Bioplastic from sorghum is India’s answer to plastic hazards

Scientists working on a plant-based alternative

In the early 1940s, Henry Ford experimented with making plastic parts for automobiles. He came up with what was called the “plastic car made from soybeans.”

Indian scientists are now working on a plant-based alternative to fossil fuel-derived plastics, by using the dry land crop plant sorghum and a few microbial strains.

Researchers have developed a sorghum that is far more effective for biomass-based plastic and will be much cheaper and more sustainable than plastic. Going forward, it is the era of ‘green technologies’ and irrespective of the cost considerations, bioplastics need to adopted, an expert said.

Since Henry Ford, when mass plastic production began from oil-based materials, its use has surged dramatically, becoming a big part of our daily lives. The resulting unwanted plastic pollution crisis and awareness of depleting fossil fuel reserves has driven research toward alternative, sustainable materials.

Extending the hunt for sustainable materials as an alternative to fossil fuel-derived plastics, Indian scientists at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) are working with the humble drylands crop plant sorghum (jowar) and a bunch of microbial minions to help shape a bio-based plastic future.

Commonly used bioplastic feedstocks (raw materials) are: cellulose, starch, glucose and vegetable oil.

“We need a good amount of feedstock. Sorghum is a rich source of starch like corn and potato. Starch based edible cutlery is popular across the world,” A. Ashok Kumar, sorghum breeder at ICRISAT, told Journos.

For example, Bakeys, a Hyderabad-based company produces edible spoons made by baking a dough consisting primarily of sorghum (Sorghum bicolor), with some additional wheat and rice flour.

A start-up in the Czech Republic is experimenting with producing an edible coffee cup composed of a cereal-based crisp waffle.

“Currently people are using sugarcane bagasse as source material for bioplastic but here we have developed a sorghum that is far more effective for biomass-based plastic and will be much cheaper and more sustainable,” Ashok Kumar said.

He was referring to sorghum cultivars (RVICSH 28 and ICSV 18542) that have high biomass yields and more ratoonability (yielding more than one harvest from a single planting) making them amenable for crafting into bioplastics.

High biomass sorghum cultivars could be used for making bioplastic which will be much cheaper and more sustainable than bioplastic from other raw materials like sugarcane bagasse. In line with sugarcane, corn, cassava and sugar beet, high biomass sorghum has very good potential with wider adaptability, is fast growing (completes life cycle in four months) and has high biomass production with its efficient C4 photosynthetic pathway. It can be grown in rain fed conditions with low-nutrients,” Ashok Kumar said.

High biomass sorghum hybrids, grown in a hectare, churn out 20 tonnes of dry mass in four months that is double that of normal sorghum and four times when compared to paddy.

Specific techniques are employed to convert these feedstocks into thermoplastic starch, poly-lactic acid, polyhydroxylalkanoates, poly-3-hydroxybutyrate, polyamide 11 and biopolyethylene, which can be processed into biodegradable polymers.

Sorghum biomass specifically, is transformed into polylactic acid which is further processed into bioplastic. In the transformation process, sorghum bagasse has to go through sacharification, fermentation and polymerisation. Bacterial fermentation of sugars derived from sorghum biomass produce lactic acid which is then synthesised by polymerisation to produce polylactic acid.

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