Idea: spoiled milk and fryer oil soap

[Anstarx]

No I'm not crazy.

Okay maybe a little.

I can’t really say I’m ever a very environmentally conscious person. I will try not waste anything but I also use disposable items for daily life and for crafting. However, I came across a thread about using rancid oil for soap which really intrigued me. The thread is https://www.soapmakingforum.com/threads/quick-question-stale-oil.35257/


I was reading an article yesterday on how the cooking oils we disposed through our sinks could accumulate into fatbergs in the sewer system which could potentially pollute out water. You could search “fatberg” in wikipedia and see what it's about.

As someone who lives in a crowded city that has an abundant water resource but less than enough clean water resource, this got me thinking.

Now, I don’t use a lot of oil in my cooking,usually a 250ml bottle can last me at least a whole year so this didn’t concern me too much at first. However, as the Chinese new year was around the corner (this Friday! Wooo!), I like to make spring rolls as a holiday tradition which are cooked through frying. That will be quite some oil.

I use either rapeseed/canola oil for frying which I know I won’be able to use for cooking again (I usually cook with grapeseed) so all of will be going down the drain. After reading the thread, I thought maybe I can make it into soap, not for washing, but just so it can go into a landfill rather than the sewers. After all, soaps are biodegradable.

Since I’m settled on that, I decided to add something else as well-a carton of expired milk from my fridge. I bought it to make alfredo sauce but then I got sick and forgot about it so it’s been sitting there for two months now. I felt a bit bad to just pour it down the drain-not because of food wasting but it will take a whole lot more water to clean these milk.

I knew that you can’t drink spoiled milk because of the bacteria, but what if I add lye? I don’t think many bacteria can survive lye. So if I use frozen spoiled milk as my liquid, add the fryer oil and lye, I can make two trash that may potentially cause water pollution into a biodegradable solid mass that can decompose safely in the landfill. I can even used the milk carton as a mold so I don’t need to wash my silicone mold!

What are you guys’ thoughts on this? I will freeze the milk tonight and try the idea after spring-roll-frying is done anyways and update later.

 

[KiwiMoose]

Ewwwwww! That's going to be stinky to make.

 

[BattleGnome]

I like the thought but is lye that readily available for you? Balancing out costs it wouldn’t be worth it to me (but I also have to pay shipping to get any form of soap making lye). If the costs work out this is a great (but smelly) idea.

I usually pour my used oils into a glass jar and toss it in the trash. I don’t have recycling in my area so jars tend to either collect or used to help dispose other things. I have also used pre-used napkins/tissues to sop up the oil. It’s all stuff that would be trash but I combine it to have a smaller footprint.

 

[Anstarx]

I like the thought but is lye that readily available for you? Balancing out costs it wouldn’t be worth it to me (but I also have to pay shipping to get any form of soap making lye). If the costs work out this is a great (but smelly) idea.

I usually pour my used oils into a glass jar and toss it in the trash. I don’t have recycling in my area so jars tend to either collect or used to help dispose other things. I have also used pre-used napkins/tissues to sop up the oil. It’s all stuff that would be trash but I combine it to have a smaller footprint.

I order my lye online. If you living in China like me you would know shipping cost is really not a big problem...The rise of internet shopping really helped developing the delivery system.

Most soap suppliers I purchase from gives free shipping for orders over 68 rmb, which is less than 10 usd. If you buy in larger quantities you can easily fulfill that as 1L of coconut cost about 18-20 rmb and 1L olive PU would cost 30-ish. I buy my lye in 1kg buckets that are 14.5rmb/kg, so around 2.1 usd/kg+free shipping. Even when some shops don't do free shipping that's usually just 1 usd/order.

I'm not going to do this often. As I said, I really don't have much waste oil to start with so this is likely just a one-time thing. I usually just water my plants with any left over milk.

