Mango Materials develops closed-loop process to make affordable methane-based PHB


At the 9th European Bioplastics Conference, it was hard to miss the sheer passion of Molly Morse, Mango Materials CEO, when she talked about the ambitions and the achievements of this start-up company, of which she is a co-founder.

As she describes it, the company has developed a very simple process that offers a win-win proposition for the environment. "Methane is a problem. It's a greenhouse gas that's twenty times more harmful to the environment that carbon dioxide," she said. "We take that methane, and using our patent-protected, biological process, transform it into a biopolymer, which means less waste, and it's cheap."

Cheaper, at least than the plant-based sugars used in many other processes, which means that the costs of production are also much lower, in addition to the fact that the organisms used by the company are all 'wild' - there is no genetic manipulation involved, only a process of natural selection. This also contributes to keeping the costs down.

"It can be any methane," Morse continued. "We feed it to our unique bacteria in the bioreactor, who turn it into the bio polyester PHB - a kind of PHA - inside their cell walls. We then harvest the PHB in powder form, clean it, dry it and convert it if necessary into pellets, which we deliver to processors. At the end of life, the products can be anaerobically digested in a process that yields new methane feedstock. So we create a plastic in a closed-loop process that is both affordable, and eco-friendly."

Mango Materials currently uses waste methane gas that is produced from anaerobic digestion of waste at wastewater treatment plants or waste methane gas that is produced from waste decomposition at landfills, agricultural facilities, or other industries. But is there enough methane around to ensure a steady supply of feedstock for Mango Material's PHB?

According to Morse, this is not a concern. She noted that there is enough unused, methane produced by landfills in California alone to yield more than 100 million pounds per year of plastic. The company reckons that in the U.S., some 3 billion pounds of feedstock are available per year. "Wherever there are people, is methane," she said. "To produce 1 gram of PHB you need 3.4 grams of methane. And we can actually co-locate, at the site of the methane."

The company's goal is to reach price parity with comparable, conventional plastics, such as PP, LDPE and HDPE, however, to do so, the process needs to repeatable at scale - something the company is working hard to achieve within the next year or two. Ultimately, the aim is to be able to sell the material at a dollar per pound, "but we need to scale the process up to make it at that price." To that end, the company is developing a Mango "standard" plant, which will have a production capacity of 1000 metric tons per year. The idea is to locate these standard plants on site - for example at a wastewater treatment plant, dairy farm or landfill - to handle the methane produced there. "Using methane to make the plastic is much more economically advantageous than using the gas, for example, to generate heat or electricity," said Morse.

PHB is a biobased, but also a biodegradable, material. It degrades in anaerobic environments and, in the right conditions, in the marine environment as well. For this reason, the company is looking at applications where biodegradability is key, such as agricultural films.

"One of the applications that I am very excited about is, for example, replacing the PE micro beads in personal care products, such as scrubs and face wash, with our PHB. It's a challenging one, but our materials won't persist in most environments, so this is an application that looks very promising. It's one of the first that we certainly will be pursuing."
Source: Plastics Today