Biogas (Anaerobic Digestion)

1. Description of the Technology
2. State of the Industry
3. Is Biogas Energy Right for Me?
4. Basic Numbers
5. Benefits, Drawbacks and Possible Pitfalls
6. Planning Issues and Regulations
7. Setting Up and Operating an Anaerobic Digester
8. Additional Resources

Description of the Technology

When organic material breaks down in an oxygen-free environment — a process called anaerobic digestion — it produces a mix of methane and carbon dioxide called biogas, as well as a nutrient-rich slurry.

That biogas, in turn, can be burned as a fuel in a boiler or furnace, used to run a generator to create electricity and heat, or cleaned and concentrated for use as a natural gas replacement.

Manure is usually the primary feedstock in farm-based systems, but many other materials can be digested, including food industry products and by-products, organic wastes from municipalities and energy crops such as corn silage, haylage and grasses

You'll find several digester models on the market, with designs that vary according to operating temperature, processing time, size, number of chambers and type of throughput (batch, continuous flow or plug flow).

State of the Industry

Although anaerobic digestion is widely used in Asia and parts of Europe, it is still relatively rare in North America. In the past, it served primarily as a method of treating manure, but now it is attracting interest as a way of generating renewable energy, especially as new technologies and control systems have improved performance.

Is Biogas Energy Right for Me?

The viability of a biogas system will depend on your access to materials: to create the right mix and volume, you may need to bring in materials from off-site.

Keep in mind that anaerobic digestion may not be cost-effective at a small scale, although you may wish to pursue it simply as a method of manure treatment.

Basic Numbers

The Ontario Power Authority estimates the capital costs for an anaerobic digestion system to be $2,400-6,200 per installed kilowatt.

Benefits, Drawbacks and Possible Pitfalls

Benefits:

• Changes the availability of nutrients in your manure, making the manure perform more like commercial fertilizer
• Reduces manure odour and pathogens
• Produces fuel that can be stored for use during peak power times or high-demand periods on the farm
• Can generate revenue through tipping fees from off-farm material

Drawbacks:

• Risk of odours if feedstocks are not managed properly
• The complex biological, mechanical and electrical systems require specialized knowledge and training

Possible Pitfalls:

• Operation and control can be complex: you need to achieve the right mix of material and the right temperature range to maximize digestion while avoiding problems like plugging, crusting and foaming
• Since anaerobic digesters are still relatively rare in Ontario, steps such as securing a building permit or insurance may take longer than expected
• Care must be taken in designing and managing biogas systems to deal with the moisture, sulphur compounds and other minor gases found in biogas

Planning Issues and Regulations

Contact your local municipality to find out what permits and approvals are required. Keep in mind that zoning changes may be necessary. You should also find out how a farm-based anaerobic digester will be assessed for property tax purposes.

If you're siting a biogas system at a livestock facility, you'll need to apply the Ontario Ministry of Agriculture, Food and Rural Affairs' Minimum Distance Separation Formulae.

Under recent changes to the Environmental Protection Act, you can receive up to 25 per cent by volume of off-farm materials at a farm-based digester without requiring a Certificate of Approval as a waste disposal site from the Ontario Ministry of Environment.

Projects greater than 5 MW may need to undergo an environmental screening process.

If you plan to connect your system to the power grid, there are additional requirements you'll need to meet.

Finally, if you are using biogas as a fuel on-site, your system must be approved by the Technical Standards and Safety Authority.

Setting Up and Operating an Anaerobic Digester

Setting up a digester requires construction and electrical skills, so consider hiring a qualified contractor.

Once the system is installed, it may take some experimenting to achieve the right mix of materials and the right temperature to maximize digestion. Expect digester maintenance to take roughly 15 to 60 minutes a day.

Additional Resources

Publications and Websites

The Ontario Ministry of Agriculture, Food and Rural Affairs has produced a number of publications on biogas, while the Integration of Renewable Energy on Farms website includes several pages of information on anaerobic digestion. As well, check the AgriEnergy Producers' Association of Ontario’s Resource Kit for AgriEnergy Projects.

Tools

FarmEnergyOnline.com offers a business plan for anaerobic digestion systems.

Associations

• Canadian Bioenergy Association
• Ontario Sustainable Energy Association