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Dutchess_III's avatar

Recycling question: Why can't they come up with a process to remove the grease from the slurry when recycling papers and cardboards that have food on them?

Asked by Dutchess_III (27171 points ) 1 month ago

At this point “Grease from pizza boxes causes oil to form at the top of the slurry, and paper fibers cannot separate from oils during the pulping process.”
From This website.
What kind of process would strip away the grease?

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24 Answers

LuckyGuy's avatar

I didn’t know that. Really? Who is going to bother to cut out the greasy portion of the pizza box.
I recycle pizza boxes and paper plates by burning them in my wood burning stove and converting them into heat. 15 pounds of cardboard has the same energy content as one gallon of heating oil. By burning it directly in my high efficiency (73%) wood burner I am effectively converting it into heating oil.
In the summer, old pizza boxes make the best firestarters for camp fires.

By the way, in my area, a used pizza box in the recycling container is sure attractant for raccoons and other critters. You will wake up to a mess all over your front lawn.

Dutchess_III's avatar

Well, I changed the question up. Now I’m asking why they can’t come up with some solution to the grease in the recycling process.

Yeah, those grease boxes will sure give you a good fire…and create creosote like a banshee!

LuckyGuy's avatar

I don’t want to derail this thread but the high efficiency stoves with reburners or catalytic converters run at much higher temps than the old stoves. There is no creosote. And no smoke once they hit the light off temperature.

jca's avatar

@Dutchess_III: Maybe a solution to remove grease that’s soaked into paper is not worth the effort and cost or maybe it would involve highly caustic solutions which would damage the environment?

Adirondackwannabe's avatar

Doesn’t the creosote come from the resins in the wood?

LuckyGuy's avatar

Yes. Food grease would burn easily. Creosote comes from unburned wood resin. That resin is burned in the reburner stage. I have had this stove for 5 years now and the flue is still clean! The new stoves are amazing pieces of work. There is less ash, virtually no smoke and the pipes stay clean.
I toss anything burnable into my stove: dirty paper plates, used cooking oil, paper towels and tissues, dirty rags pizza boxes and chicken wing bones… It all gets converted into heat leaving the equivalent amount of heating oil unused in my fuel oil storage tanks. 15 pounds of burnables saves me about $3.00 in fuel cost.

Adirondackwannabe's avatar

That would sound like so much better of a way to recycle the paper and pizza boxes. Instead of new paper convert them to energy. I wonder if it would be economical to process them into a longer burning version, I’m not sure how. Pizza box fire logs?

LuckyGuy's avatar

the new stoves are air tight. You can make them burn longer (and reduce the heat output ) by limiting the air going into the firebox. If the air intake is wide open, the stove will put out 73000 BTU per hour and consume about 10–12 pounds of wood (or paper trash) per hour. You can easily back that off to about 1/6 of that.
Take note of the numbers. In the coldest days of winter with my stove running at nearly full blast I will burn 200 pounds of wood per day. That would be 10 gallons of oil at a cost of $35! Instead, I am recycling dead trees, old rags and greasy paper into heat.

Tropical_Willie's avatar

@Dutchess_III you would have to process ALL the recycle cardboard with the the grease remover, 1 % of the cardboard would require 100 % of the degrease process.

majorrich's avatar

My father used to roll old newspapers and magazines into paper logs and put them in the stove. It was an older generation stove and would often get clogged with ashes and junk from his logs. Pizza boxes would make dandy paper logs with the food oils infused into them.

Adirondackwannabe's avatar

Should we try to flesh this idea out? There may be a decent idea in here to recycle pizza boxes for an energy source. We have enough mental horsepower to figure this out.

Dutchess_III's avatar

Can the heat from a stove such as the one @LuckyGuy has be used to create energy? Like, on a massive scale? ....

Dutchess_III's avatar

Remember! in successful brainstorming nobody tells anyone “WHAT A DUM IDEA!! U R SO STOOPID!”

Adirondackwannabe's avatar

U R so, oh. No think about it. 270 million Americans, tons of pizza boxes, and it’s stupid to landfill em. Maybe we can make a difference. Great question @Dutchess_III

LuckyGuy's avatar

@Dutchess_III There are industrial boilers called Cogen plants that burn RDF Refuse Derived Fuel, and turn it into heat as well as spinning a generator to make electricity . I know of one such plant that only worked for a short while. It used home refuse. The system failed because the equipment could not sufficiently separate out glass dust from paper. The glass coated the inside of the boiler and that hurt its efficiency. They would have to shut the boiler off, let it cool down for 2 days before they could send in a crew armed with shot guns loaded with #2 shot to break up the condensed glass coating. (I know someone who actually did this! He wore a full respirator and disposable ear protection underneath noise cancelling head phones and was completely covered in a Tyvek bunny suit as the material was considered a health hazard.)

