Decarbonisation of residual waste infrastructure: report

Executive Summary

In November 2021, the Minister for Green skills, Circular Economy and Biodiversity appointed Dr Colin Church to act as independent Chair of the Review of the role of incineration in the waste hierarchy in Scotland (‘the Review’). Dr Church delivered his First Report, Stop, Sort, Burn, Bury? in April 2022 and the Scottish Government published it and its response in June 2022. As the time for the Review to be completed was short, the First Report was unable to consider the issues around decarbonisation of residual waste management infrastructure in great depth. Dr Church was therefore asked to produce a further report to address this issue in more detail.

This Second Report, as part of the Review, seeks to evaluate the opportunities to decarbonise the residual waste treatment infrastructure sector in Scotland and in doing so considers the following questions:

• What does the current carbon impact of disposal of waste look like?
• What are the possible options to decarbonise residual waste infrastructure?
• What are the most effective and feasible options to improve existing waste management infrastructure in terms of carbon performance?
• What combination of options is the most feasible for Scotland?

The scope of the Second Report is residual waste infrastructure greenhouse gas emissions (primarily carbon dioxide from incinerators and methane from landfill), for the treatment of household (HH), and commercial and industrial (C&I) waste, with a focus on waste incineration infrastructure (including that in construction and likely to be developed). Both technology changes as well as systematic changes to decarbonise infrastructure are considered.

In preparing the Second Report, the Review team considered stakeholder feedback gathered through the initial Call for Evidence, which is summarised in the evidence document published alongside the First Report; two stakeholder events; and a number of additional contributions from stakeholders. The review also received a report from Eunomia, which set out to assess the effectiveness of options to decarbonise existing waste infrastructure. The additional contributions and the Eunomia report are published alongside the Review’s Second Report.

Greenhouse Gas Emission Reporting

The Second Report briefly looks at how greenhouse gas emissions associated with the resource and waste management sector are reported. Its conclusion is that current reporting doesn’t accurately reflect the full picture of the sector’s impact. For example, the Eunomia report identifies four categories of emissions impact for incineration:

1. Direct emissions from the incinerator

2. ‘Recycling credits’ – emissions avoided by using recycled materials rather than virgin ones

3. ‘Energy credits’ – emissions avoided by displacing other forms of energy generation (heat and/or electricity)

4. ‘Biogenic carbon capture credits’ – the allowance for burning biogenic waste and capturing the short-cycle GHGs that are then emitted (sometimes also known as ‘negative emissions’)

Of these, only 1 is generally reported (as an energy emission) and none is attributed to the waste sector.

This can lead to perverse incentives on decision makers and stands in the way of the holistic, systemic view of the resource and waste management that the Review has previously recommended. The Review therefore proposes that emissions reporting be examined and changes made to ensure decision makers can understand the full system impact of their decisions, in particular with respect to biogenic emissions (see Recommendation 15).

Emissions Trading

The Review also notes the current discussions on the extension of the UK Emissions Trading Scheme (UKETS) to cover incineration with energy recovery. Given that this could prove a useful tool to incentivise action, the Review supports this extension as one (but not the only) potential policy tool to drive decarbonisation of incineration (see Recommendation 16).

The Review considers that Recommendation 2 (from the First Report) on the need to consider the resource and waste management system as an inter-dependent system is relevant to this topic and the UK and Scottish Governments will need to consider the impact on that whole system from including incineration in the UKETS.

Options for Decarbonisation

The Review then considers options to decarbonise the sector. As stated in the First Report, the best approach on all levels is to avoid residual waste in the first place. However, for the waste that does require treatment and based on the evidence received, the most feasible and potentially impactful options appear to be:

• advanced sorting to remove recyclable material from residual waste;
• connection to heat networks; and
• deployment of carbon capture use or storage (CCUS).

The Eunomia report therefore assesses the effectiveness of these options to decarbonise existing waste infrastructure in different combinations across three scenarios (business as usual, best efforts focused on plastics and best efforts focused on food).

The Review does not see evidence that biostabilisation of biodegradable waste coupled with landfill was likely to be a major solution in Scotland, though it might offer a route for more remote communities. The Review also looks at waste-to-fuel and chemical recycling technologies. Where these do not have direct greenhouse gas emissions, it considered these to be outside the scope of the Review and its recommendations.

Advanced Sorting

This modelling shows that advanced sorting would have an immediate and significant impact on direct emissions from incinerators (49-56% reduction depending on the scenario) as well as bringing significant additional benefits in terms of recycling credits (enough to offset the remaining direct emissions). The Review therefore confirmed its provisional recommendation that more should be done to remove recyclable material from residual waste (see Recommendation 13).

However, the modelling shows continued direct emissions, a proportion of which will be due to plastic left in the residual waste that may not currently be recyclable. The Review therefore goes further in this Second Report and proposes that by 2030, all plastic should be removed before incineration (see Recommendation 17), by a combination of upstream policies such as bans on certain single-use plastic items, better source separation, and more intensive advanced sorting (see Recommendation 19). In doing this, the Review is conscious that exporting plastic waste should not be encouraged (see Recommendation 18).

Heat Networks

While there should be a diminishing need for residual waste treatment, for as long as there is a need to burn waste to treat it in a sanitary manner, as much as possible needs to be done to pursue all possible ways to decarbonise the incineration sector and to use it to support wider decarbonisation. Heat networks can be expensive and controversial to construct, and in reality offer only a partial solution for the incineration sector, as many facilities will struggle to connect to heat users. However, they do have a wider role to play in decarbonisation, whatever energy source is used, so their connection to incineration plants is beneficial, a finding underpinned by the Eunomia report. Therefore, this Second Report confirms the First Report’s provisional position that they should be pursued where possible (see Recommendation 14), but not seen as a reason to build an incinerator.

Carbon Capture, Use or Storage (CCUS)

Capturing the carbon dioxide emissions from incineration – both fossil and biogenic – is an apparently attractive solution. Indeed, the Eunomia modelling suggests that deployment of CCUS at a (generous) subset of incinerators could improve the direct emissions reduction by two-thirds compared to advanced sorting alone. Added to this is the potential for substantial biogenic carbon capture credits. Therefore, the sooner CCUS can be developed on incineration facilities the greater the impact on carbon emissions there will be. It is therefore prudent, when choosing which of the pipeline of incineration facilities to pursue, to opt for those with the greatest opportunity to decarbonise quickly (see Recommendation 20). However, there are many practical and economic barriers to CCUS deployment and it seems unlikely that deployment to a range of incineration facilities will happen to a significant extent over the next couple of decades. CCUS is therefore more likely to be a longer-term solution and will probably have a limited role to play in meeting Scotland’s current net zero ambitions. There is probably also merit in Scotland looking at emerging carbon capture and use technologies to overcome the challenges faced by incinerators that are less well placed to use existing or planned carbon dioxide transportation infrastructure (see Recommendation 21).

Decarbonising Landfill

Landfill is a significant but declining option for biodegradable waste management in Scotland. The methane produced in landfill gas is often captured and either used to generate energy or flared. The Review did have concerns as to what might happen to sites as the concentration of methane decreased (see Recommendation 22) and as the current financial incentives to capture and use the landfill gas expire in 2037 (see Recommendation 23).