Call it anecdata, but a few of the things I noticed after a couple decades in the industry: 1. Water Water is extensively used and it has to be as pure as you

Call it anecdata, but a few of the things I noticed after a couple decades in the industry: 1. Water Water is extensively used and it has to be as pure as you can imagine. This requires a regular investment in filters and energy. I wouldn't be surprised to see hundreds of water wash steps for a wafer of chips, plus water wash steps for the equipment. 2. Acids and bases You can dump these in the third world, sure, but neutralizing them tends to be favored, and also very expensive. Sulfuric or Hydrofluoric acid may require almost zero energy input, but the caustic soda, soda ash, or baking soda you need to add to passivate their waste requires a lot. 3. Silicon itself This one's a bit of a surprise. A gram of hyperpure silicon doesn't really take that much energy, or even generate all that much waste. There's the reduction cost where you burn out the oxide with coal and wood chips, plus the follow-up stages of purification and crystallization. You lose half again by wafering. But even if it's 10 grams waste per gram of chip, you're not doing all that poorly. An idling car engine makes 10 grams of waste in no time. Plus the waste is almost entirely mg-Si, CO, and CO2; very manageable. China has a bit of a silicon-tetrachloride problem from some of its purification steps, but that stuff is avoidable. 4. Photoresists These are the absolute worst. Carcinogenic and complicated to manufacture. 5. Specialty gases What's a little diborane, phosphine, or arsine among friends? These players are bad news, but you use such trivially small quantities of them that their impact is pretty light. You still have to scrub their waste gases out before you release them, and that's a bit of a pain. 6. Bulk gases Hyperpure nitrogen, oxygen, and argon get used in large amounts as well but they're almost as cheap as air in bulk. Release at will. 7. Air handling Cleanrooms require more airflow than some bitcoin farms, and specialty filters have to be changed out occasionally. It's just electricity though. 8. Packaging All that copper, tin, silver, and gold, plus whatever weird plastics they're using these days may end up being far worse for the environment than the chips they encase. 9. Actual use Unless they're generating power (PV) they're going to suck down power, whether in your cable box set to off or the switchgear. This is by far the biggest energy consumption associated with semiconductors. 10. Vacuum! Along with to a lesser extent compressed air, vacuum greases and machinery can get up there in terms of cost. Roughing pumps will spew oil, and turbo pump and cryopump units cost a lot to build, run, and maintain. 11. Organic solvents Cheap to make, expensive to dispose, doubly so when you mix them with some of the other expensive-to-dispose stuff.