What’s wrong with WRATE?

The following can be downloaded as a .pdf file.

Failures of WRATE modelling in the Wales Waste Strategy

WAG has been relying on WRATE for the Welsh Regional Waste Plans and for the 2009 review of the Wales Waste Strategy. Yet it’s badly flawed. In the ‘WRATE’ assessment ([1] Waste and Resources Assessment Tool for the Environment) for the Welsh Waste Strategy (WWS), the results show incineration very positively. Incinerator companies (eg. Viridor in Cardiff) claim their plants have negative
carbon footprints. Such results are at odds with much of the peer reviewed literature; with the Waste Strategy 2007 for England [2] and even with the previous modelling by the UK Environment Agency for WAG [3].

It has been long been clear that a lot of energy can be saved by recycling. For more than a decade it’s been established that this energy saving is very much greater than energy recoverable by incineration [4,5]. The earlier modelling clearly demonstrated that
recycling gives net reductions of climate change emissions, while incineration is a net generator of climate change gases.

WRAP’s specialist review of international studies “Environmental Benefits of Recycling” [6] shows how increased recycling is helping to tackle climate change and emphasises the importance of recycling over incineration and landfill as the appropriate way forward.

The evidence from WRAP said:
· In the vast majority of cases, the recycling of materials has greater environmental benefits than incineration or landfill.

WRAP concluded (s.14): The message of this 2006 study is unequivocal. Recycling is good for the environment, saves energy, reduces raw material extraction and combats climate change.

The WWS study found on the contrary:
The results of the WRATE assessment suggest that Energy Recovery from paper and card via a CHP Incinerator has a greater environmental benefit. These results are influenced by the way WRATE calculates the global warming potential, differentiating between biogenic and fossil fuel carbon emissions. This point is discussed further in the
results. This setting cannot be varied in the WRATE model.”

This is an anomalous result inconsistent with WS2007 and the majority of the published literature, which brings the credibility of WRATE into question.

The Industry shares criticisms of WRATE
Dirk Hazell, chief executive of the Environmental Services Association (ESA), explained to the London Remade conference (5 Oct 2009 [7]) ESA is working to develop a metric to measure the carbon footprint of waste management activities. He said the waste sector felt that WRATE – which is already used by local authorities to procure new waste contracts and take into account emissions – is “inappropriate” for some decision-making because some of the default settings were too generic.

Daniel Silverstone, chief executive of London Remade, highlighted the limitations of the government’s present approach of CO2 from waste: “While the global impacts of waste management account for 3% of carbon emissions globally and in the UK 4% of GHG emissions are traced to methane emissions, none of this takes into account the carbon impact of logistics, supply chain, manufacturing process and the global trading of recyclables.”

Bias to Incineration
The Low Carbon Transition Plan in respect of waste [8,9] takes no account of CO2-savings from recycling or emissions from incineration, considering only biogas from anaerobic digestion and (reduction of) landfill. The expected ‘saving’ is only 1 Mt of carbon equivalent, yet the envisaged combustion of wood waste and domestic waste generating electricity at high CO2 per kWh would release ten times that (but disregard it as industrial emissions).

WAG’s WRATE [1] makes unrealistic assumptions that bias results on climate impact towards incineration over recycling
# all incineration is high thermal efficiency CHP and
# the carbon intensity of future displaced electricity is the same as today’s.
# ignores the extra recyclates and their higher quality recovered from MBT of residual waste

Eunomia analysis [10] finds that one of the best performing systems is an MBT AD system – largely as a result of the benefits attributed to recycling materials that are recovered during the treatment process.

WRATE excludes emissions of carbon or biogenic origin, a fault that sets it at odds with the IPCC, which says [11]:
If incineration of waste is used for energy purposes, both fossil and biogenic CO2 emissions should be estimated. WRATE’s approach thus fails to cover the benefits of delaying emissions of CO2 (eg. using wood as building material or burying in landfill) or sequestering carbon in PVC and mixed plastics in landfill rather than combusting with release of chlorine compounds and metal toxins.

