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King County Food Diversion
Cart Tag Study
Final Analysis Summary
Prepared by Cascadia Consulting Group
for King County Solid Waste Division
May 18, 2017
Study Team
Study Questions
▶ Do cart tag prompts increase residential
participation in food scrap diversion?
▶ Which (if either) tagging frequency supports
sustained behavior change?
▶ Do cart tags have different effects under
different service arrangements?
Tag Designs
Service Arrangements across Study Areas
Kenmore
North KC
Burien
Subscription service
Universal organics service
Weekly collection
EOW collection
Study Timeline
Kenmore Burien North KC
Audit – Baseline Nov 2015 March 2016 March 2016
Tagging – Round 1 (T2, T4)
Dec 2015 Apr 2016 Apr 2016
Tagging – Round 2(T4)
March 2016 July 2016 July 2016
Audit – Midpoint July 2016 Sep 2016 Sep 2016
Tagging – Round 3(T2, T4)
July 2016 Oct 2016 Oct 2016
Tagging – Round 4(T4)
Oct 2016 Jan 2017 Jan 2017
Audit – Final Nov 2016 March 2017 March 2017 *T2 HHs were assigned to receive tags biannually; T4 HHs were assigned to receive tags quarterly.
Audit Methodology
▶ Collected contents of paired HH garbage,
organics cart set-outs
▶ Random interval sampling
▶ 150 households sampled per study area
(plus contingency, even split T2/T4)
▶ Samples represent 7% of HHs with organics
service in study area
▶ 5 material list, only food capture calculated
▶ Error range for avg. food capture rates
<+/-10% at 90% confidence
Material Sort List:
1. Food
2. Compostable Paper,
Plastic, and Food-
Related Wood
3. Non-Compostable
Paper and Plastic
Food Service Items
and Packaging
4. Yard Debris
5. Other Material
Final Analysis
Findings
Tagging Implementation
Study
Area
# T2 HHs
in study
Not
Tagged
Tagged
1x
Tagged
2x
# T4 HHs
in study
Not
Tagged
Tagged
1x
Tagged
2x
Tagged
3x
Tagged
4x
Kenmore 695 7% 25% 68% 680 1% 10% 21% 37% 32%
Burien 1,542 11% 34% 55% 1,538 3% 8% 19% 33% 37%
North KC 1,219 4% 28% 68% 1,267 2% 5% 14% 35% 43%
TOTAL 3,456 8% 30% 62% 3,485 2% 7% 18% 34% 38%
▶ Not all households were tagged – only those with carts set out on day of tagging event.
▶ Only 62% of T2 assigned households actually received two tags.
▶ Only 38% of T4 assigned households actually received four tags.
Food Scrap Diversion Behavior - Participation
▶ Significant increase in
HH participation in
food scrap diversion in
Kenmore & North KC.
▶ Participation in Burien
was very high from the
start. Increased among
T4 households but not
statistically significant.
▶ Higher participation
from T4 HHs across all
study areas, but not
statistically significant.
Study Area Baseline
Participation Rate
Final
Participation Rate
T2 HHs (%) T4 HHs (%) T2 HHs (%) T4 HHs (%)
Kenmore 50% 44% 62% 68%
Burien 77% 78% 77% 85%
North KC 61% 58% 71% 74%
Food Scrap Diversion Behavior - Efficiency
▶ Over study period,
more HHs started
participating in food
scraps diversion and
existing participants
diverted more of
what they generated.
▶ Overall, the percent
of HHs diverting
<20% of food scraps
fell from 43% to 30%.
43%
5% 7% 9%
35%
0
50
100
150
200
0-20 20-40 40-60 60-80 80-100
Ho
use
ho
lds
Food Capture Rate(baseline)
30%
7% 9%14%
40%
0
50
100
150
200
0-20 20-40 40-60 60-80 80-100
Food Capture Rate(final)
Overall HH food scrap diversion efficiency distribution
Food Scrap Diversion Behavior - Efficiency
▶ Kenmore experienced
significant jump in
participation.
