Composting Done Right

Stone Barns Center for Food and Agriculture 

Lower Hudson C.R.A.F.T.

Monday, 26 Julio 2010

Stone Barns, the Rockefeller Farm. The place is a bit high profile; therefore, demanding of top-shape performance. My bottom jaw was dragging across the pathway during most of the tour of Gregg Twehues’ composting operation in awe of his spectacular thoroughness and execution. Here’s just a taste of what Gregg offered us:

The fundamental material components of compost include carbon (the browns), nitrogen (the greens), oxygen and water. To ensure active aerobic decomposition a C:N ratio of 30:1 is necessary. In a handout, Greg provided a diagram comparing effect on temperature versus decomposition rate for compost containing C:N ratios of 60:1, 40:1, and 30:1.

The higher two ratios barely reached a maximum temperature of 140 degrees Fahrenheit after two weeks requiring longer than 50 days for full decomposition, while the prescribed 30:1 ratio reaches a maximum temperature of over 160 degrees Fahrenheit within a week and fully composts within less than 50 days. Reaching temperatures peaking 160 degrees Fahrenheit is important for burning up viable pathogens and insect larvae that may have come in with the raw compost materials, such as Late Blight infected tomato trimmings, Colorado Potato beetle infested eggplants, or blood from composted chicken renderings.

Many browns have already extremely high C:N ratios. For example, wood chips are 300:1, straw is 80:1, and leaves are 60:1. The greens have a less extreme C:N ratio. Rotted manure and coffee grounds are 20:1, grass clippings are 19:1, and alfalfa is 12:1. Therefore, to achieve the ideal 30:1 C:N ratio the compost recipe calls for two parts brown and one part green.

Greg offered a bit of trouble shooting advice for anyone having difficulty getting their compost pile to readily heat up. He suggested one of two things: First, to mix in grass clippings ("gasoline to start the fire”) or second, to soak alfalfa in water over night and a blooming protozoan population will jumpstart any pile. Other compost activators recommended are wood shavings, mature compost or sweet peat, ground oatmeal, or old wood chips.

(Video Clip of Gregg' at work atop the turner)

As much as he emphasized the importance of the abiotic characteristics of compost, his secret to his wizardly ways of turning “waste” into living soil is the focus he places on fostering the biological microbial community within the composting pile. Fungal-dominant versus bacterial-dominant compost largely determines the desirability and applicability of the final product. Fungal-dominat compost is ideal for woody plants and landscaping; bacterial-dominat compost is best for vegetables.

Sweet peat is common in garden use. Sweet peat is an immature version of compost. Sweet peat has not undergone the full time extent of composting as mature compost would and Gregg has no interest in selling such a product.

Gregg’s end goal is to always create the highest quality, fully mature compost rich in biological activity. Making compost is like making sour bread dough! A viable yeast mother full of microbial life is needed to give sour bread that unique taste and bubbly rise. Biologically active compost also starts with a viable microbial mother which Gregg sources from the neighboring woods which he finds provides the best biological activity not found in commercial brew starts.

To ensure a quality out-product, Gregg maintains meticulous quality control when screening the in-products: quality in, quality out. There is also a succession of composting treatments before the materials reach the final stage of being laid out in 150’ long, five-feet high by four-feet wide windrows for a 12 week cycle with precise temperature monitoring and corresponding turning. Materials that take extensive periods of prolonged heat and time to compost, like pine shavings with high lignin content and high-risk pathogen materials, like blood, bones, and feather, are first composted in the O2 Composting bays before entering the windrow process.

Gregg certainly put a squat to the common misconception that composting is a smelly process that attracts pest animals. “Rodents mean there’s a problem in a sustainable system. Just have to figure it out,” and figure it out is what he has been doing for nearly two decades. Gregg has got composting down to a science. He carefully monitors the status of his piles, collecting temperature readings multiple times daily, and scanning the microscope view to assess biological activity just as often.

Overall, to create useful compost, which anyone could do, the important steps are to (1) screen inputs, (2) maintain a 30:1 C:N ratio (3) monitor temperature and moisture levels, and regularly turn piles accordingly. Alternating layers of browns and greens, starting with the browns, is also good practice.

Gregg's recommended the following reading materials and resources: 

BOOK:  Teaming with Microbes

HANDBOOK: On-Farm Compost Handbook, CCE 

MANUAL: Compost Tea Manual

 Soil Food Web International and US Compost Council