 

[szaza]

Ha that's some creative thinking right there!
Aren't there any recycle points for fryer oil near where you live? We have them at the container park and I think also in some supermarkets (but that might just be because I live in a culture where eating french fries 1-3x/week is normal and lots of people make them at home)
If you just want to get rid of the oil without having to pour it down the drain, you could probably also just put it in the trash in a bottle you wanted to discarded anyway
(Although that's the less fun option) I'm not sure if making oil into soap will help it biodegrade quicker than just the oil ending up in the landfill, but maybe there's someone here who knows more about the way things biodegrade? (particularly oils and soaps)
Anyway, it would be interesting to see how fryer oil behaves in soap! So keep us posted if you decide to do it


Also, a bit of advise you didn't ask for, but since you said you don't fry very often, I thought you might be interested. If you want to use rapeseed or canola for frying, make sure they're high oleic (high in mono-unsaturated fats and low in poly-unsaturated fats if you read the label). I think it has something to do with the poly-unsaturated fats breaking down more easily with high heat. If you buy a designated frying oil (eg canola frying oil) you can be sure it's high oleic and safe for frying.

 

[paragon]

The most important think is to not pour the oil down the drain. Beyond that, follow your interests. If I were you, I'd see if I could make the fry oil into good soap. See if you can prevent DOS by using [(BHT or ROE) and EDTA and sodium citrate]. See if you can cover the smell with something complementary, if there is one.

 

[shunt2011]

The most important think is to not pour the oil down the drain. Beyond that, follow your interests. If I were you, I'd see if I could make the fry oil into good soap. See if you can prevent DOS by using BHT or ROE and EDTA and sodium citrate. See if you can cover the smell with something complementary, if there is one.

Roe nor the others are going to help with already rancid oils. The risk is already there. Maybe DeeAnna will pop in with other sage advice. And I don't know anyone who dump their oils in the drain. I would hope common sense plays a big part in that for all soapmakers or not.

 

[dixiedragon]

I'd clean the oil and use it, and assuming the soap doesn't smell funny, I'd use the soap. Unless you have some kind of medical issue (like allergies) does it really matter if somebody, say, fried fish in the oil and now you're washing your body with the soap?

You can also clean the oil and keep it in the fridge or freezer and use it to cook again.

I can't imagine the spoiled milk won't make the soap smell awful. If you have a septic tank, it's actually good to dump spoiled dairy down the drain, b/c it's basically like yogurt and it's good for the bacteria that live in the tank.

 

[Adobehead]

I admire your thinking and the research you have done. That you are giving thought to the long term effects of what you are doing today makes you one of the "good guys" in a time of our planet's environmental demise. And if you strain the oil say, through a pantyhose, to remove particles, the soap might turn out just fine. Maybe you can grate it and use for laundry. I cannot address the DOS issue, as in over 20 years of soapmaking, I have never encountered that. And will the oil be rancid? Or, just used once at high heat?

Let us know how the experiment turns out. And keep thinking long term. This is a good example of reuse and recycle. Kudos.

 

[DeeAnna]

Making soap from the used fat is a reasonable thing to do. If the fat has an obvious "fried food" odor and darker color, you might want to clean it up first, however. The odors can linger in the soap.

http://handmadesoapcoach.com/dont-throw-out-that-rancid-oil-make-soap/
https://www.soapmakingforum.com/threads/kitchen-grease.35031/
https://www.soapmakingforum.com/threads/my-procedure-for-salting-out.32717/#post-381830

I wouldn't use the spoiled milk, however. Maybe it will be microbially safe once the lye gets through with it, but spoiled milk (microbial decomposition) is not the same as soured milk (fermentation from lactic acid bacteria). I question whether the chemicals that are created by milk decomposition are something I'd want to use on my body. And there's also the issue of lingering "off" odors.

And as far as pouring any non-water-based liquids down the drain ... DON'T. Just don't.

Fats of any kind as well as any kind of non-water-based solvents have no place in a sewer system. The sewer or septic system is designed for water-based liquids only. If you must discard fat, put it into a container with a liquid tight cap and discard it in your regular household trash.

Small amounts of solvents should be allowed to evaporate in the open air in a place that is safe from people and animals. Larger amounts of solvents should be discarded safely. In the US, many places have hazardous waste disposal programs. Not sure about other countries.

