John Endres: Silicon smelting process tarnishes ‘green’ claim for solar panels

By John Endres

The proposed PacWest/HiTest silicon smelter in Newport, Washington, was touted as a “green” facility since some of its product, metallurgical grade silicon, would be further refined for use in silicon solar panels. “Smelting” involves the extraction of a metal from its ore, and “refining” involves purification of an extracted metal. Initially, it was claimed that 50% of the smelter’s silicon would be used for solar panels, but was later suggested that only 5% would be used for solar panels by the REC Silicon refinery in Moses Lake. Most metallurgical grade silicon is used in the metal alloy and chemical industries, and only a small percentage is further refined to meet the high purity demands for electronics and solar panels.

Silicon smelters have tremendous electricity demands and are highly polluting heavy industrial facilities. According to the Washington Department of Ecology, the proposed smelter would include two submerged arc furnaces and one 157-foot tall emissions stack; and estimated annual materials would include 170,000 tons of quartzite rock (silicon dioxide), 150,000 tons of blue gem coal and charcoal, and 130,000 tons of wood chips in order to extract 73,000 tons of metallurgical grade silicon per year. The estimated annual emissions would include over 766,000 tons of greenhouse gases per year, plus tens to hundreds of tons of other coal toxins per year. According to 2020 data from the EPA’s Greenhouse Gas Reporting Program, the proposed smelter would be about the 12th highest industrial greenhouse gas emitter in Washington state.

A constant supply of 105 megawatts of electricity – more than 900 million kilowatt hours per year – would be needed to produce the intense heat required to obtain molten quartz in a mixture with carbon reductants. According to the U.S. Energy Information Administration, the average U.S. household consumes about 11,000 kilowatt hours per year. The smelter’s annual electricity use would be enough to supply more than 80,000 average homes per year.

The smelter’s “carbothermic reduction” process uses carbon from coal, charcoal, and wood chips in a reaction with silicon dioxide to yield carbon dioxide and elemental silicon. Molten silicon is collected from a furnace tap-hole, and carbon dioxide plus other greenhouse gases and pollutants are emitted into the atmosphere.

How can a heavy industrial facility that produces a product, of which only a fraction is used for solar panels, be considered a “green” facility? Scientific papers describing solar panel carbon footprint calculation methods revealed some surprising and concerning issues:

• Reported carbon footprint values of silicon solar panels found in reviewed literature do not include the silicon smelting process, which is perplexing since silicon is the critical component of silicon solar panels.

• Carbon footprint calculations use a process known as Life Cycle Assessment and Life Cycle Inventory. These methods are highly subjective, yield inconsistent and noncomparable results, are not governed by a standard unifying method, and are typically performed by industry instead of independent bodies.

• According to the Intergovernmental Panel on Climate Change (IPCC), greenhouse gas emissions from biomass sources (woodchips, charcoal, etc.) are not accounted for at the point of combustion in energy and industrial sectors, including smelting. But we all know that burning wood and charcoal emits smoke (carbon dioxide and other gases). A number of reviewed papers challenge the IPCC’s biomass accounting method.

• The carbon dioxide sink loss due to the harvest of trees for wood chips and charcoal used in the smelting process is not included in silicon solar panel carbon footprints. It can take decades to more than 100 years to replace the carbon dioxide sink loss due to tree harvest.

• A clear and quantifiable definition of “green” does not exist, and “greenwashing” is a persistent problem.

• Using the provided raw material and emissions quantities for the proposed smelter, the impact of silicon smelting on solar panel carbon footprints was estimated and suggests that silicon solar panels account for more atmospheric carbon dioxide than they save. Excluding the silicon smelting process from solar panel carbon footprint calculations undermines the integrity of the silicon solar panel industry, and challenges the “green” claim of the proposed silicon smelter, and the “green” claim of silicon solar panels as well.

We are facing a climate change crisis. If we do not approach the environmental impacts of our activities with the utmost integrity and transparency, we will face ever increasing challenges to our quality of life.

John Endres, of Newport, has degrees in conservation technology and botany. He has worked in forestry, plant genetics research and protein biochemistry production and research.