▶ The percent of HHs
diverting <20% of
food scraps fell from
59% to 41%.
▶ Diversion efficiency
of new participating
HHs was lower than
experienced HHs but
increased over time.
59%
3% 4% 6%
28%
0
20
40
60
80
100
0-20 20-40 40-60 60-80 80-100
Ho
use
ho
lds
Food Capture Rate(baseline)
41%
9% 12%8%
31%
0
20
40
60
80
100
0-20 20-40 40-60 60-80 80-100
Food Capture Rate(final)
Kenmore HH food scrap diversion efficiency distribution
Food Scrap Diversion Behavior - Efficiency
▶ In Burien, food scrap
diversion efficiency
was high from the
start but still
improved over time.
▶ By the end of the
study period, half of
all households were
diverting more than
80% of all food
scraps generated.
25%
5%11% 12%
48%
0
20
40
60
80
100
0-20 20-40 40-60 60-80 80-100
Ho
use
ho
lds
Food Capture Rate(baseline)
20%
7% 7%16%
50%
0
20
40
60
80
100
0-20 20-40 40-60 60-80 80-100
Food Capture Rate(final)
Burien HH food scrap diversion efficiency distribution
Food Scrap Diversion Behavior - Efficiency
▶ In North KC, food
scrap diversion
efficiency distribution
shifted significantly
toward higher rates.
▶ Over study period,
more households
started diverting food
scraps and existing
participants diverted
more food scraps.
45%
9% 8% 10%
29%
0
20
40
60
80
100
0-20 20-40 40-60 60-80 80-100
Ho
use
ho
lds
Food Capture Rate(baseline)
30%
5%9%
17%
38%
0
20
40
60
80
100
0-20 20-40 40-60 60-80 80-100
Food Capture Rate(final)
North KC HH food scrap diversion efficiency distribution
Food Capture Rates – All HH Set-Outs
▶ Overall, average food
capture rates increased
by 20% (9 % points).
▶ Kenmore average food
capture rates increased
by 22% (8 % points).
▶ Burien average food
capture rates increased
by 8% (4 % points).*
▶ North KC average food
capture rates increased
by 37% (15 % points).
45%35%
61%
40%
54%
43%
65%55%
0%
20%
40%
60%
80%
100%
Overall Kenmore Burien North KC
Perc
ent
of
Foo
d C
aptu
red
Baseline Final
Avg. food capture rates among all HHs with paired set-outs
2014 KC = 39.5%
*Change not statistically significant
Food Capture Rates – Participating HHs
▶ Overall, average food
capture rates among
participating HHs did
not change even
though the number
of participating HHs
increased.
▶ Small changes
observed among
participating HHs within
Kenmore and North KC
study areas are not
statistically significant.
Avg. food capture rates among HHs participating in food scraps diversion
2014 KC = 66.6%
73% 74%78%
66%73%
65%
78%72%
0%
20%
40%
60%
80%
100%
Overall Kenmore Burien North KC
Perc
ent
of
Foo
d C
aptu
red
Baseline Final
Organics Contamination Rates - Overall
▶ Overall, organics
contamination rates
increased slightly but
changes are not
statistically significant.
▶ In Burien and North KC,
organics from
participating HHs had
higher contamination
than non-participating
HHs at final audit but
differences are not
statistically significant.
Overall Organics Contamination Rates
2.0%
0.8%
3.0%
2.4%2.3%
1.1%
2.6%
3.4%
2.1%
0.9% 1.0%
5.2%
2.9%
0.8%
3.3%
5.0%
0.0%
1.0%
2.0%
3.0%
4.0%
5.0%
6.0%
Overall Kenmore Burien North KC
Perc
ent
of
Org
anic
s C
olle
cted
Baseline (all set-outs) Final (all set-outs)
Baseline (participating HHs) Final (participating HHs)
2014 KC = 2.4%
Organics Contamination – HH Behavior
▶ Although changes in
contamination rates
were not significant,
the number of HHs
participating in food
diversion with >5%
contamination
increased sharply.