 

[CatahoulaBubble]

I've used sour milk for soap. It doesn't make the soap smell differently and it behaves the same but you want to make sure it doesn't have any mold in it and you don't want it clumpy because the lye won't dissolve properly.

As for using cooking oil, you can do it if you don't care that your soap smells like fried foods. Sometimes you can get a fragrance that covers it up but mostly it's going to smell. Now if you wanted to clean the oil it would make a better soap but here's the issue with that. To clean the oil you basically need to render it in water and skim the oil off the top as the impurities drop to the bottom of the pot and it's not an easy task unless you're using solid oils. You have to boil it several times in order to get the smell out of it. My grandmother used her leftover fats to make soap but it was lard and tallow mostly and she would render it by boiling and then cooling and skimming the fat off the top. She'd boil her cooking fats about 5 times in water and skim it off after each boil after it cooled. If her soap still smelled of bacon or cooking fat she'd grate up a bar of store bought soap as it cooked and the strong fragrance of the store bought soap would cover the smell of the cooking scents.

 

[Anstarx]

Thank you all for your responses! Haven't start wrapping my spring rolls yet bu now I'm determined to test out the fryer oil, maybe throw in some chicken to fry for good measure.

To answer some questions and concerns:

>As far as I know there is no recycle service for oils in my area. I know there is recycle service for large amount of cooking oil like fast food chains but not for family-sized oils.

>I really don't make fried food at all so it's very likely next time I' be frying anything is the same time next year. I will need a container and a big space for my oil to be sitting there for a year so nah.

>I've tried to let the oil cool to room temp and dump them in a trash bag. However, I dunno if there's something in my trash bags, it always leaks everywhere when having a large amount of oil. When I throw the bags into the trash collecting bin it could leak and the staff will have to clean that...I'd rather solve the problem myself

>I also went researching if oil could decompose better than soap Don't have a straight answer though one answered said that oil takes 3 years while my research before says soap takes 6 months. Either can be inaccurate or wrong so I'm still not sure.

>The oil I use won't be rancid. I'd buy the smallest amount available from supermarket when I need it so it'd be relatively fresh. It will just be frying food for several days.

>As for the milk, I might omit. After DeeAnma's answer I figured it's probably a bad idea to use spoiled milk in soap, so I'd probably just chuck the whole carton in the bin.

>Last of all, I don't have to use the soap. I will let it cure properly to see how it lathers or smells but but if it's too smelly or doesn't washes well, trash bin it goes. Wasteful, I know, but they are waste to start with. Ultimately, my goal is just to turn my potential-pollutant liquid waste into solid waste that I knew could safely decompose and won't cause problem with the help from some extra lye.

 

[Dawni]

I'm excited. More for the sprig rolls than the soap. Lol. Kidding.

Seriously though.... I've been thinking about this since forever but haven't actually done anything mainly coz I don't have the spare time to clean the oil. So I'm really excited about your experiment

 

[cmzaha]

I've used sour milk for soap. It doesn't make the soap smell differently and it behaves the same but you want to make sure it doesn't have any mold in it and you don't want it clumpy because the lye won't dissolve properly.

As for using cooking oil, you can do it if you don't care that your soap smells like fried foods. Sometimes you can get a fragrance that covers it up but mostly it's going to smell. Now if you wanted to clean the oil it would make a better soap but here's the issue with that. To clean the oil you basically need to render it in water and skim the oil off the top as the impurities drop to the bottom of the pot and it's not an easy task unless you're using solid oils. You have to boil it several times in order to get the smell out of it. My grandmother used her leftover fats to make soap but it was lard and tallow mostly and she would render it by boiling and then cooling and skimming the fat off the top. She'd boil her cooking fats about 5 times in water and skim it off after each boil after it cooled. If her soap still smelled of bacon or cooking fat she'd grate up a bar of store bought soap as it cooked and the strong fragrance of the store bought soap would cover the smell of the cooking scents.

