A few years ago I was introduced to composting, the process of using the billions of bacteria around us to convert raw organic mixtures to soil.
Advice I have received says the organic matter needs a 20:1 (optimum) carbon-to-nitrogen ratio. Compost can be made with as low as 17:1 and as high as 27:1, but experts say higher or lower will slow the process. Most farm animal manure falls nicely into the proper ratio.
These bacteria are ‘aerobes’ — they need oxygen to perform, so if the material is too wet it can slow the process. Not much composting happens in a sloppy corral, or conversely in a dry manure pile, but if you aerate a pile thoroughly, it will soon start to heat. If you’ve seen manure piles steaming in the rain or snow, you’ve seen the process in action.
About 21 C is an ideal ambient temperature. Frozen material will not support bacterial growth, however, the sugar beet processing plant in Taber, Alberta was able to stimulate composting activity under cold conditions.
A compost aerator and tractor was delivered in March and set to work on wet beet pulp and tailings, consisting of weeds and beet top scraps. These materials had been dumped in long piles or windrows about eight feet wide and three feet high. These windrows had not completely frozen, so it worked well. Once they started turning the piles, they began to heat and by the end of April had turned to compost, which the plant sold — and pretty fast. Other companies and many municipalities now operate successful year-round composting operations with household waste, lawn clippings and other organic materials.
With larger volumes of material, many work with six-to 10-foot high windrows, which are turned by larger aerators which straddle the rows. I’ve heard that year-round composting is common in Nebraska feedlots and dairies too.
Steps to composting
- Make windrows and aerate them. Manure can be windrowed with a tractor and front-end loader, but the objective is to break up clumps to achieve a fairly fine-textured particle size. Commercially available rotary aerators or turners are designed to break down material and introduce oxygen as paddles or spikes work through the pile. There are four or five manufacturers of compost aerating/turning equipment with paddles on a turning drum. They turn just fast enough (about 200 r.p.m.) to lift the material and set it over to the side.
- Sprinkle with water if too dry. You want it moist, but not sloppy. Wet manure, once it is turned, will dry out on its own in a few hours.
- Use a thermometer to check the temperature inside the pile daily. Check the windrow in several locations and record temperatures to determine an average.
- As material heats up to 60 to 65 C (140-150 F) aerate the windrow again. Don’t let temperatures rise to 72 C (163 F) or higher for that will kill the “worker bacteria.” You don’t want that! I have been told that three days of compost temperatures of 55 C (130 F) will kill E.coli bacteria.
- Composting material may need to be aerated four to six times in total. The offset machines will roll the windrow over, blending in the cold, dried outside particles of manure to the outside, so they get a chance to be ‘cooked.’ (“Equal Opportunity,” like Corb Lund says in his song “The Truck Got Stuck”) With non-offset machines it may take a bit more work to move or blend materials on the outside edge of the windrow into the middle.
When the material in the windrow smells like soil, you’re done! Once the four- to six-week “cooking” process is done, the material no longer has a bad smell even if it gets wet. The nitrogen is held in place. When the compost is applied on the land the nitrogen will be released into the ground at a rate of approximately eight to 10 per cent per year. Research has shown that up to 70 per cent of nitrogen can be lost from surface-applied raw material that is not incorporated into the soil. The compost itself will lose some nitrogen with different research showing a range of 20 to 40 per cent. Even an average loss of 30 per cent it is still a considerable improvement over the risk of losing 70 per cent with raw manure.
With properly composted material flies and fly larvae shouldn’t be an issue. Flies can develop resistance to sprays, but not to heat.
What about economics
Efforts to compost have to provide a payback in some respect, or as the common catchphrase today says “it won’t be sustainable.”
One of the larger compost equipment manufactures, Brown Bear Manufacturing of Iowa, estimates US$7 to $10 per ton of compost — perhaps C$8 to $12 here on the Prairies or B.C.
Our cost to spread raw manure in southern Alberta’s feedlot alley is somewhere around $8.50 to $15.50 per ton. Diesel costs are around $1.15 per litre while tandem trucks haul about 10 tons per load. If fields are close to the compost source you can get more loads per hour.
I found corral cleaners will charge between $85 to $155 per hour depending on how much equipment they put on a job. Tandem manure spreader trucks can haul about 10 tons of manure per load. It’s reasonable to assume that you can cover from 1/4 to two acres per load, which depending on your needs would apply 20 to five tons of compost per acre respectively.
There is a risk of nitrogen losses with both surface-applied raw manure and compost, however losses appear to be considerably less with compost.
With raw manure applied at a rate of 10 tons per acre, with a potential loss of 60 per cent nitrogen, that works out to about 161 lbs. of N per acre or 25,728 lbs. N loss per quarter section. With nitrogen price estimates in early 2018 of $440 to $490 per tonne the loss has a potential value of about $11,165 per quarter section.
It you estimate nitrogen losses with compost at about 30 per cent (or about half of raw manure) that represents as savings of about $5,500 per quarter section. Over a whole section (640 acres) that represents a total value of about $22,000 — roughly half the cost of a compost windrow turner/aerator. So while figures will vary depending on each farm operation, it appears it would be fairly easy to recover compost equipment costs over one to two seasons.
- Compost shrinks to about half the weight and half the volume of manure, cutting the spreading time and costs roughly in half.
- Since the nitrogen held in compost is released slowly (eight to 10 per cent per year) it provides a “long-term investment” toward crop nutrients.
- Compost also adds organic matter to the soil, improving tilth and moisture-holding capacity.
- High composting temperatures kill weed seeds, helping to reduce herbicide costs.
- The composting process greatly reduces the environment for flies, helping to reduce the number of those pests around the yard and household.
Compost aerating can also be done with a regular front-end loader, but the grinding/fluffing (oxygenating) part isn’t very well done and there is also wear and tear on the loader. Ideally, each piece of manure needs to have contact with oxygen so the bacteria are fed properly. A loader just can’t do it quite right. I like the idea of a machine that moves along, using rotary action, chewing the manure into uniform 1/2- to one-inch pieces, hour after hour.
With larger volumes of manure you need an outside yard, but manure can also be composted inside a barn. Brown Bear does make smaller compost turners that can be mounted on a skid steer or compact tractor with three-point hitch. Those machines cost US$23,000 and do an eight-foot wide swath. They weigh 2,000 lbs. and need a 35- to 45-gpm Hyflo hydraulic system. There is an available PTO-operated pump, for compact tractors that don’t have the Hyflo hydraulic capacity built in.
For composting in outside yards or in corrals, Brown Bear makes a three-point hitch mounted unit (PTA35) costing US$45,000. It takes a 10-foot swath and leaves a three- to four-foot high windrow. These turners require a three-point hitch, IVT or creeper gear, and 120 to 160 hp. There are lots of these machines powered by the Ford New Holland TV140. Brown Bear also has larger units.
If you are interested in more information on the Brown Bear equipment line contact the Canadian distributor, K Pederson Equipment in Rockyford, Alberta, at (403) 655-2494 or visit the Brown Bear website.