Investigating Energy Reduction in Glass Recycling in Order to Select the Most Efficient Alternative
Abstract
An investigation of various scenarios of glass recycling reveals that end product characteristics drive the critical factors in evaluating the many alternatives. When recycling glass, many issues must be investigated, however the focus here will be investigating energy consumption and the goal is to make a decision on which process is most energy efficient when dealing with glass recycling.To reduce energy consumption we identify the best combination of scenarios of glass recycling. Critical factors of glass recycling include methods of recycling process and the use of different furnaces to reduce the energy consumption, geographic locations / transportation by taking into account multiple aspects of different locations, the use of glass recycling to reduce energy use of new raw materials to produce new glass. After analyzing these critical factors of energy investigation, the conclusion of each factor will be combined to make an ideal hypothetical energy efficient glass recycling plant, by considering the process, geographic location, transportation, and materials. The best combination of these factors will have the most favorable impact on the environment because of its ability to be energy efficient.

Introduction:
When recycling glass, many issues must be investigated, however the focus here will be investigating energy consumption and the goal is to make a decision on which process is most energy efficient when dealing with glass recycling. There will be four major energy investigation aspects, each will be concluding what process is the most efficient to complete a glass recycling process. The first is considering different methods of recycling process and the use of different furnaces to reduce the energy consumption. Second is considering geographic locations and how energy use should be most effective along with introducing the most effective forms of alternative energy for glass recycling. Third is considering the energy use in transportation by taking into account multiple aspects of different locations. Finally using glass recycling to reduce energy use of new raw materials to produce new glass. After analyzing the four major energy investigations, all the conclusions will be combined to make an ideal hypothetical energy efficient glass recycling plant, by considering the process, geographic location, transportation, and materials.
First we will considering two methods of recycling process, and by analysis we can determine the best possible process for glass recycling.The use of different furnaces is important to reduce the amount of energy consumption, because the furnace is the most energy consuming aspect in a glass recycling plant [4]. There are many various recycling technologies of glass available, choosing the correct process depends on the quality of recycling needed for the final material. A few technologies are glass-to-glass (closed loop recycling) recycling and glass-to-lead recycling. For glass-to-glass recycling, glass ground into cullet, the cullet is sent to a manufacturer and melted then separated [1]. Depending on the manufacturer, different energy reduction processes are used. When sending cullet to a specific manufacturer, the size of the furnace at that specific manufacturer might consume more energy. For example a furnace can produce 500 metric ton of glass per day and that consumes 6.85 GJ/t [3]. Using cullet lowers the cost of glass because raw materials can be replaced by cullet. By using cullet instead of raw materials the energy consumption is lowered because the efficiency of the furnace is higher [1]. The furnace efficiency is lower with raw materials because more energy needs to be inputted. Over the last twenty years recycling has increased dramatically. While the rate of glass recycling is increasing the rate of furnace energy consumption is decreasing dramatically. Energy consumption had dropped from 65,500 GJ to 45,000 GJ for glass furnaces alone [2]. For glass-to-lead recycling, lead and copper are separated, shredded, recovered, and smelted. This recycling process is more costly in money and energy when compared to glass-to-glass recycling. This information will help us determine which process is best suitable for our hypothetical energy efficient plant. Glass-to-lead recycling reduced the quality of recycled. North America has a limited number of smelters for recycled glass, the result of that is transporting the products over a long distance; this is how glass-to-lead recycling is less energy efficient that glass-to-glass recycling [1]. Using these two recycling processes we can compare and contrast and choose the most energy efficient one to be able to use it in our hypothetical energy efficient plant.
Second we will be consideringgeographic locations and how energy use should be most effective in certain ones along with introducing certain forms of alternative energy. As many studies throughout the past couple of years have shown, glass recycling does save energy contrary to some people’s beliefs, but it is not near the amount of energy saved from other recycling such as paper or plastic. The actual amount of energy that is saved from glass recycling depends on how far the glass is shipped, how dispersed are the neighborhoods from which glass is collected, or whether people make special car trips to recycling centers [9]. According to the National Renewable Energy Laboratory calculations, the total energy used throughout glass recycling is the process plus the transport energy which is equal to 9.8 x 1 06 Btu + 484 kWh = 1 4.9 x 1 06 Btu primary [10]. The main use of energy comes from within the raw material inputs such as natural gas and coal to produce electricity for the recycling plants which means that this is where the main forms of energy reduction can come from. One problem within the glass recycling progression forward is that since single-stream recycling has become more and more popular in different communities, there has been challenges to securing high-quality recycled glass to make new glass containers [11]. It has also been found in various research articles that using solar energy provides the most effective energy for the machinery and furnaces used throughout glass recycling plants. Using this analysis we can compare the different geographic glass recycling locations out in the US combined with the most effective renewable energy source and use the best option in our hypothetical energy efficient plant.
