Accidental Hot Composting

In my last blog post, I shared some of my knowledge about composting in honor of International Compost Awareness Week. I began composting in 1999, when I bought my first bin (something along the lines of this). Composters like my first bin are often touted as a way to achieve "hot composting" – the black plastic container absorbs heat, or so the ad copy goes, thus encouraging organic waste to "cook" into rich black compost.

As I explained in the aforementioned blog post, hot composting occurs when wastes rich in carbon and nitrogen are mixed in the right proportions (30 C : 1 N). A few scoops of soil or finished compost (for the microorganisms within) are thrown into the mix. The pile is kept moist and well-aerated and, if one is lucky, the bacteria in the pile will begin to consume like maniacs. They eat and breed in such a frenzied manner that they generate heat in the process. This heat is a sign that waste is breaking down rapidly.

I have no idea if my first compost bin really worked – sure, the waste I put inside broke down, but when I tried to remove it a year later the receptacle fell apart, and I never really found out if the compost heated. This is consistent with stories I’ve heard from other gardeners who have invested in expensive plastic composters only to find they broke or collapsed after a year or two of use. While not all of these bins bust so quickly, they can fail to deliver in their promises to cause the kind of heating that creates crumbly black "Gardeners' Gold" within three months’ time.

A few years after my disappointing first run with hot composting I opted to try passive composting. With passive composting, you basically throw stuff in a pile and let it rot for a year. You don't aerate by turning the pile, nor do you water the pile; you simply let nature take its course and enjoy a small amount of compost each spring. In 2003, my father-in-law built me a two-sided bin with an open top, removable wooden slats in the front, and chicken wire sides. I've been passively composting ever since, harvesting compost once a year.

That is, until about two weeks ago. That's when, despite the cold and rain, I discovered that my “passive” pile out back had accidentally become a hot pile – so hot, in fact, that it has been steaming for over a week. Here's a photo in which I almost captured the faint vapor rising one cold morning when I dug into the pile:





A hot compost pile is desirable because (A) heating causes compost to form much faster – it only takes about three months; (B) the quality of the compost is higher because of all the additional microbial activity encouraged; and (C) weed seeds and pathogens are "cooked" through the pasteurization process that takes place in the pile.

Accomplishing hot composting can be tricky. Most believe they fail to generate heat because their pile isn’t getting enough sun or warmth, though my case is proof that these variables have little to do with hot composting. My pile is in a shady spot in the back of my yard, next to an ash tree. The day I first found it steaming it was about 45 degrees Fahrenheit, extremely windy, and overcast. Not exactly the scorching day you'd expect would cause yard waste to heat. Nor is my bin made of heat-absorbing black plastic, which many companies claim is an important factor in successful hot composting (cf. this model, which advertises that "this high-performance tumbler is made of 100% recycled plastic in a heat-absorbing black color which helps compost 'cook'").

I'm not 100 percent sure what I did to cause my pile to heat, but I do have some theories:

(1) The pile is big. The whole thing is at least 3’x 3’x 3’. I'm not sure if it's absolutely necessary to have a big pile in order to achieve hot composting, but it certainly helps, for two reasons: one, the greater the variety of waste I throw on the pile, the more I increase the likelihood of balancing nitrogen to carbon, and two, the more waste, the more for the microbes to eat. I currently throw any and everything I can compost into the bin, from yard waste to kitchen scraps (my own and those I’ve collected from neighbors and, occasionally, local restaurants). I throw in large amounts of dried weeds and dead leaves from the yard (for the carbon) as well as buckets of moist, nitrogen-rich kitchen scraps. This helps me get closer to striking that important carbon to nitrogen balance of 30:1.

(2) The pile has LOTS of sticks in it. In the past I omitted the sticks, as they take a very long time to break down and are a pain to pick out of my passive pile once a year. HOWEVER, I learned in my Master Composter class that sticks, because of their size, create necessary pathways in the pile for air. So I allowed a number of sticks of various sizes into the pile, which I believe helped to aerate it, thus reducing the need for turning (something I seldom do).

(3) The pile is very moist due to ample rain. One of the main reasons folks’ piles don’t' heat is because they dry out, especially mid-to-late summer. Compost piles need to be watered when it's not raining – especially if they contain a lot of carbon-rich materials like dead leaves. It has been raining a lot this spring – which has limited the amount of time I’ve been able to spend in the garden, but has worked wonders on my compost pile.

Of course, my happy composting accident has me revved up to try intentionally hot composting. So lately I've been checking the pile daily and have even started turning it with a pitch fork. It’s so fun to see all the black crumbly compost steaming in the center of the pile. If my hot pile keeps working so well I’m sure I’m going to have compost by mid-summer, which will offer a nice pick-me-up for the veggies and herbs growing in my raised beds.

Do you have a question about composting or a composting success to share? E-mail me at gardensnotgarbage@gmail.com or leave a comment below. Or, stop by the Tosa Farmers Market on Saturday, May 28 at 11 a.m. and learn about composting basics at the Historic Little Red Store (7720 Harwood Avenue).

Do You Compost?

If your answer is yes, you have my permission to skip reading this blog post.

If your answer is no, I'd like to make a special appeal to you: consider engaging in the simple, delightful process of turning organic "waste" into the resource it really is. This is International Compost Awareness Week, and in honor of the event, I'd like to challenge you to make a bold move to cease throwing kitchen scraps into the trash and instead give composting a try. In doing so you'll discover for yourself how magical (and how easy!) the act of composting can be.

