Trisha
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While the others have mentioned many parameters to watch during normal operations, there are some parameters that can be useful to measure in digester upset conditions. These can help gather information to conduct a root cause analysis for the upset.
- Speciated Volatile Fatty Acids
- Speciated Long-Chain Fatty Acids
- Volatile Solids Reduction (VSR)
- BOD
- Total Phosphorus
- Ortho-phosphorus
- Total Metals
- Dissolved Metals
- Food to Microorganism ratio (F:M)
Often however, the individual values of any parameter are not as important as the overall trend of each. Especially in the case where the digester biology has acclimated to conditions that would be inhibitory for other digesters if it occurred suddenly.
For daily operations, watching changes in operating parameters is key. Biological systems like slow, gradual changes. Some metrics and reasoning behind them are mentioned in our attached article.
Need help understanding digester performance metrics? Email me at trisha.aldovino@AzuraAssociates.com
Top 10 Things to Make Your Digester Biology Happy – AZURA
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Top 10 Things to Make Your Digester Biology Happy – AZURA
Top 10 Things to Make Your Digester Biology Happy – AZURA
If there’s a buyer located close to the digester, such as a beverage company or greenhouse, biogenic CO₂ can become a valuable revenue stream. However, transporting CO₂ over long distances is expensive, so its use is typically limited to nearby applications. Additionally, you would have to make sure that you have enough feedstock to match the volume of CO₂ you want to use.
There has been interest in using biogenic CO₂ for carbonated beverages, but this can raise concerns. Even if the gas is purified to food-grade standards, some consumers or companies may still have reservations about using CO₂ derived from organic waste like manure due to an “ick factor”. These perceptions can influence market acceptance, even when the product is technically safe and clean.
There are industrial RNG plants that successfully manage odour. In Elmira, Ontario, Canada there is a large facility that receives food waste and highly contaminated feedstocks. It is built right by neighbourhoods, but it receives no odour complaints. The company prioritizes odor management, both in their engineering design and in operations.
Odour emanates from the feedstock itself, as well as the digestate if the biology in the digester is upset. No odour should come from the digester itself because it is a gas tight system. Odour risk is higher in the feedstock receiving and digestate storage areas. But I would focus on the receiving area for sure.
In the receiving area, some things you can do:
- Receive material indoors
- The door to the receiving area only opens when there is a truck unloading feedstock
- Keep the indoor receiving area at a negative/vacuum pressure so that when the door opens, the air flows in from the outside instead of odours escaping out
- If you have a receiving pit, invest in a cover
The easiest engineering solution for digestate odour would be to store it in a covered tank. Digestate should not have odours. Digestate odour is a sign of biological upset. While Azura doesn’t currently have an article on odour, we do have an article on how to keep your digester biology happy to reduce odour risk from your digestate: https://azuraassociates.com/digester-biology-top-10/
Looking for ways to manage odour (beyond just equipment solutions)? Email me at trisha.aldovino@AzuraAssociates.com and we can discuss how to mitigate these risks for your project.
azuraassociates.com
Top 10 Things to Make Your Digester Biology Happy – AZURA
Top 10 Things to Make Your Digester Biology Happy – AZURA
Major risk during construction – TSSA Compliance
In Azura’s experience, one of the most significant and underestimated risks in biogas project construction occurs after mechanical completion: obtaining Technical Standards and Safety Authority (TSSA’s) certification. Without this approval, biogas facilities cannot legally operate. We’ve witnessed several large digester projects across Canada face months, and in some cases over a year, of delays due to unresolved TSSA compliance issues.
This risk is especially pronounced when partnering with overseas technology providers who may be unfamiliar with Canada’s national biogas code and highly specific certification requirements. Developers are often caught off guard by the time and effort required to resolve compliance issues identified during inspection. If your project still in the development phase, it’s essential to ask your technology provider about their experience with TSSA and whether they have local resources to support compliance.
Proceeding without a local EPC or technology provider experienced with the Canadian Biogas Code introduces significant risk to your project’s schedule and cost.
Major risk during Startup and Commissioning – Acceptance Testing
There are two major risks during construction that we at Azura have witnessed:
- Startup and Commissioning going much more slowly than expected (weeks or months of delay) – see our article here: Digester Startup and Commissioning – AZURA
- Technical issues during acceptance testing that can lead to legal disputes
To expand on the second point, Azura’s work as an expert on legal disputes often arise during the “handover” stage. The EPC and technology vendors guarantee that their equipment work, but the owner is left with a digester system that doesn’t produce as much gas as they expected.
Top performance risks
As for performance risks, the top biological issues that occur during operations are:
- Foaming leading to low or no biogas – see our article here: Why Is There Foam in My Digester? – AZURA
- Grit accumulation leading to costly maintenance and clean-up
- Ammonia inhibition or toxicity – see our YouTube video on how to manage this in operations: How to Manage Ammonia in your Biodigester
In Azura’s experience, almost every digester has had one or more of these issues during its operational lifetime.
Looking for ways to manage these risks? Email me at trisha.aldovino@AzuraAssociates.com and we can discuss how to mitigate these risks for your project.
For guidance with your specific project
If you need help with evaluating different feedstocks for your project, please email me at trisha.aldovino@AzuraAssociates.com or peter.quosai@AzuraAssociates.com and I can set you up with our bioprocess experts who can help you understand the opportunities and costs for each feedstock.