Donâ€™t Write Incineration Off Yet!
The term ‘energy from waste’ (EfW) covers a wide variety of combustion processes that reclaim energy from a waste material feedstock.
It in particular refers to treatment processes that harness the calorific price in waste to generate electrical power or heat. This is then distributed with the rest of our “non-renewable” and “fossil fuel” derived energy.
Using energy which would have been lost if it had been placed in a landfill, EfW energy production methods also serve to cut back the volume and weight of the original waste which will go to landfill, leaving only a small residue that requires disposal. These plants, in the form of incineration plants, are actually capable of reducing the volume of waste by as much as ninety p.c. and the weight by seventy five percent The incineration process is actually just about the most efficient at this, and the ash that’s left may also be made excellent use of in construction materials recycling applications. This ability of incineration to reduce volume and mass, is not nowadays as effective as it once was, when emissions to atmosphere were less strongly regulated. This is due to the need for sophisticated methods to be used to clean up incinerator flue gases before they can be emitted, and the air pollution control systems which provide this function. The air pollution control systems most often used in incineration plants produce waste of their own, which needs further treatment or disposal in a specifically approved “hazardous waste” landfill site.
A number of alternative strategies to incineration have just recently been developed for recovering EfW, including combustion, gasification, pyrolysis and biological processes, e.g. anaerobic digestion and the extraction of landfill gases. The quest continues for better EfW processes which:
– avoid creating polluting gases and toxins in order to reduce the need for costly and energy consuming flue gas clean-up technology
– are highly effective in reducing the volume and mass of the residue
– if not particularly good at reducing volume and mass of the incoming waste, to provide a valuable non-toxic product (e.g. anaerobic digestion produces biogas and a fertilizer).
Despite much work having been done in developing alternative EWfW technologies to incineration the commonest kind of EfW is using incineration technology, and the majority of new capacity (e.g. in the UK) is being installed as incineration processes.
This means burning residual waste ( generally after separation for recycling and composting ) in furnaces and which incorporate a boiler and generator system to supply an electricity output from the steam produced. The heat may be exploited in district heating systems (known as CHP). The technology itself is really flexible, and can process mixed municipal wastes and other waste streams, including clinical and industrial wastes.
Other processes pelletise waste inputs for burning in a refuse derived fuel ( RDF ) plant. The UK Governing Body has outlined RDF as ‘turning the flamable portion of waste, e.g. paper and plastics, into a fuel which can on occasion be stored and transported, or immediately used on site to provide heat and / or power. RDF gives the operator the opportunity to store energy and choose to generate power when it is needed the most – a rare attribute among renewable energy processes.
A key development of EfW has been thru the development of environmental technology and regulation. During the last 20 years the emissions from EfW plants have been seriously reduced thru progressively tighter regulation and improved use of flue gas treatment technologies.
Throughout Europe the older generation of incineration plants have all been closed or upgraded to meet the 1996 EU emissions directive and the further reinforced EC Incineration Directive emission came into effect in 2004.
There are no longer any reasons to hold back any EfW plants due to concerns about gas emissions as the science surrounding what constitute emissions risk to human health are now well known, and the legislation has been set at a level which guarantees the health of all those who work in these plants, or live nearby. The idea of incineration, being simply to burn the materials until there is nothing left to combust has its limitations, especially when other processes can produce useful products, so many would like to see a bigger upatke of the alternative waste technologies, like including combustion, gasification, pyrolysis and biological processes.
Unfortunately, although there’s been a major level of interest in developing new plants which will utilize the ’emerging ‘ technologies ( pyrolysis, gasification etc.), and basically thes are essential to help the all EU nations meet their duty to reduce their dependance on landfill dumping of waste. EfW plants that handle between ninety thousand and six hundred thousand tonnes of waste every year can produce between 6 and 40MW of electricity.
There was in 2004, enough capacity to provide 203MW of power from UK EfW facilities, which process has a grand total of just about 3,000,000 tons of community solid waste every year. Substantial extra capacity for the has been installed since then, and furthur plants are in the planning stage, with the result that installed capacity has more than doubled and with a similar increase in the power now being generated from previously landfill-dumped municipal industrial and commercial solid waste.
The reason that the more recently developed waste technologies are not being built in bigger numbers lies in their newness meaning that investors find it hard to take on-board the bigger risk from new processes, and which in a recessionary economic period might or might not, in unstable “immature” markets produce essential income from the sale of their products (e.g. compost or say “bio-char”).
All nations should do their utmost to gain as much value from our wastes as practical, instead of continuing historical dependence on landfilling, for the sake of minimising use of finite materials resources and avoiding groundwater pollution. After we have removed as many valuable materials from the waste as feasible, like paper, glass and plastics, the residual waste still contains valuable energy that will replace coal or oil burning.
The United Kingdom lags behind its Western european neighbors in recovering energy from waste, it is pleasant to note the accelerating number of energy from waste facilities now being built and further projects in the pipeline, will soon make the UK one of the leaders in EfW adoption.