Author: Teagan Moran, Small Farms Program, Oregon State University
Publish Date: Fall 2019
Composting and agriculture are a long standing and complimentary pairing. The ancient Akkadian Empire in the Mesopotamian Valley referred to the use of manure in agriculture on clay tablets dating back 2000+ years (Smith, Friend 2019). Many agricultural operations, just by the nature of what they do, have what it takes to practice composting: surplus plant materials and/or animal waste, access to the land and the space necessary to compost, equipment already on site, and crops and soils that can benefit from compost amendment.
Why compost and why would you want to make your own?
Farmers use compost for a variety of reasons, to name a few; it helps to improve soil structure, increases microbial activity, enhances plant disease suppression, increases soil fertility, and improves the water and nutrient holding capacity of most soils. These effects can improve the function of fine textured clay and silt soils, as well as coarse textured sandy soils. Many farmers purchase compost for use on their farm, but on-farm composting can make sense for a variety of reasons. If you have a lot of on-farm waste that would make good feedstock (feedstocks are the organic ingredients of composting processes, such as yard debris, animal manures and food scraps), but are difficult or problematic to apply to the land raw, composting can convert them into a valuable soil amendment. Examples may include manure, livestock mortalities, spoiled hay or straw, green-chop from cover crops, mint slugs, packing shed waste, etc. If you have access to organic waste nearby, you might be able to charge a “tipping fee” to accept those materials for composting. Composting can reduce the volume of organic waste (i.e. manure) stored on your farm and reduce environmental risk. On-farm composting gives you control over the feedstock and composting process, and more control over compost quality and price. For ethical reasons you might want to make best use of on-farm and local organic materials and nutrients to move towards a closed loop system on your farm. Some farmers use all their own compost on site, while others sell some as an additional farm enterprise.
Decomposition of raw materials happens on its own without human intervention – it is a biological process driven by micro-organisms (bacteria, fungi, and actinomycetes) and macro-organisms (mites, slugs, spiders, earthworms, etc.) converting organic materials into that dark, earthy smelling, decomposed organic matter we call compost. When we refer to composting we are talking about how humans intervene to manage the conditions and materials so that decomposition happens faster and in optimal conditions and where we want it to happen. Composting systems enable us to easily collect and apply the final compost product, thus turning organic matter into a form we can then add back into the soil.
The main differences between home composting and on-farm compost systems are; scale, intended use, and often, the integration and management of animal manure. Not all animal manure needs to be composted to be used. Compost releases nutrients slowly. In many ways this is a benefit, but sometimes crops want the quick release that fresh manure can offer. Knowing when to use composted or fresh manure is an important decision for farmers (Marriott, Zaborski 2015). In addition some farms compost animal mortalities, offal, and byproducts on farm.
Like any other operation, composting requires equipment, labor, and management. So what are the main questions a farmer needs to answer before starting on-farm compost? See below for questions and associated details.
Do I have an appropriate site on farm? The beauty of composting is that it can be scaled to fit the landscape and farming operation. Placement of your compost site can be influenced by aesthetic as well as functional needs. That being said, there are several key factors to consider when selecting your site:
Do you have an easily accessible and dry area with good air circulation to site the composting system? You want to be aware of runoff and avoid any site where it could go straight into a waterway, well, or across your property boundary. Leachate is any water that has come into contact with compost. Leachate can easily contaminate surface or groundwater and can pose risks to health and environment (Brewer, et all. 2013) Good drainage is essential to avoid water pooling, mud, and saturated composting materials. You can find detailed information about water quality in the Agricultural Composting and Water Quality publication linked at the end of this article. There may be zoning requirements for large compost systems. To determine if there are any minimum setbacks, contact your local county planning department. There are also specialists with the Oregon DEQ who can assist in site selection on your property.
Can the composting site remain there for 6-8 months? It can take 6 to 8 months to produce cured compost from raw waste. Will the compost system operate seasonally or all year-round? Most raw manure requires covered storage or a site for year round composting.
How will you access the composting site? You will need space to turn the materials (mixing the compost pile is important to get good quality compost) either manually or with a tractor, and to add water if necessary.
Is the ground firm enough to support heavy equipment if that is to be used? Will that ground be too wet to access at certain times? The amount of space you will need depends on how much material you plan to compost and the compost method you choose. A compost pile must be the proper height and width to insulate itself enough to get hot. A pile should be at least 4 feet high and 4 feet wide, and however long you want (Sideman. 2006). Piles less than about one cubic yard don’t have enough mass to heat up and create a thermophilic compost pile. Some people use open piles or windrows in a field, others use bays or bins to contain the compost.
For area requirements and a worksheet to identify the area you need for your compost see the On-Farm Composting Handbook found in References and Resources at end of this article.
Do I have time? Good composting requires proper management. Composting is a balancing act and you’re the approach you choose will be informed by your farm’s individual needs and goals. For example, slow composting does not produce enough heat to kill many weed seeds, rhizomes, or pathogens. Making hot compost takes significantly more effort, but it can produce a high-quality product within just a few months. You can customize the composting process to fit your time availability and specific combination of raw materials, there are different approaches to choose from. Making compost is actually quite easy, but to produce quality compost requires an understanding about the science behind the process, how to measure materials, good timing, and going through some trial and error. For a quick reference and comparison of composting methods check out pg. 13 of Agricultural Composting and Water Quality found in References and Resources below.
