Green chemistry development will take place in three overlapping phases, up to 2050. The first has been developing for some time now, the second started recently, and the third is in the research phase.
1. Biofuels in the petrochemical infrastructure
Petrochemical industry uses building blocks, simple molecules from which more complex ones are synthesized. Ethylene is such a building block. At present naphtha is the main source of ethylene – but it can easily be obtained from ethanol, and consequently from bioethanol, too. A plant producing bioethylene from bioethanol would therefore constitute a first step into the biobased economy. This plant would feed certified bioethylene into the existing Western European pipeline system, which is purchased like green electricity by the acquisition of certificates. This is an effective and straightforward way to increase the use of biomass as a resource (see table 1), as we can easily synthesize many building blocks from green resources, like bioethylene and green synthesis gas. The reverse side is that this in itself does not lead a greener chemistry, and that the structure of chemical industry remains unchanged. Moreover, policy measures like subsidies and quota might be needed to enforce green policy goals.
Chemical building blocks
|Number of C atoms||Fossil||Green resources||In the slipstream of…|
|C1||Synthesis gasMethane||Biomethanol from glycerol: BioMCNSynthesis gas from glycerolBiogas/green gas (methane)||BiofuelsBiofuelsBiofuels|
|C2||EthaneEthylene||Bioethylene from bioethanol, large scale in Rotterdam (PGG)Acetic acid (fermentation)||BiofuelsFood chain|
|C3||PropanePropylene||Glycerol, side product of biodieselLactic acid (fermentation)1,3 propanediol (fermentation)
Propylene glycol from glycerol (DOW)
|BiofuelsFood chainFood chain
|C4||ButaneButyleneButadiene||N-butanol (fermentation)Isobutene from isobutanol via fermentation (Lanxes, Gevo)||Food chainFood chain|
|C5||PentaneOlefines||Pentosugars||To be developed|
|C6||BenzeneAromatics||Hexosugars (glucose)Lignin||To be developed|
|C7,8||TolueneXylenesAromatics||HeptosugarsFatty acidsLignin||To be developed|
2. Use the full potential of catalysis, enzymes and fermentation
Europe is leading in the field of industrial biocatalysis. We can use this knowledge base for the production of biobased chemicals like lactic acid, furanedicarboxylic acid, dialcohols and other molecules containing nitrogen or oxygen. In a later stage we might envisage products from biorefinery, like butanediamide from arginine or acrylonitrile from glutamate, which would require the development of new separation technologies. For many substances the production from biomass is still under research, but some of them offer great potential because of their present production volume (between 1 and 5 Mton per year worldwide), like acrylic acid, 1,2 propanediol, 1,4 butanediol, sorbitol, terephthalic acid, and adipic acid. Characteristic of this phase is the intermediate production of relatively simple building blocks like starch sugars, proteins or amino acids. On the strategic level this phase would show loosening the bond with the energy sector and strengthening the bond with the food sector.
3. Biorefinery, use of nature’s complexity
This phase would show green chemistry’s intrinsic value: production of valuable substances directly from plants, while not reducing nature’s complexity but retaining it as much as possible for direct use or efficient reactions. The side streams, or green waste, we will use for second generation biofuels, fodder or maybe even food. Guiding principle will be obtaining the highest value possible.
In this third phase chemical industry will develop into a branch completely independent from both the fuel and the food chains. For this new green chemical sector, farmers will start growing specialized crops (plants, microorganisms) that directly produce complex substances for special purposes. That can be done by genetic modification of plants and/or microorganisms, or through the classical route of breeding, in which automation allows for much faster pathways (‘directed evolution’). Chemistry will be elevated to a higher and more elegant scientific and technological level. The sector will detach itself completely from the pipes and kilns of past centuries.
In the second and third phases, chemical industry’s spatial pattern will alter appreciably. Chemical plants will be much smaller, and less concentrated in industrial areas. Chemical industry might choose to settle near its feedstock: in biomass producing, rural areas.
Year 2050 would seem to be a good target year for finishing the green chemistry transition. The Brew report (with Utrecht University’s Copernicus Institute as the lead author), estimates that by this time sugars will be an excellent and sustainable feedstock for 14 biochemicals. Cost reduction would be decisive: assuming crude oil at $ 85 per barrel, and sugar at € 70 – 200 per ton, ongoing technological innovation and economic growth at 3% p.a.,this could result in a two thirds fossil fuel use reduction, and 250 million tons of carbon dioxide emissions reduction. Costs would be cut by € 75 billion. Extra land use would be relatively small across several scenarios. This would imply a strong economic argument for biobased resources. The Brew study investigates platform chemicals and their economic value; it does not consider chemical specialties and special products, which would carry a much higher economic value. By 2050, green chemistry will be superior in all respects.
Courtesy WTC, Dutch Scientific and Technological Committee for the biobased economy