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Water Today Title February 21, 2024

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Features

Update 2023/2/26
Research


Biochar and the elimination of PFAS in wastewater
Western University, ON, leads the world in pyrolysis technology


By Suzanne Forcese

“Currently, we are the only group in Canada piloting this technology. Likely, we are also among the very first in the world.”
--Dr. Franco Berruti, P.Eng.

WT: Dr. Berruti, you are an accomplished and internationally recognized award-winning researcher with expertise in chemical reactor technologies that has led to significant academic and industrial contributions. For this conversation, we are going to home in on “Biochar and the elimination of PFAS.”

Before we start that conversation, please introduce yourself to our viewers giving us a brief look at your teaching/research areas at Western University.

Berruti: I started my academic career in 1986 at the University of Calgary, becoming a full professor in 1992 and Associate Dean (Research and Graduate Studies) in 1994. I served as Dean of Engineering at the University of Saskatchewan (1996-2000) and at the University of Western Ontario (200-2008).

I am the Founding Director of the Institute for Chemicals and Fuels from Alternative Resources ICFAR) and I currently hold the “NSERC Industrial Research Chair in Thermochemical Conversion of Biomass and Waste to Bioindustrial Resources” co-sponsored by 11 industrial organizations.

I am recognized for my expertise in chemical reactor technologies, thermal cracking, and conversion of heavy oils and biomass and plastic wastes into value-added fuels and chemicals. I have over 350 publications in several prestigious journals, books, and conferences and I am the author of four patents.

I am involved in many international collaborations all over the world and I have received numerous awards including the Bantrel Award in Design and Industrial Practice, the SCI Kalev Pugi Award, the Ontario Green Chemistry and Engineering Award, and the Fellowship of the Canadian Academy of Engineering.

I teach courses in Advanced Engineering Communication and in Green Chemicals and Fuels.

WT: You have also co-founded two university spin-off companies. Please tell us a bit about each and the motivation behind these endeavours.

Berruti: I believe that engineering research, including academia, should focus on outcomes that would have a positive impact on society. I focused my career to highlight how significant academic research can be. I have applied my expertise towards improving efficiencies in the oil industry and having a significant positive impact on the agricultural and forestry sectors. 

Recent efforts have been focused on environmental applications, such as pollutant elimination from soils and water and odour dispersion surrounding landfills. 

Other research priority areas include as examples, waste to resources, carbon sequestration, carbon-based sustainable fertilizers, small mobile processes for remote communities, green processes, and circular economy.

To further accelerate the search for impact, I have decided to attempt the creation of spin-offs derived from my research: Agri-Therm was the first one, aimed at the development of a mobile pyrolysis technology for converting residual woody biomass and byproducts of agricultural practices into value-added liquid fuels and carbonized fertilizers. The technology was proven, and in the absence of Canadian opportunities was licensed abroad.

Later, I have been involved with colleagues and investors in the creation of another spin-off, derived from the evolution of our research activities. This second spin-off, called Bio-TechFar (bio-techfar.com), is still seeking investor opportunities.

WT: Sounds like we will be having more conversations! For now, please explain a few basics about biosolids, biochar, and the uses for outputs.

Berruti: Solid wastewater byproducts in water resource recovery facilities (WRRF) are known as biosolids, which are separated through several consecutive water treatment steps.

Biosolids are rich in micronutrients and, when used as fertilizer supplements, offer many beneficial effects on soil properties, such as improving plant growth, cation exchange capacity (a relative reflection of soil’s potential fertility), porosity, bulk density, and water holding capacity.

Biochar is one of the main products of the pyrolysis process. Pyrolysis is a thermochemical conversion that utilizes heat to decompose organic waste materials into value-added products – biochar (solid), condensable gas (liquid bio-oil), and non-condensable gas.

Biochar is a versatile product with a wide range of applications including soil amendment, gas/water adsorbent, filtration, and catalyst.

Bio-oil is a mixture of several hundred chemicals used for fuel applications.

Non-condensable gas constituted of hydrogen, carbon monoxide, carbon dioxide and methane may be used as a fuel for industrial purposes.

Biochar offers outstanding opportunities for carbon offset credits since once applied to the soil, its carbon content, which originally was carbon dioxide uptaken by plants and photosynthesis, remains locked in the soil in a very stable for hundreds of years.

