Assessing and addressing the impact of warmer autumns on the success of grain cooling - Dean Cook (FERA)

Assessing and addressing the impact of warmer autumns on the success

of grain cooling

Dean Cook

Science Strategy team

Grain Cooling

• Grain is ventilated at low-volume rate of 10m3/h/t

• Cooling must be – – fast enough to prevent insects

breeding; and temperature as low as to cause death

– Part of an integrated grain storage strategy in conjunction with drying, hygiene measures and monitoring

As a rule of thumb…….

• Cool to below 15°C within 2 weeks to prevent the saw-toothed grain beetle breeding;

• to below 10°C within a further 2 months to prevent the grain weevil breeding;

• to below 5°C by winter (xmas) to prevent mites breeding and kill insects.

Cooling targets for UK stores using low volume aeration at 10 m3/tonne/hr

Cooling starts on 1 J ul 1 Aug 1 Sep 1 Oct

Latest 15°C 16 J ul 17 Aug 12 Sep 8 Oct

date to 10°C 29 Sep 9 Oct 14 Oct 9 Nov

cool to 5°C 8 Dec 8 Dec 9 Dec 1 J an

(After – Armitage et al., 1991)

Has cooling become more difficult? – climate change

• Climate change will bring; Earlier, hotter harvests

Shorter milder winters

Extreme weather events

• Issues for cooling? High harvested temperatures

Fewer “windows” of cold night time air available

Challenge to meet targets; speed and temperature achieved

Comparison of mean monthly temperatures from 1961 to the present day.

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J F M A M J J A S O N D

1990199119921993199419951996199719981999200020012002200320042005200620071961/90

(Source: Manley, 1974; Parker et al., 1992 – updated by the Hadley Centre for Climate Prediction and Research, Met. Office, Berkshire, UK.)

Minimum temperatures for the period immediately after harvest.

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J A S O

199019911992199319941995199619971998199920002001200220032004200520062007

Target 1.

Target 2.

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J A S O

199019911992199319941995199619971998199920002001200220032004200520062007

Target 1.

Target 2.

Target 1.

Target 2.

(Source: Manley, 1974; Parker et al., 1992 – updated by the Hadley Centre for Climate Prediction and Research, Met. Office, Berkshire, UK.)

Adaptation to climate change – demonstration project

Objectives – “How well are we doing?”“How can we do things better?”

• Measure on-farm cooling profiles in grain stores on 15 farms distributed throughout the UK from harvest 2007

• To compare the performance of automated differential fan control with manual control at 3 sites using identical paired stores

• To illustrate potential problems and “best practice”

Part 1. Efficient control – using differential thermostats

Differential thermostats

Temperature probe inserted into grain

Temperature sensor at ambient

Feedback to fan control

Temperature probe inserted into grain

Temperature sensor at ambient

Feedback to fan control

Advantages of differential thermostats; trials work, East Lincolnshire 1991.

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1 3 5 7 9 11 13 15Weeks storage

Tem

pe

ratu

re °

C

Ambient

Automated store

Manually controlled store

SEPTEMBER DECEMBER

[Auto-control using a 4°C differential in conjunction with time clock (20.00-07.30, night time only) Vs manual control.]

Trial detail – differential thermostats vs manual control.

Focusing on 2 sites -

Site 1 - • Farm site, Darlington

• 700t bulk of wheat at 14.5%mc

• Cooled with pedestals at recommended spacing etc.

• Bulk divided into virtual halveshalf bulk controlled by 2°C differentialhalf bulk controlled by manual operation of fans

Darlington trial setup

4.5 – 6 m spacing between pedestals

Small pedestal/fan to deal with corner

Door

Leading edge of heap

PC running STORECHECK

Single fan between 2 –manual control

Single fan between 2 –auto control

= pedestals = sensors °C

123

456

21

3

456

Zone 1Zone 2

4.5 – 6 m spacing between pedestals

Small pedestal/fan to deal with corner

Door

Leading edge of heap

PC running STORECHECK

Single fan between 2 –manual control

Single fan between 2 –auto control

= pedestals = sensors °C

123

456

21

3

456

Zone 1Zone 2

Site 1 – Results; Temperatures at Darlington site and progress against cooling targets

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7-Sep 17-Sep 27-Sep 7-Oct 17-Oct 27-Oct 6-Nov 16-Nov 26-Nov 6-Dec 16-Dec

Date

Tem

pera

ture

°C

Auto (mean)

Manual (mean)

Ambient (minimum)

15°C Target due 18-Sep

5°C Target due 15-Dec

10°C Target due 20-Oct

Site 1 – Results; Cumulative fan hours run

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15-Sep 25-Sep 05-Oct 15-Oct 25-Oct 04-Nov 14-Nov 24-Nov 04-Dec 14-Dec

Date

No

. of

ho

urs

blo

wn

Manual

AutoUp to 40% energy saving!

