Guidance

Biowaste: examples for your adapting to climate change risk assessment

Updated 17 May 2023

Applies to England

Possible impacts and mitigation measures to consider when preparing your climate change risk assessment.

Summer daily maximum temperature

This may be around 7°C higher compared to average summer temperatures now, with the potential to reach extreme temperatures as high as over 40°C with increasing frequency based on today’s values.

Impact 1

Overheating of vessels and pipework at anaerobic digestion plants, requiring increased insulation and cooling.

The potential increase in surface temperature of infrastructure may result in expansion and stress of plant, pipework and fittings.

The mitigation for this would include:

• regular inspection and preventative maintenance of site and plant or equipment
• increased process monitoring
• making sure pressure relief systems are working effectively
• investing in increased flaring capacity to burn methane rather than emitting to the atmosphere

Impact 2

Potential for increased fires involving combustible waste stockpiles.

The mitigation for this would include:

• increased moisture and temperature monitoring
• moisture adjustment

Sites must have capacity to store and treat all inputs to prevent large stockpiles of material.

Impact 3

Increased changes in feedstock, low nitrogen waste (less grass) and slower processing times.

The mitigation for this would include:

• keeping windrows to a maximum height of 3m to encourage heat loss
• monitoring carbon to nitrogen mix and adjustment
• increased temperature and moisture monitoring and adjustment

Impact 4

Potential increased dust emissions and bioaerosols.

The mitigation for this could include:

• moisture control of material to maintain moisture levels at 40% to 50%
• monitoring bioaerosols as required by the permit
• considering boundary PM10 and PM2.5 monitoring
• stopping turning when wind direction is towards any sensitive receptor, or when particulate monitors are triggered
• damping down and sweeping operational areas daily
• harvesting clean water for use on operational areas and sanitised material
• recirculation of leachate for new feedstock

Impact 5

Increased pest and flies.

The mitigation could include:

• rejection of odorous and pest infected waste
• using approved insecticides
• making sure ducts, drains and pipe work are cleaned and site housekeeping is of high standards

Impact 6

Lower gas uptake from National Grid. Power disruption from district network supply.

The mitigation for this could include:

• contingency to slow feedstock rate to lower gas yield at times when grid off-take is reduced
• making sure that combustion contingency is available

Winter daily temperature

This could be 4°C more than the current average with the potential for more extreme temperatures, both warmer and colder than present.

Impact 1

Longer growing seasons resulting in more garden waste and sites over capacity.

The mitigation for this is to make sure composting sites have available capacity and there is correct high grass content input to oversize material (carbon to nitrogen ratio).

Impact 2

Poor crop yields and feedstock scarcity for anaerobic digestion could lead to reduced digester performance.

The mitigation for this could include:

• feedstock adaptation within the plant design
• increased monitoring of feedstock to ensure the right organic mix to maintain digester stability

Daily extreme rainfall

Daily rainfall intensity could increase by up to 20% on today’s values.

Impact 1

Unstable process conditions for compost sites causing temperature fluctuations and increased odours.

The mitigation for this could be:

• process monitoring at increased frequency
• additional sampling points in open processes

Impact 2

Land bank availability for spreading sludge, compost and digestate may experience extreme difficulty due to prolonged wet weather.

The mitigation for this would be development and management of contingency plans for on-site and off-site safe storage.

Impact 3

Leachate storage risk of over-topping.

The mitigation for this could include:

• making sure there is 750mm of free board on lagoons and tanks systems to prevent over-topping
• installing high level alarms
• making sure lagoon levels are lowered before increased forecast rainfall
• harvesting clean water to prevent lagoons tanks being overwhelmed

Impact 4

Localised flood events.

The mitigation for this would include:

• inspecting or hydraulically testing tanks and lagoons to make sure integrity is maintained as the surrounding ground dries, to prevent underlying base movement and tank fracture
• making sure all sites can contain any loss of primary containment
• preparing a flood plan with reference to the guidance Preparing for flooding: A guide for sites regulated under EPR and COMAH
• contingency for diversion and site storage when land bank is not available

Average winter rainfall

Average winter rainfall may increase by over 40% on today’s averages.

Impact 1

Potential for increased site surface water and flooding.

Mitigation for this would be to a prepare flood plan with reference to the guidance Preparing for flooding: A guide for sites regulated under EPR and COMAH.

This should include:

• identification and risk assessment of process equipment and services at greatest risk from flooding
• provision of emergency pumps to remove floodwater and identification of lowest risk location for discharge of floodwaters
• protection of control and electrical systems
• identification and protection of flat bottom tanks at risk of floating in floodwater

Impact 2

Potential for drainage systems and interceptors to be overwhelmed.

The mitigation for this could be to make sure:

• suitable measures are in place for the management of flood waters, where relevant
• drainage systems are inspected and maintained
• external areas where wastes are handled or stored are provided with contained drainage
• the site drainage system and effluent treatment plant has sufficient storage and treatment capacity

Impact 3

Access or egress from site could be affected, impacting:

• staff
• suppliers
• deliveries
• removals of product
• emergency services

Sites without an off-site emergency plan should consider these potential impacts and develop an emergency plan.

The mitigation for this would be to develop a suitable emergency plan that fully considers these impacts.

Sea level rise

Sea level rise which could be as much as 0.6m higher compared to today’s level.

Impact 1

If a site is located near the coast, there is potential increased risk of flooding.

The mitigation for this would be to review flood defences around coastal landfill sites and to produce a flood plan with reference to the guidance Preparing for flooding: A guide for sites regulated under EPR and COMAH

This should include:

• identification and risk assessment of process equipment and services at greatest risk from flooding
• provision of emergency pumps to remove floodwater and identification of lowest risk location for discharge of floodwaters
• protection of control and electrical systems
• identification and protection of flat bottom tanks at risk of floating in floodwater

Drier summers

Summers could see potentially up to 40% less rain than now.

Impact 1

Increased need for water for digesters.

The mitigation for this would be:

• contingency for importation of water and aqueous wastewater harvesting on site
• encouraging facilities to harvest and separate clean water

Impact 2

Poor crop harvest and reduced feedstock.

Mitigation for this would include:

• contingency for importation of water and aqueous wastewater harvesting on site
• encouraging facilities to harvest and separate clean water

River flow

The flow in the watercourses could be 50% more than now at its peak, and 80% less than now at its lowest.

Impact 1

River flows unable to accept discharge flow due to low dilution.

The mitigation for this would be to have an accident plan and emergency measures to divert waste or disposal if necessary.

Storms

Storms could see a change in frequency and intensity. The unique combination of increased wind speeds, increased rainfall, and lightning during these events provides the potential for more extreme storm impacts

Impact 1

Storms and high winds could damage buildings and other structures, such as stacks and tank covers, with the potential to increase fugitive emissions.

The mitigation for this could include:

• reviewing the design of vulnerable structures and buildings
• reviewing wind loading calculations, providing reinforcement if necessary
• maintaining building integrity
• reviewing ability of tank covers to withstand severe winds
• reviewing adequacy of lightning protection of digestors and their roofs