The biggest challenge we face in the energy transition is the inevitable requirement to replace or abstain from key consumer products created with crude oil. One such ubiquitous product is plastic, which is a universal input for almost all consumer products.
How Plastic is Made
Plastics are made by a process called polymerization, which in current practice uses natural gas and crude oil as the feedstock. This process involves chemically joining many small molecules, called monomers, into a covalently bonded macromolecule. This macromolecule is then broken apart by heat into building blocks that are used to make plastic.
The Problem with Plastic
As previously mentioned, one key feedstock for the production of plastic is crude oil. Crude oil-derived plastic has several drawbacks, one being that production is heavily reliant on a finite and depletable resource. Crude oil is non-renewable and demand will eventually outstrip supply with an uncertain future. Crude oil also requires extensive processing to be useful for polymerization, which further exhausts energy resources like natural gas for heating and electricity (a secondary form of energy largely sourced from some combination of natural gas, coal, nuclear and renewable sources). The processing of crude oil requires large amounts of water, which is not only becoming scarce in some regions, but can become contaminated when used to produce plastic.
Is there a sensible solution?
So, can we make plastics without using hydrocarbons and how affordable is it?
There are alternatives to plastic that can be produced from biomass or even CO2. Many times, these plastics, made from materials such as PLA (polylactic acid) and bioplastics like Polyhydroxyalkanoate (PHA), make suitable drop-in replacements for many types of products without altering consumer expectations.
To transition toward greener forms of plastic, manufacturers would need to use alternative feedstocks, such as sugarcane-derived ethylene glycol and propylene oxide, when making plastic. While this replacement would help reduce carbon emissions, it would still require large amounts of cropland to meet demand.
Also, while bioplastics like PHA are more sustainable than conventional plastics, they are still non-biodegradable and require abundant land and fertilizer to produce. Complicating matters further, fertilizer requires raw materials such as phosphate rock, which in turn requires the extraction and processing of crude oil to produce fuel for mining activities. The fertilizer itself requires natural gas as a key input to produce ammonia (a point we have discussed previously).
If this seems circular, that’s because it is.
Hydrocarbons like crude oil and natural gas are both key inputs to the production of fertilizer, therefore these alternative biomass-based pathways cannot fully decarbonize plastics production.
Though there are alternative feedstocks that can be used to produce plastic as described above, they are typically more expensive than hydrocarbon oil-derived products and do not satisfy the underlying goal of decarbonizing plastics production. Without ready access to low-cost crude oil reserves like we enjoy today, plastics would have no place in modern society. If decarbonization is our end goal, consumers must reduce consumption of plastics rather than simply seek alternative pathways for production.
Andrew Schaper is a professional engineer and principal of Schaper Energy Consulting. His practice focuses on advisory in oil and gas, sustainable energy and carbon strategies.
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