58 Comments

I wanna know about gross stuff I can divert from my trash can and put in my compost! Cat litter! Used paper products like tissues (do they contain things besides paper? will they break down ok?) Feminine hygiene products -- eek! Thank you!

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love this Q!

wanna submit a pick of your trash can contents and we can diagram it out as compost vs not compost? (how insane of a thing is that to ask lol)

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I would love to know of any examples where compost has been used in ecological restoration. I am in Australia. Lots of people don't associate compost with our native plants. Native plants have different and ususally lower nutrient needs. But I'm keen to learn how different plants respond to the carbon component in highly mature compost.

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Hiya! Because i’m not in a “fall” season and don’t have a supply of brown leaves, is it okay that most of my brown compost material is cardboard, brown paper and egg cartons?

Fwiw, i’m only using a two bin, closed roller bin system.

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HI CHARLES. Omg. What a treat. You can def use whatever you have on hand as a brown - all of those things sound very acceptable to me. You can shred stuff up beforehand to expedite breakdown, though, and make it a little easier for all the microbes to get to work.

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As some others have mentioned, I'd love to know more about what household/paper products are compostable (or, what environment is necessary for them to compost). Can I throw anything marked "compostable" into the pit in my backyard? Do I need my compost to have reached a certain stage of maturity, or have certain attributes before it can handle that stuff that is supposedly compostable but feels too plasticky to really be?

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This is such a tough question to answer, because the "biodegradable products" market is so new and so ... kind of unregulated at the moment. People can slap all kinds of labels on products and there's not a lot of consistency about what they mean or what that means the product is made from. It's getting better, though! It's just sort of weird and tricky right now.

"BPI-certified" is the gold standard for compostability at the moment, which can be nice to be aware of before tossing something into your pile.

Stuff will break down easier in a very biologically active pile. You can tell you have one of those when the pile gets hot. Hot to the touch, steam risin' from the depths etc. (Or you could get a compost thermometer and track it that way.)

The way to build a super biologically active pile is (in general) to build a big-ish pile all at once and to make sure you have your ratio of materials correct: a little nitrogen, lots of carbon, moist throughout, and properly aerated.

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I have a succulent garden (many varieties have heavy leaves full of water e.g. Cotyledon Orbiculata ‘Silver Dollar’).

I put cutting in my compost and they fully break down in a few days.

Do you think the succulent cuttings are mainly water and not much benefit for final compost or would there be a meaningful nitrogen content that helps the final compost??

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Any bio-material that you put into your compost helps your compost. :)

You, as the steward of the pile, probably want to keep the overall ratio in check - but anything that contributes nitrogen, even if it's a little vs a lot, is good to put in your pile.

Also: stuff with high water content is helping keep your pile moist without you needing to add additional water, and that is a GREAT benefit.

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Egg shells

I always compost our eggshells but they dont seem to break down or at peast seem they may take years. Lol. Is this simply a matter of drying them out and grinding them or is keeping them as whole halves for some purpose i am unaware?

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For sure, egg shells can be tough! I always crush mine into tiny, tiny pieces before adding them to my pile - but I also have a very biologically active pile, not sure if you have a pile that is passive or getting up to temps?

Def crush them, though. Grind them into tiny pieces. They'll break down! In general, the more you break stuff down into smaller pieces, the quicker decomposition you get (you are creating more surface area for microbes to get to work on)

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I'd be curious to know how many people recognise that egg shells are inorganic rather than organic (chemically speaking) and this is why they behave differently in compost. All of the other ingredients are organic - carbon materials where biodegradation implies the breaking of covalent bonds. Egg shell simply dissolves, it needs acidic conditions to do so.

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Our water treatment plant gives away biosolids compost. Is there a potential for (per- and polyfluoroalkyl substances) PFAS accumulation? See human waste “sludge” use in Maine in the 80s, later organic farms were found to be contaminated with “forever chemicals”.

In home composting, can paper products (tissue as mentioned and cardboard) be a source of PFAS chemicals? I’ve read sometimes even those marked biodegradable can contain them. And also pet hair if treated with anti-parasite medications.

PFAS chemicals seem to be everywhere/unavoidable. Some people don’t worry about it if the compost won’t be used on food crops but ultimately, all (soil and) plant life is food to someone! 🦠🪱🐦

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This is such a good question—and truly one of the toughest, mostly because we are really still learning how pervasive PFAS are (in addition to microplastics, other contaminants, etc) and the longterm impacts of that. At this point, it might be safe to assume that every single thing - including food scraps - that you put into your pile *could* contain contamination. It is just the sorry state of things. Paper products *could* all contain PFAS, yes. If you want to err on the side of caution, I would just avoid adding anything that has to be constructed/made vs occurs organically (e.g. no paper, but twigs and leaves from trees okay - no "compostable" products, but plain food waste okay). I don't have a definitive answer to this, because if I am being honest - I do not think one exists. Gah.

