Design for the Environment/Automotive Interior Door Panels

This page is part of the Design for the Environment course

Statistics Canada suggests that over 77% of average household own at least one vehicle . Although the technology of automobiles have come a long way from their predecessors, automobile technology has still not reached a level that would allow automobiles to be classified as “zero-emission vehicles.” Canadian vehicles alone have consumed over 38 billion liters of gasoline , contributing to the 24% increase in greenhouse gas emissions in Canada . With Canadians purchasing over 1.6 million new vehicles each year significant amounts of CO₂ emissions are being released into the environment. Because of such effects, companies such as Mercedes Benzare continually developing and redesigning vehicles to reduce the environmental impacts throughout a vehicles lifespan.

One concept looks at the use of lighter materials in order to reduce the overall weight of the vehicle allowing less gasoline to be consumed during the use phase of a vehicle. Although the interior consists of many parts including the instrument panel, door panels, and seats, the analysis looks specifically at the door panels. Typically, panels are made from reinforced plasticsbecause of their increased strength compared to a pure plastic. Although it is the matrix-fiber combination that determines the strength of a composite, the analysis looks at only the fiber content in a polypropylene matrix. Glass fiberis currently the most common material used in vehicles because of its strength, abundance and ease to process. Two alternatives being considered are hempfiber and clay nanocomposites because of their ability to have similar properties to glass fiber while being lighter and more environmentally friendly.

Project Information

Section 1 Group 17
N. Vanakijpaibul (Normannei)
J. Park (JPark)
T. Kim (Kimtaein)

Highlights and Recommendations

Based on several analyzes presented, hemp fiber composite is considered to be the most environmentally friendly alternative that should be used for automotive door interior panel.

Hemp fiber composite possesses sufficient mechanical properties required to be used as an interior panel. It is ranked the best in terms of environmental impact based on EIO-LCA analysis. For example, pre-manufacturing process of hemp fiber and polypropylene resin accounts for roughly 58% of air pollutants that would be released by pre-manufacturing of glass fiber. Furthermore, sensitivity analysis suggests that even with large increase in volume or increase in weight percentage of fiber, the environmental impact is generally less than that produced by glass fiber and clay nanocomposite.

Looking at the streamlined LCA, hemp fiber composite is again shown to be the best with a score of 61.75 out of 100. Large portion of this winning criterion comes from the fact that manufacturing of hemp fiber relies heavily on farming where the main source of energy comes from the sun.

Therefore is recommended that in the design of interior car panels, hemp fiber should be used.

Functional Analysis

Reinforced composites used in interior panel must withstand substantial collision impact without splintering, while allowing easy manufacturing process. However, these properties are less crucial compared to exterior panels and side-collision protective beams in the door. Other requirements for the interior include aesthetic, soft-feel, acoustic insulation, aging resistance, and no odor/fogging . Fogging is caused by the volatility of the resin which could potentially fog the windshield. Typical matrix resins used in composite includes polypropylene, polyethylene, polyurethane, and epoxy. Choice of matrix materials depend on intended mechanical property and also compatibility between the fiber and the matrix. It is found that polypropylene is an acceptable candidate for every fiber due to its compatibility (i.e. capability of blending polymer in molecular level) . Furthermore, a current trend towards recyclability regulations enforces 95% of car interior and exterior components must be recycled by year 2015 . As a result, ‘one material concept’ emerges and polypropylene is preferred due to favorable mechanical and physical properties.

Glass Fiber

Glass fiber reinforced Plastic is a composite material consisting of fine glass fibers. Since the glass fiber has superior mechanical properties for reinforcement and the moderate material price (US$1.3-2.0) , it is the most commonly used fiber reinforcement for plastics. Other advantages of glass fibers include high strength ((tensile strength of 3,450 MPa ) and stiffness, as well as moisture resistant (virgin E-glass is two to three times as strong as alloy steel ). Softening temperature of about 850°C makes glass fiber highly resistance to temperature . However, the major environmental drawback with glass fiber is its energy intensive manufacturing process with previously mentioned high temperatures. This results in the emission of greenhouse gases, traces of chlorides, and hazardous dusts .

