Graduation Year

2026

Document Type

Thesis

Degree

M.S.C.E.

Degree Name

MS in Civil Engineering (M.S.C.E.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Mahmood Nachabe, Ph.D.

Committee Member

Kyle Boutin, Ph.D.

Committee Member

Sarina Ergas, Ph.D.

Keywords

Cattails, Constructed Wetlands, Nutrient Retention, Peat Replacement, Pyrolysis

Abstract

Constructed wetlands are widely used to improve water quality by removing excess nutrients from wastewater and stormwater. Nutrients are stored within wetland vegetation, particularly in fast-growing plants such as Typha. Harvesting vegetation provides an opportunity to permanently remove these nutrients while generating biomass suitable for beneficial reuse. Converting harvested biomass into value-added products such as compost and biochar can support nutrient recovery and sustainable biomass management. In addition, increasing concerns regarding the environmental impacts of peat extraction have created interest in renewable alternatives for horticultural growing media. Therefore, the objective of this study was to evaluate the potential of harvested Typha biomass from Se7en Wetlands in Lakeland, Florida, for compost and biochar production and to assess the suitability of Typha-derived biochar as a sustainable horticultural growing media amendment and partial replacement for peat moss.

To achieve these objectives, Typha biomass was harvested and analyzed for total nitrogen (TN), total phosphorus (TP), and total carbon (TC). Harvested biomass was processed into compost and biochar, with biochar produced through pyrolysis under oxygen-limited conditions at temperatures ranging from 350°C to 1000°C. Biochar was characterized using pH, electrical conductivity (EC), cation exchange capacity (CEC-NH₄⁺), H/C ratio, hydrophobicity, and yield measurements. Based on the characterization results, biochar produced at 400°C was selected for horticulture evaluation. Greenhouse experiments compared peat-based growing media with substrates amended with Typha-derived compost and biochar using radish (Raphanus sativus) as a model crop. Growing media physical properties, plant growth, nutrient retention, and nutrient leaching were evaluated.

Harvested Typha biomass contained measurable concentrations of nitrogen, phosphorus, and carbon. Live tissues contained significantly greater TN and TP mass than detritus, whereas detritus had greater TC mass. Harvesting removed approximately 15 kg P ha⁻¹, 153 kg N ha⁻¹, and 8,352 kg C ha⁻¹ from the wetland. Harvested biomass was successfully converted into compost and biochar, with compost yields ranging from 97% to 111% and biochar yields decreasing from approximately 44% at 350°C to 28% at 1000°C. Pyrolysis temperature significantly affected biochar properties, increasing pH, electrical conductivity, and carbonization while decreasing H/C ratios and yield. Hydrophobicity decreased with increasing temperature, whereas CEC-NH₄⁺ increased at moderate temperatures before declining at higher temperatures. Among the evaluated temperatures, biochar produced at 400°C provided the most favorable balance of properties for horticulture. Greenhouse experiments showed that biochar-amended media had lower bulk density and greater total porosity than the peat-based control while maintaining favorable drainage and water-retention characteristics. Biochar-amended treatments also produced greater radish biomass and lower cumulative leaching of total inorganic nitrogen and total phosphorus, indicating improved nutrient retention and bioavailability within the growing media.

These findings demonstrate a beneficial reuse pathway for harvested Typha biomass that links wetland nutrient recovery with sustainable horticultural production. The results indicate that Typha-derived biochar can replace peat moss in horticulture, thus supporting circular nutrient management through the conversion of harvested biomass into valuable products.

Download

Share

COinS