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Yes! (I mean, Nooooooooo!) Humanure, food scraps, paper products. Hell, if we’re getting down to it, water. I’ve had a friend ask a friend in the EPA about all this. Saying they didn’t have the answer, they offered the National PFAS Testing Strategy. But that is an answer, I guess. Until we ban, test for and filter PFAS (and nano/microplastics, et al.) out of the water supply, it’ll all just keep circulating. (Soil remediation being another component?) As you point out, what we do in the meantime isn’t so clear. I appreciate your sapience.

We get out of the earth what we put in. Dude, it’s almost like everything is connected.

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Totally - it's a really thorny problem and the contamination is just SO pervasive and we don't have a lot of vetted research/science on it yet.

Also your last comment made me lol :)

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On microplastics. Sorry if this sounds ignorant or oversimplified but I like to think that it’s only a temporary problem. If you look at the reason oil and plastic exists: tree wood being new and having nothing YET capable of eating it, being an unnatural END rather than part of a cycle; then our ‘digestion’ of oil into plastic, and the discovery (and now that we see a problem, encouragement of) bacteria and fungi that digest plastic looks a lot like an eventual fix to that original problematic end. We may eventually be dealing with the issues of our plastics rotting on us as those bacteria and fungi take off with such an abundant food source. But I guess nothing is truly a problem if your picture is big enough.

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Doesn't sound ignorant or over-simplified at all! That's a very interesting way to think about it actually. ):

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Oops, ha!

Typo, I meant to say:

: )

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What is it about a material that makes it ‘green’ (higher nitrogen) or ‘brown’ (higher carbon) in composting terms? I teach and practice community composting in the UK but am always a bit stumped by this question. I know that woodier and dryer materials have a higher CN ratio but what is it that determines that? I normally fumble something about moisture and more complex plant parts like seeds and flowers requiring more nitrogen but would love to gain some further understanding on this! Thanks Cass love all the good work and educating and sharing you do !!!

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Just to be sure I am reading this question correctly, you are asking why some biological materials have a high percentage of carbon in their molecular structure than others?

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Yes exactly!

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Haha, wow - you know, in all my time teaching compost, nobody has asked me *why* certain biological entities would have a higher percentage of carbon than others.

I am trying to think of a way you might nicely summarize this for people without needing to give them a phD in plant chemistry, but it basically just come downs to the energy needs of any biological entity (and how it makes that energy), e.g. trees store carbon in their woody mass for their energy needs. So the *wood* is high in carbon. Whereas a green plant utilizes chlorophyll, which utilizes a higher amount of nitrogen in order to convert light into energy/sugar for the plants use. So the leaves are higher in nitrogen.

Does that make sense, ha.

I have a feeling you're already explaining it right!

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Thank you very much, makes absolute sense and very well explained!

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Is there any item or material which people commonly do/don't compost which they shouldn't/should compost? In other words, what common mistakes do you see people making regarding what can and cannot go into the pile?

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The mistake I see people most commonly making is, honestly, not composting enough stuff. They think they can't compost onions, citrus peels, egg shells, bread etc. And they throw that stuff away. instead of putting it in the pile. That makes me so sad! Haha.

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I'd love to hear your perspective on composting flowers of the bodega/grocery store/florist variety (not the organic, pesticide-free, homegrown stuff). I've always gotten a hard no, but am confused because all kinds of non-organic/not necessarily pesticide-free stuff gets successfully composted in bins, buckets, and piles all the time. Thank you!

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Hahah, great question.

The honest, honest answer (and I do not mean this judgmentally ), is that sometimes you get composters who are a little puritanical about their piles. There are a variety of reasons for this. Sometimes, it is purity for purity's sake and can be a bit silly. Sometimes, it's because they are making and selling compost on a schedule, and they don't have time to allow for the full breakdown of some, tougher-to-degrade chemicals that are found in some pesticides. So they just say "no" to keep things easy.

I will also note that the type of pesticides used on conventionally-grown food vs non-edible things like flowers are often different, with the latter being a bit nastier and lingering in the environment for longer periods of time. So some composters just don't want to take the risk.

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Aha! Thank you, Cass!

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If you'll indulge me - I thought of something else! I recently received a package in a "100% recycled... made from post-consumer recycled paper and printed with vegetable-based ink." It's also marked "fully recyclable or compostable." Great! Obviously I'll need to remove the shipping label sticker, but what about the adhesive that sealed the envelope? Is that also something that just requires a lot more time to fully degrade?

