The Ohio State University,
Keywords: advanced elastomers, biorubber, critical materials security, high density production
Summary:Biodiversification of global natural rubber (NR) is essential because (i) NR is the only critical agricultural product which has no back up, (ii) 14 million tonnes of global NR production failed to meet 2018 demand, (iii) rubber trees (Hevea brasiliensis) are genetically similar and susceptible to disease potentially leading to crop failure, (iv) a major outbreak of Pestalotiopsis fungal leaf drop disease has led to predictions of at least an 800.000 tons loss in 2020 production, and (v) the US imports $1.5 billion-worth of NR and $13 billion-worth of automotive products, including tires and other items essential to all economic sectors. Synthetic rubber cannot mimic NR’s unique and essential performance properties. Rubber root dandelion (Taraxacum kok-saghyz) is under development in several temperate areas of the world, with significant support from tire companies. The crop can be established in fields by direct seeding or by transplants but high planting densities are needed. Weed control is an issue for both types of field crop but are most challenging in direct seeded fields because the rubber root dandelion grows more slowly than many competing weed species. Scientists at OSU achieved chemical weed control in 2019 in field plots and this is being tested on a larger scale. Also, repeated selection for root size has led, so far, to a 240% increase in average root size. Improvements in germplasm through conventional and molecular breeding should steadily increase yield and commercial viability and reduce the current long growth season requirement for good yields. The species is suited to vertical farming systems in which the environment can be controlled, there are no dirt or weeds, and the rubber-containing roots can be harvested every two months multiple times from the same plants. This system is at least 10x more productive than field-grown rubber dandelions and provides a high through-put testing system for naturally selected or genetically modified or edited plants. Various rubber extraction methods are being used and optimized. Solvent extraction processes are challenged by the high level of insoluble gel in the rubber. Aqueous extraction processes for solid rubber are slow and struggle to achieve the purity level required by the US rubber industry. Latex extraction processes, original developed for guayule, are not suited to current field grown roots because 50-90% of the latex has coagulated into solid rubber before harvest. However, hydroponic or aeroponic systems may retain more rubber in latex form and allow rapid extraction and purification of latex. The latex can be converted easily to solid rubber. Molecular characterization, composition and performance tests have demonstrated that rubber root dandelion rubber is very similar to imported NR produced by rubber trees.