About Pyrolysis and Plastic Waste Conversion
Clean Oceans International has been exploring Plastic Waste Conversion (PWC) and smaller-scale Portable Plastic Waste Conversion (PPWC) as potential tools for addressing plastic waste that cannot be effectively managed through conventional recycling. Below are answers to some of the questions we frequently receive about pyrolysis, plastic waste conversion, and COI's approach.
What is pyrolysis?
Pyrolysis uses heat to break down materials in an oxygen-free environment, but it is not incineration. When used for plastic waste conversion, the process breaks plastic into smaller hydrocarbon molecules that can be recovered as oils, gases, and other products.
Is pyrolysis “recycling”?
This depends on how a governing authority defines recycling. Terms such as chemical recycling, advanced recycling, and plastic waste conversion are sometimes used differently. Some processes convert plastic into feedstocks that can be used to manufacture new plastics, while others produce fuels or other useful products. At COI, we use Plastic Waste Conversion (PWC) as a broader description of the technology we are researching.
Why pursue plastic waste conversion instead of simply reducing plastic use?
We strongly support reducing unnecessary plastic production and consumption. Ultimately, reducing our dependence on fossil fuels and creating a more circular economy are essential parts of addressing plastic pollution. But reduction alone does not address the enormous quantity of plastic waste already in existence—or the plastic that will continue to be produced during that transition.
Under current policies, the OECD projects that global plastic waste could almost triple by 2060. COI sees PWC as an interim solution: one potential way to manage existing and difficult-to-recycle plastic waste while society works toward longer-term solutions.
Why make the technology portable or small-scale?
Moving plastic waste long distances can be expensive and resource-intensive, particularly in remote communities, agricultural regions, islands, and other places without convenient access to recycling infrastructure. COI's vision for PWC is to bring the solution closer to the waste. Small-scale systems could potentially process plastic near where it is collected or generated, reducing transportation requirements while creating a useful product from material that might otherwise be landfilled, improperly disposed of, or escape into the environment.
What kinds of plastic can be converted?
The answer depends on the particular technology. Plastic waste conversion systems are generally better suited to some types of plastics than others. Different feedstocks can also require different preparation and processing conditions. One focus of COI's current work is HDPE agricultural plastic, including used drip tape, through research involving the “Onionator” prototype at Oregon State University.
What does pyrolysis produce?
Depending on the technology, operating conditions, and plastic feedstock, pyrolysis can produce a combination of liquid hydrocarbons or oils, gases, and solid char. Some of these outputs may be reused within the conversion process itself, while others may potentially be refined, blended, or used for other purposes. The exact proportions and characteristics of these products vary considerably depending on the system and material being processed.
What is COI's history with this technology?
COI has been exploring small-scale plastic waste conversion for more than a decade.
Is pyrolysis safe for people and the environment?
Like any industrial process, plastic waste conversion must be appropriately designed, operated, monitored, and regulated. Environmental performance can vary depending on the technology, feedstock, operating conditions, emissions controls, and how the resulting products and byproducts are handled. This is one reason COI believes continued research, testing, and independent academic involvement are important as PPWC technology develops.
What happens to emissions and byproducts?
Pyrolysis can produce gases, liquid products, and solid char, and individual systems must address how each of these outputs is managed. Emissions requirements are also governed by applicable local, state, and federal regulations. Any future PPWC deployment would need to comply with the environmental and permitting requirements of the community in which it operates.
Where could a PPWC facility be located?
A smaller PPWC system could potentially be located near existing waste-management or recycling operations, reducing the need to transport plastic long distances. Potential applications could include landfills, agricultural operations, island communities, and other areas where conventional recycling options are limited. Any future facility would be subject to applicable zoning, environmental, permitting, and regulatory requirements.
Is PPWC the solution to plastic pollution?