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Haha, for sure! Ask as many questions as you'd like. This is actually super helpful for me, too, because it helps me understand what people want to know.

There are starch-based glues that are fully biodegradable because they're derived from natural sources (like potatoes!). Woohoo. You will find many of these used in cardboard - and possibly on this envelope, as well, if they are claiming its fully biodegradable... although it might require a little research to fully determine. Either way, for the adhesive that sealed an envelope, there's such a small amount that I can't imagine it would impact decomposition time in a meaningful way.

I hope that helps but let me know if you want/need more clarity!

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Oooh! I wasn't up to speed on potato-based adhesives... thanks, Cass! I'll see if I can get additional information about this specific mailer, as now I'm curious about the manufacturer.

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Keep me posted! I’m also curious hehe

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We use cardboard, no wax and no glossy, ripped into smallish pieces in our compost bin. We collect A LOT of kitchen scraps and use the cardboard as a source of carbon (along with some dirt/soil) to compliment all that green stuff. My question: what exactly is in cardboard?

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Cardboard is just paper and wood pulp! Haha. For the most part.

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Yes, aside from the paper & wood pulp, it's the 'glue' I'm wondering about.

We enjoy your blog and seek solace in your approach to compost! Thank you for what you do!

We have a 3 bin pallet method going and collect loads of kitchen scraps from the village. We just let the worms etc. do the work. Every 6 months we spread 12+ wheelbarrows full of compost on the gardens. https://luckyfarm77.ca/

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Oh DUH, haha - I am so sorry, of course. <3 !

The glues in cardboard, for the most part (to my knowledge), are vegetable-starch based (like from potatoes) and thus fully biodegradable. It's so hard to make total guarantees, though, of course, but that is the industry standard to my knowledge!!!

This is so cool, wow! How special. And I was JUST right by you guys in the San Juan Islands, too. (My friend grew up there.) Ahh dang. I wish I had realized when I was there!! ^__^

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Here's something I've wondered: which is "better" for the environment / has a smaller greenhouse gas footprint: backyard composting or commercial composting? A gas powered truck has to come to my home for the commercial composting (bad!) but it allows me to compost more things (good!) and I assume it's a more efficient composting process and some methane capture, so is it possible it's better for the environment when it all nets out? Curious how to wrestle with these tradeoffs and whether you're aware of any analysis here.

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Haha, this is a great question that I could probably write a whole book trying to answer. As you can imagine, there is no real answer. Both options have benefits and tradeoffs and it's really just a matter of determining what matters the most to *you*.

- Is convenience an issue? (e.g. you have a demanding job and not a ton of time to compost). Curbside collection is fine then.

- Is maximizing what you can compost your goal? At home might be better.

- Is learning/participating in the process meaningful to you more than efficiency? At home might be better.

Etc.

The "greenness" of one option vs the other is so relative, I am not sure it helps to make it the deciding factor.

You're right to point out that what kind of truck comes to collect your compost and how far that truck has to go are both elements of the relative emissions, though. But many city fleets, these days, are powered on 'green energy' - although you might want to dig into what kind and how it's sourced. (Always, alas.) Commercial composting facilities do operate at a huge scale and they do not always have great solutions for all the byproducts of anaerobic digestion (the leachate, the gas). Many will just landfill the liquidy-sludge that results from this process. Gas is captured and sometimes used. Sometimes it's burned off. It really depends on the state of the downstream market for those byproducts. (This is how all waste management facilities operate at scale, though. They operate as businesses that are making a product to sell!)

My general feeling is that composting, no matter how you do it, is a net gain. On a practical level, backyard or commercial are both good—and I do think both are necessary on a spiritual/philosophical level, as well. We need to support commercial composting to deal with the sheer scale of our waste . But we NEED backyard/community operations, too, in order to ensure that we stay *in touch* with the reality of our waste on an individual level, because how we dispose of things touches every other element of how we live. (What and how much we consume, how we build things, etc.)

So, this is is a very annoying answer - but I don't think the main consideration is "Which is greener?" (this is too variable and also somewhat arbitrary, if you count for the totality of elements in each system beyond just carbon emissions) but "How do we embrace both simultaneously."

Please don't hate me for this response <3

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Would love to understand how much of the "compost" collected by LADWP actually ends up being composted...I definitely see people in my neighborhood putting landfill trash in their compost bins :( curious how much contamination from non-compostable items affects the LADWP compost process, and what practices they implement to properly sort out the material!

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I would love to know this, too, honestly!!!

I've been wanting to go visit a commercial composting facility in the area to understand more how they are doing source separation, processing etc. One day, I am going to set up a tour and write about it.