Composting is magical because it takes garbage and turns it into a useable product – compost, also known as "humus." Humus is a crucial but often lacking component of healthy soil. Adding compost to the earth reduces the need for commercial soil amendments, as well as manufactured chemical fertilizers that can run off our properties and into the rivers and lakes, polluting our water supply. Compost adds nutrients and micronutrients to depleted soil, helps soils retain moisture, and reduces erosion. This allows us to grow healthier plants, from vegetables and fruits to native flowers and even grass. It can act as mulch and side dressing and can be used to make "compost tea." Compost can be purchased, of course, but it is virtually free, after start-up expenses, once you begin converting your own kitchen waste into this natural resource.

And composting really IS easy. There are three main ways to compost -- choose your favorite. The bottom line is that anything you do to return resources to the soil, rather than send them to the landfill, is an important contribution to environmental sustainability.

The first method of composting I'm going to discuss is probably the most well-known. Hot composting is a technique whereby your aim is to "cook" your vegetable-based waste. Food scraps heat and thus break down faster into compost. Contrary to popular opinion, a pile doesn't necessarily heat because of the sun or summer temperatures. It heats when beneficial composting bacteria go to work inside a pile, heating it to degrees upwards of 160 F. This pasteurizes the pile and creates high quality compost quickly – the total turn-around time is about three months when a pile properly heats.

While this is a fantastic composting method, it can be tricky to get a pile to heat. Heating requires a carbon to nitrogen ratio of 30:1 in the waste. Carbon rich materials include things like dead leaves and hay. Nitrogen rich materials include fresh-cut grass, vegetable scraps, or manure. Many say a good rule of thumb is to mix two parts carbon-rich "brown" materials with one part nitrogen-rich "green" materials. In order to heat, the pile also needs to be adequately moist (about as wet as a wrung-out sponge) and it needs to good oxygen flow – aeration is encouraged through regular turning of the pile.

Sounds fun, doesn't it?

Um….sort of? I know I don't have time to do all these things. I would, of course, LOVE to see my big ol' pile out back get so hot it steams, but I know accomplishing this is no small task.

An alternative is what is called "passive" or "cool" composting. This is the outdoor composting method of choice for those who are extremely busy – or just plain lazy. I think I may have one foot in each of those categories, which is why this method works so well for me. The main difference between hot and passive composting is the amount of work that goes into it – and the amount of time it takes to create usable compost. For my pile, I simply dump waste into the bin. I try to layer the types of waste I add – for example, if I dump in nitrogen-rich veggie and fruit scraps I will cover them with carbon-rich dead leaves. I do this to help the carbon-nitrogen balance and to cover any offensive-smelling waste that might attract flies. Occasionally I will also turn the pile, although I admit I don't do it often enough to call it "hot" composting.

Interestingly, right now my pile is so big that it seems to be heating, despite my laziness. If it heats, it will compost faster. Otherwise, the compost from a passive pile is typically ready in six to twelve months. I usually harvest compost in late spring, just as I'm preparing my vegetable beds.

One caution: if you choose passive composting, avoid adding weed seeds to your pile. Though most weed seeds will be destroyed by heating, without the heat the seeds may survive the composting process and end up sprouting in your gardens.

The third method is worm composting, AKA vermicomposting. I've written about in the past on this blogand I own a small vermicomposting supply business; I encourage you to peruse those resources if you want to learn more. Vermicomposting is my favorite composting method, simply because it's fast, can be done indoors year-round, and produces a superior compost that plants love. Worm composting creates finished compost in approximately two to four months.

With all three methods, avoid adding meat, fish, poultry, dairy, and other animal products, as these wastes create offensive odors and can attract pests. Also avoid adding heavily processed and salty foods, charcoal briquettes and ashes, and dog and cat feces. Paper products are OK – throw those coffee filters and paper towels in with your fruit and vegetable waste. They'll break down quickly in a compost bin of any kind.

As for composting systems, you can invest in an expensive commercial compost bin, and if you want to do this, more power to you. Just make sure you read as many user ratings as possible before spending money so you have an idea of what to expect. Of course, you do not have to buy an expensive commercial bin to compost. There are plenty of plans for bins, ranging from a simple cylinder made of chicken wire to more complex wooden systems. You can also use concrete blocks to build bins. The Wisconsin DNR has a nice site with composting resources, including info on types of home composting bins. Check it out.

My passive bin is made from scrap wood and chicken wire, which allows for decent air flow around the pile. Wooden slats in the front slide up and out when the time comes to remove the compost. The two sides allow me to focus on adding waste to one side at a time; when the first side is ready, I remove any unfinished materials and place them in the other side, then begin adding new waste to the second side.

If you are unable to compost yourself, you may be able to find a neighbor to help you. I use my large bin to help neighbors compost. I also feed neighbors' waste to the thousands of red wiggler worms that eat garbage in my basement.

If you can't find a neighbor to help you compost, locate a community composting collective, like the Milwaukee Community Compost Network. Or, start a collective yourself.

If you have a big composting bin and not enough waste to fill it, you might consider offering to compost for your neighbors. You can also try to compost for local restaurants and grocers. There are many possibilities for composting. By working together, every community can turn their garbage into gardens!