Biogas (Anaerobic Digestion)
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When bacteria consume and break down biological feedstocks, like manure, in an oxygen-free environment, a process called anaerobic digestion occurs. This process produce a mix of methane and carbon dioxide called biogas and a nutrient-rich slurry.
The biogas can be used to run a generator to create electricity and heat, burned as a fuel in a boiler or furnace, or cleaned and upgraded for use as a natural gas replacement. The whole system - which consumes and treats feedstocks, produces biogas and converts it into a useable energy form - is called an anaerobic digestion system or biogas system.
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.
There are several digester designs on the market, with configurations that vary according to operating temperature, processing time, size, number of digestion vessels and type of throughput (continuous flow, plug flow or batch). For more information on the technology, see the Ministry of Agriculture, Food and Rural Affairs' (OMAFRA) Factsheet titled Anaerobic Digestion Basics.
Ontario is a biogas leader in North America, with over 30 biogas facilities operating in 2014 on farms and at centralized locations. Prior to 2000, farm-based anaerobic digestion served primarily as a method of treating manure. It is now attracting interest as a way of generating renewable energy, especially with revenue opportunities from electricity sales.
The viability of an anaerobic digestion system will depend on your access to feedstock and your ability to connect to the electrical or natural gas grids. You may need to bring in off-farm feedstocks to create the right mix and volume of materials. Mixing off-farm feedstocks can boost biogas production to make a system large enough to be economically viable.
Keep in mind that anaerobic digestion may not be cost-effective at a small scale. You can pursue it simply as a method of manure treatment since digestion is an effective way to reduce odours and pathogens. See OMAFRA's factsheet Biogas Incentives and Requirements: Building a Farm-Based Biogas System in Ontario for information on:
The University of Guelph's anaerobic digestion calculator estimates the capital costs for a larger anaerobic digestion system to be $3,000-$8,000 per installed kilowatt (kW). Smaller systems (less than 100 kW electrical capacity) may cost more. A digester should operate up to 8,000 hours per year, although some operators may run less and focus on peak power production times. The The Independent Electricity System Operator administers the Feed-In Tariff (FIT) Program that offers long-term contracts to successful applicants for electricity generated from eligible renewable sources, for projects larger than 10 kW and generally for projects up to 500 kW. Details on the FIT Program, including the prices paid for electricity generated from renewable sources, are available from the Independent Electricity System Operator.
For proposed biogas electricity projects generally larger than 500 kW, there is a Large Renewable Procurement (LRP) process - please see Independent Electricity System Operator's LRP website for details.
A dairy herd of 100 cows produces enough manure to generate a continuous 25 to 30 kW electrical output from the manure. Adding 50 per cent of off-farm feedstocks, such as grease trap waste from restaurants, can increase the electrical output anywhere from three to 10 times the original production.
See the Energy Yields from a Farm-Based Anaerobic Digestion System web page on the OMAFRA website for more information.
Designing, constructing and operating an anaerobic digestion system can bring significant new opportunities to a farm operation, but also involves complexity and challenges.
Contact your local municipality to find out what permits and approvals are required. It may be advantageous to get municipal council support for your biogas system before applying to the FIT Program.
There are three primary routes to having biogas systems approved to receive off-farm feedstocks in Ontario:
There is no formalized approval mechanism for non-electricity biogas systems using only exempt wastes, such as agricultural waste, although many construction and safety rules and regulations continue to apply.
If you're siting a biogas system as part of a livestock facility, OMAFRA's Minimum Distance Separation (MDS) Formulae apply. MDS aims to minimize nuisance complaints associated with livestock production. There are also setback distance requirements if you're siting a biogas system that is not part of a livestock facility. This is outlined in the Nutrient Management Act, under Ontario Regulation 267/03.
OMAFRA has more information on the approvals for biogas systems:
Publications and Websites
University of Guelph's anaerobic digestion calculator helps to determine if an anaerobic digester project is economically viable.
For more information:
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