Gardening is great for the soul and the planet.

But if you’re like me and you have two very not green thumbs, you can still help make the world healthier with your trash. Of course, I’m talking about compost.

It’s packed with nutrients  that plants need to grow. And on top of all that, the compost pile itself is full of life. But there’s more to it than just throwing your dinner scraps into a pile.

The microbes that are making you the best fertilizer in town have needs, and that’s where this video comes in. Here’s how to make the best possible compost, based on the ingredients microbes  need to sustain their lives. [music] For those of you new to  the whole composting thing, we’re going to break this down – no pun intended – into three parts. The setup, the active phase, and the curing phase.

So let’s start at the start, with setting up your compost pile. All compost starts with whatever you put in there. Ideally, you’d have a mixture of greens, like food scraps, and browns, like outdoor scraps, in the pile.

But don’t get too caught up on those color labels. Coffee grounds are literally brown, but in your compost heap, they’re considered greens. The real difference between  composting greens and browns is how much carbon versus nitrogen they have inside of them.

Food scraps, like coffee grounds and veggie  scraps, tend to have more nitrogen in them, while outdoor waste, like dried leaves and wood chips, tend to have more carbon. They both have both of those elements. It’s just a matter of how much.

Which is why your nitrogen-rich coffee grounds count as a green. Soil and waste experts at  the University of Idaho say that a carbon to nitrogen ratio of about 30 to 1 will put you on the path to success. So if you made a big stir  fry for dinner and have a ton of unused veggie stems that you want to toss, you can complement them  with a nice bundle of leaves from outside. … In your compost, that is.

Please.. Dont… eat them, compliment them in your compost. And if you don’t know whether something you want to compost is a green or a brown, you can look up online how  much carbon and nitrogen is in pretty much anything you’d put in compost.

Now, I know that adding a whole  extra step of going outside and collecting even more stuff for your compost, when all you wanted to do was  get rid of your dinner waste, seems laborious. But trust me, it’s worth it. If there’s too much nitrogen in your mixture, it’ll break down into ammonia gas.

And that is not a smell your neighbors will appreciate coming from your compost pile You also probably shouldn’t overload your compost with the ten lemon husks left over from making a pitcher of lemonade all at once, since too much acid can lower the pH of the whole pile, which also leads to that ammonia smell. On the other hand, if there’s not enough nitrogen, your compost heap won’t be able to get hot enough to really make the magic happen fast. More on the heat in a minute.

And while you’re thinking about how long this whole composting thing is going to take, consider what your inputs are made out of. A lot of the same things that  take us a long time to digest will take a while to break  down in the compost, too. Carbs are easier to break down than cellulose, which is easier to break down than lignin, another plant fiber.

So fruits and veggies, which have lots of sugars and starch in them, aka simple carbs, break down fast, while wood and leaves are more packed with lignin so they maintain your pile’s structure for longer. Meanwhile, stuff that’s full of water will release that moisture as it breaks down, which can give you less of a compost pile and more of a compost river. Which is not what we want.

You want your compost to have somewhere between 50-60% moisture content, so that your microbes have enough water and oxygen to do their jobs. That said, microbes are  gonna microbe no matter what, so if your pile is a bit too wet or too dry, things will still break down. They need some water for them to move around and maintain their metabolism.

But if you fill up all of the air gaps with water, then those microbes won’t be able to breathe and it’ll really start to smell  like a pile of wet garbage. There’s a very scientific squeeze test you can do to make sure you have the right moisture levels. Put on a glove, take a handful of your compost mix, and squeeze.

You’re looking for about a drop  or two of water to come out. If it feels dry, you can add some water. If you’ve got a waterfall, you can add some dry ingredients.

Or if you want to get really precise, you can use the gravimetric method. That’s where you weigh a sample of your compost, cook it in a convection oven or microwave until totally dry, weigh it again, and calculate how much of the sample was water based on the difference. Once you have the moisture levels all worked out, the last thing to think about is the size of each item you’re tossing.

If everything you put into your compost is less than an inch around, it’ll break down faster  because of the surface area. But there’s no need to break  out your mortar and pestle to pulverize your compostables into confetti. Slightly bigger pieces means there’ll be open space  for that oh-so-vital oxygen your little microbes need to turn your potato peels into garden food.

If you do a little bit of prep to break down a mixture of food and woody scraps for your microbe friends, they’ll return the favor by taking  on the break down from there. Now, everything I’ve said so far applies to the kind of compost that’s just scraps. If you’re working with worms or have a neighborhood compost pickup that does industrial processing, you might be able to handle a  different combination of inputs.

The big thing is that, well, you can put big things into the heap if you’ve got worms and machinery helping you out. But, worm compost setups  require a lot more maintenance because you need to keep their  environment healthy for them. That basically just means harvesting your compost more promptly to make sure the worms  haven’t overwhelmed themselves with their own poop.

Other than that, it’s a similar process. This episode is sponsored by Arizona State University’s  College of Global Futures. That’s where you can learn how to create a more equitable, sustainable,  and promise-filled future for everyone, and do it all online.

