Project Overview
Approved for funding through ERA’s Biological GHG Management Program in 2013, University of Calgary researchers investigated the use of Alberta-grown biomass – agricultural and forest crop residues – to clean up chemical contaminants in produced water from oil sands operations. Over the course of the 9-month project, a variety of biochar samples were produced, characterized, and tested, and the results of the research were published in a peer-reviewed journal.
Activated Biocarbon Produced from Alberta-grown Biomass
The recovery of bitumen from oil sands, mining and in situ use large volumes of water that, once used, is contaminated with organic compounds. Biochar – activated carbons produced from biomass – are well-known adsorbents that can remove organics from water and provide a long-term sink for atmospheric carbon. To maximize this carbon sink, it is important to reduce the energetic cost and increase the yield associated with making an adsorbing biochar.
Studies show that residual biomass in Alberta can be converted to an activated carbon and used to remove toxic and corrosive organic compounds from oil sands produced waters. This can help oil sands processing and reduce greenhouse gas (GHG) emissions, creating a long-term store for atmospheric carbon. The project focused on developing a new technology for converting aspen wood chips from northern Alberta into an adsorbing biochar with enhanced yield, improved adsorption capacity, and lower cost than existing technologies.
Promising Initial Results, Biomass Adsorbing Biochar Production Requires Further Work
During the project, experts in biochar production and activation were consulted in the experimental design. The project built a novel, three-chamber pyrolysis unit to study how temperature, gas composition and the volatile fraction generated during pyrolysis affect the yield and surface area properties of the produced biochar. The project investigated the pyrolysis of aspen wood chips and the conversion of the produced volatile species and bio-oil into biochar. Two approaches were explored to create biochar with high yield and good adsorption.
First – controlling pyrolysis conditions such as temperature, gas flow rate, and how long the material stayed in the reactor. At pyrolysis temperatures between 420°C and 650°C, the deposited volatiles were carbonized and converted to material similar to the primary biochar. Deposited volatiles had no effect on nitrogen and carbon dioxide adsorption. The results showed that the yield of biochar can be increased without a decrease in adsorption capacity by creating conditions that facilitate the deposition of the volatiles.
Second, bio-oil formed in the previous trial was added to biomass prior to pyrolysis. The results demonstrated that it was possible to increase the yield of biochar by recycling bio-oil to biomass while maintaining adsorption properties.
Overall, residual biomass from Alberta forest production can be pyrolyzed to produce an adsorbing biochar that has the potential to clean oil sands production water while reducing GHG emissions and creating a sink for atmospheric carbon. Although the results are promising, further work is needed to develop a rapid, cost-effective process to create an adsorbing biocarbon from locally grown biomass. Research results were published in a peer-reviewed journal and disseminated among the research community and industry via conferences and poster presentations.
What’s next?
Post-project, laboratory work continued to improve the development of an adsorbing biochar using Albertan biomass. To further advance the concept, industry partner interest in removing organics from produced waters is required. Additionally, engagement with policymakers to realize the potential benefits of introducing regulations in this area.
Follow-up work was done in 2014, exploring the feasibility of using biomass to mitigate emissions and remediate contaminated water using process-affected water from oil sands operations as a case study. Using activated biochar for greenhouse gas mitigation and industrial water treatment, results found that activated biochar removed 75% of total organic carbon from produced water in SAGD operations or 90% of total organic carbon from a synthetic tailings water sample.
Biochar shows promise for treating contaminated oil sands water; however, it is not commonly used on a large scale in commercial oil sands operations. Research is ongoing to develop and optimize biochar-based technologies for treating oil sands process-affected water. Long-term effectiveness needs further investigation, and ongoing research and development should focus on scalability, cost-effectiveness, and environmental benefits.