There are thermoelectric generators that convert heat directly into electricity but they are expensive and only operate in the 5–8% efficiency range. They are useful for making electricity from waste heat like car or truck exhaust .

Let’s look at some numbers using rough rules of thumb. The average home uses an equivalent of 750 gallons of oil for heating and cooling. People down south use no oil but use more electricity for A/C instead. Let’s call it 720 gallons per year for easy math. So that means 2 gallons per day. To generate the equivalent heat or electricity a household at 15 pounds per gallon we need about 30 pounds of pizza boxes per day. How much does a box weigh? Call it a pound. So we need 30 boxes per household per day.

I had been toying with running some hot water coils through my flue to get a little free heat and reduce hot water costs but it was not worth the trouble – or the risk of a water leak or a fire.

My stove can absolutely be modified to make electricity. I have thought of experimenting with something like a small steam engine 1 hp is ~2500BTU/hour. My stove is capable of outputting 73000 BTU/hr or 30 hp! About ¼ of that heat goes up the flue as waste heat. Typically I run at much lower say 25000 BTU/hr or 10 hp. So I am wasting 2.5 hp. Think of a 3 hp generator. They typically put out 2 kW.
If I could buy a relatively small, low maintenance device that converted my waste heat to electricity I’d do it!

LuckyGuy's avatar

Ooo! And if I did not need the heat in my home I could send it all to the device to generate more power, increasing the output to 10 hp! .

kritiper's avatar

They probably could. But it’s the rats, mice, flies, cockroaches, silverfish, ants, stink and whatever else have you that is the reason they don’t want to deal with it.

LuckyGuy's avatar

Here is a link to someone trying to do this. NT6
It does not seem very practical. He mentioned thar the noise is deafening.

LuckyGuy's avatar

Here is a link to a place that makes steam engines and the power plant. they have units in the range we are discussing but they are huge! 2 -3 cubic meters with the unit broken down! Price in the $5000 to $10000 range.
Claverton Energy Research Group

Electricity from the power company is sounding pretty good!

Adirondackwannabe's avatar

@LuckyGuy Are you thinking a mixed wood and trash burner?

LuckyGuy's avatar

Yep. From my other calculation above it is clear we don’t produce enough burnable trash to make it worthwhile.
I do have a virtually unlimited supply of wood so it would be handy if I could generate my own electricity. Sadly, the systems would be big and maintenance nightmares.
Maybe if there was no other way and the power plants shut down.

From the site I linked to above:

“3) STEAM POWER PLANT 8 HP
Steam power plant consisting of (1) Single cylinder double acting steam engine 8 hp, cylinder dia 4″xstroke 4″, complete with reverse mechanism, hand lubricating pump for cylinder lubrication, drip lubricator for crosshead lubrication and 16″ pulley (2) Water tube Yarrow type boiler suitable for biomass firing with 80 sq ft heating surface including economizer and superheater, test pressure 300psi,working pressure 160 psi complete with water feed pump,water level gauge set, pressure gauge, safety valve, fire grates and 20ft chimney 1 set+ interconnecting pipe lines, valves, pipe fittings etc.Boiler is insulated with cerawool. Shipment volume 2 cu. mt.
COST US$ 4500/- with CD

(4) STEAM POWER PLANT 10 HP
Steam power plant consisting of (1) Double cylinder double acting steam engine 10 hp, each cylinder dia 3″xstroke 4″, complete with reverse mechanism, hand lubricating pump for cylinder lubrication, drip lubricator for crosshead lubrication and 12″ pulley (2) Water tube Yarrow type boiler suitable for biomass firing with 90 sq ft heating surface including economizer and superheater, test pressure 300psi,working pressure 160 psi complete with water feed pump,water level gauge set, pressure gauge, safety valve, fire grates and 20ft chimney 1 set+ interconnecting pipe lines, valves, pipe fittings etc. Boiler is insulated with cerawool. Shipment volume 3.5 cu. mt.
COST US$ 5600/- with CD”

Adirondackwannabe's avatar

Yeah, I worked on the pizza box idea for a while, but I couldn’t overcome the collection and handling economics. There’s enough supply, except it’s dispersed all over the US.

JLeslie's avatar

@Adirondackwannabe Maybe if there was a 25¢ return on the box. Another idea is I could see places like universities possibly being able to utilize the boxes for energy. At a large university there is a huge concentration of pizza boxes.

longgone's avatar

In Germany, the government issues lists of what to recycle. Greasy paper would never make it to the recycling basket, in my house. Instead, it gets burned with the regular waste.

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