The benefits of bio-based polyethylene production must be weighed against environmental impacts before it becomes widespread. It was found that bio-based polyethylene was more beneficial compared to petroleum-based polyethylene due to their environmental impacts and energy consumption. Overall, the results showed that bio-based high-density polyethylene has the lowest adverse effects, followed by bio-based low-density polyethylene.
Background
Bio-based polymers are preferred over petroleum-based polymers because they are considered an environmentally friendly material and are obtained from renewable sources (Madival et al., 2009). While petroleum-based polyethylene is produced from natural gas or the petroleum sector from crude oil. Bio-based polyethylene and petroleum-based polyethylene can be used for many different plastic applications.
Problem Statement
It can also be obtained from sugar beets or from starch crops such as maize, wheat or other grains (Shen et al., 2009). Both can be widely used for food packaging, shopping bags, detergent bottles, cosmetics and personal care, auto parts, toys and other products.
Objective
Scope
Petroleum Based Polyethylene
- Production of Petroleum Based Polyethylene
An array of distillation columns is used to separate ethane from other components in natural gas (Bian et al., 2009). The catalyst particles are suspended in the ethylene liquid as the ethylene gas is pumped from the bottom of the reactor bed to the top. Temperatures in a fluidized bed reactor can be modeled using an energy balance (Bian et al., 2009).
Bio-based Polyethylene
- Production of Bio-based Polyethylene
Polyethylene exits the reactor as granular powder, which is melted and flows through a film extruder. The friction between the surfaces can be reduced by adding release agents (Bian et al., 2009). While the by-product of milling is sugarcane fiber which is known as bagasse.
Characteristic of HDPE and LDPE
Low-density polyethylene (LDPE) is a polyethylene produced by a high-pressure process, which is why it is often referred to as high-pressure polyethylene. The main technique used for the production of LDPE is autoclave and tubular high pressure technology. The ethylene-polymer mixture is continuously discharged to a high pressure at 250 bar separator, where polymer precipitates and most of the unreacted ethylene is recovered, recompressed and recirculated to the reactor.
Properties
Ethylene is compressed up to 3000 bar and fed to the reactor when oxygen or organic peroxide is injected to start the radical polymerization at C.
Technical Substitution Potential
Applications Today and Tomorrow
Life Cycle Assessment
The impact of process plant construction and equipment maintenance and the impact of disposal were excluded (Harding et al., 2007). In doing so, we analyzed individual feeds in order to assess the ecological risks posed by the production of polyethylene. The life cycle inventory of ethylene production was developed based on literature data (Czaplicka-Kolarz et al., 2010).
The main use of ethylene is conversion to low-density, high-density polyethylene (Czaplikka-Kolarz et al., 2010). In the case of ethylene, naphtha plays a major role in all impact categories, especially the photochemical ozone formation potential (POCP). Based on the LCA analysis, it was found that the largest environmental impact in the production of ethylene is the naphtha refinery (almost 70%).
Economic and environmental issues are the main factors considered in the choice of raw material and ethylene production processes. There have been several improvements and advances in conventional ethylene production technology in the past forty-five years. While in purification and recovery, there has been progress in the operations of various units such as in distillation, cooling and separation (Czaplicka-Kolarz et al., 2010).
Carbon dioxide released in other areas of production such as fossil electricity generation was also taken into account (Harding et al., 2007).
Life Cycle Assessment Standard
Using the CML2 Baseline 2000v2.03 assessment method, the Life Cycle Impact Assessment (LCIA) of HDPE and LDPE is summarized in Table 2.5. Impact Category Unit HDPE LDPE. they do not describe the LCA technique in detail, but only define the following sections: a) study objective, b) life cycle inventory analysis, c) life cycle assessment, d) life cycle interpretation, e) reporting, and f) critical review. ISO 14041 – Environmental management – Life cycle assessment – Definition of objective and scope and inventory analysis – This standard has detailed the objective and inventory analysis of the study.
With the help of this standard, the purpose and scope of the study, the functional unit and the system boundaries of the study were formed. ISO 14042 - Environmental management - Life cycle assessment - Life cycle impact assessment - This standard dealt with the intricacies of the life cycle impact assessment procedure. ISO 14043 - Environmental management - Life cycle assessment - Life cycle interpretation - This standard discussed the issues related to life cycle interpretation procedure.
It was useful to structure the information from the inventory phase and determine the significant problems with the inventory data, impact categories. Conclusion and interpretation of the results based on inventory analysis was done with this standard. This standard discussed the guidelines for defining the purpose and scope of the study, inventory analysis, impact.
ISO 14049 - Environmental management - Life cycle assessment - Examples of the use of ISO 14041 for the definition of objectives and scope and inventory analysis - This standard was used to study the given examples of the development function, the distinguishing function of comparative systems, the determination of inputs and outputs of the unit processes and system boundaries, examples of allocation procedures.
