A Gasification Process Beats Incineration for Biosolids Management

A proven gasification process enables responsible biosolids management with capability to produce renewable energy and a marketable product.

A Gasification Process Beats Incineration for Biosolids Management

The Ecoremedy gasification process is fully automated but generally requires an on-site operator to monitor the controls.

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Biosolids management has become more challenging with tight emission regulation for incinerators and concern over PFAS placing structures even on land application.

Ecoremedy now offers a gasification technology for municipal wastewater treatment plants that aims to resolve those issues. It converts biosolids into a marketable product while reducing emissions and operating without fossil fuel input. The U.S. EPA has affirmed that the process is not a form of incineration, the company observes.

The Fluid Lift gasification process is self-sustaining and has been shown to destroy PFAS and other pollutants of concern. Unlike incinerators, the process does not release pollutants such as dioxins and furans. It can be used to create FlexChar, a biochar containing 1% to more than 60% carbon. It also can be tuned to maximize recovery of renewable energy.

The design uses industry-standard components to produce a modular solution that can operate economically at any scale, according to the manufacturer. Advanced controls help maximize performance and flexibility.

A single unit can process 15 to 75 wet tons per day, depending on the feedstock, from dewatered biosolids. Systems can be optimized in real time to achieve multiple combinations of nutrient recovery, waste reduction and energy recovery. David Mooney, president and chief technology officer with Ecoremedy, talked about the offering in an interview with Treatment Plant Operator.

Is this a brand new technology?

Mooney: We have proved out this technology over the last 20 years in the agriculture industry. It is new and unique to the biosolids sector, and it has been shown to work very well there.

What is the rationale for bringing this technology to a new market?

Mooney: Roughly two-thirds of the biosolids produced in U.S. wastewater treatment plants are land-applied. The rest is landfilled or incinerated. Incinerators cannot operate within emission requirements without upgrades that make them cost-prohibitive. Landfills face social pressure from neighbors complaining about odor, and they face more regulatory pressure about PFAS, microplastics, pharmaceuticals and other contaminants in their leachate. Meanwhile, various states have placed extreme regulatory strictures on land application. We offer a solution that empowers communities to manage biosolids in an environmentally friendly manner.

How does gasification differ from incineration?

Mooney: Incineration is simply burning something. In that instantaneous reaction a tremendous amount of heat energy released, and air pollutants are created. Gasification stretches that combustion process out over time. First we convert carbon to carbon monoxide and a hydrogen-rich gas. Then seconds later that gas burned simply by adding oxygen to it. The process is orders of magnitude cleaner than incineration in terms of emissions.

In simple terms, how does the gasification process work?

Mooney: We have married a proven, simple gasification process with a conventional direct-contact drying facility. Rotary-drum drying basically burns natural gas to evaporate water from the biosolids. We start with the same dewatered material that goes into a rotary drum dryer. It serves as the fuel source for the gasifier and provides all the energy needed to self-sustain the process. We can operate with cake at 15% solids and up.

What is the end product of this process?

Mooney: We concentrate all the biosolids down to its ash fraction or to a carbon-rich biochar that we call FlexChar. The material is sterilized, and the chemicals are reduced to nondetectable or trace levels. The volume is reduced by 95-98%. The material can go to landfill or to value-added products. Our system can uniquely flex from no carbon to high carbon in the biochar product. Operators have flexibility to make real-time decisions based on market conditions. We can convert all the carbon in biosolids to renewable energy. Or if the user has market drivers that make it advantageous to produce a high-carbon biochar, we can give them that.

What can the FlexChar product be used for?

Mooney: Biochar made from biosolids is best suited for agronomic benefit. The carbon in the biochar acts like a sponge and holds moisture, which can be very beneficial for sandy, fast-draining soils. Another application is in concrete. Adding carbon to concrete improves its strength and its porosity rating. If concrete containing biochar is used for pouring basements, it will dramatically reduce the seepage of groundwater through the basement walls.

How is renewable energy captured in this process?

Mooney: We provide a renewable energy facility inside the fence of the wastewater treatment plant. The biosolids itself is the fuel source and also the energy demand. The primary use of the thermal energy is to evaporate the water, but the system balance almost always is such that more energy is produced than is needed for the evaporation. So the customer can choose the form in which to receive that excess energy. They can take it as a high-carbon FlexChar in which the carbon represents the excess energy that was in the system. Or they can receive Class A dried biosolids for land application or for sale as a fuel source. 

Can the excess energy be used on site for process heating?

Mooney: That is another option. The excess energy can be captured in a heat loop for heating digesters or buildings, or for other purposes. 

How much operator attention does the gasification process require?

Mooney: The process is fully automated, but it is necessary to have a full-time operator on staff to monitor the controls.

How long does it take to deploy this technology at a treatment facility?

Mooney: We offer different models and sizes. They include modular units that we can design, fabricate, deliver, install and commission within 12 months of receiving a purchase order. The larger facilities take a little more time on site to assemble. Everything we build is a modular type of deployment. Our smallest models come as preassembled plants. All our components are American made using American steel.  


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