A New Circular Economy Example: Closing The Loop For Poop

When their children reach the age for “potty training” many parents read them the book, “Everyone Poops.” That isn’t just a reality for humans – it applies to all animals including those raised for meat and dairy products. In all these cases the manure or sewage that is generated presents various hazards including human and animal pathogens, air pollution, water pollution, and greenhouse gas emissions. Yet at the same time these waste streams represent potential resources including water, fertilizer and energy. The failure to fully tap those resources is problematic – one could modify a line from a 1970s fundraising campaign to say that “waste is a terrible thing to waste.”

Fortunately there are technological solutions to both deal with the hazards and enable the resource recovery opportunities. Municipal sewage treatment systems generally do a good job of mitigating environmental and public health risks, but most systems only recover part of the resource potential. Manure from farm animals is typically re-utilized as a fertilizer, but some of the nutrient content is lost and the environmental issues persist. Manure is usually applied to crops that are not for direct human consumption because of the potential pathogen issues. Thus, for both cities and farms there is definitely room for improvement.

There is a new technology called Varcor™ that is in the initial commercialization phase and it represents a true step-change for manure and sewage handling. It offers an unprecedented opportunity to fully recover fertilizer components in highly usable forms. It takes care of pathogen issues and prevents pollution of air and water. It is also attractive from an energy and greenhouse gas perspective – a picture that gets even better if the system is integrated with anaerobic digestion technology.

There is an interesting back story. Janicki Industries is an aerospace engineering firm based in Seattle Washington which was started in the early 1990s. It was mostly working on custom equipment solutions for airline companies and military contractors but did end up with a project associated with biomass combustion. Based on Janicki’s engineering prowess, the Gates Foundation gave the company a grant to develop on a sewage treatment system that could generate energy and clean drinking water which would also be suitable for the developing world. The goal was met with what came to be called the Janicki Omni-processor and there is a famous video of Bill Gates drinking water from the plant as a show of confidence in its safety. Based on these experiences, the company decided to spin off a company focused on waste-treatment called Sedron Technologies which is now in Sedro-Woolley, Washington. In 2017 Sedron started working with a very large organic dairy operation in Texas called Natural Prairie Dairy looking for a better way to handling the manure from their 14,000 cows. That seemingly unlikely relationship between engineers and ranchers proved to be quite important in terms of achieving a practical outcome.

Dairy and other manures are routinely used as crop fertilizers because they contain nutrients that crops need to grow such as nitrogen, potassium and phosphorus. Cows or other animals don’t make those fertilizer elements, they simply fail to absorb all that is in their feed (the same is true for people). Both organic and conventional farmers use manure in various forms, but organic growers are particularly dependent on this source since the organic rules don’t allow them to use nitrogen made through the Haber-Bosch process that supplies much of what is needed for agriculture. Organic farmers are allowed to use manure from conventionally fed animals because otherwise they wouldn’t have a sufficient nutrient supply. Manure is a problematic fertilizer for several reasons. If it is applied at an optimal rate for nitrogen, the amount of phosphorus will probably be too high and that can lead to water pollution. Manure can harbor human pathogens and those are not fully eliminated by composting or most other standard manure handling practices. Also, cows etc generate manure on a daily basis, but it can only be practically spread on fields at certain appropriate times in the season and so it has to be stored – often in its original high moisture content “slurry” form. During that waiting time a good deal of the original nitrogen content which is in the form of ammonia (NH₃) is volatilized into the air and from there it can disperse widely, get into water and cause “eutrophication.” It takes many tons of manure to fertilize an acre of a crop, so even if the original slurry is dried, the hauling process takes a lot of energy and the drying process leads to even more wasted nitrogen through ammonia loss. Once the manure is spread on the land it needs to be tilled into the soil to prevent even more nutrient loss and that means the field where it is used can’t be “no-till” farmed – a foundational practice for climate-smart and erosion-preventive farming. So yes, manure gets used, but there are issues.