No single technology is. Reducing unnecessary plastic production and consumption, expanding reuse, improving conventional recycling and waste-management systems, preventing litter, and removing plastic already in the environment all have important roles to play. PPWC addresses another piece of the problem: what do we do with plastic waste that already exists and cannot be practically managed through existing recycling systems?
COI is exploring PPWC as one tool within a much larger effort to keep plastic out of our communities, waterways, and oceans.
What is pyrolysis?
Pyrolysis uses heat to break down materials in an oxygen-free environment, but it is not incineration. When used for plastic waste conversion, the process breaks plastic into smaller hydrocarbon molecules that can be recovered as oils, gases, and other products.
Is pyrolysis “recycling”?
This depends on how a governing authority defines recycling. Terms such as chemical recycling, advanced recycling, and plastic waste conversion are sometimes used differently. Some processes convert plastic into feedstocks that can be used to manufacture new plastics, while others produce fuels or other useful products. At COI, we use Plastic Waste Conversion (PWC) as a broader description of the technology we are researching.
Why pursue plastic waste conversion instead of simply reducing plastic use?
We strongly support reducing unnecessary plastic production and consumption. Ultimately, reducing our dependence on fossil fuels and creating a more circular economy are essential parts of addressing plastic pollution. But reduction alone does not address the enormous quantity of plastic waste already in existence—or the plastic that will continue to be produced during that transition.
Under current policies, the OECD projects that global plastic waste could almost triple by 2060. COI sees PWC as an interim solution: one potential way to manage existing and difficult-to-recycle plastic waste while society works toward longer-term solutions.
Why make the technology portable or small-scale?
Moving plastic waste long distances can be expensive and resource-intensive, particularly in remote communities, agricultural regions, islands, and other places without convenient access to recycling infrastructure. COI's vision for PWC is to bring the solution closer to the waste. Small-scale systems could potentially process plastic near where it is collected or generated, reducing transportation requirements while creating a useful product from material that might otherwise be landfilled, improperly disposed of, or escape into the environment.
What kinds of plastic can be converted?
The answer depends on the particular technology. Plastic waste conversion systems are generally better suited to some types of plastics than others. Different feedstocks can also require different preparation and processing conditions. One focus of COI's current work is HDPE agricultural plastic, including used drip tape, through research involving the “Onionator” prototype at Oregon State University.
What does pyrolysis produce?
Depending on the technology, operating conditions, and plastic feedstock, pyrolysis can produce a combination of liquid hydrocarbons or oils, gases, and solid char. Some of these outputs may be reused within the conversion process itself, while others may potentially be refined, blended, or used for other purposes. The exact proportions and characteristics of these products vary considerably depending on the system and material being processed.
What is COI's history with this technology?
COI has been exploring small-scale plastic waste conversion for more than a decade.
- In 2015, COI presented the concept of Portable Plastic Waste Conversion at TEDx in New York City, including its potential use in remote communities and at sea.
- In 2021, COI began collaborating with PDO Technologies to further explore pyrolysis and the development of Portable Plastic Waste Conversion (PPWC) systems.
- Today, COI is also working with Dr. Skip Rochefort at Oregon State University to advance and test small-scale approaches to plastic waste conversion.
Is pyrolysis safe for people and the environment?
Like any industrial process, plastic waste conversion must be appropriately designed, operated, monitored, and regulated. Environmental performance can vary depending on the technology, feedstock, operating conditions, emissions controls, and how the resulting products and byproducts are handled. This is one reason COI believes continued research, testing, and independent academic involvement are important as PPWC technology develops.
What happens to emissions and byproducts?
Pyrolysis can produce gases, liquid products, and solid char, and individual systems must address how each of these outputs is managed. Emissions requirements are also governed by applicable local, state, and federal regulations. Any future PPWC deployment would need to comply with the environmental and permitting requirements of the community in which it operates.
Where could a PPWC facility be located?
