LEGO’s new sustainable plastic plants are made from plants, but are they green?

From August 1 2018, LEGO will begin distribution of the company’s first set of sustainable bricks, “Plants from Plants”, in the form of botanical elements, such as trees, bushes and leaves. Announced on March 1, 2018, these new elements will be made from sugarcane-based polyethylene.

This new era of production marks the beginning of the Danish company’s commitment to replacing current oil-based plastics with sustainable materials in core products and packaging by 2030.

fake plastic trees
Image: The LEGO Group (2018)

The rub here is that only 1%-2% of all LEGO materials are made from polyethylene. Much of company’s products, such as their quintessential bricks, are manufactured from ABS (acrylonitrile butadiene styrene) plastic, to which The LEGO Group have not found a satisfactory replacement as of yet.

Sustainable Materials

Sustainable materials are those which are renewable and that provide environmental benefits, whilst protecting public health throughout their life cycle.

Current oil-based plastics are not considered sustainable due to the crude oil’s non-renewability and the processing of which is a major producer of greenhouse gasses (GHGs), such as CO2, which contribute significantly to global climate change.

The switch from fossil fuels to sustainable plant-based production of plastics therefore must be inherently better for the environment and, in turn, human health. Or is it?

Oil vs. Plant-Based Production

As opposed to the naphtha cracking process used to extract and polymerise ethane into polyethylene (fossil-PE), sugarcane-based production of polyethylene (bio-PE) consists of the dehydration of bioethanol into ethene and then polymerisation. The bioethanol is produced via fermentation of the sugar from sugarcane, by yeast. Both fossil-PE and bio-PE are indistinguishable from one another as the resulting products are chemically identical ([CH2-CH2]n).

General overview of the processes for the production of polyethylene via sugarcane (green) and crude oil (orange)
General overview of the processes for the production of polyethylene via sugarcane (green) and crude oil (orange), culminating in the common processes (blue) (created from information from Kikuchi et al., 2013).

The production of polyethylene from sugarcane bioethanol reduces the direct consumption of fossil fuels to fertilisers, harvesting machinery, and transportation. It has been estimated that the GHG emissions from bioethanol dehydration are less than half of those by naphtha cracking.

Environmental Impact

There is much more to be considered than just fossil fuel consumption when considering a large-scale conversion to plant-based materials. Most notably, physical space. Between 1975 and the 2006/07 season, Brazil alone increased production of sugarcane-based bioethanol from 0.6 to 18 million cubic meters. And it has been documented that the expansion of agricultural land for biomass resources, such as sugarcane production, has displaced food crop production. Furthermore, increased land for biomass production could lead to ecologically damaging deforestation, a reduction in biodiversity, and soil degradation.

For the moment, much of the expansion for sugarcane crops has been resigned to degraded and pasture lands. The improvement of agricultural practices and the development of new sugarcane species have also resulted in a reported increase in crop yields by up to 33%. Genetic manipulation also allows for more environmentally resistant crops, which aids in increasing yields before expansion.

The expansion of sugarcane for bioethanol production also brings another issue — the increased use of fungicides, insecticides, and herbicides. The latter of which, often spread from airplanes, has been reported to damage smaller producers’ fruit trees.

Although a practice in decline, manual harvesting includes sugarcane trash burning. This burning leads to GHG emissions which may potentially damage human health, as well as the environment; conditions which fall under the criteria of sustainable materials. However, research is still divided on whether trash burning is detrimental to human health and further research has shown that the GHG emissions (mainly CO2) are reabsorbed by photosynthesis in the next season of crops.

The Verdict

Research has determined that the move to sugarcane-based bioplastics is more environmentally responsible, by reducing GHG emissions and our dependence on fossil fuels. Although this will only replace approximately 1%-2% of all LEGO bricks, this is still a huge number of products produced from sustainable materials, with more planned for the future.

However, this is merely a step in the right direction and not a final solution. GHGs are still produced from the infrastructure surrounding sugarcane harvesting and bioethanol production, and trash burning is still common practice. Furthermore, the increase in land use and agrochemicals potentially reduces biodiversity and long-term soil viability. And, ultimately, polyethylene remains non-biodegradable.

The future of sustainable plastics is uncertain but promising research and responsible business practices are paving the way to a much more environmentally friendly future.

Reference List

Babu, R. P., O’Connor, K., & Seeram, R. (2013). Current progress on bio-based polymers and their future trends. Progress in Biomaterials, 2(1), 8.

Chen, G., Li, S., Jiao, F., & Yuan, Q. (2007). Catalytic dehydration of bioethanol to ethylene over TiO2/γ-Al2O3 catalysts in microchannel reactors. Catalysis Today, 125(1-2), 111–119.

Goldemberg, J., Coelho, S. T., & Guardabassi, P. (2008). The sustainability of ethanol production from sugarcane. Energy Policy, 36(6), 2086–2097.

Macedo, I. C., Seabra, J. E. A., & Silva, J. E. A. R. (2008). Green house gases emissions in the production and use of ethanol from sugarcane in Brazil: The 2005/2006 averages and a prediction for 2020. Biomass and Bioenergy, 32(7), 582–595.

Kikuchi, Y., Hirao, M., Narita, K., Sugiyama, E., Oliveira, S., Chapman, S., … Cappra, C. M. (2013). Environmental Performance of Biomass-Derived Chemical Production: A Case Study on Sugarcane-Derived Polyethylene. JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 46(4), 319–325.

Luca, E. F., Chaplot, V., Mutema, M., Feller, C., Ferreira, M. L., Cerri, C. C., & Couto, H. T. Z. (2018). Effect of conversion from sugarcane preharvest burning to residues green-trashing on SOC stocks and soil fertility status: Results from different soil conditions in Brazil. Geoderma, 310, 238–248.

  • Nice review with plenty of numbers! Plant-based plastics can be distinguished from plastics made from fossil-fuels: the plant-derived plastic is radioactive including 14Carbon, while the 14C in fossil-fuel derived plastics has long decayed. Thus manufacturers’ claims can be tested in the final product and do not rely on an easily (and sometimes profitably) defrauded trail of paperwork.