backyard compost

Backyard composting

The compost center is the soil-building factory of productive backyard ecosystems. It’s where household by-products and low value organic materials are processed into higher value, micro-biologically active humus by teams of bacteria, fungi, nematodes, and earthworms. The ability to produce one’s own compost is of huge significance to the economic performance of backyard food production. Consider the $60 – $140+ price tag per yard of bulk compost delivered to your home, or if bought by the 20-quart bag, the price can be $300 and up for a yard of compost.

Backyard compost bin make from stakes, pieces of pallet & chicken wire

Backyard compost bin made from stakes, pieces of pallet & chicken wire

It’s sometimes argued that at the individual home scale the amount of organic material is too small to compost properly, that it’s unsightly, smelly, and should be done ‘elsewhere’. Since it takes energy in the form of transportation fuel to move organic material from our homes to ‘elsewhere’, and we then have to travel back to ‘elsewhere’ to buy back our organic material in the form of compost, I’ll argue that it’s economically and environmentally prudent to examine ways to compost at home that address these issues. I have no doubt that commercial & municipal scale compost operations are necessary, valuable, and play an important role serving restaurants, businesses, hospitals, institutions, and other gathering places that produce organic wastes appropriate for composting at scales sufficiently large  enough to warrant the expense of transportation.

First, let’s consider the processes of composting. There are inputs to the process, laborers, essential components, and an output. The inputs may be kitchen scraps, plant material from the garden, coffee grounds, grass clippings, hay, straw, animal manure, woodchips, soy ink newspaper, sawdust, cardboard, fallen leaves, hair clippings, nail clippings, lint, and other organic by-products. In the backyard compost system, it’s wise to omit meat  & dairy waste. In this instance backyard piles are indeed generally too small to ensure that they will heat up to sufficiently process these materials without going rancid. Buying boneless cuts of meat and watching expiration dates closely so you eat all that you buy can go a long way to minimize these products in the waste stream.

Inputs are categorized as carbons (or browns), which are materials that have a carbon to nitrogen (C:N) ratio of 30:1 or more such as dry hay, leaves, sawdust, and newsprint and nitrogens (or greens), which are materials that have a C:N ratio of less than 30:1 such as vegetable scraps, chicken manure, and green vegetation. It’s ideal to build a compost pile with a C:N ratio of 30:1. Here’s a table below of some of the most common compost inputs and their C:N ratio. Nature is highly variable and these values are not absolute but do provide a useful guide. It is not of absolute imperative that the ratio of the pile be exactly 30:1. The reductionist perspective of calculating out the C:N ratio to the microgram is unnecessary. Composting rewards good approximation and intuition.

Material

% Carbon

% Nitrogen

C:N Ratio

Alfalfa pellets

40.5

2.7

15.00

Blood Meal

43

13

3.31

Cottonseed Meal

42

6

7.00

Soybean Meal

42

6

7.00

Legume Hay, dry

40

2.25

17.78

Nonlegume Hay, dry

40

1.25

32.00

Fresh manure, cow

15

0.8

18.75

Fresh manure, horse

30

0.75

40.00

Fresh manure, laying hens

15

2.25

6.67

Fresh manure, broiler chickens

25

1.6

15.63

Wheat or oat straw, dry

48

0.5

96.00

Grass clippings, fresh

12.5

1.5

8.33

Fallen leaves

25

0.7

35.71

Newspaper or cardboard, dry

40

0.1

400.00

Woodchips or sawdust

37.5

0.1

375.00

Coffee grounds

25

1

25.00

Vegetable wastes, fresh, leafy

10

1

10.00

Vegetable wastes, starchy

15

1

15.00

Kitchen scraps

15

1.5

10.00

Fruit wastes

8

0.5

16.00

Seaweed, fresh

10

1

10.00

Weeds, fresh

15

2.5

6.00

If I make a pile out of only fresh leafy vegetable waste (C:N = 10). This pile is significantly under the 30:1 target and the pile will tend to be slimy and smelly. If instead I make a pile out of only dry wheat straw, with a C:N ratio of 96:1, I will be significantly over the 30:1 target and the pile will tend to be dry, crumbly, and will break down very slowly, if at all. Now, if I build a pile out of 2 parts fresh leafy vegetable waste and 1 part dry wheat straw (by weight, not volume), the C:N ratio with be about 27:1 which is close enough for a pile to break down rapidly and evenly.