Hemp Fiber

Natural fiber reinforcing fiber such as hemp has recently been adopted in North American automotive industries for use in interior panel and other parts. Hemp fiber possesses a numerous advantages over glass fiber. The most important factor, especially in automotive industries, is its light weight (its density is less than half of glass fiber) , provided equivalent mechanical properties compared to glass fiber. Hemp fiber, being natural fiber, is safe during handling process as it does not affect human lungs when inhaled and it is non-abrasive to equipments and tools , thus eliminate wear on the tools. As the name suggests, hemp fiber is a natural material which, at the end of its useful life, can be either composted or combusted for recovery of its good calorific energy through incineration . Hemp grows easily, requires little to no weed control and is abundant in many regions of the world. Other advantages include good acoustic property, good thermal insulation, absence of splintering, and excellent formability . However, a major drawback is its hydrophilic nature, or in other words a tendency to easily absorb water and moisture . Therefore, prior to manufacturing process, hemp fiber must be chemically treated.

Clay Nanocomposite

Currently, nanocomposite materials, more specifically clay based nanocomposites, have caught the interest of many industries for the future of material due to their improved mechanical, thermal and electrical properties , to name a few. Not only this, nanocomposites are also much lighter than their counterparts , being further attractive in the automotive industry. Incorporating nanocomposites in a vehicle is expected to reduce related carbon dioxide emission by more than 5 billion kilograms and save 1.5 billion liters of gasoline over the life of one year’s production of vehicles (Details in Streamlined Life Cycle Assessment and Economic Input-Output LCA). Although many types of clay are available, the clay used in clay nanocomposites is montmorillonite; an environmentally friendly, naturally occurring clay found in large deposits in Europe and the United States . However, similar to natural fiber, a disadvantage of this type of clay is its hydrophilic nature. In order for it to mix within the matrix, the clay needs to be surfaced treated beforehand .

EIO-LCA Analysis

Estimation Method of Manufacturing Cost

EIO-LCA Table

Based on estimations of material densities, required volume of one interior door panel, and cost, it is possible to approximate the manufacturing costs needed for the analysis of the Economic Input-Output LCA. For this analysis, difficulties were in finding accurate manufacturing costs, necessitating the use of the so-called 1-3-9 rule for manufacturing costs. This rule incorporates the use of alpha and beta factors, where alpha is a tooling factor taken to be 1.08 and beta is a waste allowance factor taken to be 1.09. Costs of raw materials are based on several sources found on the internet. It was assumed that 100,000 units wouuld be manufactured (4 units per car). Another important concern was that these current monetary values (of year 2008) had to be converted to the monetary value in 1997, in order to use the EIO-LCA analysis which is modeled based on information in 1997. According to , inflation rate was 19.7% when converting from 2008 to 1997 value. A summary of calculations are shown in the table.

With these manufacturing fabrication costs it was now possible to use these values in the EIO-LCA analysis. Industry sectors selected for the EIO-LCA model of each material are as follows; Glass fiber: Glass and glass product, except glass container, Hemp fiber: Fiber, yarn, and thread mills, Clay nanocomposite: Sand, gravel, clay, and refractory mining, Polypropylene: Plastics material and resin manufacturing.

As a result, massive amount of data is obtained and presenting all would be impossible. Therefore, only the summary of air pollutants, green house gases, energy and toxic releases are tabulated and shown below.

Conventional Air Pollutants

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During the pre-manufacturing process of each fiber, CO is determined to be the largest air pollutant released from each, with glass, clay and hemp fibers producing 5.37, 3.68 and 3.38 metric tonnes of CO into the air. With all three fibers it is interesting to see that truck transportation sector produces the most amount of CO compared to all the other sectors combined. Looking at the second most released air pollutant from each fiber reflects the difference in pre-manufacturing of each one. Glass and hemp fiber both produce 2.81 and 0.584 metric tonnes of NOx, while clay produced 2.88 megatonnes of SO2. With the amount and type of air pollutants released from each fiber, once mixed with the polypropylene resin, the amount of CO produced released now becomes 8.1, 7.27 and 5.33 metric tonnes respectively. However hemp’s second largest air pollutant has now changed to 1.852 metric tonnes of VOC with, while glass and clay composites released 2.68 and 4.27 tonnes of NOx and SO2 respectively. This change can be described from the wt% of fiber put into each matrix. Hemp and glass have a 50wt% and 30 wt% of fiber respectively, whereas clay has only a 8wt% of clay in the matrix. It is shown that the pre-manufacturing of the fiber produced more air pollutants compared to their resin counterparts. Turning to clay, it is remarkable to note that only 8% of clay produces more air pollutants than 92% of polypropyleneresin, due to heavy air pollutants released from mining process.