Assumptions on carbon intensity of displaced electricity:
Electricity from incineration does offset carbon emissions from substituted generation, but the future electricity mix has to be modelled. Current policy requires a progressive reduction in the carbon intensity of the future fuel mix, which substantially reduces the
benefits as future electricity comes with much lower carbon emissions. Although a “sensitivity” test was carried out using what is claimed to be a ‘2020’ energy mix in WAG’s WRATE report, this is not based on the reductions in carbon intensity included in current policy as detailed in the UK Low Carbon Transition Plan [9].

Moreover, a 2030 mix is more typical for an incinerator contracted for 25-30 years from 2015. The UK plan shows approximately 75% reduction in carbon intensity (from over 300 to ~80 g CO2/kWh) is anticipated between 2020 and 2030. To contribute positively on
climate change post-2030, any incinerator should produce electricity with a carbon intensity under 80 gCO2/kWh. However the carbon intensity of incineration, even if biogenic carbon is ignored, is more than 300 g/kWh. Thus incineration becomes unarguably, in the words of the Environment Agency [12] a “carbon sinner” rather than a
“carbon sink”.

Assumptions on carbon in future waste
Indeed, future incineration would be still worse, as the biogenic proportion of residual waste reduces with increased recycling. Whilst unsorted waste is calculated to derive 66% of the calorific value from biomass this falls to 38% when recycling ~45% and then to just 30% biomass when recycling ~60%. This is because the wastes that tend to be pulled out for recycling/composting are those like paper and kitchen waste with high biogenic proportions. This concentrates the plastics and composite materials in the residual waste (and burning is not the Best Practicable Environmental Option [13] for plastics wastes). Thus the carbon intensity of incineration, if biogenic carbon is ignored, would rise to more than 600 g/kWh in 2030.

Bias against biostabilisation and good landfill management
WRATE underplays the extent to which stabilisation-type treatments decrease the environmental impact of material that is landfilled after being stabilised. It hardly allows for the reduction in respirability of treated residues (despite the high values 80-90% found in practice). It largely ignores the biological changes undertaken in the processes – it
attributes them with high methane emissions and thus climate change impacts. This has an impact on not only the GWP indicator, but also the Eutrophication indicator (relating to nitrogenous emissions, principally ammonia from landfill). The consequence is that any
system that is assessed using WRATE and which includes a residual landfill or MBT/compost element will almost invariably appear to perform worse than a mix including higher levels of incineration. Almost uniquely amongst modern LCA models, WRATE penalises MBT and compost-based options.

WRATE fixes the capture rate of landfill gas at 75% (change promised in a future issue of the software) so makes no allowance for good management, in gas capture and in capping with an oxidising layer (as appropriate for landfilling 90% stabilised biowaste).

When the flawed methodology for stabilised biowaste was raised at the WRATE Users conference (18 Nov. 2009 in Birmingham) the EA’s Terry Coleman said he had previously been unaware of the flaw in their methodology. Yet it had been raised by Eunomia consulting and by New Earth Solutions who conducted the EA-validated biostabilisation

Inconsistent with the EA’s guidance on generating power from Biomass
The Environment Agency’s Biomass: Carbon Sink or Carbon Sinner [12] points out the need to take into account emissions from transport, nitrogen fertilizer production, land use changes and conversion efficiency, because these could increase the biomass total to as
much or more than the emissions from gas-fired power. For example, short-rotation coppice woodchips for electricity would emit 35-85% fossil GHGs compared with gas CCTG per kWh. Yet WRATE assumes zero fossil GHGs in biomass. The fossil GHGs released in producing and supplying the food that we waste should similarly be included in assessments that claim GHG savings from energy recovered from that waste.

WRATE does not properly assess carbon emissions from incinerating waste wood, taking it to combust with zero CO2. Its “bio-CO2” of course goes immediately into the atmosphere, whereas alternative use on land has slow release, some delayed for decades or recycled into biology, while alternative burying in landfill sequesters the lignincarbon
(~30%) indefinitely. Proper LCAs include the wood-carbon sequestered long-term in landfill or spread on land as char. The EA has developed its Biomass Environmental Assessment Tool [14] that addresses WRATE’s deficit in GHG accounting, but only for the segregated biowaste streams.