A smaller PPWC system could potentially be located near existing waste-management or recycling operations, reducing the need to transport plastic long distances. Potential applications could include landfills, agricultural operations, island communities, and other areas where conventional recycling options are limited. Any future facility would be subject to applicable zoning, environmental, permitting, and regulatory requirements.
Is PPWC the solution to plastic pollution?
No single technology is. Reducing unnecessary plastic production and consumption, expanding reuse, improving conventional recycling and waste-management systems, preventing litter, and removing plastic already in the environment all have important roles to play. PPWC addresses another piece of the problem: what do we do with plastic waste that already exists and cannot be practically managed through existing recycling systems?
COI is exploring PPWC as one tool within a much larger effort to keep plastic out of our communities, waterways, and oceans.
About PDO Technologies
COI has collaborated with PDO Technologies in the development of Portable Plastic Waste Conversion (PPWC). The following questions address PDO's specific pyrolysis technology, its outputs, environmental performance, and potential applications. Specifications and performance figures in this section refer specifically to PDO's technology and should not be assumed to apply to all pyrolysis systems.
What are the outputs of PDO's pyrolysis process?
On average, PDO's process produces approximately 80% liquid fuel, 13% non-condensable gases, and 7% char. The non-condensable gases and a portion of the char can be reused within the process, reducing its external energy requirements.
What happens to the remaining char?
Char that is not used on-site for energy generation can be briquetted and used as a low-energy fuel source, with an energy content of approximately 8,000 BTU/lb. The remaining alternative is disposal in a landfill.
What type of technology does PDO use, and has it operated under real-world conditions?
PDO uses low-temperature pyrolysis operating at approximately 510°C. PDO's technology has been used in commercial-scale operations in Oregon, Minnesota, and Georgia, processing up to 50 tons of plastic per day.
What emissions does the process produce, and how are they monitored?
Emissions from PDO's processes have been well-characterized and fall below applicable regulatory limits. Emission limits and monitoring requirements vary by jurisdiction. Facilities must comply with applicable local, state, and federal permitting requirements and use approved testing and reporting methodologies. PDO is currently located in Oregon, and the emission factors and limits can be found here. California limits can be found here.
Does PDO's process generate hazardous waste?
According to the Resource Conservation and Recovery Act (RCRA) definition, PDO's process does not generate waste classified as hazardous.
What is the energy balance of PDO's process?
Using the common metric Energy Returned on Energy Invested (EROEI), PDO’s machines return 4-7 times the amount of energy used during the conversion process. When compared to traditional fossil fuel extraction, refining, and transportation, PDO’s machines use 96% less energy, 58% less water, and 14% fewer greenhouse gas emissions.
What types of plastic can PDO's process handle?
PDO’s process has been tested on all “classic” plastics (resin codes 1-7). Resin codes #1 (PETE) and #3 (PVC) are not desirable for use in the technology. Feedstock for individual projects would be determined by local waste streams and community needs, potentially through relationships with municipalities, businesses, agricultural operations and other local sources.
How does the resulting fuel compare with conventional diesel?
The liquid produced through PDO's process is not used independently as conventional diesel fuel. When blended with certified diesel at a ratio of 1:3, the resulting product meets the applicable standard specification for diesel fuel.
Have emissions been studied after the resulting fuel is used in a diesel engine?
PDO does not currently have data specifically characterizing diesel-engine exhaust from blended fuel produced using PDO technology. Published research has examined the combustion and exhaust characteristics of pyrolysis-derived oils, and continued research into the environmental impacts of these fuels is important. Read more here.
Has PDO's fuel been used long enough to evaluate its effects on engines?
PDO reports that fuel produced using its technology has been in use for approximately 25 years. When PDO's product is blended with commercial diesel so that the resulting fuel meets the ASTM D975 diesel fuel specification, no adverse impact on the engine is anticipated. Testing and analysis will continue as the technology develops.
How does pyrolysis temperature affect the resulting products?
