As a synthetic chemist, it is a very embarrassing question if asked about our personal carbon footprint. Frankly, it is much greater than normal citizens. We use flammable and non-flammable solvents very regularly. Most of the chemical reagents we use are of 99.9% purity requiring large amounts of energy to manufacture and purify. These chemicals are shipped from all over the world and require extra care in transportation. We often use rare metals in reactions, these require a great amount of energy to isolate. Yes, we are guilty of a larger carbon footprint than normal citizens. But no one asks how can we reduce it?
This question bugged me for quite sometime. We can do all those things that normal citizens do but as chemists can we do something more? One of our major contributions come from our use of solvents. I thought, looking into solvent disposal might give a hint into some simple steps that may be taken to reduce emissions. So I had a chat with our department‘s Safety Officer. He started the conversation with a very blunt question, “Why do you ask?”. May be he thought, I am one of those extreme climate change activist. After I explained to him what I wanted to know about it and that I meant no harm he said, “I was taken aback because no one wants to what happens to it after it’s dumped.” So he realised some people care and he was happy to answer any question I had.
One of the companies Oxford regularly uses for it’s waste disposal is Grundon. While we are in the lab, we separate our solvent waste in Hydrocarbons (Petrol, Diethyl Ether, Ethyl Acetate), Chlorinated (Dichloromethane, Cholroform) and Acetone (Wash acetone with lots of water). Chlorinated wastes needs to be disposed by incineration to avoid formation of dioxins where as hydrocarbon can be used for energy recovery. But what he thought is that the HC waste is used to create the high temperature furnace for the incineration of chlorinated waste. What about acetone? He said, “Most of it is taken by cement industry. If they see it’s dark in colour they won’t touch it, but otherwise they use it.” But is recycling not possible for any kind of waste? “No, I think it’s too energy intensive to get clean solvent than to just burn it off.”
He digressed and gave some interesting statistics, Oxford University produces a lot of waste. The only chemistry department that has comparable volume of waste is Cambridge. “Sure, but that’s because we are the biggest chemistry department in the UK, right?” Yes he says, “I talk to most Russell group universities about what they do about waste management. It turns out some universities don’t produce more than two barrels a month! And here we fill couple a day.”
Anyways, ending the talk I said, “So the best we can do is make sure we separate the different types of solvents with care?”. “I guess, but I don’t think that will make a big difference unless everyone does it.” From all this, the conclusion I could come up with is that we can do the following to help cut emission in someway.
- Minimise use of chlorinated solvents. (even though DCM is my favourite, low-boiling and polar)
- Try not to mix chlorinated and non-chlorinated solvents. (I often rinse column tubes with DCM even if I have done a hydrocarbons only column. I guess using ether is a better option but it is much more expensive than ethyl acetate. Thus, although acetone (not wash acetone) is high-boiling it is the best option or use ethyl acetate?).
- Turn the temperature of the oven lower?
- Do smaller scale reaction when one can (reduces a lot of things, smaller columns, less solvent and lesser time for same results, most of the times).
- Spend time thinking which experiment to do, make sure you have a strong justification (saves time, saves waste!)
These are conclusions based on my experience and the very little data that I have gathered. I am hoping to look into it a bit further and try and collect some hard statistics on this issue. If anyone has anything to add to this, I would be really happy to hear from you.
Akshat Rathi 
liked the fact that you are being conscientious…. good job pal!
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Excellent subject for a post. Very thought-provoking.
Yes, I agree, not mixing chlorinated solvents with non-chlorinated is a good start: if there is any chlorinated solvent in your mixture you have to dispose of it in the chlorinated waste. I regularly use ethyl acetate for test tube rinsing. DCM is not only chlorinated but also carcinogenic too, so (though it and chloroform are wonderful solvents) they should eb avoided when possible.
Minimizing chemical orders, reducing scale to what you need, is another idea: order only what you need, don’t get that bigger bottle just because it is cheaper per gram – it is still more and the cost to dispose of it when you don’t use it more than compensate for that “saving”.
Now I shall have to think about what else we can do (as chemists) to reduce our environmental damage.
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