Why do piles with different C:N ratios behave differently? The answer lies primarily with the laborers of the compost factory. The workforce consists of a diverse collection of organisms including bacteria, fungi, nematodes, and earthworms. There are billions of microorganisms in a teaspoon of living soil. These critters are absolutely essential to life on earth. As our understanding of soil has developed, we have learned that it is not simply the presence of the appropriate proportions of elemental nutrients that produces fertile soil, it is the presence of trillions of living micro-organisms living, dying, eating, decaying, cycling materials, and all the while making nutrients available to plants that leads to vital, fertile soils.

Compost thermometer in a backyard pile at 110* F

Compost thermometer in a backyard pile at 110* F

As the micro-laborers go about their lives, they are happy to break down complex organic compounds into their elemental constituents, of which carbon and nitrogen are by far the most plentiful, but these workers have a few basic requirements, namely water and oxygen. When the C:N ratio of a compost pile is less than 30:1, there is a proportionate excess of nitrogen and lack of carbon. This is the stinky, smelly pile. Anaerobic bacteria thrive in this moist, oxygen deprived environment, producing hydrogen, ammonia, organic acids and methane . When the C:N ratio is greater than 30:1, there is not enough nitrogen for the microbes to build their bodies at the rate they would like and populations to not grow large enough the process the material quickly. This results in the dry, crumbly, unproductive pile. The 30:1 ratio provides the optimal balance, providing an environment where there is sufficient fuel & building material for the microbes to do their work as they like and for their to be enough air infiltration into the pile to keep aerobic populations in charge. This balanced pile will smell earthy and generally pleasant.

Just as we would not last long without water and oxygen, soil life also need them. In arid climates it may be necessary to add water to piles at times, but in most temperate climates rainfall provides enough moisture. Oxygen is relatively ubiquitous on the surface of our planet, although as I’ll talk about next in the “what doesn’t work so well” section, we sometimes go to lengths to keep out the elements that are essential to healthy compost.

We have a belief in America that you can’t do something until you buy the something you need to do it. Therefore it’s not a surprising that many people want to buy a composter in order to start composting. Which is understandable, but many “composters” often look like these;

 

Which is a problem because these “composters” don’t work very well at producing compost. In addition they require resources to build and transport when suitable alternatives exist locally, such as reclaimed wood, hay bales, shipping pallets and more. We need to ask about bins we may buy, how well is water going to get in? How well is oxygen going to circulate? There may be a few vents but most have not nearly enough to allow for rain water to percolate freely or for sufficient oxygen flow. As a rule of thumb, if you wouldn’t put your cat or dog in it for say, an hour, you shouldn’t attempt to compost in it either.

The process we call composting has been happening for 500 million years, recycling organic material on the planet for all terrestrial life that has ever existed. It’s therefore not advisable or necessary to use a plastic space capsule to do it.  A pile on the ground will compost. Anything we do beyond that should be done to improve compost outcomes and integrate composting with our human desires for order and a sense of place. We don’t want to sacrifice function for form, because then what’s the point of doing it at all?

Why don’t I compost in a pile on the ground? The dog would eat it, probably get sick, and nearby skunk, raccoon and squirrel populations would usher me down a short, slippery slope to a backyard compost hell-scape. The dog would incur vet bills, the wild animals would eat into the the amount of compost I have left over for my plants, and both would spread the heap around. So I need a solution. I have tried using plastic compost bins and while they provide a place to put food scraps for a year or two, they have not generated a useful compost. At the conclusion of the experiment I was left with the liability of a rather nasty cube of mostly intact vegetable matter enclosed in a plastic shell.  Out of pocket cost: $50. Compost for the garden: 0.

There are other options between the free-for-all hell-scape and the garbage-pod space capsule approaches. In order to consider these, let’s examine the human ecosystem as it relates to compost production and use. We eat every day for the most part and thus most of us generate kitchen scraps and other organics for composting at a small but steady rate. This is a challenge to the optimum construction of a compost pile, which is to build a pile all at once at a minimum size of 1 cubic meter, mixed to approximately our 30:1 C:N ratio. Then we leave the pile to break down, possibly turning and churning the pile. In an optimal pile, total breakdown is around 3-4 weeks, during which time we do not want to add fresh organics, but we are still producing them at the same steady rate.