• Detailed Graphs of Air Pollutants

Global Warming Potential

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From the graphs shown above, it should be obvious that the main (by far) contributor of global warming potential is CO2, where clay nanocomposite produces the most (1,839 tonnes) while glass and hemp composite release 1126 tones and 556 tones respectively. The greatest contributor to global warming potential for glass fiber is due to power generation and supply sector (240 MTCO2E). This is followed by the release of carbon dioxide emissions due to glass and glass products sector (196 MTCO2E). The next main contributor of global warming potential is methane with total emission of 62.5 MTCO2E. Major source of methane emission is waste management and remediation services sectors, with 35% of total methane emission. Other significant sources include oil and gas extraction and coal mining sectors (both at 21%).

Similar to the glass fiber, power generation sector for the hemp fiber also has large emission of global warming potential which is mostly CO2 (80.2 MTCO2E). However, unlike the glass fiber, the pre-manufacturing stage of a hemp fiber causes significant amount of N2O emission due to cotton farming sector(67 MTCO2E). Note that this may not correctly reflect the actual sectors of hemp fiber production, due to limitation of options available in EIO-LCA model. However both kinds of farming do require use of fertilizer that could potentially oxidize with air and in turn produces N2O. With total GWP of 82.7 MTCOE, the largest emission among all sectors, cotton farming (or hemp farming) has the strongest environment impact for the hemp fiber.

Clay has an amazingly high amount of GWP emission (1300 MTCO2). Sand, clay and refractory mining sector emits 566 tonnes of carbon dioxide, and power generation and supply sector also emits 429 MTCO2E. Clay has 86 MTCO2E of methane emission. 40.4 MTCO2E of methane is caused by oil and gas extraction; pipeline transportation of clay and coal mining sector are also shown to have significant amount of methane emission (both are 19% of total emission).

Lastly, the polypropylene resin emits quite large amount of CO2, 486 MTCOE and 76 MTCOE of CH4. Plastic material and resin manufacturing has the largest amount of carbon dioxide emission (143 MTCO2E) and just like composites, power generation and supply sector also has large amount of carbon dioxide emission (123 MTCO2E). For methane, major sector is oil and gas extraction, and waste management and remediation services (53% and 21%).

• Detailed Graphs of GWP

Energy

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With the amount of air pollutants released into the air from each fiber, this mirrored the amount of energy consumed during the pre-manufacturing of each fiber. Looking at charts above, it is shown that natural gas and then coal were the two major sources of energy for all three fibers with clay consuming the most, then glass and hemp respectively. When comparing the fibers to the matrix, only glass and clay fibers consumed more energy with glass and clay consuming 10.5 and 20 TJ of energy. The PP matrix resin of hemp consumed 5.85 TJ of while the fiber consumed only 3.24 TJ.

• Detailed Graphs of Energy

Toxic Release

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The greatest contributor to toxic releases from glass fiber composite is 389kg of land releases. According to the EIOLCA data, 46% of land releases are from copper, nickel, lead, and zinc mining; 42% of land releases also come from mining of gold, silver, and other metal ore. The second largest contributor is 183kg of air releases, which is mainly caused by glass and power generation sectors.

Secondly, hemp fiber has 81.8kg of underground releases, which are mainly underground release due to the noncellulosic organic fiber manufacturing sector. Total air releases then has the second largest environmental impact with 72.6kg of toxic releases. Major source of air releases is the sector of cellulosic organic fiber manufacturing with 25.4kg of total air releases (24.6kg of point air and 0.8kg of non-point air).

