No/low-cost chipped woody debris nutrient composition benefits and tradeoffs for denitrifying bioreactors

Woodchip cost and sourcing availability may be barriers for denitrifying bioreactor implementation. This survey comparison of nutrient composition improves understanding of the spectrum of widely available wood media. Sixteen new woodchip types purchased from bulk suppliers and six chipped debris media sourced for free at the supplier were analyzed for carbon (C), nitrogen (N), phosphorus (P), cellulose, and lignin. Results were presented in context of woodchips harvested from saturated and unsaturated portions of operational bioreactors. The municipal debris was not significantly different from the bulk woodchips in C or cellulose concentrations (e.g., medians 46.7 vs 47.7 %C, respectively) but had significantly greater N and P concentrations (e.g., 0.45 vs 0.27 %N, respectively). The lower C:N, C:P, and lignin:N ratios of the chipped debris versus bulk supplier (e.g., C:N of 103 vs 177, respectively) highlighted that the role of macronutrients in supporting a diverse “bioreactor ecosystem” (e.g., decomposers who make C available) is not fully understood. Useful ranges of nutrient and fiber composition were provided for future modeling efforts.