Disposal of used agar plates

[elaruu]

Would I be able to wrap sealed (with parafilm) used agar plates up in a bin bag and place in with general waste? Or should I be doing something else with them? Previously I have opened them up and treated with bleach, but I have ~200 to get rid of and that is not an appealing job.

(We don't have an autoclave.)

Thanks.

[Marama T]

You shouldn't be opening them up, as this spreads mould spores and other microbes into the air. Definitely better to wrap and throw away. We bought a cheap pressure cooker to sterilize our plates before disposal.

[elaruu]

OK. Thanks. I was opening them up and soaking them in bleach inside a fume hood, so hopefully nothing spread. Much more preferable to wrap and throw away if that's acceptable.

[macca]

I would get your school to invest in a pressure cooker. We put them in an oven bag then pressure cooker on high for 15 mins. They really should be destroyed under heat and pressure. Then they can safely go in the bin.

[Labbie]

We use to use ovenbags, then into the Microwave did it's job

[macca]

We use to use ovenbags, then into the Microwave did it's job

lol I heat my lunch in ours

[RosalieL]

Yep, cheap pressure cooker and oven bags. I have purchased some autoclave tape as well (so I can be sure it has reached the right temp for long enough) but haven't used it yet.

[bigmack]

When I first started , I was told by my off sider to store them in the fume hood until the GA lit a fire to burn off excess green waste then bring them over and chuck’m on the bonefire .
I knew no better but after about 6-9months I was asking when was the bonefire ment to happen . Discovered that the school had been banned from lighting anymore fires due to upsetting neighbours .

Thats when I realised we had a perfectly capable pressure cooker in the cupboard .

Regarding bleach . One school I was doing casual work at , the Labbie there would tape all the petrie dishes in a stack And submerge them in a bucket if bleach leaving them over night with a brick on the top to keep them submerged .

[elaruu]

Thanks for the info bigmack. So you think the bleach would get in if submerged overnight even if not opened? I'll probably give that a go. And will also investigate the pressure cooker idea. They scare me a bit. I have never used one.

[Marama T]

Pressure cookers are really simple to use. I read the instructions carefully when we got ours coz I'd never used one either, and it turns out to be idiot-proof. Close the lid and press go! It won't work if I haven't shut it properly and it won't open until it's cool enough to be safe. Did you know bleach reacts with oxygen in the air to form formaldehyde? I flat -out refuse to use it for any purpose because breathing in formaldehyde is dangerous - check it out on RiskAssess. Suspected of causing cancer, suspected of causing birth defects, blah blah blah. Also, it makes me feel too ill to function. It surprises me that anyone can buy bleach, to be honest.

[elaruu]

Thanks Marama T. I didn't know that! I do hate to do it though. I do it in the fume hood but the smell still escapes. I have only actually done it twice here since I started a year and a half ago. It would be good to find an alternative. I will defo investigate getting a pressure cooker.

[bigmack]

Always remember that pressure cookers are sold in shops where idiots can buy them . They have to be made idiot proof and safe or we would be hearing reports on the news of people being killed or badly burned by them .

Depending on the size if them , you’ll be lucky to fit more than about 25 plates in a typical size one . I could get about that in mine . So it will take a while to get through 200 of them . Trick is not to let them build up . I tried to do mine the day they were finished with them .

As far as the bleach goes .I asked her the same and she showed me . Despite the kids wrapping tape around them , the Bleach did get in .
Personally , I never did it as I had a Pressure cooker.

[RosalieL]

Side note: The plates shouldn't be completely sealed by sticky tape. There should be a gap. If you're using parafilm, it goes all the way around. It's to do with tape creating an anaerobic environment and growing the wrong type of nasties.

[elaruu]

Side note: The plates shouldn't be completely sealed by sticky tape. There should be a gap. If you're using parafilm, it goes all the way around. It's to do with tape creating an anaerobic environment and growing the wrong type of nasties.

So are you saying being sealed with parafilm is ok because it lets oxygen in? But tape doesn't? Just clarifying as I wasn't sure if that's what you meant. The current ones are sealed with parafilm. Previously they always used tape but I introduced them to parafilm .

[elaruu]

Always remember that pressure cookers are sold in shops where idiots can buy them . They have to be made idiot proof and safe or we would be hearing reports on the news of people being killed or badly burned by them .

Depending on the size if them , you’ll be lucky to fit more than about 25 plates in a typical size one . I could get about that in mine . So it will take a while to get through 200 of them . Trick is not to let them build up . I tried to do mine the day they were finished with them .

As far as the bleach goes .I asked her the same and she showed me . Despite the kids wrapping tape around them , the Bleach did get in .
Personally , I never did it as I had a Pressure cooker.

The 200 is for a single (depth study) experiment (2 classes)

[RosalieL]

Side note: The plates shouldn't be completely sealed by sticky tape. There should be a gap. If you're using parafilm, it goes all the way around. It's to do with tape creating an anaerobic environment and growing the wrong type of nasties.

So are you saying being sealed with parafilm is ok because it lets oxygen in? But tape doesn't? Just clarifying as I wasn't sure if that's what you meant. The current ones are sealed with parafilm. Previously they always used tape but I introduced them to parafilm .

Yes, that's right. The parafilm allows for oxygen to pass through but tape completely seals it. I love parafilm It also feels more "sciencey"!

[elaruu]

Can I use a microwave (with the plates in an oven bag)? I read in another post that this is possible.

[Marama T]

I've never done it but have heard it works beautifully. Good luck!

[RosalieL]

Can I use a microwave (with the plates in an oven bag)? I read in another post that this is possible.

My only concern would be making sure it is hot enough for long enough without destroying the microwave. I don't know if autoclave tape works in the microwave but that would at least tell you if it has reached the right temperature for long enough. I have heard microwaving the plates works but haven't ever done it. Hopefully the ones who use this method are able to comment further!

[Labbie]

Can I use a microwave (with the plates in an oven bag)? I read in another post that this is possible.

Yes it works. Heat until they have melted down, to a right old mess. Use two oven bags incase one splits.