Pyrolysis: Turning ag residues into fuels and fertilizers

Posted on April 10, 2013

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by Rebecca Gotto, Saskatchewan Research Council

SRCphotoFarmers and agricultural processors in Saskatchewan produce a tremendous amount of crop and livestock residues, such as wheat and flax straw, oat hulls and poultry litter, that must be managed. Researchers at the Saskatchewan Research Council (SRC) see this as an opportunity and are currently working to find out how these residues and other waste materials can one day be used in a practical way through a process called pyrolysis. Pyrolysis can turn these agricultural residues into materials that can be used as fuels and fertilizers. Pyrolysis breaks down material using heat in the absence of oxygen. The process results in three things: a bio-oil (liquid), a gaseous fuel (gas) and a granular biochar (solid/charcoal). SRC Research Engineer Dr. Erin Powell, says that while pyrolysis itself is not new, finding applications that are practical for the average person is. “Bio-oil and biochar have both received a lot of interest in recent years. In Saskatchewan, there is a lot of interest around finding uses for agriculture and livestock residues. Farmers are looking for avenues to manage residues and waste, and creating value-added products from that material makes it even more attractive.” SRC’s Process Development team is one of just a few groups in North America doing diverse research and client work using a pyrolysis platform. This includes biomass preparation, assessment of pyrolysis and its end-products, technology development and downstream value-added processing of bio-oil and biochar. SRC recently finished work on a provincial Agricultural Development Fund (ADF) project that focused on making pyrolysis viable and practical for Saskatchewan farmers.

As part of this project, SRC demonstrated a one tonne/day mobile pyrolysis unit based on Advanced Biorefinery (ABRI-Tech Inc.) technology. This unique unit is operated at SRC’s Saskatoon location but could also be transported to feedstock locations around Saskatchewan for remote processing. Powell says the mobile aspect of the technology is what really makes it unique. “The capability for remote processing allows for biomass densification. This means that you can sidestep a fundamental economic hurdle in biofuels. Transporting biomass is expensive because of its bulk volume, whereas liquid fuel from biomass has a higher energy content and is far more economical to transport. As a result, pyrolysis products can be generated locally then transported for processing into valuable fuels, fertilizers and chemicals.” SRC then used the unit to evaluate several different agricultural and livestock residues to see how they pyrolyzed and find out what potential uses could be made for the end-products. They also assessed what might be needed to make the technology commercially viable. In a follow-up project with ADF, SRC focused more on the practical application side including value-added upgrading of the oil and char products that were created in the first project so that they are useable for the average person. SRC developed a method for turning bio-oil into a heating fuel oil suitable for agricultural use, and using biochar and microbes to remove unwanted compounds from manure before disposal. SRC’s research in this area will assist farmers and agricultural processors, in Saskatchewan and beyond, by helping them find practical solutions for their waste and residue problems. The hope is that these residues will one day be used to produce fuels to heat homes, power cars, and create products for bioremediation and soil improvement.