Japanese knotweed composting feasibility

study, Delaware County, NY

Laurence Day, Jessica Rall — Delaware County SWCDSusan McIntyre — Delaware County DPWCharles Terrance — SUNY Delhi

Managing Invasive Species(e.g. Polygonum cuspidatum)

• We need a variety of Disposal Options

• Effect of climate change on

invasives = ?

[photo of knotweed at stream site]

Stream Rehab & Realignments

Problem: Invasives at Stream Rehab Sites

Drying extricated plants for burning, during a wet summer…

Delaware County Solid Waste Composting Facility, Walton

Biosolids composting requires sustainedtemperatures ≥55° C for 3 consecutive days.

Why not compost removed knotweed?

Might this compromise weed-free status of the county’s compost?

“Sentinel Chamber”

(Compost)

LIVE

Knotweed sample collection site

30 Samples each of 4 Tissue Types

Wrapped in Nylon Netting “Wontons”

Compost+Wanton+Compost+…

Filled “Knotweed Sentinel”

1. Three sentinels buried in compost for 3 days.

2. Six sentinels buried in compost for 6 days.

3. Moist heat only, 52° - 55° C for 3 days.

4. ‘Equipment blank’ placed samples in wontons & sentinels, then into growth chamber for 6 days.

5. Control Group planted directly into growth chamber at SUNY Delhi.

Four Treatment Groups + Control

Nine Sentinels Buried in Compost Two Groups: 3-days or 6-days

55° - 63° C, mean=61.3° C (142° F)

Moist Heat Treatment

52° - 55° C for3 consecutive days

Inspection and Potting

Growth Chamber, Summer Conditions27° C “days”(lights on)

19 ° C “nights”(lights off)

100% GROWTH vs. 0% GROWTH

CONTROL GROUP

COMPOST-BURIED GROUP

Both composting (≥3 d at >55° C) and moist heat (≥3 d at 52°-55° C) effectively killed all growth of roots and crowns (P<.01).

Root and Crown samples much more likely to sprout and grow than leaf or stem samples.

Sentinels performed well, although heat softened plastics; careful removal needed.

RESULTS

Temperatures adequate to safely compost biosolids are also appear effective on Japanese knotweed vegetation.

It appears feasible to compost knotweed at the Delaware County SWM facility, not compromising “weed-free” status of compost.

Simple, inexpensive “Sentinels” proved useful to safely assess composting feasibility for invasives.

Conclusions

NY Biosolids Composting Locations

(26 Locations in 19 Counties)

Epilogue

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