and diethylene glycol in the presence litharge (PbO) catalyst. Subsequently, the modification of CO was confirmed using proton nuclear magnetic resonance (¹HNMR) spectra analysis. In the next stage, the biobased polyester polyurethane nanocomposites (PEPUNC) were prepared by incorporating 3 wt% OMMT nanoclay within PEPU through in situ polymerization technique. The produced PEPU was confirmed by Fourier transform infrared spectroscopy (FTIR) and ¹HNMR spectra analysis. Further, the degradation properties of developed PEPU subjected to soil-burial, UV exposure and hydrolytic-salt water medium were noted by FTIR spectroscopy. Corresponding weight loss, mechanical measurements and morphological studies through scanning electron microscopy (SEM) analysis were studied. The results showed that the addition of OMMT nanoclay within the PEPU matrix produces significant improvement in the degradation rate which indicated the susceptibility of OMMT nanoclay to humidity upon exposure to soil burial. The produced microorganisms from the soil resulted in significant chemical and morphological changes in the entire structure of the PEPU. Additionally, the highest degradation and percentage of weight loss was observed under soil burial as compared to UV exposure and hydrolytic-salt water medium.     

Biodegradation of the Films of PP, PHBV and Its Blend in Soil

Films of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(propylene) (PP), PP/PHBV (4:1), blends were prepared by melt-pressing and investigated with respect to their microbial degradation in soil after 120 days. Biodegradation of the films was evaluated by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, and X-ray diffraction. The biodegradation and/or bioerosion of the PP/PHBV blend was attributed to microbiological attack, with major changes occurring at the interphases of the homopolymers. The PHBV film was more strongly biodegraded in soil, decomposing completely in 30 days, while PP film presented changes in amorphous and interface phase, which affected the morphology.     

A spectrophotometric method for detection of enzymatic degradation of thin polymer films

An assay method has been developed for monitoring the enzymatic degradation of thin films of translucent polymers. The method was based on the observation that when a solution-cast film of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was exposed to a solution of a depolymerase fromPseudomonas lemoignei, the surface of the film roughened and the film became visibly turbid. This increase in turbidity could be measured spectrophotometrically and was reproducible during the initial stage of degradation. Turbidity correlated very closely with film weight loss early in the degradation but reached a maximum value before extensive degradation had taken place. For a given set of films, this correlation was independent of the concentration of the enzyme used, although it did vary with the mode of enzyme exposure. The turbidity was associated with the exposure of crystalline domains due to the removal of amorphous material from the film surface. The increase in crystallinity at the surface was verified by attenuated total reflectance infrared spectroscopy (ATRIR). In conjunction with SEM, weight loss, and ATRIR, the film turbidity assay provided much semiquantitative insight into the mechanism of the enzymatic degradation reaction. This assay was used to study the enzymatic degradation of films of PHBV solution blended with cellulose acetate esters (CAE). The presence of only 25% of CAE of degree of substitution 2.9 severely hampered the enzymatic degradability of PHBV, a result which is consistent with the environmental degradation of these same samples exposed to activated sludge.