Last of all, two major toxic releases for clay are land release and total air release. About 60% of 160kg of land releases are generated by copper, nickel, lead and zinc mining; 15% comes from power generation and supply. Another major contributor, total air releases are also mainly caused by power generation and supply (62% of 104kg).

Regarding the prolypopylene resin, 264kg of air releases and 164 kg of land releases are major toxic releases. Air releases are primarily generated by plastics material and resin manufacturing and land releases are mostly caused by mining metals. Among three composites, clay composite with highest weight fraction of polypropylene (92%) should have the highest amount of toxic releases because the total amount of toxic releases from polypropylene is solely dependent on the weight fraction of the resin inside.

Consequently, by adding the total toxic releases from resin and reinforcement, clay composite has the greatest amount of total toxic releases. Also, the glass fiber composite and the clay composite have similar amount of total toxic release, yet the hemp composite releases only 50% of the clay composite.

• Detailed Graphs of Toxic Release

Sensitivity Analysis

Increasing Volume of Composite

Due to uncertainties in many assumptions made throughout this report, a sensitivity analysis should be used as a precaution prior to concluding the results. One of the concerns associates with the functionality of each type of composite, which lies in the fact that tensile strength of hemp and clay composites (26.9 MPa and 29.8 MPa [32, 50]) are much weaker than that of glass composite (74.1 MPa [44]). Therefore, a redesign of the interior panel is needed. For our purpose, it is sufficient to assume that an increase in volume (i.e. increase in thickness of the panel and certain location which may be more susceptible to the load and impact) would compensate for the weakness in tensile strength of the hemp and clay composites. We increase volume of hemp and clay composite by 25% and 50% to test for the effects of air pollutants, global warming potential, energy and toxic releases.

As a result of this analysis, a clear conclusion becomes apparent. Hemp fiber composite, despite a 50% increase in volume, has less environmental impact than glass fiber composite. However, release of global warming potential released and energy consumption by an increase of 50% in volume of clay nanocomposite could exceed twice the values of glass fiber composite. This is mostly due to large portion of polypropylene. For hemp composite, the volume increase also adds extra weight which turns out to be 10% and 30% heavier than the weight of glass fiber composite (originally about 13% lighter). As for clay composite, it is still lighter than glass fiber composite by roughly 13% despite an increase in volume (originally 69% lighter).

Graphs: Increasing Volume Of Composite

Increasing Weight Percent of Reinforcement Material

Another possible variation is the change in proportion of reinforcement composite and the resin. We have selected a linear increase of wt% of hemp fiber from 50% to 60% and 70% while reducing the resin from 50% to 40% and 30% respectively. The same is done to clay nanocomposite, which we assume an increase of clay from 8% to 18% and 28% while reducing the amount of resin accordingly. Results are tabulated and included below.

An interesting trend can be observed here. Impact on environment caused by hemp composite remains roughly the same (or even reduced in some cases) as we increase the wt% of hemp fiber. Unfortunately, clay composite maintains the same trend as we have observed in the previous sensitivity analysis. Large amount of increase in environmental impact is not lowered due to impact caused by both mining and resin manufacturing.

Graphs: Increasing wt% of Reinforcement Material

SLCA Analysis

The Streamlined Lifecycle Assessment analysis is a way of evaluating the environmental impacts of a product or process during its lifespan. For products, the analysis compares five general stages of a products life: premanufacturing, manufacturing, packaging/transportation, use and end of life and evaluates each stage with environmental impacts: material choice, energy use, solid residues, liquid residues, and gases residues. Based on guidelines found in books such as "Streamlined Life Cycle Assessment" by T.Graedel , scores from 0 to 4 are given accordingly with 4 being the highest possible score. The analysis is shown as follows.

