The mass-balance way of making chemicals

Raw materials are prepared

Neste makes naphtha

Porvoo, Finland

Neste mixes up to 10 renewable biobased raw materials—sources include waste animal fats and used restaurant oils—to make an oil that it converts into naphtha at its biorefinery in Porvoo, Finland. Toward the end of 2020, Neste started to test a plastic-derived pyrolysis oil in its oil refinery in Porvoo. Neste aims to consume more than 1 million metric tons per year of plastic waste in its refinery by 2030. “A challenge that Neste and other refiners face is that the quality of pyrolysis oil is very dependent on the plastic feedstock that was used to produce the oil,” says Isabella Tonaco, a Neste vice president.

Naphtha produced from any of the three sources—fossil fuel, bio-oils, and plastic waste—is identical, according to Neste. In general, an independent auditor certifies how much renewable oil enters the process—an amount that determines how much of the naphtha a company can claim to be renewable. Neste sells its 100% renewable naphtha—which it has branded Neste RE—to Borealis and several other firms as a raw material for base chemicals.

Borealis makes phenol

Porvoo, Finland

Borealis receives the renewable naphtha from Neste and uses it to make benzene, cumene, phenol, and other base chemicals. Borealis can assign 100% of the Neste RE it buys to phenol, but in practice, it assigns about one-third to phenol and the rest to other chemicals for the purpose of making other mass-balance renewable products.

“For us, renewables and plastic recycling are definitely a priority to support the journey to circularity,” says Thomas Van De Velde, a senior vice president at Borealis. “The limiting factor for renewable phenol is currently the limited availability of renewable naphtha. But it is increasing month by month.”

Covestro makes polycarbonate

Krefeld, Germany

Covestro combines phenol—including mass-balance-certified phenol purchased from Borealis—with acetone to produce bisphenol A, which it then combines with phosgene, creating polycarbonate. This atomic dilution limits the renewable component of the polycarbonate to a theoretical maximum of 72%.

Covestro received its first shipment of certified renewable phenol from Borealis in October 2020. Covestro is experiencing “considerable interest” in mass-balanced products from customers in certain segments, says Jimena Ruesta, head of sustainable strategy for polycarbonate at Covestro. Nevertheless, “the market is still small and has to be developed,” she says.

Plastics converters create products for consumers

Germany and beyond

Plastics-conversion companies melt polycarbonate pellets from Covestro into forms such as furniture and automotive dashboards with the intention of selling them at a premium. Covestro hopes that a product at the end of its useful life will be chemically recycled into pyrolysis oil once again.

“In the past year, we have seen several consumer brand owners want to be certified so they can prove their products were produced with sustainable raw materials,” ISCC’s Knelsen says. “One of the biggest challenges is to market mass balance without becoming too technical.”