New Alternative Vehicle Hydrocarbon Liquid Fuels from Municipal Solid Waste Plastics

Millions of vehicles on the road today are releasing a large amount of carbon dioxides (CO2) causing the climates to change drastically. Studies indicate that the CO2 released from vehicles is the main contributor of global warming. Alternative fuels developed from waste plastics have the potential to have a positive impact on the environment in two ways. First of all, the presence of waste plastics in the landfill causes fertile soils to decay and these waste plastics can be used for the production of high quality alternate fuels. Removing these harmful waste plastics from landfill and converting them into liquid hydrocarbon fuels can create a more stable environment than the one we are living in. This technology is environmentally friendly and projected to be produced at a very low cost compared to the current commercial fuels. Preliminary results showed that the NSR fuel has many similar characteristics as the current gasoline.


Introduction
Plastic is a macromolecule polymer, formed by polymerization of hydrocarbon materials and it has the ability to be shaped by the application of reasonable amount of heat and pressure. Plastics contain compounds such as carbon monoxide, sulfur and nitrogen. Plastics are being used all over the world, and afterwards, these plastics turn into waste plastics. The types of plastics include high-density polyethylene (HDPE, code 2), low-density polyethylene (LDPE, code 4), polypropylene (PP, code 5), and polystyrene (PS, code 6). According to a recent study, in the U.S., 30 million tons of total plastic are produced each year, with only about 4% now being recycled [5]. The rest of the waste plastics either end up in landfill or incineration. The waste plastic that ends up in the landfill when littered does not degrade for thousands of years causing lands to become infertile and environmentally unsafe for its habitants around them. Due to excessive amount of waste plastics discarded everyday, a large amount of them end up in incineration facilities. When incinerated, waste plastics release toxic gases such as carbon monoxide (CO), which causes health hazards, sulfur dioxides (SO 2 ) when incinerated, which contributes to acid rain, nitrogen oxides (NOx) which contribute to ozone depilation and acid rain, and carbon dioxide (CO 2 ), greenhouse gases that contribute to global warming.
Plastics like polyethylene bags are very lightweight. They do not stay steady in the landfill. If the plastic bags are not recycled, eventually they will find their way into water stream and end up in the Ocean region. Not only plastic bags but any plastic materials that are not recycled end up in the Ocean as well. This is proven in a study conducted by Charles J. Moore (Long Beach, California) about the Great Pacific Garbage Patch, which shows the horror and impacts that waste plastic can have on oceanic and marine life. According to his study, the Garbage Patch is estimated to be twice the size of Texas and contains ∼ 3.5 million tons of waste material and 80% of it is waste plastic litter [9]. According to C. J. Moore's 1999 study, there were 6 times more waste plastic in this part of the ocean than the zooplankton that feeds ocean life [9]. Also another study performed in 2002 showed that even off the coast of California, waste plastic outweigh zooplankton by a factor of 5 to 2 [10].
Many researches have been conducted to convert waste plastics into renewable energy sources. This is possible because plastics are originally made from crude oil. Crude oil is a very limited natural resource that is used to make transportation fuel, plastics and other products. Crude oil is a non-renewable energy source and since it is a natural resource it will deplete in the near future.
Successful methods have been carried out to convert waste plastics into liquid based fuels [1,8,12]. These methods include various procedures to convert the waste plastics such as Pyrolysis, in which the contents of waste plastics are thermally degraded to produce liquid-based fuels and other products without the presence of oxygen [3,   4,6,7,14]. The process described in this particular paper to convert solid waste plastics into renewable energy sources is accomplished utilizing a basic form of thermal degradation. The basic form of thermal degradation has been tested and proven to produce fuel that can be used as an energy source [2,11,13,15].
The final product produced obtained from utilizing the thermal degradation process is in the form of liquid and it contains hydrocarbon materials. The experiment conducted to produce the liquid fuel is carried out in a stainless steel reactor system (Figure 1). Figure 2 shows the process in which the waste plastics is processed using thermal degradation and distillation process.

