Biosolids Management

This project was funded through the Manitoba Government’s Conservation and Climate Fund, and was focused on researching the problem of biosolid waste, in the province of Manitoba but also more broadly. The project also sources and converted samples of biosolid waste into stable, sterile biocarbon material. As a waste management and greenhouse gas reduction solution, the carbonization of biosolid waste into a valuable and environmentally sustainable product merits further consideration. 

The Problem with Biosolids

Biosolid waste, also known as sewage sludge, is the semi-solid material left over from municipal wastewater treatment. While it’s often repurposed as fertilizer due to its high nutrient content, there are several concerns associated with its use.

Biosolids can contain a mix of various pollutants, including heavy metals like lead, cadmium, arsenic or mercury, pharmaceuticals, hormones, pathogens, bacteria, viruses, protozoa and parasitic worms. They can also contain harmful substances like PCBs, PFAS, dioxins, BPAs and dozens of other harmful substances.

Exposure to biosolids has been linked to health issues such as burning eyes, nausea, vomiting, boils and rashes. There’s also concern about the long-term health effects of consuming produce grown with biosolids. Wastewater treatment can also concentrate varied pathogens and antibiotics, leading to the selection of antibiotic-resistant bacteria.

Biosolids also contribute to environmental damage. The use of biosolids can lead to the buildup of pollutants in soils and leaching into waterways, which can have detrimental effects on ecosystems, groundwater and even drinking water. The treatment and use of biosolids also releases methane, a powerful greenhouse gas.

Manitoba Context

In Manitoba, the most common biosolid management techniques include landfilling, land application, and incineration, all three of which are harmful to the environment.

In 2022, 38,540 tonnes of biosolids were mixed with wood chips and street sweepings or clay to make a fabricated soil, used to “cap” landfills. An additional 15,767 tonnes of biosolids were applied to agricultural land surrounding Winnipeg farmland.

Despite efforts, biosolids still pose a threat to the environment. Biosolid materials disposed of in landfills or used to cap landfills will continue to generate methane for years or decades. Methane is a powerful greenhouse gas that is from 28 to 86 times more potent than carbon dioxide at heating the atmosphere. Based on calculations on methane generation capacity and the organic composition of biosolids, it is estimated that approximately 27,000 tonnes of biosolids will produce 2,100 tonnes of methane.

The use of biosolids as agricultural fertilizer does recycle nutrients, but can also contain heavy metals (lead, mercury, cadmium, arsenic) that can leach into the land they are applied to. Heavy metals, as well as excess nutrients leaching from these biosolids, disrupt plant root growth within the soil and can contaminate nearby land and water systems. Recently, researchers have seen an increased concentration of pharmaceuticals, microplastics, and polyfluoroalkyl substances (PFAS) in human waste. These pollutants also disrupt plant life and pollute our lakes, waterways, and other important habitats. Some of these pollutants can even be taken up by the plants into their edible portions, which can affect human health.

Size and Scope

The size and scope of the problem with biosolids is considerable, in both Manitoba and around the world. First and foremost, population growth combined with an absence of advancements in biosolid waste management technologies is contributing to ongoing environmental degradation. And without proper methods of sanitation and wastewater management, the risk of diseases caused by bacteria, viruses and parasites is biosolid waste is high, especially in developing countries. This problem of biosolid waste will grow exponentially and only get worse as the global population grows to 9.8 billion by 2050. When wastewater treatment plants are overwhelmed at max capacity, wastewater often is dumped in bodies of water untreated. It is estimated that 90% of worldwide wastewater is released back into the environment without any treatment. This can contribute to environmental degradation and major health problems.

Another issue that has had little exploration is the public perception of biosolid application to agricultural land. Livestock manure has been generally accepted by the population as a fertilizer, but the use of biosolids (also called sewage sludge or human waste) to grow food is a social concern. The public is not only worried about health effects but also the effects to air quality, the contamination to drinking water, and even decreases in property values. These concerns are valid. There is a marked increase in pharmaceuticals, pathogens, PFAS, and microplastics found in human waste as mentioned earlier. The conversion of biosolids into biocarbon material is a more sustainable approach that can help to persuade the public to approve of such methods. 