▶ At final audit, 1 in 5
participating HHs had
>5% contamination
in organics carts.
Participating HH contamination rate distribution
69%
10%3% 3% 2%
12%
0
50
100
150
200
250
<1% 1%-2% 2%-3% 3%-4% 4%-5% >5%
Ho
use
ho
lds
Contamination Rate(baseline)
63%
7% 6% 3% 1%
20%
0
50
100
150
200
250
300
<1% 1%-2% 2%-3% 3%-4% 4%-5% >5%
Contamination Rate(final)
Food Scrap Generation – HH Behavior
▶ Across all study audits,
food scrap generation
was higher among HHs
participating in food
diversion compared to
non-participating
households.
▶ Less food scraps among
non-participating HHs
may indicate underlying
demographic differences
(e.g. HH size, age, etc.).
2014 KC avg. = 49.1 lbs/hh/mo
31.8
40.035.2
48.7 49.652.9
0.0
10.0
20.0
30.0
40.0
50.0
60.0
Baseline Midpoint Final
Lbs
Foo
d G
ener
ated
Per
Mo
nth
Non-participating HHs Participating HHs
Avg. HH Food Scrap Generation Rates
Study Questions & Answers
▶ Do cart tag prompts increase residential food
scrap diversion? YES!
▶ Which (if either) tagging frequency supports
sustained behavior change? BOTH!
▶ Do cart tags have different effects under
different service arrangements? Bigger impact
in areas with lower participation at the start.
Final Takeaways
▶ Participation is (still) highest where organics service is universal and weekly.
▶ Increasing food diversion requires “activating” new households. (i.e. get households not currently diverting food scraps to start participating.)
▶ Cart tag “prompts” can activate new households to participate in food
diversion and also increase diversion from households already participating.
▶ Cart tag “prompts” effects increased with repetition.
▶ Increased food diversion may lead to higher contamination.
▶ Households that generate less food waste may be less likely to participate in
food diversion.
Lessons Learned
1) Cart-based audits can cause a stir…
‒ Field crew must be professional, well prepared
‒ Successful de-escalation requires all hands
(field crew, customer service staff, project managers)
…but the data gathered is valuable.
‒ Only way to assess household-level behavior
‒ Can improve program targeting, cost-effectiveness
Lessons Learned
2) Cart tag placement is labor-intensive…
‒ 2-person team can tag 500-700 HHs in a day.
‒ Tagging staff must be professional, organized,
efficient, hardy, and comfortable with data tracking.
…but technology can create major efficiencies.
‒ Spotio app cut tag placement times by 20-30%.
Lessons Learned
3) Cart tags designed for
recyclability do not hold up
well in heavy rain.
‒ Tag placement should be done
during dry weeks or alternate
design should be considered.
Lessons Learned
4) Single cart tagging events
do not reach all households.
‒ Tag placement should be done
repeatedly, at regular intervals,
to ensure all households receive
information.
‒ Study outcomes represent
effects of 2x year tagging.
Outreach Recommendations
▶ Focus on starting the behavior; rather than ‘doing more’
▶ Tag cart to start behavior at least 2x/yr
▶ Keep tag message focused (audience testing needed)
1. Place food in yard waste cart
2. Keep out contaminates
▶ Focus on contamination message separately and in priority
Outreach Recommendations
▶ Use tagging as part of an integrated campaign to change social norms and overcome barriers
Strategy Tactics
Raise awareness that you can compost at curb • Traditional Media• Social media• Direct mail
Provide tools and education to make it easy • Through grassroots outreach – events, outreach, one-to-one
• If possible, at point of YW service signup or service level change
• Collect commitments
Prompt to start behavior or modify behavior (contamination) • Curbside cart tags• Collect commitments
Provide feedback • E-communications• Social media• Direct mail
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