Generally speaking, I do know that commercial composting facilities can process more types of stuff than your average community compost might - that they produce a lower-quality product, though, because they're operating quickly, at such vast scale, and using anaerobic processes with high temps (to eliminate pathogens). The byproducts (methane gas, a liquid sludge) are sometimes burned off and landfilled, respectively, which is bad and polluting :(

But I do think there are active developments to make these processes more and more efficient, and find better places for the byproducts.

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Ooh if it's possible to arrange a group tour, would be awesome to have an open invite! And thanks for the general context - makes me feel better knowing my compost efforts aren't entirely sullied by contamination :)

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Second question 😬

My compost tends to be very wet (in those roller bins). Is that okay? Mine never seems to looks as awesome and beautiful as what i see online or what i purchase at the store 😜🤓😩

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If things look wet, add more carbon and try to balance it out. Too wet = you're going to suffocate the oxygen-loving microbes that are responsible for the type of decomposition you want.

Compost tumblers are super hard to get right. I always recommend against them, particularly for beginners. My advice would be to throw it away and start over with a single bin system. Is that an option for you?

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same issue here! I'll occasionally buy coconut coir or wood chips to balance and dry it out. it's a terrible waste, but my tumbler is on a balcony rather than in a yard where I could source browns naturally.

is there a better way to prevent these tumblers from getting so moist? is there anything I can do to reduce the prevalence of compost balls (which then need to be busted up by hand)?

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Yes, tumblers are so tricky.

Do you mind if I ask what kind of neighborhood you live in? You might have options in the surrounding area to source & bring home browns vs buy 'em.

Tumblers are very tricky and moisture is a common problem for folks who use the. Adding more browns is really the only way to reduce the moisture, unless you want to pre-dehydrate some of your food scraps before adding them. (Which is also possibly just as wasteful as purchasing wood chips etc). Are you familiar with bokashi, by any chance? It's basically fermenting your food scraps in advance of composting them, which might help with your moisture issue.

Re: the balls, how often are you turning the tumbler?

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thanks for your reply! I'm in a suburban neighbourhood in the Windsor region of Ontario.

on the dehydrating, that's a great idea! 90 some-odd percent of energy around here is hydroelectric, so I will certainly be drying things like coffee grounds before tossing them in.

regarding tumbling frequency, probably 4 times per week or so.

I'm not familiar with bokashi but I've heard the term here or there - sounds like it's time for a rabbit hole. thanks!!

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Oh cool! Canada friend.

Dehydrating could def help, and so cool to know you guys are 90% hydro-electric!!! That's exciting.

I would turn your tumbler less for awhile and see if that helps with the balls. You might know this, so forgive me if I am telling you obvious things, but the "turning" is just meant to introduce airflow throughout the pile - but it also *disrupts* the formation of microbial communities that help decomposition. You want to leave things along for a week or two at a time. Then maybe one or two turns.

How you build the pile (e.g. what you put into your tumbler) can help create airflow. Bulkier stuff will create air pockets that will keep your microbes happy and alive.

Let me know how that works for ya!

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I've been told by a friend that toilet paper in a composting toilet is a no no because the bleach inhibits bacterial growth. This is a bucket system with sawdust and a urine diverter. What say you?

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I say it’s fine honestly haha - you can also buy unbleached toilet paper of course!

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Can I hire you full time to compost at my house? You are a magic ❤️

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Yes! Free of chrage

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Not exactly compost but what do you think of solar digesters?

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No strong opinion. Every device has its use and place in the industry. If a solar digester gets somebody to compost, I'm all for it.

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How much “food” can I add to compost without attracting large wildlife (there are a lot of bears in my area)? I currently put food scraps in a closed compost bin and only add yard/garden waste to my open three bin system, but I wonder if that is overly cautious.

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I wish there was an easy answer to this one! I don't think there's a quantifiable amount of food that will or will not attract a bear - your overall maintenance of your pile & strategies to suppress odors will more likely be a determining factor here. People I know who live in bear country are very fastidious about what they will or will not add to their pile (e.g. no meat, bones, dairy, cooked food) and they *all* use very thick biocaps (a six-inch layer of sawdust or wood chips).

I do not think you are necessarily being overly cautious. You sound like you are being smart! Bears are very tough to keep out of a compost if they want in and you should do what you can to avoid attracting their interest.

Worm bin inside is also a really great solution!!!!!

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I also refrain from composting veg outside for this same reason- but I have been thinking about building a worm bin inside for ages- haven't gotten around to it. I had one in my living room years ago and it was great- no smell, easy access. It was a dual purpose piece of furniture- worked as a coffee table :)

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Ha LOVE this! Coffee table worm farm!!!

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