We are at a crossroads in recycling technology, so let’s choose a path that considers climate change and long-term economic success, says Jeffrey Dewey, research intern at Beam Project.
Plastic film is bulletproof glass to microbes. By keeping food fresh and microbe-free for weeks, plastic packaging reduces food insecurity and saves billions of dollars. Moreover, since food accounts for one quarter of all greenhouse gas (GHG) emissions, saving food reduces emissions. The benefits of plastics, unfortunately, are tarnished by their negative ecological and climate impacts.
Whether a stiff pipe or flexible fabric, 99% of all plastics today come from processing petroleum or natural gas into a solid. Fossil fuel and petrochemical companies are shifting investments towards plastics as renewable energy sources grow to displace them in meeting global energy demand. Since 2010, global investments in petrochemical facilities topped a staggering $200bn. The industry’s hopes lie in an estimated 3-4% annual increase in plastic demand over the next 30 years from developing countries in Africa, the Middle East, and Asia.
Increased GHG emissions are inevitable whenever fossil fuels are involved. A report from the Center for International Environmental Law calculated that plastic production currently accounts for more GHG emissions than aviation. By 2050, it is estimated that increased demand will translate to tripled annual emissions, approximately 2.8 gigatons CO2 equivalents (eCO2). The report notes policy can have dramatic impacts; eliminating single-use plastics globally would cut emissions by half. However, implementing global policies poses a significant challenge. Thus, growing demand for plastics, coupled with an increased awareness of its environmental damage, are fuelling interest in recycling technology innovations.
UK needs e-waste infrastructure to recover precious and critical metals
Pyrolysis, a type of chemical recycling, is currently leading the recycling investment race. Major companies, including Dow, BASF, Shell, General Electric, and Milliken, have recently partnered with pyrolysis-based startups. However, these investments ignore not only climate change, but also changing economic calculus.
What is pyrolysis? Plastic wrap dropped on a hot pan reacts with oxygen to generate CO2, other gases, and an impossible-to-clean black char; this is combustion. Heating plastic to 300-500 degrees Celsius in the absence of oxygen breaks it down into a mixture of petrochemicals and oils; this is pyrolysis. Pyrolysis only qualifies as recycling when the resulting petrochemicals and oils are resynthesised back into plastics instead of burned for energy. Proponents highlight the ability to use pyrolysis to process plastics that conventional recycling cannot. Unlike the Greek hero Achilles, however, this technology has not one but two fatal flaws: CO2 emissions and narrow marketability.
An independent calculation found that Agilyx, a pyrolysis firm partnered with General Electric, produced 3.23kg eCO2 for each kg of polystyrene (PS) processed. Similarly, BASF, a corporation that has itself invested in pyrolysis, found that pyrolysis of polyethylene (PE) produces 3.34kg eCO2 per kg fuel produced. As a comparison, synthesizing 1kg of new plastic requires between 3.1kg eCO2 (PS) and 1.8kg eCO2 (PE). Furthermore, simply landfilling 1kg of plastic waste only emits 0.06kg eCO2. Taken together, these data indicate pyrolysis has higher emissions than landfilling old plastic and producing new plastic. Mechanical recycling is the real emissions-saver; mechanically recycling and repurposing 1kg of plastic waste reduces CO2 emissions by 1.5-2.1kg eCO2 due to decreased plastic production.
Along with its GHG emissions, pyrolysis also possesses technological shortcomings that limit its ability to navigate unstable markets. Pyrolysis relies on high fossil fuel costs to outcompete virgin plastic resin and fossil fuels. Low oil prices disrupted pyrolysis in 2016, and now the pandemic, along with a Saudi-Russia price war, is driving plastic resin prices to historic lows. The technology is not versatile enough to compete. Pyrolysis is only efficient at recycling a subset of plastics that excludes polyethylene terephthalate (PET), which comprises 10% of all plastic waste. Furthermore, pyrolysis and other chemical recycling technologies cannot survive oil price instability by expanding into the rapidly growing market of electronic waste recycling.
I am pursuing a chemistry Ph.D. specifically because technologies can have a positive influence in the world. A recently discovered recycling technology, magnetic density separation (MDS), meets my utopian expectations of science.
Despite making up over half of plastic waste, polypropylene (PP) and PE cannot be separated by traditional mechanical recycling. MDS conquers this challenge by using magnetic iron oxide nanoparticles to modulate the apparent density of water, thus separating and purifying the denser PP from lighter PE. When powered by a renewable energy grid, MDS is almost entirely CO2 emission free.
