Turning Waste into Black Gold
Margit Kaltenekker
Agriculture Agent
Inflated fertilizer prices and supply issues don’t have to be the end game for adding fertility to the fields around your farm. Composting manure, and/or livestock mortalities, and offal, is a reliable way to recycle nutrients on your farm, turning waste products into a valuable source of decomposed organic matter, rich in microbial life and concentrated nutrients. Some refer to Compost as ‘Black Gold’ because it is so highly valuable as a soil amendment. Many agricultural operations already have all the necessary elements to begin composting, just by the nature of what they do: surplus plant material (bedding, spoiled hay or straw, green chop ), and/or animal waste, access to land and a level area necessary to make compost, as well as equipment on site (a tractor or skid steer with a bucket, and spreader)….making compost a feasible, beneficial and economically attractive solution to address soil and crop fertility.
But why bother composting compared to just spreading manure out of the dry lot? Sure, manure applications can be effective where a
quick release of nutrients are desired, but risk losing nutrients to volatilization or runoff. Composting is a controlled decomposition process transforming biological wastes into a biologically stable humic substance, increasing fertility and structure of soils. Some of the advantages of composting include: the slow release of nutrients (an advantage to some crops); decreased viable weed seeds and pathogens; easier to apply than manure because of reduced volume and weight of waste material; increased microbial profile that will serve as a bio-stimulant to fields; reduced environmental risk; fewer restrictions on timing applications (for specialty vegetable crops).
Compost is created by the aerobic decomposition of organic materials by soil borne organisms. During the composting process, fungi, bacteria, actinomycetes, and protozoa consume oxygen (O2), while using the carbon rich, biodegradable organic materials (manure, spoiled hay, straw, green chop) as their food source. These materials are referred to as ‘feedstocks’. Through this process, the biological activity releases heat, water vapor and carbon dioxide (CO2). Expect 50% of the carbon in the organic material to be lost to respiration, but nitrogenous compounds are converted to more stable organic forms (slow release N). This results in a drastic reduction in the volume of materials, while creating something completely different in physical and biochemical form: COMPOST!
Composting is best achieved when warmer weather and favorable conditions that stimulate the growth of microorganisms are achieved and maintained over a period of 4 – 6 months. The Kansas Department of Health and Environment (KDHE) has various Regulations applicable to Manure and Livestock Composting that need to be followed. So be sure to read them! Then take these necessary steps to begin:
Identify a suitable location: This needs to be a flat or level open area, away from any water sources, or risk of runoff to waterways.
Gather Organic Materials: These need to be blended together to provide the energy and nutrients for the microbial activity and growth while providing an appropriate Carbon to Nitrogen (C:N) ratio of about 20 - 40: 1 . Cattle Manure itself has a C:N ratio of 20:1; Horse manure 25:1; Hog or Poultry manure are 5 -10:1. Adding dry feedstocks (bedding, hay or straw) increases the C:N appropriately.
Ideally a compost windrow or heap, is generally 4’ tall by 4’ wide, and however long you want. This depth and width of the pile allows for enough biological activity to heat up and digest the organic materials, without drying out too easily. Many larger livestock operations use specially designed bins under cover, much like a greenhouse structure.
Building the Windrow: It may be necessary to chop some of the feedstocks to incorporate them evenly together with each other or run them through a manure spreader to chop. If that isn’t possible, create a series of alternating layers in shaping the windrow or pile, starting with dry organic materials at the bottom, then manure, dry organic materials, and so on. Add some moisture to the dry materials if they are bone dry. After some weeks, the materials will be mixed and turned with a bucket loader, through an aeration process once they have begun to break down.
Aerate the pile: Make sure to add oxygen to promote aerobic decomposition. Turn the pile when temperatures are above 160°F/65°C. Every so often (depending on moisture and temperature), turning the pile will cool the temperatures and increase aeration, stimulating further biological activity to further the composting process, and decrease noxious odors caused by anaerobic conditions.
Moisture is an important variable! A windrow that is too dry or too wet (or soggy) will not perform correctly. A 40-65% moisture content needs to be available without hindering aeration, thus slowing the microbial digestion. One of the best tests is by ‘feel’. Take a handful and squeeze it. If it can’t be ‘squeezed’, it is too dry. If it leaches water, it is too wet. The feel of a moist sponge that literally ‘springs back’ is ideal, giving way to a soft, moist, cake-like texture. In rainy seasons a tarp is entirely appropriate to protect the windrows from saturation.
Temperature range: Should promote vigorous aerobic activity of thermophilic organisms. The ideal range is 140°- 160°F, (43° - 65°C). Monitor temperatures daily with a 20- 30” Compost Thermometer.
Once the compost feedstocks are mixed into a windrow and the temperature and moisture conditions favorable for microbial activity are stimulated, the composting process begins! There will be two main phases of most importance: the active phase and curing phase. The activephase requires the most attention to daily or weekly management, lasting about 3 – 9 weeks, largely dependent on the materials and conditions. The curingphase lasts another few weeks allowing the compost to combine forces into its final form.
During the active phase, there are three temperature related stages: the initial mesophilic stage of the first few days, where temperatures increase rapidly as the microorganisms digest the most readily available compounds; the longer thermophilic stage (140° – 165°F; 43° - 65°C) where more complex materials are decomposed; followed by a slower, cooling stabilization phase where the more resistant materials are slowly digested to completion. In total the thermophilic and stabilization stages may last from 10 – 100 days. During the thermophilic stage a lot of oxygen is consumed by the microorganisms that may result in offensive odors, requiring the need for aeration. Aeration may only be required once or twice during the entire process. But temperature, feel and developing an eye for the final product are also good indicators to judge how often one needs to turn the windrows.
The Curing phase occurs best at ambient temperature and lasts from one to several months – as complex chemical reactions result in the final stable form of ‘finished compost’. There are many more resources and intricate details to be considered in pursuing the Art and Science of composting. Guaranteed it is a sometimes necessary and satisfying process recycling nutrients right on the farm – recycling waste into ‘Black Gold’!
Check out these resources and references:
Composting at Livestock Facilities Information Sheet , Kansas Department of Health and Environment.
Making and Using Compost ,University of Missouri Extension
Composting: The Basics , ATTRA Sustainable Agriculture; A great resource for gardeners!
On Farm Manure Management Through Composting , Nova Scotia Environmental Farm Plan, nsefp.ca
