Asserting carbon offsets from landfill gas flaring at regina’s landfill site
Fate of Elm Diseases in Municipal Composting
1. The Fate of Elm
Diseases in a
Municipal
Composting
Environment
2. PROJECT OVERVIEW
Goal:
To determine whether or not elm diseases are
destroyed during composting
Implication:
Determine whether or not diseased
wood must be kept out of compost
feedstocks
4. BACKGROUND – PROJECT IMPETUS
Edmonton’s Gore composter processes
biosolids and wood chips
Parks Branch provides clean green wood
Diseased wood from Forestry is diverted to
landfill
Reduces risk of
disease spread
Parks Branch is a
major consumer of
Gore compost
5. BACKGROUND – PROJECT IMPETUS
Possibility of diverting a portion of
Forestry’s diseased wood from the
landfill.
There are other contributors of wood to the
Gore process
Not necessarily screened
Need to determine the fate of some
common local plant diseases during
composting
6. BACKGROUND – SOME COMMON
DISEASES
Dothiorella ulmi
D. ulmi-infected elm
makes up the majority of
landfilled wood
Verticillium dahliae
and V. albo-atrum
Have been isolated from
elm in Edmonton area
Have wide host ranges
7. LITERATURE REVIEW
Plant pathogens can be inactivated by
exposure to heat
Heat tolerance varies by organism and form
No time-temperature guidelines for plant
pathogens in North America
Human pathogens: 55oC for 3 days
8. LITERATURE REVIEW
Verticillium dahliae
Eliminated in small-scale composter when material
turned, Tmax ≈ 70oC, and T > 50oC for 10-14 days
V. albo-atrum & Dothiorella ulmi
Nothing in the literature
D. ulmi laboratory incubation tests suggest that
typical composting temperatures should
be adequate
Fungi and fungi-like species
Some species survived T > 55oC
9. SPECIFIC OBJECTIVES
Determine to what degree D. ulmi, V.
dahliae, and V. albo-atrum are inactivated
by time-temperature conditions in Gore
composter.
How likely is it that these organisms will be
eradicated in the Gore composter?
Does diseased wood need to be diverted from
the composter?
10. OVERALL EXPERIMENTAL PLAN
Wood chip inoculation experiments
Place bagged infected wood chips in the
Gore system during the high-temperature
phase
Periodically recover bags and evaluate
pathogen survival in composted
elm wood
11. PROCEDURES - WOOD CHIP
INOCULATION
Wood chip inoculation procedure optimized
Inoculum prepared from fungal cultures
Wood chips sterilized by autoclaving, then
sprayed with inoculum and agar plugs placed
Incubated for 26 days at 22°C
Verticillium
Dothiorella ulmi albo-atrum
Control Verticillium dahliae
12. PROCEDURES – SAMPLE
PREPARATION
Infested wood chips sealed in sterilized
Ziploc bags (with air space).
Organisms affected by temperature only.
Ziplocs placed into nylon mesh bags
“Sample bundles” created
One bag for each organism,
plus a temperature probe.
15. PROCEDURES – SAMPLE
COLLECTION AND TESTING
Sample bundles and compost samples
collected periodically
Every day or two for first week, and weekly or
biweekly thereafter.
Wood chips tested for pathogen survival
Temperature data examined
17. RESULTS – PATHOGEN SURVIVAL VS.
TEMPERATURE
Sample Location
X1 X2 X3 X4 X5 X6 X7
≥ 70 °C 0 0 0 0 0 0 8.7
Total amount ≥ 65 °C 0 0 0 0 0 0 11.2
of time ≥ 60 °C 0 0 0 0 0.8 0 13.7
(days) that ≥ 55 °C 0 0 0 0 2.6 3.2 21.5
various ≥ 50 °C 0 0 0 0 12.3 16.0 35.6
temperatures ≥ 45 °C 0 0 0 7.1 20.3 26.5 39.7
were ≥ 40 °C 0 0 5.5 11.1 26.1 30.0 39.9
exceeded ≥ 35 °C 0 0 11.7 17.6 34.4 38.5 40.0
≥ 30 °C 0 0 21.3 30.1 38.6 38.9 40.1
Pathogen D. ulmi + + - - - - -
survival at V. albo-
end of atrum + + - - - - -
composting V. dahliae + + - - - - -
18. RESULTS – PATHOGEN SURVIVAL VS.
TEMPERATURE
Bags at locations where pathogen
destruction was seen were compressed.
Testing was done at room temperature in
compressed (anoxic) bags
Pathogens survived anoxic conditions
19. CONCLUSIONS
Appears that D. ulmi, V. albo-atrum, and V.
dahliae will be inactivated if temperatures
exceed 40°C for more than 5.5 days.
Likely to occur in interior of pile; perhaps not in
outer layer.
Important to ensure that all materials from
exterior zones in Stage 1 get mixed into higher
temperature zones in subsequent stages.
May not need to divert diseased wood to
landfill.
20. RECOMMENDATIONS
Repeat trial 2x more, with modifications to
improve procedures, e.g.
Better sorting of wood chips
Use of rigid sample containers
Study temperature profiles in Gore Stages 2
and 3 (curing) in detail
Potential small-scale reactor study
Pinpoint time-temperature requirements
Determine suitable indicator organisms
22. CONTACT INFO
Kristine Wichuk
kwichuk@ualberta.ca
Daryl McCartney
daryl.mccartney@ualberta.ca
23. The Fate of Elm
Diseases in a
Municipal
Composting
Environment
24.
25.
26. RESULTS – COMPOST
Pathogen survival not affected directly by
MC, pH, or C:N
MC : ~53% to ~62% at start
~32% to 55% at end
pH : ~7.6 to ~7.8 at start
~7.3 to ~8.4 at end
C:N: varied throughout pile at start and end
27. RESULTS – PATHOGEN SURVIVAL
X2, Day 42
X7, Day 42
D. ulmi V. dahliae V. albo-atrum