Pre-manufacturing Process

Matrix

Propylene is derived from petroleum, a limited source of energy. During a petroleum refinery process called steam cracking, heavy molecular weight hydrocarbons are broken into lighter ones by means of heating (roughly 800°C), hence the intensive energy consumption. (Petroleum refinery is in fact the 2nd most energy-intensive industry in the U.S. ) Approximately 10% of waste is released to landfill and underground injection wells, while approximately 24% of toxic materials released through water surface discharge ). Major point air source include toxics such as ammonia, sulfuric acid, n-hexane, etc . Refining process also generates liquid residues from wash waters used in spinning, distillation and cooling processes.

Fiber

In the table, all three of the materials received a score of 4 for material choice, because of the abundance of each raw material (sand for glass fiber, clay for nanocomposite) and the renewability (hemp can be grown). However, due to the difference in processing methods for each material, (melting for sand, farming for hemp, and mining for clay) varying degrees of residues are created and scores are given accordingly. The raw material required during the premanufacturing process of glass fiber mainly comes from sand and recycled glass. Sand, one of the most abundant resources found on earth, is extracted and processed along with recycled glass, soda lime, silica, and other additives in a gas fired furnace. The furnace heats up this mixture of glass at the temperature of 1260°C for 16 hours to create glass marbles, which is further processed to create glass fiber. However, during the process of glass manufacturing, because of the intensive amount of energy needed, carbon dioxide (from burning of fossil fuels), oxides of nitrogen (from burning of gas in air), and sulfur (from glass melting process) are released into the air . As well as creating air residues, glass dust and discharged cooling water containing emulsified oil are also produced Hemp fiber, on the other hand, is a 100% natural product. Main advantages include its biodegradability, renewability, and carbon neutrality. Because hemp is a natural product, the major source of energy is from the sun. Unlike most farms, pesticides, fungicides and weed controls are not needed when growing hemp . However, the drawbacks lie in the use of fertilizer such as phosphorous and potassium which are the causes of eutrophication that could potentially contaminate water bodies. Similar to glass fiber, montmorillonite clay is extracted through mining. However because of the mining process required, there are considerably more drawbacks including the large amounts of carbon dioxide produced from the use of heavy machinery. When protective measures are not taken, damage to the environment can be extensive, including ground water contamination and mine dumps .

Manufacturing Process

Matrix

Polypropylene is composed of many propylene monomers (thus polypropylene) through a polymerization process with a use of titanium tetra chloride (TiCl3) and triethyl aluminum (AlCl3) catalytic agents . Propylene is first fed to a reactor that is constantly stirring along with hydrogen and catalysts to form polypropylene. The length of polymers depends on temperature and concentration of hydrogen added. It is then discharged in powder form along with catalyst residues that need to be removed through dechlorination process. Once clean, this polypropylene, mixed with antioxidant materials, is then melted and extruded through dies to form laces which need to be strengthened by quenching process. Approximately 23,500 Btu of energy is required for manufacturing one pound of polypropylene. There are no major solid and liquid residues (water is recycled), but major fugitive and point air emissions include ammonia, propylene glycol, etc (through leakages)

Fiber

Manufacuturing Stage of Glass Fiber

During the manufacturing stage of glass fiber, previously manufactured glass marbles are melted in an electric furnace. The strand of glass fiber is then produced by rotating a cylinder with tiny holes to allow the flow of molten glass by centrifugal force and breaking into small pieces by air stream . The manufacturing process can be considered as a closed-loop process since cullets can be reused. However, large amount of heating and cooling energy is required for melting and cooling glass processes and hazardous fugitive glass dusts and glass fragment are produced as well as green house gases such as CO2, NOx, and SOx due to the electricity used . Hemp is cut with a sickle-bar mower once its height is approximately 3 meters. It is then retted on the field with help of rain, dew and sun to separate bast fibers from hurds and tissues, a crucial step in determining quality of hemp fiber . Residues left from retting process can either be used in fertilization or incinerated for energy recovery. Once completed, fibers need to be heat-treated and thus causing gaseous residue in the form of carbon dioxide as fossil fuel is burnt to produce electricity. After the extraction of montmorillonite, the clay needs to be surfaced treated in order to make it compatible with a specific polymer . One method of surface modification involves using dodeclammonium chloride which is created mixing a concentration of hydrochloric acid and dodecylarmine in distilled water . This mixture is then poured into a hot mixture of montmorillonite and water and stirred vigorously at temperatures of 80C . The mixture is than separated in a centrifuge to obtain just the clay. After being washed several times in hot distilled water, the clay is finally dried in a convention oven . Because of the use of distilled water, liquid residue is created during the mixing and washing phases of surface modification.