Materials and Functional Unit under Consideration
System Boundaries
Standard Guideline
Inventory Datasets and Assessment Methods
- LCI Libraries
- Ecoprofiles Plastic Europe 2005
- Impact Assessment Methods
- IMPACT 2002+
The LCI data derived from the databases just presented were analyzed using various impact assessment methods. The impact categories considered in this method are carcinogens, non-carcinogens, ionizing radiation, global warming, water acidification, ozone depletion, aquatic eutrophication, respiratory organics, respiratory inorganics, land occupation, terrestrial ecotoxicity, terrestrial acid/nutri, non-renewable energy , mineral extraction and aquatic ecotoxicity. Carcinogenic kg chloroethylene equivalents in air (kg C2H3Cl equivalent) Non-carcinogenic kg chloroethylene equivalents in air (kg C2H3Cl equivalent) Respiratory inorganic substances kg PM2.5 equivalents in air (“kg PM2.5 eq).
Ionizing radiation Bq C-14 equivalents in air (Bq C-14 eq) Ozone layer depletion kg CFC-11 equivalents in air (kg CFC-11 eq) Respiratory organics kg ethylene equivalents in air (kg C2H4eq) Aquatic ecotoxicity kg triethylene glycol equivalents in water. Terrestrial asid/nutri kg SO2 equivalents in air (kg SO2eq) Land cover m2 organic arable land (m2org.arable) Aquatic acidification kg SO2 equivalents in air (kg SO2eq) Aquatic eutrophication kg PO4--- equivalents in a P-limited water. Global warming kg CO2 equivalents in air (kg CO2eq) Non-renewable energy MJ primary non-renewable (MJ primary) Mineral extraction MJ surplus (MJ surplus).
The relevant damage units are DALY for human health, PDF*m2*yr for ecosystem quality, kgeq CO2 to air (written “kg CO2 eq”) for climate change, and MJ primary non-renewable (written . “MJ primary”) for resources. Carcinogenic, non-carcinogenic substances, depletion of the ozone layer, ionizing radiation, respiratory inorganic and respiratory organic substances belong to the category of damage to human health. Aquatic ecotoxicity, ozone depletion, terrestrial ecotoxicity, terrestrial acidity/nutrients, soil occupation, aquatic acidification and aquatic eutrophication fall under the category of ecosystem quality damage.
Global warming falls under the category of climate change damage and non-renewable energy and mineral extraction fall under the category of resource damage.
Impact Assessment Results
- Carcinogens
- Non-carcinogens
- Respiratory inorganics
- Respiratory organics
- Aquatic ecotoxicity
- Terrestrial ecotoxicity
- Terrestrial acidification and nutrification
- Aquatic acidification
- Aquatic eutrophication
- Global warming (carbon dioxide emission)
- Non-renewable energy
- Mineral extraction
While the production of petroleum-based and bio-based HDPE showed that they had the same values for global warming and terrestrial acid/nutrients. Airborne arsenic emissions were the source of non-carcinogens for the production of biobased HDPE and LDPE. Waterborne emissions of copper and aluminum were the main contributors to aquatic ecotoxicity in the production of petroleum-based HDPE and LDPE.
Biobased HDPE and LDPE did not have waterborne emissions contributing to terrestrial ecotoxicity. Bio-based LDPE thus always had a lower value of terrestrial ecotoxicity compared to oil-based LDPE. Production of LDPE for both petroleum-based and bio-based had produced greater value of soil-based acid/nutrient compared to the production of HDPE.
Aquatic acidification values for biobased HDPE and LDPE were influenced by both air and water emissions during the production process of the resins. During the production of biobased polyethylene, ammonia released into the water caused the acidification of the water. In addition, it was partly attributed to the agricultural component of biobased HDPE and LDPE production.
Results show that the production of petroleum-based polyethylene used a higher value of non-renewable energy compared to bio-based polyethylene.
Damage Assessment Results
The values of mineral extraction came from raw materials that reacted in the process. Substances involved in mineral extraction were zinc, copper, lead and others. per year) is the unit to measure the impact on ecosystems. PDF·m2·yr represents the fraction of species that have disappeared on 1 m2 of land surface during a year (Humbert et al., 2005).
Table 4.2 found that petroleum-based LDPE has the greatest impact on ecosystem quality compared to other polyethylenes. Petroleum-based LDPE with an ecosystem quality rating of 0.0278 PDF·m2·year means a loss of 2.78% of species per 1 m2 of the earth's surface in one year. Human health was the sum of the values of carcinogenic, noncarcinogenic, inorganic and organic substances in the respiratory tract.
DALY (Disability Adjusted Life Years) is the unit to measure the impact on human health. Morbidity refers to the time of a lower quality of life due to a disease (Humbert et al., 2005). This meant that the production of petroleum-based HDPE with a human health score of 3.11 x 10-6 DALY implied the loss of 3.11 x 10-6 life years over the total population.
Conclusions
Recommendation
Environmental Assessment of Plastic Manufacturing Processes: Comparison of Petroleum-Based Polypropylene and Polyethylene with Bio-Based Polyhydroxybutyric Acid Using Life Cycle Assessment. Environmental Management - Life Cycle Assessment - Examples of application of ISO 14041 to goal and scope definition and inventory analysis. Assessment of the environmental profile of PLA, PET and PS clamshell containers using the LCA methodology.
APPENDIX K: Terrestrial acidification and nutrition comparison table for petroleum-based polyethylene and bio-based polyethylene.