Third we will be considering the energy use in transportation and multiple aspects of location. Any research done on glass recycling must include the impacts of transportation. It is beneficial to compare the transportation of virgin materials with recycled materials because 23% of glass used is recycled while 77% is virgin materials, research will show how both materials impact the environment by transportation [5]. Because transportation causes GHG emission, we must consider the plant location to minimize GHG emission as well as minimizing all other transportation costs [5]. Method for calculating the optimum location for glass container plant. Using 30% recycled glass and 70% virgin materials: Many factors can be used to calculate this optimum location, but the principal factors are as follows:
1- Minimum distance to all resources: virgin materials and recycled glass.
2- Minimum distance to market consumers of glass: food and beverage and glass bottles.
3- Minimum distance to mass glass recycling operations, such as Michigan where money is paid for glass turned in [6]. Distance weighting linear programs such as this may be solved by a simple model. Distances are represented by a physical map, such as of midwest states. The map is mounted on a stiff substrate, such as Bristol Board.
A- weights may be simulated by pennies which can be stacked on the map to represent the relative value of the principal factors in relevant distance from each other [7]. When all weights are in place in their relative geographical location, the balance point determined by a finger held beneath the weighted map is the optimum plant location. This balance point may be adjusted slightly to move it to the best interstates and railroads. This method of determining the optimum location is rigorous, yet simple and practical. The goal is to evaluate these three principal factors individually and together by performing an analysis and be able to predict the best possible location for our hypothetical energy efficient glass recycling plant.
Finally we will be considering glass recycling to reduce energy use instead of using new raw materials that would consume more energy. Glass recycling saves raw material, for example more than a ton of natural resources are conserved for every ton of glass recycled, including 1,300 pounds of sand, 410 pounds of soda ash 380 pounds and 160 pounds of limestone feldspar [16]. Glass recycling also reduces the need for energy, for every 10% of the cullet energy costs in the manufacturing process used by about 2-3% [16]. The cost of recycling is in the utilization of energy contrasted with making glass from raw materials surprisingly, cullet melts at a lower temperature [15]. Therefore, we can save energy required for melting the glass. The total energy, or reflects the energy needed to manufacture a variety of materials comprises two parts: (1) transportation energy and processing, and (2) the embedded energy. The first component in the material processing and transportation, the concept is simple; but the second component, embedded energy, is more complex. Inherently contain embedded energy in energy raw materials for the manufacture of the product [14]. Energy factor needed based primarily on the amount of energy we produce one ton of a given material. The total energy consumption is a direct fuel associated with raw materials acquisition and manufacturing, transportation fuel consumption, and the results of the energy embedded in the electricity consumption. Although the factors that greenhouse gas emissions are carbon coefficients electrically-fuel mixture and fuel products, based solely on the energy consumption of the method; therefore, the process required to make a ton of total specific energy of the material is the sum of all fuel types of the energy consumption[14]. Using this analysis we can compare the energy use of recycled glass to raw material glass and propose the best option for our hypothetical energy efficient glass recycling plant.
The hypothetical plant will consider the glass recycling process, geographic location, transportation, and materials to be able to make the most energy efficient glass recycling plant possible.
Methodology
The goal is to create a hypothetical glass recycling plant focused on optimum energy efficiency. This will be done by finding the most effective energy efficient processes as well as utilizing the best geographic location plan for transportation of the recycled materials in the state of Ohio. By doing this, we will be able to model the maximum amount of raw material saved which will in turn create the most effective energy efficient plant for a certain location. To reduce energy consumption we identify the best combination of scenarios of glass recycling. Critical factors of glass recycling include methods of recycling process and the use of different furnaces to reduce the energy consumption, geographic locations / transportation by taking into account multiple aspects of different locations, the use of glass recycling to reduce energy use of new raw materials to produce new glass. After analyzing these critical factors of energy investigation, the conclusion of each factor will be combined to make an ideal hypothetical energy efficient glass recycling plant, by considering the process, geographic location, transportation, and materials.
Every factor that will be analyzed will be compared to other aspects to be able to make a decision on what the most efficient option is. Figure 1 shows the different factors of energy efficiency that will be analyzed in this paper. The best combination of these factors will have the most favorable impact on the environment because of its ability to be energy efficient.
? Comparing the methods of recycling processes
Glass-to-glass
Glass-to-lead
? Data on different furnaces used for the glass recycling process
Size of furnace and Heating of furnace
? Best geographic locations throughout Ohio to have plants located based on:
Population
Weather conditions
? Most effective transportation methods and routes used for glass collecting
Distance to all resources: virgin materials and recycled glass.
Distance to market consumers of glass.
Distance to mass glass recycling operation.
? Glass recycling energy consumption compared to raw materials
Figure 1: Process of How to Obtain an Energy Efficient Glass Recycling Plant