WT: How do biosolids factor into water resources recovery facilities? What are the benefits?

Berruti: In wastewater treatment plants, water is separated from solids. Then solid streams can be treated physically and chemically. The resulting solid (biosolid) is a unique blend of organic and inorganic materials, trace elements, chemicals, and even contaminants.

As such, biosolids after treatment can be returned to the soil for use in agriculture and mine reclamation sites.

In some countries, land application of biosolids is more prevalent than in others, compared to incineration and landfill, due to higher disposal costs.

According to the literature, 660,000 dry Tonnes of biosolids are produced annually in Canada, 43% of which are utilized for land applications.

In the United States, approximately 55% of seven million dry Tonnes of biosolids, generated from wastewater treatment facilities, were applied to soil in 2004.

In Australia, 75% of all biosolids produced are currently diverted to land applications for soil amendment.

WT: Unfortunately, biosolids can also be contaminated. There has been increasing attention drawn to PFAS – the forever chemicals entering our water. What are the sources of PFAS in our water?

Berruti: Per-and polyfluoroalkyl substances (PFAS) are a series of manufactured chemicals, with non-stick and oil/water repellent properties, found in fabrics and materials with non-stick and fire-resistant properties such as carpets, food-packaging, Teflon, and fire-fighting foam.

There are 8,000 types of PFAS compounds, including short and long-chain compounds with their hydrophobicity and toxicity increasing with chain length. They are named based on their characteristics with the PF as a root, followed by an indication of their chain length and their associated functional group --carboxylic (A) or sulfonate (S).

When PFAS-containing products are produced and disposed of, PFAS compounds can end up in soils, groundwater, and surface water, where they accumulate and persist as non-biodegradable, toxic compounds in the environment and can cause serious human and wildlife issues including certain types of cancer, liver/kidney damage, cardiovascular problems, birth defects, and immune system disorders.

WT: Your research points to pyrolysis as an answer to these very serious problems. Please describe the basic technology that you are working with. What is the Pyrolysis Reactor?

Berruti: The bench-scale Mechanically Fluidized Reactor (MFR) developed at the Institute for Chemicals and Fuels from Alternative Resources (ICFAR), is composed of two main sections, the reactor, and the condensation system.

The reactor section includes a mechanically fluidized cylindrical vessel. An induction unit is used to provide heat.

Feedstocks are precisely weighed and then introduced into the hopper.

A screw feeder conveys the feedstock from the hopper to the reactor.

The feedstock is well mixed inside the reactor operating at either 500°C or 700°C via a mechanical agitator driven by an electrical motor.

The condenser apparatus is composed of two condensers in series placed in a cold-water bath, where a mixture of ice and water is used for cooling.

After the second condenser, the residual gas goes through a cotton filter and then to the exhaust line where it can be sampled and characterized.

A screw connected to the bottom of the reactor is used to extract the biochar which is then collected in a sealed biochar container.

WT: Have you been able to eliminate PFAS in this process?

Berruti: Three processed biosolids from three water resource recovery sites (S1, S2, S3), under pyrolysis temperatures of 500 and 700°C, were examined. After pyrolysis was performed at 500°C, PFAS compounds were completely removed from the biochar in the S1 sample, and up to 98.7 wt% in the S2 and 7.3 wt% in the S3 biochars.

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Further reduction was achieved by pyrolyzing the biosolids at 700° C, with PFAS undetected in the S1 and S3 biochars and reduced by 99.6wt% in the S2 biochar.

WT: How do you envision the Pyrolysis Reactor Technology working in wastewater treatment facilities?

Berruti: Transferring pyrolysis technology to the wastewater treatment facilities is feasible by installing adequately sized pyrolysis reactor technologies or by using mobile pyrolysis units.

In addition, the cost of the process could be decreased due to the continuous availability of the biosolids and minimizing the transportation fees to disposal facilities and converting biosolids into valuable products locally.

Pyrolysis technology creates a win-win situation for both environment and the economy.

The self-sustained pyrolysis process is a promising approach for fighting against climate change as waste organic material is one of the major greenhouse gas contributors causing global warming with severe climate change and environmental impacts.



suzanne.f@watertoday.ca







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