Cattail (Typha spp.) biomass harvesting for nutrient capture and sustainable bioenergy for integrated watershed management
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High levels of phosphorus loading in Lake Winnipeg, Manitoba, Canada are causing eutrophication and algal blooms of increasing intensity and frequency. Phosphorus is also a strategic and limited natural resource critical for plant growth, and essential for agriculture and global food security. This research study demonstrated an innovative environmental engineering approach to address multiple sustainable development challenges. Cattail (Typha spp.), a large competitive emergent aquatic plant, was harvested to capture and remove nutrients that would otherwise cause eutrophication in aquatic systems, and utilized as a biomass material for industry. Cattail reaches maturity in less than 90 days, and late summer/early fall harvests yielded average 15 to 20 t DM/ha, and captured 30 to 60 kg/ha/year of phosphorus. Once harvested, nutrients locked in plant tissue are prevented from being released into the environment via natural decomposition. Utilizing harvested biomass as a bioenergy feedstock provided a further benefit displacing fossil fuels for heating, and generated valuable carbon offsets. Cattail was compressed into densified fuel products, and combustion trials revealed an average calorific heat value of 17 MJ/kg to 20 MJ/kg, comparable to commercial wood pellets. Average ash content was 5 to 6%, and no major concerns identified regarding combustion emissions and ash. Estimated greenhouse gas (GHG) mitigation potential from coal displacement was one tonne of cattail biomass generated 1.05 tonnes of CO2 offsets. Additionally, up to 88 % of total phosphorus was recovered in ash following combustion in solid fuel burners. Harvesting cattail biomass offers greatest feasibility if combined for multiple purposes: nutrient capture, habitat, bioenergy, carbon offsets, water quality credits, and higher value end products and biomaterials (i.e. biochar). Economics of harvesting need to be further explored at the pilot and commercial scale for this novel renewable and sustainable ecological biomass feedstock. From an agricultural context, this biomass resource is presently undeveloped. It is a plant species prized for its nutrient capture and water quality benefits, and a biomass feedstock for bioenergy and high value end-products that grows on marginal agricultural land, not competing with prime land and food crops.
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