MDS has another advantage over chemical recycling technologies like pyrolysis: its versatility. As was recently pointed out in The Engineer, recovering precious metal waste from electronics is a growing economic and ecological concern. However, with a few system adjustments, MDS has the ability to sort not only plastics, but also metals, by their inherent density.
Pyrolysis is currently diverting investments away from climate friendly technologies like MDS. However, we are still at a crossroads in recycling technology; let’s choose a path that considers both climate change and long-term economic success.
Jeffrey Dewey, Ph.D. Candidate, Department of Chemistry, University of Chicago
It seems that waste plastic is ideal for CCS: just bury it deep and it will stay there.
Why apply complicated, energy using technologies if the aim is Climate Change Reduction?
This is a great point! The problem with using plastic for CCS right now is finding a replacement material. Non degradable bioplastics, which are made form plant/microbial sources, are a great alternative. However, only 1.2 million tons of those plastics are made each year, whereas global plastic demand is ~360 million tons. I think with climate focused investments, bioplastics can take over demand, but it will take many decades.
Taking a step back, the ecological implications of plastics that don’t degrade can be devastating. Landfilling properly costs quite a bit, and many countries don’t have the infrastructure/capital/land to do it. The balance between climate, ecology, and costs have driven our society to incinerate ~20-30% of all plastic. The ultimate goal from an ecological and climate perspective is to use as little material as possible.
Agreed that landfilling plastic waste is a legitimate, economic and environmental solution. The writer cannot simply wave his hands and assert electricity consumed by MDS is zero carbon. It isn’t. It comes from a mixture of gas, renewables and even a bit of coal – just like everybody’s else http://gridwatch.templar.co.uk/
Parts of UK that generate energy-from-waste (EfW) benefit from a proportion of plastic in general waste, as it increases the calorific value that otherwise might need supplementing by fossil fuels to achieve the required combustion temperature
Yes it costs £millions to engineer a landfill site properly: lining, cell construction, leachate extraction, landfill gas management and finally capping and restoration. Nevertheless the unit price is remarkably economic. The UK was pressed by the EU to reduce landfilling and given the UK’s reluctance to follow the EfW/”incineration” route the only other option was to artificially hike the cost of landfill by means of taxation make recycling even remotely competitive. This has now reached the level of QUINTUPLING the cost to waste producing industries https://www.letsrecycle.com/prices/efw-landfill-rdf-2/efw-landfill-rdf-2020-gate-fees/ with the actual cost (before tax) around £23 per tonne, after tax £115. A real cost, to real businesses that could otherwise be spent on investment or better wages
Not content with skewing the market in this way, the extractive industries (clay=bricks, sand & gravel=concrete) too were hit with a “virgin aggregates tax” an attempt to suppress the creation of void space for new landfill sites
Trevor, nothing you say addresses the current and future climate implications of plastics.
On landfilling. If it is a carefully planned way to reduce CO2 in the environment using bioplastics, then it might have a place in this world. However, landfills currently provide no value to society except to literally hide our waste until we run out of land. Recycling more plastic reduces our waste, energy consumption, and CO2 emissions. In general, we need to think more about the 50-100 year horizon of our society and make investments that will carry into the next century.
MDS has negative emissions and energy use because it replaces plastic that normally comes from natural gas and petroleum that is cracked, purified, and synthesized. By the numbers, new plastic takes ~70 MJ/kg whereas recycled plastic takes 2-5 MJ/kg. When writing this article I got a study that specifically shows MDS reduces emissions even if it’s incorporated at the tail end of current recycling streams, which is inefficient. If interested, I can send it to you or any other readers through twitter @DewingScience
Now that natural gas power plants are coming online, energy from waste does not reduce emissions, and actually increases emissions dramatically. See the CIEL report (pg58) in the article.
Jeffery why have you not considered renewable energy for pyrolysis? That would surely change the equation.
The relatively low temperatures around 500 deg C are readily available from CSP systems as superheated steam. Why on earth would you use fossil fuels to do this?
It’s a great question, and every technology should be evaluated in terms of replacing fossil fuels for renewable sources. A couple of issues in the case of pyrolysis.
Most importantly, pyrolysis right now relies on fossil fuels, so I’m taking it on it’s grounds. Secondly, pyrolysis is much less energy efficient due to its high temperatures and requirement for resynthesis of new plastics. Lastly, pyrolysis produces oils and char that tempt companies to burn rather than recycle these products. We should use our renewable energy as efficiently as possible and limit even the chance for emissions.