In the backyard, we want to bring out household organics (which are generally nitrogens) when the household storage bucket is full, which is every few days, it really depends on your household. Then we want to spread them evenly in the bin, adding a layer of carbons and repeating with more nitrogens until we have a full bin. To do this we need a place nearby to store the carbons. This works until the first bin is full. Then we need a second bin to use while the first one composts down. A third bin is the best option; 1 that has finished composting and is used as needed, 1 that is actively breaking down, and 1 that is being built. Bins have been made of shipping pallets, cut apart and re-assembled to the desired form, various wire supported by stakes driven in the ground, hay bales stacked to form the sides and back of a bin with 1 or 2 dropped in front as a “door”, stacks of concrete blocks, and sod from the yard.

Austrian permaculture teacher and practitioner, Sepp Holzer, offers even another approach. No bin is built at all. Instead, two parallel rows of Holzer raised beds are built and organic material is placed in the space between. Holzer’s beds are shaped roughly like windrows of wood and soil. Holzer’s method is to fill the space between the raised beds with compostable material and then grow crops in this space, back-filling down the row a little at a time. As the row becomes full, the oldest material is ready to be removed and used elsewhere in the garden. In this way Holzer gets a yield of vegetables and compost with minimal input of energy or materials.

The earlier mentioned skunks, raccoons, squirrels and other urban scavengers will undoubtedly find your pile eventually. Your personal desire for order will dictate the lengths you take to fence these critters out of your bins. Squirrels frequently visit my bins and while they sometimes leave a corn cob in the yard, they generally keep their activities confined to the bins so I’m willing to trade a little compost for their services of tilling and mixing my compost. Burrowing animals may try to come in from below. If this is a problem, wire screening can be buried 6″ down and 6″ out all around the bins, forming an L that burrowers will be turned back by.

Using design and planning to account for the function of soil and human ecosystems it is possible to produce compost in a way that supports the soil health, efficiently makes use of organic wastes generated by households, manages animal interactions, and creates the foundation for a prosperous backyard garden.

Finished compost in backyard pallet bin

Finished compost in a backyard bin made from shipping pallets

Economics of the Rain Barrel

Rain barrels are the rage right now. A 55 gallon re-purposed food barrel at the downspout is one’s statement of their stance on storm water run-off and urban regeneration. Sort of like what the Prius is to gasoline consumption. Sort of.

The assumption I make of those who urban homestead is that they do it to improve regional & household ecology AND economy. I don’t want to discount those who homestead as a hobby for enjoyment & recreation but the focus of this, and most blog posts on this site, will be on ecosystem services and household economics, so let’s take a look at how the rain barrel does on these two fronts.

2 rain barrels daisy chained together

2 rain barrels daisy chained together

Economics is essentially the study of why people do one thing instead of another, the incentives that are in play and the thinking that happens at the margins of decision making. It’s not always about money. Economics gets a bad rap in that regard. It’s a tool, and like any tool it can be used in many ways. Economic theory and analysis can be used to drive a bubble of mortgage backed derivative purchases to the point of global economic crisis as easily as they can be used to empower a resurgence of localized, sustainable agriculture.

So what are some things that may motivate a person to install a rain barrel, or 2, or 3?

1. To reduce the impact of combined sewer overflow (CSO) events that occur during periods of heavy rain & run-off which deposit untreated sewage into waterways
2. To reduce demand on ground-water resources
3. To reduce the energy that’s required to obtain fresh water (i.e. energy used to pump from ground or surface reservoirs)
4. To increase resiliency during prolonged dry spells
5. To develop a deeper connection to weather and climate patterns
6. To save money on the water bill

There are undoubtedly more. I expect that many people are inspired by 1 thru 5 and that of that group some are driven to action. I will hypothesize that #6 is what tips the scales though. Let’s face it, money still matters. Accepting that there are motivators that matter besides money, but that people do want to know if their actions make financial sense, let’s look at the payback for rain barrels.

First, what is the investment? Like anything, there is variability. If you’re willing to buy the barrel and do the work yourself to add the fittings you will likely be in the $30-$45 range. I went this route, bought 55 gal. food barrels for $20 apiece, and spent about $20 more apiece on fittings. I’ve since seen barrels as low as $12 and could probably get the price on fittings down a bit now that I know exactly what works. To my amazement, I’ve seen completely fitted and plumbed rain barrels, made from re-purposed food grade barrels, for $45, before delivery or pick-up. I find that rather incredible given my DIY costs. At these prices, rainwater storage is in the ballpark of $0.60 to $1.00 per gallon. I suggest keeping the $1.00 per gallon figure in mind when shopping around for rain barrels. For simplicity’s sake in this analysis I’m going to use $50 per 55 gal. barrel as the requisite investment.