Climate Change scientists internationally have called this a “critical climate accounting error” [15] and propose fixing it by tracing the actual flows of carbon from smokestacks, whether fossil of bioenergy. Biomass should receive credit to the extent that it adds carbon from enhanced plant growth or uses residues or biowastes. Alternative use of biowastes on land that builds soil carbon or serves as compost has likewise to be credited.

Failure in comparison with validated life-cycle analysis
WRATE does not give robust results in comparison with internationally adopted life-cycle analysis. It may work for relative comparisons of incineration options, but fails for comparison with non-thermal alternatives as shown eg. by the very different outcomes of using the ATROPOS model for Ireland’s waste management options (Greenstar [16]).

With a similar dispersed settlement pattern and urban-rural mix to Wales, this found that “scenarios using incineration were amongst the poorest performing” while those using MBT were much better.

The detailed review by AEAT [17] for the European Commission similarly found that MBT when sequestration is taken into account performs much better than energy from waste.

The graph shows their findings when landfill gas is allowed for and incineration is competing with wind power (or other renewables) as applies when incineration competes for subsidy with renewables, as in the UK. The lower line applies when Carbon sequestration is included (which WRATE fails to do), when MBT to landfill (Col.4) comes out much better than incineration (Col 2) including MBT output to incinerators (Col.5) and almost as good as recycling/composting (Col.6). WRATE takes the landfill comparator as Col.1 (raw waste) which the Landfill Directive excludes.

[1] National Assembly for Wales, Environmental Life Cycle Assessment of Waste Management Options for Priority Waste Measures” Env Agency Wales report for Welsh Assembly Government, 2007
[2] DEFRA, Waste Strategy for England 2007, May 2007, Cm 7086. 2007.
[3] National Assembly for Wales, Future Directions For Municipal Waste Management In Wales – A Paper For Discussion, WAG, 2007.
[4] Morris, J., Recycling versus incineration: an energy conservation analysis. Journal of Hazardous Materials, 1996. 47(1-3): p. 277-293.
[5] Denison, R.A., Environmental life-cycle comparisons of recycling, landfilling and incineration: A Review of Recent Studies. Annual Review of Energy and the Environment, 1996. 21(1): p. 191-237.
[6] WRAP, Environmental Benefits of Recycling – An international review of life cycle comparisons for key materials in the UK Recycling Sector Sep 2006. 2006, Waste Resources Action Programme, Banbury.
[7] Waste Management News, 6 October 2009
[8] Support for EfW announced in Renewable Energy Strategy, 15 July 2009 http://www.letsrecycle.com/do/ecco.py/view_item?listid=37&listcatid=5334&listitemid=52924
[9] Department for Energy and Climate Change (DECC), The UK Low Carbon Transition Plan – Presented to Parliament pursuant to Sections 12 and 14 of the Climate Change Act 2008 National strategy for climate and energy 2009.
[10] Eunomia Research & Consulting and EnviroCentre, Greenhouse Gas Balances of Waste Management Scenarios – Report for the Greater London Authority January 2008.
[11] IPCC, 2006 IPCC Guidelines for National Greenhouse Gas Inventories – Volume 5 Waste. 2006.
[12] Environment Agency, Biomass: Carbon sink or carbon sinner? 2009.
[13] Welsh Assembly Government, PLANNING POLICY WALES Technical Advice Note (Wales) 21 Waste, 2001.
[14] BEAT2 – available free at http://www.biomassenergycentre.org.uk/BEAT
[15] T.D. Searchinger et al. Fixing a critical climate accounting error, Science 326, 527-528, 23 Oct. 2009
[16] Greenstar, 2008 Meeting Ireland’s Waste Targets – the Role of MBT, Final report, Eunomia Research & Consulting and TOBIN Consulting Engineers,
[17] AEAT 2001, Waste Management Options and Climate Change: Final Report for DG Environment http://ec.europa.eu/environment/waste/studies/pdf/climate_change.pdf

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