Experimental process description
The process uses thermal cracking to heat the waste plastic to form a liquid slurry, at a temperature ranging from 370°C-420°C, then the liquid slurry turns into vapor; that vapor is then condensed/distilled (see Figure 1) to produce the liquid hydrocarbon fuels. It should be noted that no chemicals are used to carry out this process and the end product is filtered using a commercial fuel purifier that operates using coalescence and centrifugal force.  Experiments conducted in a mini-scale have been performed with the majority of waste plastic types: high-density polyethylene (HDPE, code 2), low-density polyethylene (LDPE, code 4), polypropylene (PP, code 5), and polystyrene (PS, code 6). These plastic types were investigated singly and in combination with each other. In a laboratory scale, the weight of a single batch of input plastic for the fuel production process ranges from 350 gm to 5 kg. The waste plastics are collected, optionally sorted, cleaned of contamination or without cleaning and grinded into small pieces prior to the thermal liquefaction process. In the double condensation process, two different types of fuel are collected at two types of different temperature range. The double condensed fuels are classified as NSR-1, NSR-2. NSR-1 (gasoline) will be collected at 200-240°C and NSR-2 (diesel) in the range of 240-360°C. Also during the fuel production process, some very light gas is produced (C 1 -C 4 ). The gases include methane, ethane, propane and butane. These gases can be utilized as a heat source to carry out the fuel production process. A very minimum amount of solid carbon residue is leftover from the production step. The residues contents are similar to contents which are used for road and roof carpeting.
The initial and double condensed fuels were tested by the GC/MS to identify their compositions. A hydrocarbon chain length of (C3-C27) (see Table 1) is present in the NSR fuel with a retention time ranging from 2 min to 27 min. After fractionating the NSR fuel, hydrocarbon chains are broken down into shorter ones because different temperature is used for each of the fuels. NSR-1 hydrocarbon chain was in the range (C 4 -C 12 ) (see Table 2) and NSR-2 in the range (C 9 -C 27 ) (see Table 3). These data indicate that the NSR fuels have a wide range of hydrocarbon groups resulting in a higher thermal content. The thermal content allows the fuel to burn for a longer period of time resulting in efficiency when used in compatible engines.

Fuel analysis and discussion
The initial and double condensed fuels were tested by the GC/MS to identify their compositions. A hydrocarbon chain length of (C 3 -C 27 ) is present in the NSR fuel with a retention time ranging from 2 min to 27 min. After fractionating the NSR fuel, hydrocarbon chains are broken down into shorter ones because different temperature is used for each of the fuels. NSR-1 hydrocarbon chain was in the range (C 4 -C 12 ) and NSR-2 in the range (C 9 -C 27 ). These data indicate that the NSR fuels have a wide range of hydrocarbon groups resulting in a higher thermal content. The thermal content allows the fuel to burn for a longer period of time resulting in efficiency when used in compatible engines.
Experiments conducted showed that 2 mL of initial fuel could burn for about 5 min; also, emission released from burning of the fuel contains very low concentration of benzene, toluene, styrene, xylene, and naphthalene and contains low traces of sulfur.
Results obtained from Elemental Analyzer (EA) -2400 series II CHNS mode indicate that the initial fuel contains 86.44% carbon and 13.96% hydrogen. The average of the fractionated fuels contains 86.00% carbon and 13.00% hydrogen. Empirical formula indicates that all the fuel's carbon and hydrogen ratio is 1:2.

Diesel car test emission result
The NSR-2 fuel was tested in a diesel engine to measure the emission released from burning the fuel. The results are listed in Table 11.

ASTM test results
The fuels produced have been also tested according to the       Table 10: ASTM fuel additives test result of waste plastic to produce NSR-1 fuel.

Figure 9:
Comparison graph of NSR-1 and gasoline-87 kilowatt output consumption using gasoline generator.

Electricity production
Since the claim is that NSR-1 has similar properties as gasoline, the NSR-1 fuel was used in a gasoline-based generator to test its capabilities ( Figure 9). Both NSR-1 and gasoline were injected into the gasoline generator one after the other to compare the kilowatt output of the two. The results showed a significantly higher kilowatt output from NSR-1 than gasoline.

Conclusion
As mentioned above, the fraction fuels are obtained at a certain temperature; NSR still has the option to produce the fuels under different temperatures and see if better results are obtainable from the previous temperature profile. Through the use of GC/MS and FTIR, we can assure the identification, accuracy of the fuel to meet the standard requirements for commercialization of the NSR fuel.