1. The most difficult way to expand production is the German nano nitric acid process. Its by-products are nitrogen oxides and sodium nitrate. If it is not handled well, it will explode. The by-products of ammonia process and sodium process are sulfuric acid and sodium sulfate. Sulfuric acid is a kind of chemical fertilizer, and sodium sulfate is more difficult to treat, but it needs to transport the digestion radius. The oxalic acid method is the least difficult to expand production, and its by-product is calcium oxalate. After high temperature heating, it is carbon dioxide, which evaporates, which is equivalent to no abandoned products.
2. Energy cost. The production process of sodium nitrate is cheap, because everyone knows to find a place where electricity is cheap to produce.