Comparison of insect control costs

PROCESS COST FUNCTIONS

Fumigation 150-200p/t - Disinfests

Bulk insecticide admixture 50-75p/t - Prevents and disinfests

Cooling (manually) 50 p/t - Prevents mc Cooling (automatic) 29 p/t movement

- Prevents infestation - Preserves quality - Disinfests over a

season

Trial detail – differential thermostats vs manual control.

Focusing on 2 sites -

Site 2 - • Co-operative store, Cambridgeshire

• Two 6000t silos of wheat at 14-15%mc

• Cooled with upward aeration systemOne silo controlled by 4°C differentialOne silo controlled by manual operation of fans

Site 2 – Results; Temperatures at Cambridgeshire site and progress against cooling targets

Site 2 –Results; Daily spot temperatures (8am) at Cambridge site

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05-Oct 20-Oct 04-Nov 19-Nov 04-Dec 19-Dec 03-Jan

Date

Tem

per

ature

°C

Ambient

auto bin (D2)manual bin (D4)

1 2

Hours run1. (2-Nov)Auto; 98Manual; 83

2. (4-Dec)Auto; 142Manual; 155

3. (7-Jan)Auto; 156Manual; 236

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10°C Target due 14-Oct

5°C Target due 9-Dec

Site 2 –Results; Daily spot temperatures (8am) at Cambridge site

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05-Oct 20-Oct 04-Nov 19-Nov 04-Dec 19-Dec 03-Jan

Date

Tem

per

ature

°C

Ambient

auto bin (D2)manual bin (D4)

1 2

Hours run1. (2-Nov)Auto; 98Manual; 83

2. (4-Dec)Auto; 142Manual; 155

3. (7-Jan)Auto; 156Manual; 236

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10°C Target due 14-Oct

5°C Target due 9-Dec

Part 2. Monitoring exercise – how well are growers doing?

Monitoring exercise overview

iButtons monitoring ambient and fan temperature

Results – monitoring 12 sites across the country

  Location Air flowP=PedestalU=Under-floor

Differential Target (oC)

Target met

Best performing

Berwickshire ~10m3/t/hP

No 

15105

On time1 week early1 week early

Worst performing

Suffolk ~10m3/t/hU

No 

15105

10 weeks lateNot metNot met

• Only 1 site achieved the 15°C target on time• 3 sites achieved the 10°C target on time• 3 sites achieved the target of 5°C on time• 11 stores cooled to 10°C• Only 4 stores cooled to 5°C and below

Five day running mean of ambient temperatures at monitoring locations

Oxfordshire – why stop cooling?

Leicestershire – only cooled on 2 occasions

Lincolnshire – the importance of the correct differential

Part 3. What about the future?

David Bruce Consulting Ltd

Weather data – UKCP09

Weather Generator of UKCP09 hourly weather

Assumptions• Time into future, in 30yr windows. 2020-2049• Emissions scenario. High• ‘Percentile’ is probability of change being as

large as embodied in the data:– 90% (‘very likely’)– 50% (‘as likely as not’)

• Control ‘historical’ data. 1960-1989• Location: Odiham, Hants

Cooling parameters

• Strategy - diffstat control set at 4oC• Sensor at 0.5m depth• 4m bed, 14.5% mc, 25oC, 10 m3/h.t, start 20

Aug• Target temperature 5oC by end December• Also cooled to end February with the same

target of 5oC

Summary of climate change results

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Control(historic)

90% likely 50% likely

Climate change scenario

Tem

per

atu

re,

oC

Target temperature for cooling

88%

61%

38%

Conclusions

• Not all storekeepers are hitting their cooling targets

• Need to continue to improve operator practice

• Differential thermostats can help you achieve cooling targets and can save up to 40% energy-use and running costs

• Future climate change may impact on cooling targets but……will still be able to control insect pests

We would like to thank…….

Participating stores and in particular, Stuart Vernon (Grower, Country Durham), Andrew Ruff and Philip Darke (Camgrain) who took part in the differential control trials.

 The work was funded by – Warwick HRI's Defra-funded Innovation network for

adapting agriculture to climate change. Defra through the Sustainable Arable LINK programme

Thank you for listening!