GHGMP Project Reports by Region

Composted manure has a good fit with organic growers

Urban and rural partners join forces to solve "waste" management issues

A unique composting project that makes good use of a growing supply of poultry manure and yard wastes could be an important nutrient source for organic crop producers in B.C.'s Lower Mainland.

The project, aimed at improved nutrient management and reduced greenhouse gas emissions, involves the Delta Farmer's Institute and City of Vancouver, along with other funding bodies. Composted yard trimmings from the city are incorporated in the composting process for poultry manure. The end product - a blended compost - can be used by organic growers who produce a range of horticultural crops. The project is one of a series of demonstration projects partially funded by the federal Greenhouse Gas Mitigation Program (GHGMP).

"Research continues to fine-tune the composting process and application rates," says Dr. Art Bomke, a soil scientist and associate professor of agroecology at the University of British Columbia (UBC) in Vancouver. "The system is producing a good product now, but it can be improved."

The overall objective is to minimize the social and environmental impact of B.C.'s intensive poultry industry by preventing over-application of manure nutrients while maintaining sustainable crop production systems.

Combining composts

In the research project launched last year, composted yard trimmings from the City of Vancouver are incorporated into the poultry manure composting process. About 40,000 tonnes of trimmings, which include grass clippings, leaves and woody prunings, are hauled to the city landfill site in the municipality of Delta, put through a tub grinder and then composted in windrows. "It's a fairly low-tech process and the material contains a lot of woody material, so it's slow," says Paul Henderson, with the city landfill site.

After about one year, the mostly composted material is hauled to nearby farms where it is used to form the base on which windrowed piles of poultry manure can be composted. "The material is used to make a 30-centimetre deep base that can trap leachate from the poultry manure compost," says Bomke, noting that such a base is needed because of the area's high rainfall.

The dry poultry manure hauled from farms throughout the Lower Mainland is windrowed and turned at least five times over one month to complete the composting process. Once left to "cure," the windrow is covered with a layer of the yard trimming compost to protect it from the elements.

The finished composted product can be used by organic growers - and others - as a nutrient source.

More fine-tuning

While researchers know the basic composting process some fine-tuning is still needed.

One fine-tuning aspect involves increasing the carbon source in the compost. Carbon, which comes from sawdust and woodchips or straw if available, is a key element in successful composting. A proper ratio of carbon and nitrogen is needed for microbes to fully digest all the ammonia, which will then leave a stable form of nitrogen in the manure. If the process isn't completed, nitrogen can be lost to the atmosphere.

Poultry manure supplies a high nitrogen source, but is generally short on carbon for composting purposes, says Bomke. Much of the poultry litter comes from broiler and turkey operations where birds are raised on wood shavings.

In compost produced with low carbon sources, as much as 50 percent of nitrogen is lost in the form of ammonia and about 60 percent of carbon in the form of carbon dioxide is lost, says Bomke. With additional carbon, most of these compounds could be captured in the compost. Though forestry is a primary industry in B.C., there has been increasing demand for wood byproducts such as wood chips and sawdust for a range of uses.

"I believe the economics of the compost product supports sourcing wood fibre as an additional carbon source," says Bomke. He adds the yard trimming/manure combination makes an excellent compost. "It is a very uniform product from a nutrient standpoint with nitrogen and phosphorus levels in the manure component only fluctuating plus or minus 10 percent. It is almost as good as commercial fertilizer." Composting also reduces the total manure volume by about 60 percent, eliminates strong odours associated with land application of raw manure, and destroys most manure pathogens.

As the composting project continues in 2004, Bomke and the co-investigator on the project, Wayne Temple, a UBC Research Associate, will be researching the benefits of adding carbon, and looking at optimum compost application rates. Support for the project is provided by the UBC Agroecology Group, Agriculture and Environment Partnerships Initiative, Investment Agriculture Foundation, the City of Vancouver, Vancouver Foundation and the GHGMP.

Nutrient crunch

Finding creative ways to handle livestock manure is critical for British Columbia producers, says Bomke. Since dairy, poultry and hog operations import nearly all feedstuffs from outside of B.C., a large portion of nutrients used to produce crops on the Prairies is exported to the Lower Mainland region.

"All those nutrients end up here," says Bomke. "The nitrogen and phosphorus used to produce crops in Alberta and Saskatchewan, for example, is exported in the grain and is excreted in livestock manure here. Through compost and manure we are reusing the nutrients exported from Prairie farms."

The problem is that Lower Mainland agriculture is producing more manure than producers can use. "We have quite an excess of nutrients in the region," says Bomke. "We have to develop sustainable techniques that use what we can here and then export the rest." Along with composting, other techniques being considered include burning manure to produce heat for the greenhouse industry or developing biogas co-generation plants that use the methane from manure to produce electricity.

Composted manure is a good nutrient source for organic growers in particular. The high temperatures in properly composted manure kill all pathogens and other undesirable elements, making it a suitable nutrient source by international organic certification standards.

In the Delta area of B.C., the composted manure is used on a range of horticultural crops including sweet corn, bean, peas, potato and broccoli.

More information on the GHGMP is available on the Soil Conservation Council of Canada Web site at www.soilcc.ca.


Regional reports will be posted as information becomes available. Please check back regularly for updates.