Operating temperature influences the mixture of hydrocarbon molecules produced during pyrolysis and, consequently, the characteristics of the resulting products. PDO's technology operates at approximately 510°C. Other pyrolysis technologies may operate at substantially different temperatures and produce different product profiles. For more information on fuels created from 700°C and 900°C refer to this article and for more information comparing the impacts of different temperatures, click here.
COI has collaborated with PDO Technologies in the development of Portable Plastic Waste Conversion (PPWC). The following questions address PDO's specific pyrolysis technology, its outputs, environmental performance, and potential applications. Specifications and performance figures in this section refer specifically to PDO's technology and should not be assumed to apply to all pyrolysis systems.
What are the outputs of PDO's pyrolysis process?
On average, PDO's process produces approximately 80% liquid fuel, 13% non-condensable gases, and 7% char. The non-condensable gases and a portion of the char can be reused within the process, reducing its external energy requirements.
What happens to the remaining char?
Char that is not used on-site for energy generation can be briquetted and used as a low-energy fuel source, with an energy content of approximately 8,000 BTU/lb. The remaining alternative is disposal in a landfill.
What type of technology does PDO use, and has it operated under real-world conditions?
PDO uses low-temperature pyrolysis operating at approximately 510°C. PDO's technology has been used in commercial-scale operations in Oregon, Minnesota, and Georgia, processing up to 50 tons of plastic per day.
What emissions does the process produce, and how are they monitored?
Emissions from PDO's processes have been well-characterized and fall below applicable regulatory limits. Emission limits and monitoring requirements vary by jurisdiction. Facilities must comply with applicable local, state, and federal permitting requirements and use approved testing and reporting methodologies. PDO is currently located in Oregon, and the emission factors and limits can be found here. California limits can be found here.
Does PDO's process generate hazardous waste?
According to the Resource Conservation and Recovery Act (RCRA) definition, PDO's process does not generate waste classified as hazardous.
What is the energy balance of PDO's process?
Using the common metric Energy Returned on Energy Invested (EROEI), PDO’s machines return 4-7 times the amount of energy used during the conversion process. When compared to traditional fossil fuel extraction, refining, and transportation, PDO’s machines use 96% less energy, 58% less water, and 14% fewer greenhouse gas emissions.
What types of plastic can PDO's process handle?
PDO’s process has been tested on all “classic” plastics (resin codes 1-7). Resin codes #1 (PETE) and #3 (PVC) are not desirable for use in the technology. Feedstock for individual projects would be determined by local waste streams and community needs, potentially through relationships with municipalities, businesses, agricultural operations and other local sources.
How does the resulting fuel compare with conventional diesel?
The liquid produced through PDO's process is not used independently as conventional diesel fuel. When blended with certified diesel at a ratio of 1:3, the resulting product meets the applicable standard specification for diesel fuel.
Have emissions been studied after the resulting fuel is used in a diesel engine?
PDO does not currently have data specifically characterizing diesel-engine exhaust from blended fuel produced using PDO technology. Published research has examined the combustion and exhaust characteristics of pyrolysis-derived oils, and continued research into the environmental impacts of these fuels is important. Read more here.
Has PDO's fuel been used long enough to evaluate its effects on engines?
PDO reports that fuel produced using its technology has been in use for approximately 25 years. When PDO's product is blended with commercial diesel so that the resulting fuel meets the ASTM D975 diesel fuel specification, no adverse impact on the engine is anticipated. Testing and analysis will continue as the technology develops.
How does pyrolysis temperature affect the resulting products?
Operating temperature influences the mixture of hydrocarbon molecules produced during pyrolysis and, consequently, the characteristics of the resulting products. PDO's technology operates at approximately 510°C. Other pyrolysis technologies may operate at substantially different temperatures and produce different product profiles. For more information on fuels created from 700°C and 900°C refer to this article and for more information comparing the impacts of different temperatures, click here.