In Burlington Vermont the water bill works out to about 1.2 cents per gallon. This accounts for both water coming in, which is metered and waste water going out, which is not directly metered but is billed per the same volume as incoming. This is the price you pay at the outside tap when you fill up a watering can from city water, regardless of the fact that the water is not entering the waste water stream. For every gallon of water you use out of a rain barrel, you save 1.2 cents. If you’re on private well water supply, the economics are quite different, and are determined by the depth of your well and your energy cost for pumping that water to the surface. This is an area worth looking at, but I have not examined those numbers yet.

The next piece is the tricky part. How much rainwater do you use? Unless you count the number of watering cans you fill, there’s a big unknown here.

That’s because the amount of rainwater captured and used is a function of 3 variables:

1. How much rain water storage do you have? (1 55 gal. barrel? 10 55 gal. barrels? One 2,000 gallon cistern?)

2. How much building footprint area are you collecting from?

3. What are your rainwater use patterns? Did you empty the barrels before a big rain or not?

To collect all the rain that falls on your home, you need a barrel large enough to store the largest expected rain event. Say that is 2″ and your home has a 1,000 square foot footprint.

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You will need 1,250 gallons of storage. That’s about twenty three 55 gal. barrels. That one rain barrel at a downspout is more like 1/23rd of a Prius now. At a 1,000 sf home, one rain barrel is only collecting the first 0.09″ of rain. Everything after that is going out the overflow and on to the usual places.

Ok, so you don’t want to buy 23 rain barrels and line them up all the way around your house. That’s reasonable. Let’s say that you will buy 4 rain barrels and put 2 on either side of the house at the downspouts. From November to April you bypass the barrels completely so you don’t get 440 lb blocks of ice. In Vermont this reduces the annual precipitation you can capture from 36″ to 24″ Let’s also say that you watch the weather closely and when it’s raining frequently or there is a storm approaching, you draw the barrels down so the maximum amount of new rain fall will be captured. Let’s say that in this way you’re able to capture and use 30% of the 24″ of rain that falls on your house during the non-freezing months. The rest is overflow during the heavier rain events. This equates to 4,500 gallons. Not bad. At 1.2 cents per gallon you have saved $54 on your water bill for the year, had you used that same amount of water from the tap. I ballparked the investment at $50 per barrel, so the payback here is a little under 4 years, assuming gutters and downspouts are already in place and you are simply diverting those to the rain barrels.

For readers in the Champlain basin of Vermont, you can improve the payback on rainwater collection further. Check out incentives from the Let it Rain program for downspout disconnection, rain barrels, rain gardens, cisterns and permeable pavers offered through June 30, 2013.

Interestingly, if you maxed out storage to collect all of that 2″ deluge rain event, your investment on 23 barrels would be $1,150 and you’d collect 15,000 gallons, offsetting $180, for a payback of 6.3 years. This is about 50% longer than the 4 barrel scenario. At some point there are diminishing returns to catching every last drop. Between catching nothing and catching everything, there is a sweet spot where you use what you catch and you need what you use. If reducing peak storm water run-off and the associated ecological benefits is your primary goal, you will need to size your system large enough to catch a significant portion of that 2″ (or more) rain event. If providing water for gardens and fruit trees is the goal, you may wish to size smaller, or at least size proportionately to the water demand of your plants.

An alternative to the 55 gal. food barrel is the 275 gal. Intermediate Bulk Container (IBC). These cube shaped liquid storage tanks are sized for transport on pallets. If you’re buying re-purposed be absolutely sure to ask and verify the original contents. You do not want petroleum oils, non-organic soaps or other nasty unknowns in your water. I’ve seen this type of re-purposed tank for sale for $75-$150, which works out to about $0.30 to $0.50 per gallon of storage.

photo: Sun, Rain, Earth, A Self-Sufficiency Journey

photo: Sun, Rain, Earth, A Self-Sufficiency Journey

photo: Sun, Rain, Earth, A Self-Sufficiency Journey

photo: Sun, Rain, Earth, A Self-Sufficiency Journey

I haven’t yet gone into detail on uses of collected rain water, consideration of roofing materials, and the 3 crucial components:

1. An adequately sized overflow line

2. A first flush

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diverter to bypass the dirtiest water

3. A winter bypass to avoid frozen disasters.

My next post on rain water collection will tackle these topics.