During the composting process farmers need to regularly check on the pile and respond accordingly (this takes time). If a pile gets too wet or too dry the decomposition process can slow right down, this can manifest with strong undesirable odors. A wellmanaged compost system will not cause excessive odors. To learn more about the science behind composting check out the recommended reading list below and keep a look out for local OSU Extension sponsored compost workshops.
Do I have the right equipment?
You have the option to use existing on-farm equipment to manage the compost pile or to invest in specialized compost production equipment. That decision would be influenced by your scale and intended use, you can customize your composting based on your available resources and needs. The On- Farm Composting Handbook found in References and Resources below can help guide those decisions. Onfarm compost can be done manually if at a manageable size for the labor available. For larger compost systems farmers most often use a tractor with a front loader for building and turning the piles, some farmers invest in windrow turners to efficiently turn piles. Manure spreaders can be used for application. A temperature probe will be needed to gauge timing for turns.
What should I compost? The materials you put into your compost pile have a major impact on how well the composting process works and the quality of the final compost. The key to good composting is to have a variety of materials, a balanced carbon to nitrogen ratio, and good moisture content. That being said, the list of materials appropriate for composting is a long one. A comprehensive list on what to compost and the ratios can be found in The On-Farm Composting Handbook in resources list below. WSU’s Compost Mix Calculator is free online spreadsheet that can help you estimate the C:N ratio and moisture content of your new compost pile (https://puyallup.wsu.edu/ soils/compost-mix-calculator/).
Do I need a permit or license? Due to the scale of most small farm compost systems, small farms tend to be exempt from Oregon Department of Environmental Control’s (DEQ) permits. Exempt facilities still need to maintain compliance with environmental performance standards. DEQ’s composting rules are structured such that the type of permit issued is based on the level of risk posed by a composting facility and anaerobic digesters to public health or the environment. The type and amount of feedstock composted is used to establish criteria for determining when a composting facility permit is required and when a facility is exempt from permitting requirements. The feedstock types include:
Type 1: Source-separated yard and garden wastes, wood wastes, agricultural crop residues, waxcoated cardboard, vegetative food wastes including department approved industrially produced vegetative food waste
Type 2: Manure and bedding
Type 3: Dead animals. Meat and source-separated mixed food waste. Industrially produced nonvegetative food waste
According to Oregon Administrative Rules (OAR) 340- 096-0060, Oregon allows the following conditional exemptions of facilities from obtaining a permit:
Composting less than 100 tons of Type 1, or Type 2, or both types of these feedstocks during a calendar year
Composting less than 20 tons of Type 3 feedstock during a calendar year
Composting less than 40 tons of Type 3 feedstock with in-vessel container system (which are designed to prevent vectors and nuisances)
Composting operations that produce silage on a farm for animal feed
Home composting operations
Farms that possess a Confined Animal Feeding Operation water quality permit (CAFO) issued by the Oregon Dept. of Agriculture, when the composting facility is incorporated into the operating plans required by the CAFO permit.
More information can be found at: https://www.oregon.gov/deq/mm/swpermits/Pages/Composting- Regulations.aspx
Each farmer should look closely at his or her own farm and financial resources to determine whether or not it would be advantageous to adapt and dedicate the space, labor/time, and equipment to composting (Runk, 2019). If you think on-farm composting may be a good fit for you, then these resources will help you dive deeper and get your composting operation started:
On-Farm Composting Handbook, Northeast Regional Agricultural Engineering Service and Cooperative Extension, 1992 https://campus.extension.org/ pluginfile.php/48384/course/section/7167/ NRAES%20FarmCompost%20manual%201992.pdf
Agricultural Composting and Water Quality, Oregon State Extension 2013 https://catalog.extension. oregonstate.edu/em9053
Extension Backyard Composting, Washington State Extension, 2017 https://s3.wp.wsu.edu/uploads/ sites/2056/2019/04/eb1784e-Backyard-Composting. pdf
Soil Fertility in Organic Systems: A Guide for Gardeners and Small Acreage Farmers. Washington State University Extension Publication PNW646, 2013 http://cru.cahe.wsu.edu/CEPublications/ PNW646/PNW646.pdf
No Turn Cold Composting, Oregon State University Extension https://extension.oregonstate.edu/ gardening/techniques/no-turn-cold-composting
WSU Compost Mix Calculator https://puyallup.wsu. edu/soils/compost-mix-calculator/
Marriott and Zaborski. 2015. Making and Using Compost for Organic Farming.
Rynk. 1992. On-Farm Composting Handbook
Sideman. 2006. Composting in the Back Yard or on a Small Farm
Smith. 2019. Composting in the Home Garden, University of Illinois Extension
Smith and Friend. 2019. Composting for the Homeowner, University of Illinois Extension Oregon