There are many different waste streams that are produced. Some are suitable for incineration and for others, incineration is an essential method of disposal.
Mixed Municipal Waste
Mainly untreated household and domestic waste which also includes industrial and commercial waste that is non-hazardous is sometimes referred to as municipal solid waste (MSW).
The content of the of this waste stream can vary significantly from location to location and region to region. The image above sets out the broad component parts as within any given typical load. Whilst the current disposal methodology is to place it into land fill, there is now a momentum to avoid landfill in favour of incineration. This is motivated by the fact that the deposition of the materials takes many years to decompose and the land is not usable, if at all. In addition to this, landfill has a serious impact on water quality as toxins and pollutants will leach out into the soil and water.
Municipal Solid Waste
The table below illustrates the composition of MSW as it appears in a recycling centre. However, the figures shown are indicative and do not represent a consistent picture as it will vary from region to region, country to country and seasonally. This is because peoples disposal habits change throughout the year.
The definition of waste is very wide and can be open to interpretation. However, in the context of incinerator waste types they fall broadly down into two main component parts i.e. hazardous and non- hazardous.
The Environmental Protection Agency (EPA) classes hazardous waste into four main categories;
- Ignitability, or something flammable
- Corrosivity, or something that can rust or decompose
- Reactivity, or something explosive
- Toxicity, or something poisonous
Waste is generally considered hazardous if it has the potential (or if the material or substances it contains) to be harmful to humans or the environment. Examples of hazardous waste include (but not limited to);
- Chemicals, such as brake fluid or printer toner
- oils (except edible oils), such as car oils and lubricants
- Equipment containing ozone depleting substances, such as fridges
- Hazardous waste containers
- Hazardous medical waste
The waste classification code, also referred to as LoW (List of Waste) or EWC (European Waste Catalogue), contains some common classification codes in parts 2 to 6 of the guide. This comparative list classes all the various waste and classes them as ‘mirror hazardous’ (MH), mirror non-hazardous (MN), absolute non-hazardous (AN) and absolute hazardous (AH).
Details of these classification and applications to waste stream are detailed in the publication ‘Waste Classification – guidance on the classification and assessment of waste’ May 2018.
Hazardous Waste Incineration
For the purposes of the WID (Waste Incineration Directive), ‘hazardous waste’ means any solid or liquid waste as defined in regulation 6 of the Hazardous Waste (England and Wales) Regulations 2005. However, the requirements of the WID which apply to hazardous waste are disapplied by Article 3(2) to the categories of waste set out below.
Sewage waste – Where sewage waste is to be placed in to an incinerator is sometimes mixed with other waste for incineration such as municipal waste, bio waste.
Clinical waste – where there are other sub categories related to each individual waste stream
These requirements include those relating to the reception, sampling, analysis and combustion temperatures applying to hazardous waste: Combustible liquid wastes including waste oils provided they meet the following criteria:
- The mass content of poly-chlorinated aromatic hydrocarbons, e.g. poly chlorinated biphenyls (PCB) or Penta chlorinated phenol (PCP) amounts to concentrations not higher than those set out in the relevant Community legislation;
- These wastes are not rendered hazardous by virtue of containing other constituents listed in Schedule 2 of the Hazardous Waste (England and Wales) Regulations 2005 in quantities or in concentrations which are inconsistent with the achievement of the objectives set out in Article 4 of the Waste Framework Directive; and
- The net calorific value amounts to at least 30 MJ per kilogram.
Please not that this section is only for guidance and Inciner8 considers the thermal treatment of waste based on a specific caste study of the individual waste stream being incinerated.
Bio mass is defined as plant materials which includes wood, logs, chips, bark, and sawdust. Other biomass sources can include agricultural waste products like fruit pits and corncobs.
It is advised that the moisture content is reduced as much as reasonable possible to ensure clean and constant combustion and increased burn rate of the waste fuel.
The calorific value of biomass is estimated to be between 12.5MJ/kg – 19MJ/kg which translates to 3.4 kw/kg – 5.2kW/kg.
Although this can vary greatly dependent upon the constituent parts of the fuel mix, moisture content and particle size of the waste will impact on the burn rates of the incinerator machine.
Refuse Derived Fuels (RDF)
What is RDF?
Refuse Derived Fuel (RDF) is a fuel produced from various types of waste such as commercial waste, industrial waste, and municipal solid waste. RDF can be used to generate energy at recovery facilities which generate heat, electricity, and hot water.
How is RDF made?
Any non-combustible materials such as metals and glass are removed when the waste is sorted. The left over waste is then separated according to weight. Heavier materials are discarded due to their low calorific value, which will result in them not burning well. The lighter materials with higher calorific value can then be used for RDF.
The calorific value of RDF is estimated to be between 9 MJ/kg – 19MJ/kg- this is again very depended on the constituent parts of the fuel and vary significantly.
All of our incinerators are designed to burn RDF with varying compositions composition and quality. However, the performance of the machine totally dependent on the quality of the waste fuel being placed into the machine. Therefore, high moisture content, particle sizes and the batch loading method employed will impact on the burn rates.
Solid Refuse Fuel (SRF)
You can convert RDF to SRF by moulding the waste into pellets. Waste plant and biomass plants often require a certain standard of fuel. SRF would be the preferred method for this particular standard.
The advantage of going through this process that it allows the fuel to complete and any moisture contained is taken out – and the density increased which gives is a much more higher CV than loose RDF. However, SRF plants will process and pre-sorted waste into a homogenous shredded particle of no more than 30mm in size with a moisture content of less than 15% and a calorific value (CV) of 18-22mJ/kg.
Medical waste is defined as waste generated during the diagnosis, testing, treatment, research, or production of biological products for humans or animals (World Health Organisation).
The image below sets out the different types of waste generated in the medical industry and the process by which the waste can be segregated.
The ideal scenario will be to ensure that the medical waste is not mixed and incinerated in separate specific batches.
The advantage of doing so is that the waste will be consistent as it goes through the incinerator and therefore the readjustment of the machine is minimised to ensure that the incinerator burns at its optimised settings.
Medical waste incinerators are used by hospitals, dentists, laboratories, clinics, and other businesses generating medical waste.
The need to control outbreaks of disease and the general management of animals needs to be considered carefully and ethically. The incineration of animal stock is legislated and enforced through the EU Animal By-Products Regulation 1069/2009 and E U Implementing Regulation 142/2011.
What is Animal Waste?
Animal waste is classed as any ABP (Animal By-Product) or other materials associated with the care of an animal. Animal by-products include carcasses or body parts of animals, soft tissue, manure, or meat meant for human consumption but withdrawn for commercial reasons. Other materials associated with animal care include bedding, animal feed, and faeces.
The DEFRA website contains the different categories of APB’s, and if your waste site will need approval depending on which category APB’s you have.
Animal incinerators can be used by farms, breeders, kennels, veterinary clinics, and pet cremation services.
This blog is part 2 of a 6 part series on “Everything You Need to Know About Incineration”, brought to you by our expert technical team at INCINER8.