2.1. Glass recycling processes

There are many various recycling technologies of glass available, a few technologies are glass-to-glass (closed loop recycling) recycling and glass-to-lead recycling. In the process of glass-to-glass recycling, glass is ground into cullet, the cullet is sent to a manufacturer and melted and then separated [17]. For glass-to-lead recycling, lead and copper are separated, shredded, recovered, and smelted.
The glass recycling processes all have a general basis of sorting, shredding, and separations as shown in Figure 2. There are barriers to each process by identify the quality of material being recycled and used. For example some barriers for glass-to-glass recycling are difficulty identifying glass composition, cost, and is very labor intensive [17]. For glass-to-lead, when compared to glass-to-glass recycling is not as cost effective, safer working conditions however an important barriers is the lack of high-quality glass. North America has a limited number of smelters for recycled glass, the result of that is transporting the products over a long distance; this is how glass-to-lead recycling is less energy efficient that glass-to-glass recycling because melting furnaces are more popular than smelting furnaces [1].

Figure 2: General Process For Glass Recycling [2]

2.2. Glass recycling furnaces

Depending on the manufacturer, different energy reduction processes are used. When sending cullet to a specific manufacturer, the size of the furnace at that specific manufacturer might consume more energy. As the rate of glass recycling increases so does the consumption of energy such as figure 3 illustrates. Recycling is increasing in all fields, and society is becoming more aware of environmental issues and negative effects. One of the issues of focus here is the use of glass recycling furnaces. Figure 3 shows that with increasing recycling rates the energy consumption is increasing. While demand for recycling is increasing so is the rate of producing recycled products, this has in turn increased the energy consumption for every furnace being used in glass recycling plants. For this reason we need to focus on minimizing energy consumption of furnaces so they do not proceed to increase in the future, doing so will help the future environment.

Figure 3: Glass Consumption Rates Compared to Energy Consumption Rates [1]

When sending cullet to a specific manufacturer, the size of the furnace at that specific manufacturer might consume more energy. Figure 4 shows the importance of the glass furnace. Every plant has a furnace because glass must be purified to produce good quality products. Data on 24 furnaces were collected, the average production is 656 metric tons melt/day. For these furnaces a level of 25% cullet is used and 75% normal glass [3]. When plotting the data of the pull rate of the furnace versus the energy consumption we obtain a linear relationship:

Where E is in MJ/ton of melt and x is the capacity of metric tons/day [3]. We can use this relationship to minimize the consumption of energy for furnaces. The smaller the value of E the more energy saved.The goal is to make a decision on which process is most energy efficient when dealing with glass recycling.

