Technologies Turn Manure into Fertilizer, Energy and Water

Primary agriculture is responsible for more than 10 per cent of the total greenhouse gas emissions caused by human activities. It is estimated that up to 40 per cent of these farming-related emissions come from the production of livestock, including manure stored in open-air earthen storage areas or applied to the land as fertilizer. Untreated sewage that is used as fertilizer may also contaminate groundwater and nearby lakes and rivers.

The growing number of concentrated hog-feeding operations that have sprung up across Canada in recent years—particularly in the prairies and central Canada—has increased concerns over the environmental impacts of pig manure. In 2000 alone, approximately 20 million hogs were slaughtered in Canada, and the market opportunity exists for the industry to triple in size over the next decade.

To help hog producers tackle these issues, a group of federal, provincial and private-sector partners is demonstrating some simple and cost-effective manure treatment technologies on farms in Western Canada. The $800,000 program, which involves assessing the impact of new technologies on odour, emissions, soil and water quality, nutrient retention, and volume reduction, is managed by the Canadian Environmental Technology Advancement Corporation—a not-for-profit corporation established by Environment Canada to help small and medium-sized enterprises commercialize environmental technologies. Nearly 25 per cent of the funding is being provided by the Technology Early Action Measures component of the federal Climate Change Action Fund.

A liquid-solid separation system implemented last December has resulted in a noticeable reduction in odour at one test site. Manure is drawn along a conveyor belt over a screen, and rotating paddles are used to separate the solids from the liquids. The solids are then composted and the liquids can be treated and used to flush barn storage areas. Flushing helps prevent the manure from decomposing anaerobically or without oxygen—the process responsible for creating odour and greenhouse gas emissions. The next step will be to quantify the results through sampling and analysis.

In October 2000, a continuous agitation system was put in place at another test site that uses electrically powered mills to circulate liquid manure. The mills float on the surface of a manure storage lagoon, and have impellers below that rotate the solids in the slurry. This prevents the solids from settling on the bottom and introduces oxygen into the top layers—thus speeding aerobic decomposition. Consistent solid suspension also allows the manure to be more readily removed for application to the land. Now that the ice on the surface of the lagoon has melted, scientists will conduct a profile of nutrients, bacteria and solids at different levels, to determine the mills' effectiveness.

Tests carried out last fall confirmed the usefulness of a new mobile near-infrared spectroscopy instrument that can determine quantities of 22 different nutrients in hog manure in about two minutes—a vast improvement over previous methods in which samples were analyzed in a laboratory, with results available in a week to 10 days. Knowing these values enables producers to match nutrients with soil requirements, and helps to prevent possible over-fertilization.

Pilot projects will soon be launched to test two enclosed digestor systems—an aerobic system that reduces volume, odour and emissions and produces potable water, and an anaerobic system that creates methane for the production of heat or electricity. Still under formulation is a closed-loop system that separates solids and liquids, removes the ammonia and potassium nutrients, treats the water for drinking and other uses, dries the solids, and re-adds the nutrients to enrich the fertilizer value.

If the use of such technologies becomes more widespread and is applied to cattle, sheep and other livestock as well as hogs, scientists estimate that current greenhouse gas emissions from livestock manure could be reduced by as much as 50 per cent, or 320 kilotonnes per year.

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