If you freeze the oil and water if is much easier to remove the fat from the frozen water and most of the solids will be on the bottom. Any on the bottom of the fat can easily be scraped off. Frozen lard and tallows are the easiest, OO freezer quite solid and some of the other liquid oils will just be a bit softer but still solid enough to separate from the frozen water. You might have to freeze them more than once to scrape off all the water.

 

[dixiedragon]

Rendering tallow from an old thread - I think you would use this same process for cleaning used cooking fats. It wouldn't take as long because you aren't having to actually render the fat to separate it from meat and connective tissue. So IMO, just add the water, salt and baking soda, melt thoroughly (don't burn). Let it sit at room temp until the oil and water have separated, then put in the fridge or freezer to solidify the fat on top. Lift out the solidified fat, scrape debris off the bottom of the cake and discard the water. I think you want to let it sit at room temperature b/c you want the oil and water to thoroughly separate, giving the yucky bits time to fall to the bottom of the pot.

I put it into a pot of water that's filled halfway up the fat. I pour a good half cup or so of salt into it. I mix oh about 3 tablespoons of baking soda into water and pour it on as well. It creates a reaction and releases carbon dioxide, so beware as it heats of spilling over. I did an experiment not using baking soda in the render, and by the third it still smelled extremely meaty. Whatever the reason, it helps a ton reduce the overall finished product's odor. BEWARE OF EVAPORATION, and fill with fresh water as needed.

I heat it on medium low for a good half hour, and then lower the temperature to full low. I simmer for, oh, 4 hours or more, until the fat looks like a gelatinous gooey sinus infection lol. I strain it through a sieve into a glass Pyrex baking dish, used cheesecloth in the sieve once but can't find it anywhere after I ran out, so sieve it is.

I refrigerate it for at least 4 hours or so. It needs to cool completely through. Overnight is best.

Look at the liquid now. Below the fat in the dish after its cooled, the water is a deep muddy brown and STINKS like what I would *think* a dead body smells like. I almost gag at this point when I go and dump it in the field for the coyotes to sniff out haha.
Once I didn't do this, and I'm assuming I used cleaner pieces of fat and cut most trimming off compared to other times, so you may or may not get this.

It looks like it's pretty clean fat now, but there's more cleaning that can occur, and I want it very very clean to prevent smell, dos development, and just the yuck factor of bits being left behind. That water was so nasty, and if it was that bad there's more cleaning throughout the fat that needs to happen.

Scrape any funk off the base of the fat disc and discard.

Pop out the solid fat disc and place in the pot. Fill with water to cover an inch below the fat, or so. This isn't an exact science, so close is fine.. Add about a quarter cup of salt and another few tbs of baking soda. Heat on low, and melt it. I keep it here for a couple hours or so. I strain it out into the cleaned out Pyrex. Cool for at least 4 hours. It just needs adequate time to harden completely through. If you pop it out too quickly, the bottom of the disc will still be water logged. The water beneath the fat disc this second render is a murky slightly tinted white. Very murky.
Scrape the base of yucks again.

I do it again. This time I use about between 1/8 and 1/4 cup of salt. Honestly I dump and eyeball it, but for instructions sake, start with these and make it your own. The water after cooling is a cloudy white, but getting cleaner looking.
Scrape discolored base.
I do it the fourth time. The water is almost clear after this render and cooling. This is how I know most of the impurities are gone. I DON'T use salt this final render nor baking soda. The salt may be what clouds the left over water in the above rendering, but I know it still needs the extra rendering based on the smell too. The smell is nonexistent practically by the fourth render and cooling. The water left beneath the disc doesn't smell either by the fourth time. Is four necessary, probably not. I just want a clean clean product if I'm going to do it myself and not purchase it.
Now is it necessary on bigger batches, yes and so is a fifth. If you're doing a lot at once, it may need 5 renders.
If you split your 5 lbs into 2.5 renders each, 4 is good. If you do all at once, use a big enough pot for the bubbles of salt and baking soda reacting, and plan on 5 renders, and potentially 6 depending on how little the odor remains.​