ECONWARD’s Counterplan for Landfill-Bound Organics

North Americans are becoming increasingly adept at diverting green waste and pre-consumer food waste for composting or biogas projects. But postconsumer food scraps—or the organics fraction of municipal solid waste (MSW)—are another story. They inevitably end up in landfills mixed with other materials and are nearly impossible to separate.

This waste is a universal problem for communities around the world, as it makes up about one-third of landfilled trash globally, where it generates leachate and methane emissions and makes compaction difficult due to its high water content.

Spanish technology developer ECONWARD is targeting this challenging organics stream with a system that enables it to be pulled out and prepared for anaerobic digestion to make renewable natural gas.  Branded as Biomak, it leverages thermal hydrolysis, which uses pressure and heat to break down organic material to the point that it separates from the inorganics.

ECONWARD COO Joe Ayala compares the process to using a pressure cooker that makes meat tender enough to fall away from the bone. Following hydrolysis, a mechanical process further separates most of the remaining organics, which drop through a screen while the nonorganic fraction passes over the screen.

Biomak’s continuous autoclaving system, which kills pathogens that are disruptive to anaerobic digesters, can manage 8 tons an hour per unit.

Ayala is convinced the technology will open opportunities for more food waste digester projects. They produce the most biogas, yet due to the feedstock’s complexity, only 6 percent of operational RNG projects take food waste today. And no operators accept the organics fraction specifically from municipal solid waste to the knowledge of Patrick Serfass, executive director of the American Biogas Council.

“But if you can decontaminate the material and blend it to make it more homogeneous, you’d have a significant advantage over other systems without much competition for the feedstock.

“The ability to unlock the organic fraction of municipal solid waste and process it efficiently would enable recycling of millions of tons of material across the U.S.,” he says.

Serfass, who has been watching Biomak, says that by breaking down organics with heat and pressure versus mechanically the technology has two advantages important to biogas projects: the smaller organic material is easy to separate from plastics and metals and it’s easier to turn the material into biogas.

Thermal hydrolysis prior to anaerobic digestion reduces the residence time by up to one third. It destroys pathogens harmful to “good” bacteria essential to the process. And it produces more biogas, as bringing in fully hydrolyzed material prior to digestion increases the system’s efficiency from 60 to 90 percent, according to Ayala.

“We are seeing source separation initiatives to divert from landfill. And there are high hopes around the country for good organics management programs, yet contamination remains a problem,” he says.

It’s especially prevalent in multifamily or densely populated communities as implementing effective source separation programs in these areas is extremely hard.

“Source separation of the organics fraction of municipal solid waste works well in small towns, but in big cities around the world you open organics bins and see nonorganic materials because the system is saturated, even in communities that have tried to implement source separation programs for years,” Ayala says.

Southern Idaho Solid Waste is a regional solid waste district serving seven counties. The agency has been able to maintain very low tipping fees over the past 30 years, meaning that traditional recycling programs would be difficult to develop and would require hefty rate increases.

Just the same, the intention is to divert the entire organic fraction from the waste prior to landfill.

“However, we do not believe that source separated diversion is an effective or efficient option,” says Nate Francisco, executive director and CEO, Southern Idaho Solid Waste.

“I am a big believer that the waste management industry should focus on separation of materials from the stream at the landfill rather than at the curb.  Traditional recycling methods that rely on human behavior for source separation are labor intensive and often end up needing secondary processing to remove contaminates,” Francisco says.

He saw promise in Biomak after learning about it at a conference, then traveled to Spain to watch the system in play.

“ECONWARD’s technology would allow us to divert a much larger amount of organics and create a clean, valuable feedstock for anaerobic digestion and renewable natural gas production while allowing us to save landfill space and generate revenue to cover the additional operating costs [we would incur],” he says.

Some landfill operators that Ayala talks to say if they bury waste, they can generate revenue from landfill gas. He tells them they will still get that income from digester gas and it’s a better quality, but that the greatest payoff will be in not having to bury the garbage, ultimately mitigating emissions and other problems.

“Though there are leachate management and gas collection systems, they are stop gap measures. We need to address the problems of organics by diverting them from landfill. If we can separate and recycle the organic fraction onsite, we are preventing a long-term problem because when those organics go into landfills those sites will continue to emit methane for decades,” Ayala says.

All three components— the hydrothermal treatment, anaerobic digestor, and gas clean up system—run about $40M total. Ayala estimates a five-year return on investment though figures over time the biogas and extended landfill life together are worth hundreds of millions.

ECONWARD has one system up and running in Madrid, Spain with capacity to process 200 tons of waste per day. Now the technology is ready for commercialization in North America, with several projects at different levels of development.

The first gas is projected to come online in 2026.