Mainstream solar photovoltaic technology based on crystalline silicon cells has a few direct dependencies on fossil fuels: - Coking coal makes up part of the f

Mainstream solar photovoltaic technology based on crystalline silicon cells has a few direct dependencies on fossil fuels: - Coking coal makes up part of the furnace charge used to produce crude metallurgical silicon from silicon dioxide. - Backsheets, encapsulant materials, and electrical insulation are made out of organic chemicals manufactured from oil and gas. For the first part, I believe that charcoal produced from biomass can replace coking coal with only modest process changes. It has already been demonstrated on a small scale. One particularly interesting idea is to use charred rice hulls to make silicon: they already contain silica and carbon together, and are available in large quantities as a cheap byproduct of rice production. For the second point, it is necessary to replace feedstock chemicals that currently come from fossils. One fairly general path is to hydrogenate carbon dioxide to methanol with electrolytic hydrogen. The methanol can be converted to simple olefins like propylene and ethylene, and from there a huge variety of plastics and polymers are further accessible. China is already operating methanol-to-olefins plants on a large scale; unfortunately, their methanol is produced largely from coal. https://www.chemengonline.com/worlds-largest-single-train-methanol-to-olefins-plant-now-operating/?printmode=1 https://www.chemengonline.com/worlds-largest-single-train-me... But the process from methanol is the same whether the methanol comes from coal or (like the Iceland methanol plant run by Carbon Recycling International) carbon dioxide and renewable energy: https://www.frontiersin.org/articles/10.3389/fchem.2018.00446/full https://www.frontiersin.org/articles/10.3389/fchem.2018.0044... Solar also has the same incidental dependencies on fossil fuels as the rest of society -- e.g. the electricity to make the aluminum for module frames may have come from a coal fired plant, the ships that carry modules across oceans burn fuel oil, and so on. But these incidental dependencies are relatively small. A shipload of solar panels does not require more fuel oil to transport than a shipload of coal, but the shipload of solar panels will produce far more electricity before they are used up.