Biobased chemicals – The future of renewable chemicals
The origin of raw chemical materials can be divided into two classes: petrochemical or biobased. But what to think about molecules made from biobased carbon but with the same synthesis routes as their petrochemical counterparts. What to think of this?
Petrochemical: a molecule made from petrochemical sources such as coal, natural gas or oil. While originally being tiny plants or animals, million years of sand of mud has covered it and increasing pressure and heat has resulted in the formation of these petrochemicals. Due to the long timelines of this process, it is considered not renewable.
Biobased chemicals: molecules that contain carbons from “natural sources/biomass”, this is measured by the insertion of carbon-14 isotopes. Older materials have less than 14C present and petrol-based chemicals have none. Biobased chemicals have to originate from plant-based materials, either direct or indirect.
Origin of biobased chemicals
There are several ways to produce bio-based chemicals. Most straightforward would be to extract/isolate certain molecules from a plant or a fruit amongst others. Example of this are oleochemicals such as fatty acids, glycerin and fatty alcohols. Castor oil is commonly used in polyurethanes and other vegetable oils find applications in alkyd paints.
There are however limitations to the array of molecules that can be isolated easily. Instead, you can have (modified) microorganisms convert sugars into the desired molecule by fermentation. Examples are for example succinic acid, 1,4-butanediol or lactic acid, which can all be used as a building block for bioplastic production. The production of these molecules is done by feeding the micro-organisms glucose-rich syrup which is converted biochemically to the desired molecule. By using these modified organisms also molecules which are not commonly found in nature can be produced.
Alternatively, the biomolecule is chemically converted to the target molecule. Examples are the production of Cyrene or 2-methyl-THF from cellulosic biomass. These molecules require multiple chemical steps and would normally not be present in nature.
While these three methods provide valuable tools in obtaining biobased molecules, even some previously never being produced by petrochemical means, they are also currently limited. Not all molecules can easily be produced from sugars, either by fermentative or chemical means. Especially aromatic moieties are hard to obtain via this route, while they play an important role in many chemical industries. Furthermore, the downstream processing of fermentation reactions can be difficult and labour-intensive.
Petrochemical methods towards biobased molecules
To still be able to produce a similar array of molecules as we have now, one of the methods that could be thought of is to produce similar building blocks as currently used in the petrochemical industry, starting from bio-mass.
Already several producers are able to supply renewable diesel which is produced by reducing fatty acids towards their analogous alkanes. Instead of burning this for fuel, one can also imagine it being further cracked/reformed into important chemical building blocks.
Another method of producing these could be to utilize biobased synthesis gas (syngas), a mixture of carbon monoxide (CO) and hydrogen (H2). This syngas can also be used to create chemical building blocks such as ethylene and propylene for example.
Currently, syngas is made almost exclusively from coal and natural gas. Producing it from bio-mass likely requires an increased energy demand, however, the feedstock would be fully renewable. Coal and natural gas might for now be easier, however, they previously required the same energy input. This was done by a long era of heat and pressure from being buried under layers of sediment. As mentioned this is just not sustainable, as this process is relatively slow.
All techniques are required
The methods described above are by no means all the methods that are available. The reality is that not a single solution will exist, some chemicals will be easier to be produced via fermentative methods while other building blocks are more easily obtained via thermal cracking of renewable diesel.
Are you interest in learning more about the current availability of biobased chemicals and want to explore the possibility to replace your petrochemical raw materials with those of a renewable origin? Feel free to contact our product manager Maarten Sijm.