Composite Mat

Glass fiber reinforced plastic is a composite of polymer matrix and glass fiber strand mat. During the fabrication of fiber strand into a fiberglass mat, the polymer resin is readily sprayed onto the fiber . Even though the composition of the matrix is different for each product type, normally the resin requires toxic catalyst for solidification of the liquid resin. Normally used catalysts such as methyl ethyl ketone peroxide (MEKP) and accelerator such as dimethyl aniline (DMA) are both highly flammable and inhalation of their vapors may be fatal . Another shortcoming includes dust fragments of fiberglass that are hazardous when inhaled. Hemp reinforced fiber mat can be manufactured by a compression molding method. In this method, a layer of polypropylene is stacked with randomly oriented layer of hemp fiber, alternating with another polypropylene sheet. This process can be repeated to meet the desired thickness and strength. However, it is important to use Dupont Mylar films to cover both top and bottom of the mat in order to obtain a smooth surface finishing. The stacked mat is then compressed under a heated mold at 200°C for approximately 10 minutes , consuming the shape of the mold. It should be noted that, at this stage, necessary internal fasteners may be added into the mold and thus eliminate the use of adhesives . Although there are three ways of processing clay nanocomposites, the best method is melt-intercalation because of the absence of a solvent allowing it to be an environmentally benign approach . The melt intercalation process involves annealing a mixture of the polymer and the clay above the softening point of the polymer allowing the two to mix directly in the molten state . Because of the absence of a solvent, solid, liquid or gas residues are minimal or not present.

Packaging and Transportation

As seen in the table all three fibers and polypropylene received the same score because packaging and transporting of each material is similar to one another. At the stage of transportation, glass fiber, clay and polypropylene resin are both in a powder or small particle state which are packaged into plastic bags before packaged in cardboard drums. Because of similarity in packaging, the energy use for each fiber is virtually the same. Used plastic bags can be recycled while cardboard drums can be reused. One of the possible ways to recycle plastic involves burning plastics in order to breakdown the polymer into their constituent monomers, which to a certain extent creates air pollution.

Use

Gasoline Reduction

At the use stage, environmental impact solely depends on the weight of insulation panel; the lighter the car, the less CO2 produced. Clay nanocomposite, being the lightest among the 3 materials, received the best score, while the traditional heavy glass fiber mat received the least score accordingly. As the heaviest composite among the alternatives, the weight of one interior door panel with 30% E-glass fiber-70% polypropylene reinforced plastic is approximately 1.8kg. Due to the weight, cars with glass fiber reinforced insulations will consume more fuels and end up emitting more greenhouse gases. Hemp fiber reinforced mat at 50% fiber and 50% polypropylene matrix yields a total weight of roughly 1.5 kg, about 190 grams lighter than glass fiber reinforced mat. Thus one automobile with 4 insulation panels can potentially save 4.57-6.45 liters of gasoline, assuming an estimated life span of 175,000 km. It is also estimated that 13.6 kg of CO2 emission will be reduced. As seen in the table, with clay nanocomposite is the lightest composite of the three, the weight reduction results in saved fuel consumption. Assuming that the vehicle travels 175,000 km throughout its lifetime, using gasoline about 11.9 – 16.79 litres of gasoline is saved while using diesel saves approximately 10.15 – 11.55 litres of diesel. Similarly, during the use phase of the vehicle, although CO2 emissions are still released, the reduction in weight saves 35.351kg and 33.211kg of CO2 in gasoline and diesel respectively.

End of Life

Although hemp fiber and clay are both biodegradable, they are not recyclable once mixed in a matrix that is not biodegradable (i.e. polypropylene). Reinforced fiber composites are impractical to be separated because of their multiphase nature which the two phases are intermixed in a small scale. Due to non-biodegradability, hemp fiber composite and clay composite have been degraded to the same level as glass fiber composite, hence the same score pattern. Despite the materials being non-recyclable, another available option of incineration may be employed. Considering this process, small amount of energy can be created. However, amount of air pollution (CO2) and solid residues created are significantly large .

