[Peter]

The technologies used for anaerobic digesters and landfills might be different because it is often beneficial to do some hydrogen sulfide treatment in the digester, while this level of control is not possible in a landfill.

Why is in-situ treatment beneficial?

In anaerobic digesters 6,000ppm H2S likely indicates high dissolved sulfide concentrations. Dissolved sulfides can inhibit anaerobic digestion -reducing biogas yields and throughput. Dissolved sulfides can also bind to trace metal nutrients and cause nutrient deficiencies.

What are in-situ treatment options?

Hydrogen sulphide can be consumed by sulfur oxidizing bacteria in the digester headspace or iron can be added to react with dissolved sulfides and prevent them from becoming gas. Air injection paired with a sulfur net inoculated with sulfur oxidizing bacteria can be one of the cheapest options however air injection can also make it more challenging to hit strict RNG quality targets.

With or without air injection iron can be added as iron chloride solution, iron oxide powder, or iron hydroxide powder to react with sulfide in the digester and quickly reduce sulfide concentrations in the biogas.

[Peter]

The challenges of poultry waste biogas systems are typically around excess ammonia, excess grit, and managing salt. Possible strategies can include:

– codigestion with watery feedstocks;

-codigestion with carbon rich feedstocks; and

-sidestream ammonia removal.

Ammonia is very concentrated in chicken manure and ammonia causes digester upset by inhibiting methanogens. For more on a ammonia check out our video on the topic – https://youtu.be/xva-OzOGFHg?si=SCxZ3K7hXRtWze6c

[Peter]

@gazeol-renouvelable_hatem Makes a good point about “odor, safety, or visual impacts are being managed with proven solutions.”

It is not enough to just engage the public – the odor solutions need to work. There are many plants working with very little odor because of investments made in feedstock receiving, digestate management, and diligent process operations. When considering the cost of such measures remember there is only one chance to make a good first impression with the community.

[Peter]

Many digester owners select feedstocks based on two main factors: fuel value (how much methane or energy the material can produce) and economics (hauling costs, contract length, tipping fees, etc.). However, as we see it, making decisions solely on these criteria can be short-sighted.

We encourage clients to take a more holistic approach by balancing fuel value with other key characteristics such as degradability, nutritional content, contamination levels, and how each of these factors interacts with the specific design and biology of their digester system. At Azura, we’ve seen firsthand how a poor match between feedstock and system can lead to operational disruptions, reduced gas yields, and dead bugs.

To assess fuel potential, the Biomethane Potential (BMP) test is the industry standard. However, BMP tests are time-consuming and costly, which may not make sense for early-stage projects or when resources are limited.

In many cases you can accurately estimate the methane production potential of manure and agricultural residues without a lengthy and expensive BMP test, by analyzing key feedstock characteristics. Most of the characteristics are similar to forage characteristics that are analyzed for animal nutrition – such as:

• Total and volatile solids (dry matter and organic matter)
• Protein, fat, and carbohydrate composition
• Recalcitrant organic matter (e.g., cellulose, lignin, woody stems, and other hard-to-degrade components)

At Azura we apply correction factors based our experience with manure and food waste feedstocks collected across North America to account for recalcitrant materials that are unlikely to break down and produce biogas. This ensures a realistic estimate that avoids overestimation. We call this refined metric Total Digestible Energy (TDE), a fast and practical estimate of biogas production compared to long BMP tests.

Building an in house database of TDE can help predict biogas production for digesters receiving feedstocks from multiple sources. It can be a useful tool for plant operators to understand the nutritional value of what they feed their digesters, identify nutritional gaps, and closely monitor if they are efficiently converting feedstock to gas.

[Peter]

Thanks Gurkeerat, for the projects that you see is whole liquid digestate typically applied as fertilizer or is wastewater treatment more common?