There are frequent accidents at anaerobic digestion plants during construction and operation due to gas explosions and exposure to toxic hydrogen sulfide gas. Many of these accidents are preventable through proper risk mitigation measures. During construction, risks can be reduced through adherence to the Construction Design and Management regulations, which require principal designers and careful attention to interfaces between equipment. During operation, permanent gas monitoring, confined space procedures, training, and permit-to-work programs can help protect workers from gas exposure. Incident reports show common risks involve maintenance activities, mixing of feedstocks, and overloading of digesters leading to gas release.

1. RISK MANAGEMENT –
CONSTRUCTION AND OPERATION
#UKADBiogas @adbioresources
CHAIR:
ANDY COOPER, CLARKE ENERGY
PANEL:
ALLAN JOYCE, BALMORAL TANKS
LES GORNALL, PROJEN
MAJA ROSIAK, XYLEM WATER SOLUTIONS
DAVID PLEWS, ESTERLINE

2. Risk Management
Construction and Operation
Dr. Les Gornall
Process Consultant
Purple Seminar 2nd July 12.00 hrs

3. Risk Management
Reference: Waste Management World - Local Generation AD Plant, 2011
• Learning from mistakes
Fires and explosions
H2S - One Breath is Death
• Bunds (spill containment)
• Other Hazards
• Construction &Design Mgt.
• Interfaces between equipment

4. Learning from mistakes – Fires and Explosions
• Close to 10,000 biogas installations in EU
• One event every month or two
• Injuries occurred on about half, some serious
• EVERY ONE WAS PREVENTABLE
*See Zebec report and Google map of incidents in refs

5. Frequent Key Words in reports
• Explosion + during commissioning (Take Off)
• Explosion + maintenance (Landing)
• Explosion + welding
• Explosion + bolt or material failure
• Explosion + Intern or Trainee
• Explosion + unknown causes

6. Gas Explosions
• The dangerous gas condition is 5%-15% methane in 95% air
a LITTLE Gas in a LOT of Air
RISK MITIGATION
• DSEAR and ATEX
• Permanent gas monitoring
• Personal gas monitors
• Permit To Work
About once a month in the UK a structure is blown up by a little gas in a lot of air.

7. How Many H2S and Asphyxiation incidents?
• 2005 Rhadereistedt 4 deaths + 12 injured
• 2008 Malvar Philippines 4 deaths
• 2009 Lowbrook farm UK 1 Death + 1
injured
[Started UK –AD safety review]
• 2010 UK rendering plant 2 injured (n/ miss)
• 2012 NI Farm 3 Deaths + 1 injured
• 2013 Kelheim 4 injured , 2 seriously
Ref Zebec and Google Maps

8. Frequent Key Words in Reports
• Asphyxiation + Commissioning (Take Off)
• Asphyxiation + Maintenance (Landing)
• Toxic Gas + Unexpected
• Toxic Gas + Intern or Trainee
• H2S + Unloading Organic Wastes in Reception
• H2S + Mixing different Organics in Reception
• Stirring Slurry
H2S inside the digester can reach 3,000 – 10,000ppm,
Treated by Thiobacillius this typically reduces to 1,200 – 2,000 ppm
At 1,000ppm H2S One Breath is Death
Reduction to typically 50-500ppm is achieved by ferric chloride dosing

9. Reducing risk to the environment with Bunds…
CIRIA report C736 - Containment systems for the prevention of
pollution
I=H-h

10. ….Increases risk to operators
Biogas H2S
/ CO2
sludge
Biogas,
CH4, H2S
CO2
Biogas,
CH4, H2S
CO2
When a digester is overloaded Biogas is heavier than air
and foam sludge can break containment ending in the bund
PRV
Bund

11. Manage the Risk
• Managers and Operators
must be able to identify a
confined space
• Special AD issues – mixing
organic feeds can release
gas – Good ventilation
systems and Standard
Operating Procedures
required
• ADBA safety committee –
training-needs matrix –
see the ADBA AD Manual

12. • 2013 Angermuende 1 Death (feed bin)
• 2013 Otter Mountain - fall through roof of fermenter , 1 seriously injured
• 2014 UK 1 Death (crushing accident during construction of an AD Plant)
Other Hazards

13. CDM
• Control of the safety during design and construction is
governed by the CDM 2015 regulations
• Client has more responsibilities
• Need for Principle Designer
http://www.hse.gov.uk/construction/cdm/2015/index.htm

14. Interfaces between equipment
Equipment packages from different suppliers?
• the digester gas train,
• food waste depackaging,
• buildings and civils,
• electrical control gear, etc.
• Pay great attention to the interfaces
• Use Chemical industry quality disciplines : PFD , P&ID,
[HAZOP], SIL, URS , FDS , SMART TOOLS , O&M Manuals
and Risk Registers during Design and Construction
This makes commissioning take off quicker and safer

15. Thank you!
Dr. Les Gornall
D.Phil., BSc.(Hons), C.Biol., FRSB
Process Consultant
PROjEN Ltd
Part of CAPITA
DD: 01928 752 568
Mob: 07921 388 422
Email: les.gornall@capita.co.uk
Shanks Westcott Park – Buckinghamshire (AD Plant)

16. RISK MANAGEMENT –
CONSTRUCTION AND OPERATION
#UKADBiogas @adbioresources
CHAIR:
ANDY COOPER, CLARKE ENERGY
PANEL:
ALLAN JOYCE, BALMORAL TANKS
LES GORNALL, PROJEN
MAJA ROSIAK, XYLEM WATER SOLUTIONS
DAVID PLEWS, ESTERLINE