Societal Analysis

• Glass fiber

Aside from the environmental impacts that occur, societal impacts are of another concern. With glass fiber, noise pollution is the biggest problem that is created by the machineries used in pre-manufacturing and manufacturing stages. A glass-forming machine used in the pre-manufacturing stage creates extremely loud noise levels of up to 106dB, which is considered to be potentially hazardous . Moreover, the transportation of the products and raw material also contribute to noise pollution as well.

• Hemp fiber

Hemp leaf and flower contain hallucinogenic substance delta-9 tetrahydrocannabinol (THC). Therefore, growing hemp is strictly controlled and hemp grower must obtain an approval prior to cultivation. The exact global position must also be reported. The Controlled Drugs and Substances Act (Canadian) requires hemp and its parts to contain less than 0.3% THC when tested in the approved manner . In U.K, other restriction requires hemp farm must not be easily accessible by public or locate within reach of school or leisure areas . It should also be noted that while it is legal to grow hemp in Canada (after approval), it may be considered illegal in the U.S.

• Clay nanocomposite

Similiar to glass fiber, noise pollution is a problem that occurs with mining during the pre-manufacturing stage of clay nanocomposites. However mining is a process where the enviormnetal damages can be much more extensive including acid mine drainage, and water contamination. Modern mining practices however have greatly improved and ultimately aim to restore the environment to being pristine as possible . Cases studies have been done looking at mining villages and looking at the impacts including noise, dust and visual pollution

Cost Analysis

Economic analysis looked at the two most significant stages of each composites lifespan; the pre-manufacturing of each fiber, and the cost during the use phase. The alpha and beta cost estimation formula is used to look at the manufacturing fabrication cost for 100,000 units. It is noted that a 1997 EIOLCA model was used, and hence an inflation rate of 19.7 is applied to the calculate the respective cost .

Because of the different fiber matrix content in each composite, varying amounts of each material is needed as seen in the table in EIOLCA. For glass fiber which costs is $3.05/kg , 928.8g is needed, averaging approximately $2.83. Its PP matrix similarly, requires 760.20g of PP is needed giving a total manufacturing fabrication cost of approximately $1450271.00 which is the same as $1164567.61 in 1997. Similarly the total manufacturig fabrication costs of hemp fiber and clay nanocomposites are $439,270.34 and $1,470,614.78 respectively. From the results, clay nanocomposite has the highest manufacturing cost, approximately 3.3 times higher than hemp fiber and 1.26 times higher than the baseline glass fiber.

During the use phase it was assumed that an average vehicle would travel 175 000km throughout its lifetime while the cost of gasoline would average $0.80/L. The dimension of interior door panel is estimated to be 60cm x 40cm x 0.5cm, resulting in a volume of 1,200 cm3. In addition, a varying factor of ±5% and ±10% are used for the sensitivity analysis. For example, 95% of 60cm, 95% of 40cm and 95% of 0.5cm yields a volume of 1028.85 cm3. Thus, with this variation of volumes and weight % of fiber and resin, different weights of one interior door panel are calculated as demonstrated in the table below. According to , gasoline saving factor is calculated to be amount of dollars saved per liter of gasoline per reduction in weight of the car per distance travelled (i.e. $0.34- $0.48/L /100kg /100km). Reduction in weight is calculated by subtracting the upper and lower values of hemp fiber and clay nanocomposite weight from the base material, which is glass fiber composite (i.e. 1068.59-955.22=113.37). Using gasoline cost of $0.80 and estimated distance travelled of 175,000km throughout a car’s lifespan, the total amount of dollar savings are estimated as shown in the table below. From these calculations, it is interesting to note that despite all changes made towards efforts in weight reduction of the interior door panel the amount saved is quite insignificant with hemp fire saving only $8.31/door (or $8.31x4= $33.24), and clay nanocomposite saving $21.64/door (or $21.64x4= $86.56), through each composites lifespan respectively.