Is AD Right For Me?
The opportunities for developing on-farm anaerobic digestion systems are growing. However, before deciding whether to build an anaerobic digestion system, the 10 key questions below must be answered (see also the document on this page). Only potential anaerobic digestion projects that answer ‘yes’ to the majority of these questions should consider investing the time and money to build an anaerobic digestion system.
10 key questions:
1. Feedstock: do you have sufficient feedstock for your anaerobic digestion system? Y / N
Anaerobic digestion systems require a certain volume of feedstock to be economically viable. While this may change with advancements in technology and energy contracts, a general rule of thumb is that a minimum 7,000 – 15,000 tonnes/year of feedstock is required (depending upon type of feedstock).
- For example:
- A dairy farm milking 100 – 150 milking cows (roughly 5,000 tonnes manure/year) would need to source 25% very high-energy off-farm feedstock (such as dough) to ensure it produces the minimum amount of biogas necessary to be economically feasible.
- If the dairy farm milks 250 – 300 cows (roughly 12,000 tonnes manure/year), it would only need 25% medium-energy off-farm waste (such as silage or food waste) to ensure it produces the minimum amount of biogas necessary to be economically feasible.
While neighbouring farms can combine their feedstock into one project, it must be possible to pipe this feedstock or cheaply transport it over very short distances (a few km). If this is not possible, it is likely that the cost of transportation will be too high.
2. Cost: Are you willing to spend $1 - $4 million on your anaerobic digestion project? Y / N
Anaerobic digestion systems require significant investment. Based on experiences across North America, the average system in BC will cost $1 - $4 million. A good rule of thumb is that capital costs of an anaerobic digester system are $3,000-12,000 per installed kW (depending upon size). Thus, while a 100 kW system will likely cost in the region of $1 - $1.2 million, a 500kW system will likely cost in the region of $2 - $2.5 million.
Despite the significant investment, a properly planned and executed anaerobic digestion system will not only pay for itself, but will generate meaningful income for your farm/facility.
3. Time: Do you have enough time to invest in building and running your anaerobic digestion system? Y / N
As with any on-farm construction project, you have several options as the project owner. You can oversee construction yourself, hire a general contractor to oversee the construction, or opt for a design-build system in which your involvement is minimized. While the cost of removing yourself from construction may be higher, the risk of cost and schedule overruns is decreased.
Regardless of the option you select, you will still be involved during construction (which can take anywhere from 6 months to 2 years), as you will need to understand how to operate and maintain your anaerobic digestion system once it is functioning. Once operational, due to automation, your anaerobic digestion system will likely require an average daily interaction of 30 – 60 minutes.
4. Grid interconnection: Are you close enough to the BC Hydro or Terasen gas grid to sell your energy? Y / N
BC Hydro requires that you have a three-phase power line on your property with which to connect your anaerobic digestion system if it is over 100kW. For projects under 50kW, a single-phase power line is adequate, while for projects of 50- 100kW, a single phase power line may be adequate (this depends upon voltage level, feeder characteristics, point of interconnection, etc. To learn more about 50- 100kW, you will need to contact BC Hydro directly). If you do not have three-phase power, you must pay to have it built. While there is no general rule of thumb for this, a 1 – 2 km extension can cost as much as $1 million.
If your property is serviced by Terasen gas, you may be able to upgrade the biogas to biomethane and sell it to Terasen. However, due to the cost of the biogas upgrading equipment, only large projects (those generate 500kW electricity equivalent or more) will likely be able to afford this option.
5. Space: Do you have enough space to build your anaerobic digestion system? Y / N
While anaerobic digestion systems do not have a particularly large footprint, some land is nevertheless required to build on. To ensure that you have adequate space, you will need a minimum of 1 acre allocated to your project. This requirement may increase if your anaerobic digestion system involves multiple digesters or the need for additional digestate storage.
Furthermore, to ensure that project costs are reasonable, this land must be in close proximity to both your feedstock and grid interconnection point.
6. Storage and land: Do you have enough manure storage to store, and land to land apply the digestate from your anaerobic digestion system? Y / N
If you are a dairy or hog farmer using only manure from your farm, it is likely that you will already have enough storage capacity for the digestate. However, if you are a poultry or other type of farmer, or if you bring feedstock onto your farm from neighbouring farms, you may need to build/expand your manure storage. Furthermore, anyone building an anaerobic digestion system must follow a nutrient management plan. This plan may mean that you have to find somewhere else to spread some of the digestate from your anaerobic digestion system .
7. Farm set-up: Is your farm well set-up for your anaerobic digestion system? Y / N
It is easier to install anaerobic digestion systems on farms that have alley scrappers rather than slatted barns or flush systems. Furthermore, anaerobic digestion systems operate much more efficient on farms that use straw for animal bedding, rather than sand or sawdust. While having slatted barns/alley scrappers and bedding on sand/sawdust does not mean that you cannot build an anaerobic digestion system on your farm (as manure collection issues can be overcome and bedding can be changed), it may add complications that could increase project costs.
To determine the suitability of your specific farm operation, it is recommended that you contact a professional consultant.
8. Co-products: do you have use for excess heat or nutrients from your anaerobic digestion system? Y / N
When burning biogas to produce electricity, roughly 50% of the energy is converted into heat (thus a 50kW combined heat and power system will generate roughly 60 -70 kW heat). While some of this heat is used to heat the anaerobic digestion system, the majority will be vented to the atmosphere unless there is a large heat load/need less than 1 – 2 km away. While venting is not detrimental, the project will generate more meaningful income for your farm/facility if the majority of the excess heat is utilized.
The same is also true for nutrients. Because the anaerobic digestion process results in a dramatic improvement in the availability of nutrients, digestate can replace synthetic fertilizer. This will generate more meaningful income for your farm/facility.
9. Operational changes: do you anticipate any changes to your current operations? (e.g., herd expansion, new barn, production change, etc.) Y / N
While it is difficult to state if these changes will have a positive or negative impact on your anaerobic digestion project, it is important to keep these in mind as once built, the anaerobic digestion system will be a part of your farm/facility operation for 20 years or more.
10. Off-farm feedstock: are you prepared to use off-farm feedstock in your anaerobic digestion system? Y / N
While you may have an aversion to bringing off-farm feedstock onto your farm (e.g., food processing and restaurant waste, source separated organic waste, etc.), it is very difficult to build an economically feasible anaerobic digestion system in BC without some (10% – 25% total feedstock volume) off-farm feedstock. The volume and type of off-farm feedstock required will vary depending upon the volume of on-farm feedstock availability. For an example, see Question 1 or the ‘Feedstock’ page.
