Managing Stable Waste by Composting

March 2003

Prepared by: Basil Bactawar  MSc., Livestock Industry Development Specialist,
British Columbia Ministry of Agriculture and Lands

The challenge

The horse population in British Columbia is estimated to be about 90,000. About 30,000 of those are found in the Lower Mainland and 24,000 in the Okanagan. A mature horse produces about 2 cubic feet of manure and bedding. This is equivalent to about 40 kilograms of manure and soiled bedding daily. It is estimated that about 1200 tonnes of stable wastes are produced daily in the Lower Mainland.

Generally, livestock manure with low C:N ratio (20:1 or lower) can be used to supplement nutrient requirements and enhance crop growth. Most stables in the Lower Mainland use sawdust, wood shavings or a combination of both as bedding which results in higher C:N ratios. These C:N ratios, above 50:1, limit the direct use of raw stable waste as fertilizer. Waste with high C:N ratios can induce nitrogen deficiency in growing crops since the microbes in the waste compete with the plant roots for limited nitrogen.

A study commissioned by Horse Council BC (HCBC) in collaboration with BC Ministry of Agriculture and Lands and Agri-Food Canada (Pacific Agri-Food Research Centre - Agassiz) showed that stable waste could be composted successfully. This provides an option in dealing with the high volumes of manure on farms and equestrian centres. The study above will be referred to as HCBC Study in this factsheet.

The questions and answers that fallow are a general guide when composting stable waste. Horse owners are advised to supplement the information on this factsheet with information from the B.C Agricultural Composting Handbook. It is available on the Internet at http://www.agf.gov.bc.ca/resmgmt/publist/Waste_Mgmt.htm.

How do I clean my stable so that the waste can compost?

Daily removal of soiled bedding and manure is the most common cleaning practice in stables. This is followed by the addition of fresh sawdust, wood shavings or a combination of both. By using daily removal, the stable waste would contain approximately equal proportion of manure and urine soiled bedding. This mixture of manure and soiled bedding composts well.

How do I construct my composting pile?

Composting can be done in various ways, and the size of pile is not critical. In general, composting bins or piles should be larger than 3ft x 3ft x 3ft, but not grater than 10ft wide and 5ft high to allow for aeration. In the Coastal Regions, compost piles or bins should be covered during winter. Refer to BC Agricultural Composting Handbook for more detail

How do I know that the composting process is taking place?

When the pile is heated up, it is an indication that composting is happening. Pile temperatures between 32^oC and 60^oC indicate rapid composting. The ideal range for composting is 35^oC and 55^oC. You may be able to see water vapor escaping from the pile when it is heating. A temperature probe or soil thermometer should be used to keep track of pile temperature. Figure 1. shows the average temperature reached for four types of windrow composting during HCBC study at Pacific Agri-Food Research Centre,

In the legend, SPPA means static pile passive aeration, TP is turn pile, SPC is static pile covered and SPU means static pile uncovered. Ambient is the air temperature outside the piles.

Do I need to add anything to start the composting process?

As mentioned previously, if cleaning of the stable is done to achieve about equal amounts of manure and soiled bedding, the addition of a nitrogen source is not necessary. It is advisable to add some mature compost as you build a new pile because it provides microorganisms that would stimulate the composting process.

Do I need to add water to the composting pile?

If the raw compost materials feel like a freshly wrung out sponge, the pile likely has the proper amount of moisture. If water runs out of the pile or you can squeeze water from a handful of compost, then it is too wet. If no moisture appears on your hand when you squeeze the raw materials, then the pile is too dry.  Stable waste composted well in the HCBC study without the addition of water. The starting material had moisture content of about 66 percent, and this study was done during the cold months of the year. If composting is done during the warmer months of the year, the pile may lose moisture, and perhaps the addition of water may be required to maintain moisture contents above 40 percent for efficient composting.  Methods for determining moisture content of compost can be found in B.C. Agricultural Composting Handbook.

Do I need to turn the compost?

Once the compost pile is constructed (mixing manure and bedding materials), it should begin to compost, but turning it can be beneficial. Manure and bedding dumped in a pile will compost slowly. To achieve more uniform composting, turn the pile within two to four weeks of building the pile. More turning may not be required. This depends on how well the material is composting (moisture, aeration and C:N ratio) Turning the composting pile after that is a judgement call and the decision to do so would be based on available farm resources(labour,equipment,etc.

How long does the composting process take?

In the HCBC Study, composting was completed between 40-45 days when the temperature of the composting pile approached ambient temperature as can be seen in Figure 1. The compost was allowed to cure for another 45 days. Mature compost was ready in about 90 days or 3 months. It may take longer if some composting conditions are not fully met.

Would composting reduce the volume of the initial waste?

Yes. You would expect the composting pile to be reduced to about half of its initial volume. General reduction in stable waste volume after composting is desirable because less space would be required for storage, and it would be less costly to haul compost than stable waste.

Would compost reduce the parasitic transmission potential of stable waste?

Strongyles are the most abundant roundworm found in horses and ponies. Three previous studies have shown that temperatures above 45^oC adversely affect strongyles eggs hatchability and larval survival. HCBC Study showed that there was a significant reduction of larvae 56 days after the start of composting. In the present study, the temperature in all piles reached values higher than 45^oC, and lasted close to three weeks. Therefore it is reasonable to assume that composting is likely to reduce the parasitic transmission potential of stable waste.

Acknowledgment

Most of the contents of this factsheet were taken from the report on the Composting of Stable Waste, a project was funded by the British Columbia Agriculture Environment Partner Initiative, BC Agriculture Council. 

This document was reviewed by Geoff Hughes-Game, BC Ministry of Agriculture and Lands.

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