The aim of this series is to provide a literature review on the current status of Energy from Waste (EfW). Due to the length it will be split into three parts. Part 1: Introduction to the topic, a brief history, classifications and policy influences. Part 2: Proven capability, scalability and efficiency. Part 3: Alternative technologies, barriers and gaps in current understanding. Part 3 below!
The waste management hierarchy classifies waste management options in terms of their environmental and economic efficiency . The generally accepted waste hierarchy format is as follows: Reduce, Reuse, Recycle, Recover and Dispose. Although the waste hierarchy is often used in decision and policy making , Finnveden et al identifies Life-cycle Analysis (LCA) as a better tool recommending the waste hierarchy as a starting point only. Their paper indicates scenarios where the waste hierarchy it is not valid for sole use .
The first tier of the hierarchy is for the reduction of waste, this point is generally accepted however the next tiers are debated in most countries . In particular the order with which incineration and recycling should go is regularly discussed . EfW is now positioned in the ‘Recover’ section, before 2008 it was classified as ‘Dispose’ along with waste to landfill .
Recycling and Landfill
In reality there are usually numerous ways to handle a particular waste, see table 1. The main competition for EfW is recycling of materials and waste to landfill, the majority of waste is landfilled . Landfilling although comparatively cheap  is thought to have significant environmental implications , . Jeswani identifies significant greenhouse gas savings through EfW in comparison to landfill, even when landfill gas is recovered  however his study does not take into account the auxiliary fuels required for incineration, or transportation distances . EfW is often used to reduce the volume of wastes (up to 90% reduction ) or reduce harmful substances before land filling. Lobbying parties promote EfW over alternatives due its reduction to landfill and fossil fuel use .
Recycling has been recognised as more favourable than incineration for most substances , . It allows the conservation of energy by reducing the use of virgin materials . Although some LCA have shown substances where incineration is more efficient for example when recycled plastics replace impregnated wood . Environmental groups often argue that EfW reduces the incentives for recycling , although Porteous noted that increased incineration use in Europe has not reduced recycling processes . As a general rule incineration is preferred if recycling or other material recovery is not possible , and EfW installations often work in coordination with recycling. DEFRA states that wherever recycling and reusing is not viable, energy recovery from incineration is recommended with disposal as a final resort .
The main advantages of EfW incineration are it makes optimal use of the land and can be located in residential areas due to its little odour and emissions . It also reduces the volume of waste, requires little pre-treatment and can operate in all weather conditions . In addition the bottom ash can usually be reused and it produces heat and electricity . The disadvantages are high costs both capital and operational, the negative public opinion and the extensive policy changes particularly in terms of environmental regulation .
Barriers/Gaps in Current Knowledge
Earlier technologies released toxic emissions such as dioxins and heavy metals which posed a threat to human health , as a result incineration gained a bad public image and is still not accepted in some countries . Despite the new technology dramatically decreasing air emissions and irradiating threats to human health , ,  it is still a significant barrier for the industry, in particular in terms of gaining planning permission. Additional issues such as noise or increased traffic from heavy vehicles could also contribute to the bad image . Further research should aim to discover why the public still have issues with EfW despite its being a relatively clean process and what could change their minds. Consideration needs to be taken in terms of positive media coverage and incentives for domestic properties e.g. free hot water or reduced energy tariffs.
Policy and legislation affecting the industry is constantly changing, EfW projects therefore need to be adaptable to these changes . Friedhoff highlights the issue of lengthy implementation timelines and private contracts which span up to 25 years . Adamson adds that combining unpredictable rapid changes in the industry (policy, technology and waste heterogeneity) with 25 year contracts could result in significant financial losses for investors .
There is a lack of subsides and incentives for EfW despite its being described as a renewable energy source in the UK’s recent Renewable Energy Strategy and being a solution to waste management issues. This makes it costly to invest and operate. ROCs tend to be focused more on wind, wave, solar and hydro and the RHI provides subsidies for capturing heat but not for the infrastructure to distribute it, which is one of the major costs for a EfW plant . The lack of incentives for the industry is a huge barrier. There are gaps in the current knowledge about how best to implement incentives, the altering of the Waste Framework Directive to allow recovery status provided some relief but there are still inefficiencies and bias within this.
Operational barriers influence the industry, such as the existence of district heating networks, quantity of available feedstock, transportation and the shortage of skilled workers . Jamasb highlighted the absence of heat delivery networks as a significant barrier to EfW in the UK .
The amount of feedstock is of particular concern; the quantity needs to be defined before further expansion of EfW plants. Sweden has to import waste for its EfW installations . There is a significant lack of research in this area in terms of both the quantity and quality of waste available and therefore a risk of demand outstretching supply. Waste is very heterogeneous and various from location to location and times of the year, this is a challenge for EfW plants. There needs to be detailed classification and identification of types of waste and how they vary to be able to increase the efficiencies of EfW installations.
Additional gaps in knowledge noted throughout research include the lack of a defined end point for bottom ash. The usefulness and viability of the waste management hierarchy is often debated, including whether LCA is a better option for determining both economic and environmental efficiency. The most effective utilisation of waste in terms of producing heat or electricity is largely unknown since it depends on the waste composition which is highly heterogeneous. Models and tools should be used to determine the best technologies and operations allowing more efficient plants and more accurate estimates of output.
Summarised findings and Conclusions
To conclude incineration has evolved from a simple waste management operation to a resource recovery strategy. EfW is part of a hierarchy of waste management and is highly interlinked with recycling and landfilling activities. EfW currently has demonstrable capability both large and small scale but there is potential to significantly increase its contribution both to energy supply and waste processing operations. It is thought that life cycle analysis should play a greater role in policy and decision making affecting the industry. The main barriers to EfW include public opposition, rapidly changing policy, lack of incentives and the heterogeneity and availability of feedstock. Operational and institutional barriers also influence the industry. EfW is capable of processing vast amounts of waste, reducing landfilling activities and greenhouse gas emission in addition to helping meet the world’s ambitious renewable energy targets.
EfW Part 1: https://ecopostblog.wordpress.com/2014/02/25/energy-from-waste-efw-p1/
EfW Part 2: https://ecopostblog.wordpress.com/2014/07/04/energy-from-waste-efw-p2/
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