Turning Animal Waste into Electricity

In keeping with the old saying "Waste not, want not", an Alberta farm is the future site of IMUS – a new technology that will turn manure into a source of electricity, heat, fertilizer and reusable water – all while reducing greenhouse gas emissions and other environmental impacts.

The Integrated Manure Utilization System — known as IMUS — is being constructed at Highland Feeders in Vegreville, Alberta, one of the province's largest feedlots. The system is capable of treating manure from cattle, dairy cows, chickens and pigs. The pilot-scale unit will use manure from 7 500 head of cattle, which is less than a quarter of the 37 000 head of cattle at the feedlot. Construction is expected to be completed in June 2004 at which time it will begin generating electricity.

The technologies that make up the IMUS unit are not new, however, for the first time these technologies are being integrated into a single system. Moreover, integrating them has resulted in innovative developments of some of the technologies.

How it works:

Manure is taken to a large container called a hopper, where unwanted materials such as sand and dirt are removed. From there the mixture goes into an anaerobic digester specially designed to maximize the production of methane (natural gas) from the decomposition of the manure. Anaerobic means it does not use oxygen, and therefore generates methane and not carbon dioxide.

The methane gas is then piped to a co-generation system, an electrical-mechanical system that simultaneously produces both electricity and heat. In this pilot project, the manure from 7 500 head of cattle will produce about one megawatt of electricity. In three or four years, the scale of the project will be increased to produce up to three megawatts of electricity — enough power to supply a town of 5 000 people. It is conceivable that a larger IMUS plant could produce enough power to sell to a local electric utility.

Next, the mixture is put through a centrifuge and is separated into solid and liquid. At this point, lime is added to the liquid to remove phosphates and nitrogen. The removed phosphates and nitrogen are added into the solid to produce bio-based fertilizer that is formulated into granules or pellets, depending on the desired end use.

The liquid that results from the process is sent to a water treatment facility which will strip out any ammonia and adjust the pH level. Once treated, this water will be used for crop irrigation on the farm.

Importance of IMUS

Back when farms were family owned and operated, the relatively small volume of animal manure generated could simply be collected, stored for short periods, and spread on the fields as fertilizer.

Today, as the livestock industry expands in Canada and large conglomerates predominate, public concern is growing over the risks associated with the economic, social and environmental impacts of disposing of manure. For example, manure used on fields as fertilizer can create greenhouse gases, nitrous oxide and ammonia. If it is spread on a field, as opposed to being injected into the soil, there is also the risk that rain will wash it into nearby waters, where it can promote the growth of algae and unwanted bacteria and, potentially contaminate the drinking water.