Figure 4: General Glass Life Cycle [1]

2.3 Glass recycling transportation

These processes and furnaces all have to be placed in a glass recycling plant, how do we know where the best geographic locations throughout Ohio are to have plants located? The most effective transportation methods and routes used in Ohio for glass collecting and recycling must now be analyzed. There will be a linear weighing program used for the mapping of Ohio represented by a simple model. Distances are represented by a physical map of Ohio. The map will be set on a nail to balance and all of the glass collecting and recycling plants will be represented by nails on top of the map in relevant distance from each other [7]. The map will tilt in favor of the heaviest area, that area distinguishes where the best plant should be located. Transportation is a big issue for energy because transportation causes GHG emission. The model will consider the best location to minimize transportation in Ohio thus minimizing GHG emissions and costs. A big aspect is not transporting the recycled material to consumers but the transportation of collected glass to take to a recycling plant. The most efficient Ohio glass factory should use the largest quantity of recycled glass, located where natural gas is cheapest and transportation costs are lowest. Glass recycled for cullet production is concentrated in 8 major Ohio cities – Akron, Canton, Cincinnati, Cleveland, Columbus, Dayton, Toledo,and Youngstown. Since glass recycling is costly and some programs are being shut down. We are aiming to minimize transportations which will minimize the fuel cost, thus helping glass recycling plants from being shut down. Most cullet is shipped by truck, so the interstate road system helps to determine the optimum location.

Figure 5: Ohio Map, Indicating Glass Recycling Plants (Yellow) and Glass Collection Plants (Blue)

Looking at the map of Ohio in figure.5 the collection plants have been indicated by blue stars. There are 8 blue stars illustrating the names of the major cities. The major glass recycling plants are indicated by yellow stars. Between these 8 collection centers, the best possible collection center for optimum energy efficiency should be Strongsville, Ohio that is served by Ohio Natural Gas, in Cleveland, Ohio. It is the best suitable option because the model illustrates so and it has the lowest cost of natural gas in Ohio ($/MCF) 1.97 and is close to other natural gas suppliers in the North who might bid a lower price [18]. A glass recycling plant placed in Strongsville will be close to 4 glass recycling cities. Also, as mentioned before the interstate road system also helps to determine the optimum location. As shown in figure 5 Strongsville is close to I-71 and I-80 and I-90, making transportation miles minimal for this location.

Figure 6: The Best Location for building a glass recycling Plant in Ohio to Minimize Transportation Energy Consumption

The process of recycling glass is a major contribution to the reduction of waste and pollution since the material is recyclable endlessly. It involves melting down of the substance and molding it into different products suitable for use. In addition, the significant advantage of recycling glass is the cost savings reaped during the manufacturing process. It reduces the usage of energy consumed when making new glass materials globally. Moreover, the comparison of processing raw materials and recycling the cullet proves that the latter requires low temperatures to melt, hence beneficial to the firms. The amount of power required is significantly less than the amount consumed while manufacturing new glass from raw materials [22]. The energy saving capability of recycling glass material is relatively small and depends on different factors such as the distance of transporting raw materials as well as the correction of the waste.
The process of transforming the waste glass requires a low-emission furnace that is significant in reducing the general energy efficiency used in the operation. Well-planned programs of correcting the waste are beneficial since they save the energy used for transporting the material to the manufacturer’s. Similarly, the process lessens the use of natural resources. Moreover, recycling aids in reducing the energy required for incinerating the waste glass deposited in the landfills. Since the material cannot decompose, there is the need to reduce the amount disposed of in the environment through burning that requires high temperatures [22]. Therefore, it is essential to implement the processes of recycling glass as a strategy to reduce the energy consumed globally.
The conclusion of each factor of glass recycling will be combined to make an ideal hypothetical energy efficient glass recycling plant, by considering the process, geographic location, transportation, and materials. The best combination of these factors will have the most favorable impact on the environment because of its ability to be energy efficient.