Carbonization as a Solution

Managing large amounts of biosolids and their associated contaminants is a major challenge. The carbonization of biosolids is increasingly being investigated as a potential method of not only reducing biosolid volumes but transforming biosolids into a new value-add product: biocarbon (also called “biochar”). Research has shown that carbonizing biosolids through pyrolysis is a sustainable approach that can substantially reduce greenhouse gas emissions, contaminants, transportation costs, and material volumes.

Carbon Lock Tech has developed a patent-pending technology for converting organic waste of all types into stable biocarbon. The technology is based on pyrolytic carbonization, a process by which organic material is thermally broken down into constituent materials such as carbon, hydrogen, nitrogen, etc. A key requirement of the process is that it takes place in the absence of introduced oxygen. If oxygen is present the material will combust, and the carbon will be emitted as carbon dioxide. Pyrolysis prevents combustion and “locks” a large portion of the carbon in the organic waste.

Carbon Lock Tech’s system is designed to convert almost any type of organic waste into stable biocarbon, including agricultural, agri-food waste, residential and commercial food waste, and biosolid waste. Once produced, biocarbon is chemically stable and can remain in this state for hundreds to thousands of years. It is porous and binds well with other materials, which makes it a valuable product for industries as varied as agriculture, construction, green infrastructure and manufacturing. In some cases, it can also help these industries reduce their environmental and carbon footprints.

Environmental and Economic Benefits

In addition to removing and sequestering carbon from the atmosphere, there are several other benefits to carbonizing biosolids. Carbonization also destroys organic pollutants in the biosolids such as pathogens, microplastics, pharmaceuticals, PFAS (Per and polyfluoroalkyl substances), and pesticides, while remaining a low emitter of NOx and SOx compounds when compared to incineration and landfilling . The heavy metals found in biosolids merge into the skeleton of the biocarbon structure where they are immobilized during pyrolysis and render the product safe for land application.
Pyrolysis also effectively removes moisture, reducing material volume by up to 70% of the original biosolid input . As a result, this reduction makes transportation more energy efficient as a greater amount of material can be transported at a lower cost with fewer emissions. 

Studies on biosolid carbonization indicate that the energy content of syngas and bio-oils are greater than the energy required for pyrolysis, suggesting it as a promising method for energy recovery compared to other biosolid management techniques.

In 2022, the Canadian government announced the Greenhouse Gas Offset Credit System. This system works on the basis of green technologies, such as carbonizing biosolids, creating carbon credits that can show in a transparent way how much greenhouse gases were prevented or removed from the atmosphere. Third party carbon emitters, such as airlines, mining companies, etc. can then purchase these credits to offset their carbon footprint. The carbon sequestration capabilities of biocarbon make it an excellent candidate for the carbon credit system as it can sequester carbon dioxide, methane, and other greenhouse gases and generate the credits needed by other industries. This solution could provide Manitoba with an opportunity to reduce methane emissions and generate revenues through the sale of carbon credits.

Next Steps

The research undertaken under this Conservation and Climate Fund grant shows preliminary and promising results. Additional research is both underway and planned, and will benefit directly from the investments made into equipment and research skills developed by Carbon Lock Tech engineers.

Biosolid waste is a major environmental problem in Manitoba (and across Canada and throughout the world) and solutions like carbonization are rapidly being explored. Companies in the USA and Canada are already converting biosolids into biocarbon materials at scale.

Carbon Lock Tech intends to develop its research knowledge and processing capacity here in Manitoba and begin to scale its carbonization technologies to offer this solution to communities throughout the province.

For more information about this project, please contact us.

 

Project Name
Addressing Methane Emissions and Nutrient Loading through Biosolids
Carbonization

Funder
Government of Manitoba

Partners

  • City of Selkirk
  • RRC Polytech

Team

  • Atish Kulkarni, Biocarbon Research Lead
  • Caitlyn Yim, Biocarbon Engineer (EIT)
  • Kevin Danner, Project Manager
  • Ryan Zaari, Technology Development Lead
  • Sujindra Subedi, Laboratory Research Analyst
  • Terry Gray, Technical advisor

Project Date
January 2023 to June 2023

Purpose
This research project investigate the problem of biosolid waste in Manitoba, noting two major issues: methane generation and nutrient loading in waterways and lakes. Samples of biosolid waste were obtained from the City of Selkirk’s wastewater treatment system and carbonized into stable biocarbon. It was concluded that biosolid waste can be successfully converted into sterile, stable biocarbon and used as a carbon sequestration pathway.