What can I compost?

Can I compost bread?  Can I compost corncobs?  Can I compost leather gloves?  In a perfect world and under ideal conditions, the answer to all of the above is yes.  Unfortunately, this world is far from perfect, so that yes can be followed by a long string of asterisks.

One of the most common questions asked by those new to composting is “what can I compost?”

In truth, anything derived from plant or animal matter will biodegrade … eventually.  But time, temperature, and a slew of other variables will impact the practicality of choosing composting as a recycling method for any given material.

Generally, the home composter will do just fine using a tight, easy-to-turn vessel that contains excess liquid and deters marauders.  

Any mesh, drainage holes, or air vents in the composting unit should be 1/4 inch or less if deterring mice and the snakes that follow them is a priority.

With this type of composter, almost any kind of food waste (except meats and dairy) can be used as a feedstock.  Tear or chop big/dense leftovers like chunks of bread and corncobs into smaller pieces to expose more surface area to feasting microbes.  This helps all of the food waste degrade at a similar rate.

As for those gloves, while leather is compostable, so many manufactured products these days are processed, treated, or coated with chemicals that the leather might not be compost-friendly for the home compost pile.

Unless the manufacturer says an item is compostable in a home system and proves it with certification from a legitimate third-party, don’t put it in your compost pile.

Read the certification information carefully.  A lot of so-called “compostables” available in the marketplace cannot be composted where processes are simply not sufficiently robust to break down the material – and that would include nearly all residential composting efforts, as well as some city-owned and commercial operations.

Only a few US facilities use designs and/or technologies that can handle the full range of urban organic wastes.  (McGill is one of them.)

Good prep = rapid biodegradation

Chopping and shredding is something every large composting facility does to create a uniform particle size prior to composting.

These plants also mix thoroughly, ensure adequate airflow throughout the composting mass, and make certain the blend is neither too wet nor too dry.  

They also screen the compost post-processing to break up clumps and sift out any bigger, partially composted materials.  These are re-blended and added to a new composting pile to complete their decomposition.

The closer the home compost-maker can come to emulating these management practices (which are all about process control), the faster the rate of decomposition and higher the rate of composting success … even when breaking down tough ingredients.

That’s why modern, high-rate composting operations can handle things like biodegradable plastics and petroleum hydrocarbons when the home compost pile struggles with corncobs.

Don’t try this at home

While most things can be successfully composted at home, meat and dairy, along with the cooking juices and fats-oils-grease (FOG) in which they were prepared, cannot.

These types of foods will harbor pathogens, and the typical home composting effort will not reach the kill point temperatures required to neutralize them.

Pet waste falls into the same category.

However, small amounts of plant-based oils – provided they were not used to cook meats or dairy – can be composted at home.

We are talking about the salad dressing swimming with the leftover lettuce at the bottom of the serving bowl or the spritz of olive oil coating those uneaten air-fried veggies – not the 3 gallons of waste oil from the turkey fryer.

Unfortunately, there’s not much you can do with banned FOG except pour it into a non-recyclable container and toss it into the trash.  It won’t compost in the anaerobic environment of a landfill, but it won’t clog your pipes, septic system, or sewer lines, either.

In other words, never ever pour fats, oils, or grease down the kitchen sink.  And – no – a hot water chaser will not make the gunk magically disappear from your piping system.

The good news is FOG will compost at a facility using a good, commercial process.

In fact, commercial kitchens routinely send grease trap waste to composting facilities.  If your community doesn’t have a composting operation that can handle this type of food waste, perhaps it’s time to give the folks at City Hall a nudge.  

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This post also includes information on reducing the amount of FOG going to the landfill or sewer system from your kitchen.