ZwitterCo and Mott Corp. on May 10 announced a multi-year, exclusive partnership to deliver wastewater solutions for manure digesters, food-waste digesters, breweries and distilleries in North America that can increase the value of coproducts and lower the carbon intensity (CI) score of the resulting biogas or renewable natural gas (RNG). The partnership follows Mott&rsquo;s acquisition of Digested Organics, ZwitterCo&rsquo;s North American channel partner.
ZwitterCo develops membranes to deal with challenging wastewater streams. While traditional membranes often require extensive cleaning and replacement when exposed to fats, oils and other organic compounds, ZwitterCo&rsquo;s superfiltration membranes regenerate performance after processing saturated organic streams, according to the company. Mott specializes in filtration and flow control solutions, traditionally in the aerospace, semiconductor and healthcare spaces. With the recent acquisition of Digested Organics, Mott is expanding its business to incorporate broader water and agricultural solutions.
ZwitterCo&rsquo;s membrane technologies and Mott&rsquo;s filtration and flow control solutions can provide a novel wastewater solution for anaerobic digestion (AD) facilities. ZwitterCo Co-Founder and CEO Alex Rappaport explains that digestate produced by anaerobic digestion is an extremely crude wastewater that requires several operational steps to convert it into valuable fertilizer and clean water for reuse. According to Rappaport, the company&rsquo;s superfiltration membranes uniquely solve a long-stranding performance limitation for standard membranes, which are prone to rapid and irreversible clogging when filtering complex waste streams. He said companies like Digested Organics are able engineer robust systems where superfiltration membranes play a key role in the filtration process and help improve overall system performance and economics. &ldquo;Our exclusive partnership with Mott exemplifies that high standard, and collectively we provide biogas facilities with a unique nutrient recovery process that reduces off-site hauling, generates valuable fertilizer, and produces clean water at an affordable price,&rdquo; Rappaport said.
ZwitterCo&rsquo;s superfiltration membranes are used in the nutrient recovery process post digestion, are positioned after bulk solid removal and serve as an ideal pre-treatment to reverse osmosis, according to Rappaport. As a result, the membranes are able to help improve overall economics of an anaerobic digestion system by removing suspended solids and harsh organics that would otherwise negatively affect downstream performance of the system.
ZwitterCo superfiltration membranes are currently used as part of Digested Organics&rsquo; nutrition recovery system at Brown County Organics in Greenleaf, Wisconsin. The system treats approximately 1 million gallons per day of manure digestate, according to Rappaport, making it one of the largest nutrient recovery systems in North America. The installation reduces offsite hauling by 50 percent and produces more than 100 million gallons of clean water annually.
The technology solutions offered by ZwitterCo and Digested Organics can be installed at both existing and new greenfield anaerobic digestion projects. &ldquo;Currently, operational sites can often be limited by seasonal temperatures and available land to spread their digestate and therefore pay high fees to haul excess digestate off-site,&rdquo; Rappaport said. &ldquo;Essentially, these facilities are paying to throw away valuable nutrients and water that could be used to help support crop yields and operations onsite. Adding a nutrient recovery system can significantly reduce the treatment cost for managing digestate, produce a concentrated fertilizer that can easily be stored onsite, and generate clean water for reuse that lessens the demand on public water supply. The transition from hauling to a nutrient recovery system would be seamless and have minimal to no impact on operations.&rdquo;
According to Rappaport, the implementation of a Digested Organics nutrient recovery system that features ZwitterCo superfiltration membranes greatly increase the value of digestate by separating it into distinct coproducts, such as bedding, phosphorus, ammonia and clean water. He also noted that Digested Organics&rsquo; ability to concentrate manure prior to digestion produces higher value feedstock by removing constituents without biogas potential, concentrating constituents that do have biogas potential, and reducing the amount of material that must be hauled to digestion sites. &ldquo;This benefit leads to higher production of biogas with smaller volumes of feedstock,&rdquo; Rappaport said.
The two technologies can also help reduce the CI of biogas and RNG produced via anaerobic digestion systems. Rappaport explains that two major contributors that negatively impact CI scores for biogas and RNG are lagoon storage of digestate and hauling the digestate off-site. &ldquo;Both practices result in carbon being released into the atmosphere, which is harmful to the environment and reflected by increased CI scores,&rdquo; he said. &ldquo;Digested Organics&rsquo; nutrient recovery system featuring ZwitterCo superfiltration membranes addresses both issues by concentrating digestate into smaller volumes that can be safely stored onsite without negatively impacting the environment and significantly reducing the need to haul digestate off-site. This can contribute to lower CI scores, resulting in higher valued RNG.&rdquo;
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ZwitterCo superfiltration (permeate in the center) enables this manure digestate treatment process by protecting the RO from small molecule, heavy foulants.

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Side view of ZwitterCo superfiltration membranes.

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ZwitterCoâ€™s superfiltration membranes.

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ZwitterCo's membranes regularly clean in under one hour and fully recover and restore performance even after severe fouling events.

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Before and after wastewater being treated with ZwitterCo's superfiltration membranes.

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The bottom jar shows the wastewater stream sent through ZwitterCoâ€™s superfiltration membranes. The middle jar is the concentrate following membrane treatment. The top jar is the permeate from the membranes, which is clean water for reuse. 

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ZwitterCo and Mott Corp. are partnering to deliver wastewater solutions for manure digesters, food-waste digesters, breweries and distilleries in North America that can increase the value of coproducts and lower the CI soore of the resulting biogas. 

ZwitterCo, Mott partner to improve CI, economics of AD systems

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