25 comments on Anaerobic Digestion (AD) in Ontario – A Regulatory Obstacle Course
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You would probably want at least a hundred milking cows. As an example, there is a local farm not far from here with 140 milking cows that runs a 50kW generator using manure alone. The net metering connection for that size generator is much simpler than would be the case for a larger system under the SOP. Many larger projects are planned - some tied to other endeavours such as ethanol production.
I'm afraid I can't answer your carbon tax question. The problem isn't really that AD would need a subsidy - the problem is that mains power in Ontario is essentially subsidized, making it difficult for alternatives to compete. The price AD would require to be viable is not that different from current electricity pool prices, and if natural gas shortages were to push up the price of power in a few years time then AD under a 20 year contract would look cheap. When you consider the externalities that AD addresses, it would look even cheaper.
Ranking the obstacles would be difficult. Probably getting a affordable grid connection regime up and running would be the first priority. Once the cost of grid connection was predictable and consistent, it would be much easier to estimate at what power purchase price projects would be viable.
Thanks again for a most informative posting, Stoneleigh. I note that you have set this discussion mostly in the context of dairy operations. Is there any reason AD is not applicable to feedlots?
AD can be used with various farming operations, but it is more compatible with some manure management systems than others. Total solids content is a very important parameter and different manure management systems produce waste at very different solids contents. I've added a figure to the story on this point (under The Benefits of Anaerobic Digestion) because I don't know how to put graphics in comments.
Essentially, there are different digester designs (covered lagoon - unheated and so not applicable to northern climates - complete mix and plug flow), each of which works with a different total solids content. Raw manure is excreted with a total solids contents of 8-25% depending on type of animal. For swine the figure would typically be 9.2-10%, for beef cattle 11.6-13.0%, for dairy cattle 11.6-12.5%, and for caged laying hens 25%. Manure can be diluted by process waters, misters, spilled drinking water or washing water, or it can be thickened by air drying or the addition of bedding materials. When designing a digester, all water in the manure-handling system and all processes affecting the total solids content of the resulting manure must be accounted for in order to choose the appropriate digester technology.
Flushed manure with less than 3% solids cannot be processed to produce energy in the heated digesters necessary in the Canadian climate. Complete mix digesters are suitable for slurry-based manure management systems, which result in manure with a total solids concentration of 3-10%. Plug flow digesters are used where the manure to be handled has a higher solids content, typically 11-13%, than for the complete mix design. Plug flow digesters are suitable for use on dairy farms as long as they do not use flush systems, but not for swine operations as the total solids content of swine manure is insufficient for this method of handling.