The Varcor™ system that Sedron developed with Natural Prairie Dairy is a continuous process that eliminates the storage step and the fertilizer waste and pollution issue that entails. The slurry goes into a dryer with a rotating conveyor that generates three outputs – dry solids, a saturated liquid and steam. The steam is then sent through a widely used compressor technology called Mechanical Vapor Recompression (MVR). MVR is a technology that is also used for water desalination and making dry milk powder. The compressed steam and saturated liquid go into a unique and patented distillation process which returns much of the heat back to the dryer while condensing out separate streams of clean water and nitrogen in the form of aqueous ammonia.

The ammonia can be used as a fertilizer but the Varcor™ system adds a step to turn that into stable ammonium product which is much easier to store and apply to a crop. The dry solids that come from the drier are a much more potent fertilizer than the original manure. There is enough heat in the process to eliminate any human or animal pathogens. Both of these fertilizer outputs have been approved for use under the OMRI and USDA organic standards which for the first time allows those farmers to apply without the need for tillage, to utilize precision and “variable rate” application, and to use other state-of-the-art farming methods that were once only practical in conventional systems. Donald De Jong, co-owner and CEO of Natural Prairie Dairy sums it up this way: “As a third-generation dairy farmer, what to do with the cow poop has always been challenging and messy. The Varcor™ system turns this challenge into an opportunity, allowing us to create a closed loop system by upcycling manure into clean water, rich, stable NPK fertilizer and usable aqueous ammonia. It’s a game changer.”

For a dairy operation like Natural Prairie Dairy that grows much of its own animal feed and which raises animals in a dry environment, the fertilizer and water output of the Varcor system will result in cost savings within their own business operation. Other animal operations that don’t produce all of their own feed will be able to recover their Varcor™ investment through fertilizer sales. In either scenario this could be a significant contributor to the sustainability of agriculture. Stanley Janicki, the CRO
CRO
of Sedron Technologies describes their goals for the technology: “From an energy standpoint, the Varcor™ is incredibly efficient but the true efficiencies and greenhouse gas savings lie in avoiding the manure application on fields and the storage of manure in lagoons. Being able to eliminate those things gives us a tremendous tool in solving greenhouse gas emissions in any agriculture installation that utilizes a manure lagoon.”

This technology is also positive because it represents locally recovered nitrogen which is independent of a connection to the problematic global natural gas supply which is used today to make Haber-Bosch nitrogen. That linkage is also beginning to be addressed through smaller scale, local Haber-Bosch systems using hydrogen generated with wind or solar power rather than from natural gas. The fallout from the war in Ukraine has heightened the urgency of greater fertilizer supply independence.

The Varcor™ system makes a lot of sense as a stand-alone system connected to all categories of animal production, but it can also be linked to anaerobic digestion (AD) which gives access to the other potentially wasted resource in manure – energy. Some progressive animal farms and municipal sewage districts use AD to convert most of the remaining organic chemicals in the manure or other feedstock into methane which is then burned to generate clean energy. These systems are capital intensive and somewhat challenging to operate, but are now a well established technology option for many situations. The “digestate” that comes out of an AD system is another potential feedstock for a Varcor™ system and it delivers just as much recoverable ammonium nitrogen and around a 33% more concentrated source for the dried fertilizer product that the system generates. The energy from the anaerobic digester system has considerable market value because it qualifies under the Low Carbon Fuels Standard (LCFS) and/or of the energy can be used for the relatively small electricity demand of the Varcor system. In a typical rural setting for an animal operation, the electricity needs could also be supplied with wind or solar energy.

While this system was developed to solve issues for animal farms, it is fully applicable to municipal sewage treatment systems. A first such installation is currently under construction near Seattle. Using this approach for human waste (including food waste) would allow recovery of phosphorus and potassium that have only had marginal fertilizer utility as “biosolids” in the past and which now could be in fully safe and functional forms for agriculture (potassium and phosphorus are key minerals for plant growth and they are mined from finite resources in only a few countries around the world). In the process of cleaning up the water they will release, typical sewage treatment plants actually use quite a bit of energy to convert ammonia back into nitrogen gas. Now that there is this new option, that stands out as an unnecessary waste of both energy and fertilizer.