Task 2 commences with the identification of WtE techniques. The three-step data collection strategy used for this task is illustrated in the figure below.
In Task 1, the main waste treatment pathways were defined and arranged into five groups as follows:
Group WtE pathway
Group 1 Combustion plants: Combustion plants which utilise waste as a secondary energy source in combination with other types of fuels (these installations include all kinds of conventional power plants used for the generation of mechanical and/or electrical power generation and heat, as well as recovery boilers)
Group 2 WI plants: Waste incineration plants dedicated to the thermal treatment of waste, with recovery of the combustion heat, through the direct incineration by oxidation of waste
Group 3 CL plants: Cement and lime production plants Group 4 AD plants: Anaerobic digestion plants
Group 5 Other WtE plants: Other waste-to-energy plants (including pyrolysis, gasification, plasma treatment and hazardous waste incineration) Within each group, the techniques are split into two subgroups: the first subgroup lists techniques which are considered to be proven techniques that could be implemented immediately in any Member State to improve the deployment of WtE with respect to energy recovery. They will have a Technology Readiness Level (TRL) of at least 9 (for further discussion of TRL, please refer to Section 4.2.2 below).
The second subgroup lists emerging WtE techniques which are considered ‘Technologies to watch’. These technologies all have a TRL level of 8 or less. This TRL level indicates that they are currently not commercially mature but may offer potential in the future. An evaluation of all techniques was performed according to the methodology described below in Section 4.2.
4.1.1 Summary of WtE pathways
A high-level summary of the advantages and disadvantages of each of the five WtE pathways is provided below.
Advantages Disadvantages
Combustion plants
co-incinerating waste Existing combustion plants may be able to be modified, avoiding
extensive new build
The efficiency of electrical energy recovery can be high due to high boiler operating temperatures and pressures
Requires the whole combustion plant to be permitted by the relevant national environmental agency and to be compliant with the IED
The percentage of waste by weight that can be co- incinerated with most non- waste feedstock is small in many cases (often around 5%)
Waste incineration plants
Proven and bankable technology which tolerates a wide range of wastes
Ideal for district heat and cooling connections to increase overall plant energy efficiency
Electrical energy recovery efficiency in a steam boiler is limited due to the
corrosive nature of waste feedstock
The siting of waste incinerators can be
controversial due to public perception
Cement and lime (CL) plants
Some of the waste material content is recycled into the cement clinker
The thermal conversion process will always recover a high proportion of the waste input energy content regardless of plant location
CL plants require a highly processed waste-derived fuel (SRF) with exacting quality standards which requires energy to produce
The demand for cement is variable meaning that CL plants demand less waste feedstock during periods of low economic activity
CL plants can have higher emissions compared to WI plants
Anaerobic digestion
(AD) plants AD plants are relatively uncontroversial due to low or negligible emissions
AD plants produce a digestate by-product which can be spread on land under most
circumstances
Energy recovery through a gas engine gives low overall electrical efficiency
Collecting large quantities of suitable uncontaminated organic feedstock can be challenging
products (such as
polymers) rather than just heat and power
Although not an advantage of the
technology itself, due to the innovative nature of some other WtE
processes, financial support through grants or incentives may be
available in some Member States
transition from
demonstration scale to commercial reality
Some waste streams suitable for other WtE processes are limited in size and availability
The energy efficiency of each pathway is also summarised below for both current average (Av) and optimised (Opt) net annual average energy efficiency. Average net annual average energy efficiency represents the current situation, optimised net annual average energy efficiency represents the efficiency WtE could reasonably achieve if improvement techniques are implemented. The methodology which has been used to calculate these efficiencies is explained in full within Section 4.2.
Energy recovered as electricity, efficiency 1 Energy recovered as heat, efficiency 2 CHP
recovery efficiency 3 recovery Energy to fuel, efficiency Av
% Opt % Av % Opt % Av % Opt % Av % Opt % Electric Heat Electric Heat
Combustion plants 4 36 40 - - - - WI plants 22 5 33 6 72 7 80 8 17 9 51 9 27 10 66 10 - - Total 68 Total 93 CL plants 11 - - 75 80 - - - - - - AD plants 18 12 23 13 - - 18 14 18 14 - - - 41 15 Total 36 Others 20 16 35 17 75 16 80 8 - - - - - 40 18
Net annual average efficiency:
1 100% electrical load. 2 100% heat load.
3 CHP - 80% of heat sold annually, 100% electrical load.
References:
4 LCP BREF, coal / lignite pulverised combustion.
5 ISWA CE report 2015, gross existing plant efficiency corrected to net efficiency.
6 AEB Amsterdam / Martin GmBH statistics, refer also High Steam Parameters for Boilers and
Superheaters proven technique.
7 CEWEP.
8 Ricardo estimate based on known boiler efficiencies.
9 Annual average efficiency based ISWA CE report 2015 existing CHP plant gross efficiencies, corrected to
10 Annual average efficiency based on optimised AEB / Martin GmBH net electrical efficiency and ISWA CE
report 2015 high efficiency CHP plant gross efficiencies, corrected to net efficiency with annual average heat load.
11 CEMBUREAU.
12 ISWA CE report 2015, AD plant net efficiency.
13 UK Department of Energy and Climate Change, Advanced AD net efficiency. 14 ISWA CE report 2015, net efficiency with annual average heat load.
15 ISWA CE report 2015, net efficiency of biomethane production at 100% annual load. 16 Typical net power / heat only efficiency of a gasification system as an emerging technique.
17 High efficiency claimed by optimised emerging techniques suchas Two Stage Combustion with Plasma
with energy recovery through an internal combustion engine.
18 Typical net efficiency of an emerging technique producing a fuel product.