ASU’s programs help people make a positive impact on the world with their careers. For example, through ASU’s online programs, you could earn a Master of Science or Graduate Certificate in Biomimicry. Biomimicry is a field where you can leverage or  mimic biological principles to find new and innovative solutions to contemporary problems.

You’ll study biology,  chemistry, and sustainability to examine how life has survived, evolved and thrived on Earth. And you can apply that knowledge to fields like sustainability, engineering, and business. Or think a little more out  of the box and apply it to transportation, product design, architecture, and education.

Maybe you’ll even get a job in a related field like urban planning. You can start it all in ASU’s online program. And thanks to ASU for supporting this SciShow video.

So that’s the basics of  setting up a good compost heap, but now let’s talk about what it looks like when the magic happens. Your microscopic recycling team will eat the scraps in your compost pile to get the nutrients they need to live. While they’re turning your  trash into their energy, the pile will start to shrink down because of all the carbon they’re taking out.

So they’re using up the carbon for their cells and for energy. And they’re using the nitrogen in your pile to make their enzymes, proteins, amino acids, nucleic acids, and generally all the rest of the stuff they need to be alive. Once the microbes start using up the good carbon and nitrogen in your pile, things really start rolling in what’s called the active phase of compost.

As they breathe, they turn  carbon into carbon dioxide, and that gas exchange starts shrinking the pile. But that shrinkage makes air  pockets harder to come by. Which is where you, the owner of this compost heap, come in!

Depending on your setup, aerating your compost pile could be the most intensive  part of the whole thing. For the kinds of setups that are a big container or even just a pile on the ground, you have to shovel it occasionally. You’re turning over the compost to add air back into an oxygen depleted system.

But that’s also why some compost setups are more like a drum or a wheel that you can spin, so you can take some of the manual labor out of the aeration process. You don’t have to do this all the time though. Generally, the compost will tell you when it needs more air.

If you start to smell rotten eggs, that’s a sign you might need to add some oxygen to your pile. Because that is the lovely  scent of an anaerobic system, and that is not going to break down your waste into a usable final product. Or if you want to be more proactive and check on your pile’s oxygen levels before it gets to that unfortunate point, there’s another test to measure that, too.

You can weigh a sample of the compost, then completely saturate it with water so that all the air bubbles are filled. But make note of how much water it took to get to that point. Whatever volume of water you added can be presumed equal to  the original volume of air minus the original sample volume.

Whether it’s by smell or measurements, you can get a sense for the amount of oxygen in your pile and tinker with it to keep your microbes healthy. And while you’re managing the oxygen levels, you might also be addressing creeping temperatures in your pile. As your little trashy organisms become active, things will start to get hot in your compost heap.

Like, 65 degrees Celsius hot! And you know who loves those warm environments? More productive microorganisms that get lured over to help out with your compost.

With them on board, decomposition happens really quickly. That fast, hot decomposition is the main feature of the active stage of composting. Plus, there’s an added bonus to those high temperatures.

Seeds can’t stay viable when it’s that hot, so you can compost seeds without worrying about accidentally growing a tree in your pile. And soaring temperatures keep dangerous pathogens at bay too. But even microbes find some temperatures to be too hot.

When it gets above 71 degrees Celsius, nobody’s happy. And that’s when you might aerate the pile or add water to lower the temperature. Once most of the nutrients are all used up and things start to cool off in the compost, those original microbes come back for the curing phase.

Curing your compost just means that the cooler dwelling microbes are putting the finishing touches on the pile. This part of the process can be shorter or longer depending on how you approached the input stage. If you had wonky nutrient ratios earlier on, this step could literally take all year.

But it really is important  to give it the time it needs, because a product with the wrong balance of acids, salts, carbon, oxygen, and water can end up killing anything you try to grow in it. You’ll know you’ve got a nice finished product when there’s a moderate amount of water, somewhere in the 35-60% range. And in terms of salt, we’re not talking about the  fancy pink himalayan salt you use to cook with.

We’re talking about electrolytes. Fruits and veggies have electrolytes like potassium in them. So when you’re adding them to your pile, you’re giving your microbes a little salty treat.

Since you don’t want your  final product to be too salty, you can measure salt content by testing its electrical conductivity! And this measure isn’t just about salt because it will be affected  by how moist the mixture is. But you’ll get a general idea of  the amount of electrolytes in there.

And if it’s too salty, don’t worry, because the microbes will eat  that extra salt over time! Just let your microbial  buddies keep on composting. And this is where you can be nice to yourself.

Maybe you’re watching this video  after you started composting and you’re realizing that  the conditions you set up at the beginning of your journey are suboptimal. That is okay. It’s not a lost cause.

It’ll just take longer. When you’ve completed a full round of compost, that’s when the coolest part happens. You get to use yesterday’s discarded food scraps to grow tomorrow’s meals!

Then you can refill the compost pile and start all over again. But this time, you’re already set up for success. There will still be microbes there ready to tackle the new compostable material when you add it.

When you take care of the microscopic critters in your compost pile, they’ll take care of your trash. It’s all a matter of making sure they have the nutrients, water, air, and temperature they need to thrive in their favorite environment: your waste. [ OUTRO MUSIC ]