How can your organic waste generate income?
Material waste is present all over the planet: in oceans, landfills, remote islands, Antarctica and even in orbit around the Earth. We produce 2.12 billion tonnes of waste per year. To put that figure in perspective, if we could load all this waste into trucks, they would go around the world 24 times. These figures are alarming, but various actors are putting in place plans to reduce the amount of garbage produced.
One of these plans is to turn waste into energy, including electricity, heat and fuel. Some types of solid waste can be converted into gas to power generators, while others can be broken down by anaerobic digestion to create methane-rich biogas. In this round-up, we will examine some of the most interesting methods for turning waste into energy, as well as the equipment available to process it.
Is the energy recovery of waste green?
It is important to put the idea of producing energy from waste in context, which the waste hierarchy can do best. The waste hierarchy tool indicates an order of preference for actions to reduce and manage waste.
It places energy production (value) below waste reduction, reuse, recycling and composting, which means that these are the options that must be considered first in waste management, but above waste disposal, which means that energy recovery of waste is preferable to landfilling.
The truly “green” nature of waste energy recovery depends on the efficiency of the plant that converts waste into energy and the proportion of biodegradable waste. This determines whether the approach is considered a “value” or a simple “elimination” of waste.
There are many ways to generate energy from waste. These include combustion, gasification, pyrolysis, anaerobic digestion and recovery of discharge gases.
Burning: Burning what’s left
First, combustion. In this case, the heat produced by the combustion of waste produces heat that causes a turbine to produce electricity. This indirect approach to energy production currently yields about 15-27%, but the potential for improvement is significant. The fact that an approach to waste-based energy production can be considered sustainable depends on the “lower calorific power” of waste entering the process. As far as waste incineration is concerned, this figure must be 7 MJ/kg, which means that paper, plastics and textiles are best suited to the combustion method to produce energy from waste.
Of course, combustion produces emissions – 250-600 kg of CO2/tonne of treated waste – but this is offset by the fact that there is no need to burn fossil fuels. However, there are other pollutants emitted by combustion in the form of combustion gases.
Gasification: Waste is a gas
Gasification, rather than directly causing turbines, involves producing gas from waste. Everyday waste, whether it’s product packaging, lawn mowing, furniture, clothing, bottles, appliances, etc., is not so much fuel as food for chemical processing at very high temperatures. Waste is combined with oxygen and/or steam to produce “syngas,” a synthetic gas that can then be used to make many useful products, from fuels for transport to fertilizers, or be converted into electricity.
But the problem is that gasification is often followed by combustion, resulting in the same emissions problems as combustion. The same problem can apply to what happens after the waste is pyrolysised.
Gasification is also not a particularly efficient mechanism for energy production, as pre-processing requires a lot of energy and reactors must be closed to be regularly cleaned.
Pyrolysis: no oxygen, no problem?
Pyrolysis differs from other methods cited to date by the fact that the decomposition of various solid wastes is done at high temperatures, but without oxygen or in an atmosphere of inert gases. This means that the process requires lower temperatures and that emissions of some air pollutants associated with combustion are lower.
It should be noted, however, that Friends of the Earth does not consider the energy generated by gasification or pyrolysis to be truly “renewable” because it releases CO2 from fossil fuels, such as plastics and synthetic textiles, as well as biological materials.
Anaerobic digestion: tackling organic matter
Anaerobic digestion can be used to produce energy from organic waste such as food and animal products. In an oxygen-free tank, these materials are broken down into biogas and fertilizer.
This is a high-potential approach. If we treated 5.5 million tonnes of food waste in this way, we would generate enough energy to power about 164,000 households while saving between 0.22 and 0.35 million tonnes of CO2 compared to composting.
The extraction of biogas produced by the biodegradation of materials at landfills is another way to extract useful energy from waste. Although this is a declining approach due to the reduction in the amount of organic material landfilled, it makes a significant contribution to the UK’s energy supply: last year, it produced 3.04 TWh of green electricity.
The transformation of plastic waste into energy certainly makes sense from a chemical point of view, since plastics have the same origin as fossil fuels. We have already looked at the two main techniques used: pyrolysis, which involves heating plastic in the absence of oxygen, and gasification, which involves heating waste with air or steam, creating gases that are used to produce gasoline or diesel, or that are burned to produce electricity.
New techniques, such as cold plasma pyrolysis, offer the possibility of creating fuels such as hydrogen and methane, as well as chemicals useful to industry.
But there are obstacles to the wider adoption of techniques for converting plastic into energy. The gasification of plastics requires significant investments, including advanced controls and pre-processing facilities. In addition, the development of plastic recycling plants presents the risk of limiting these facilities, while decision-makers can instinctively opt for waste management strategies where general waste is treated together, rather than separating the different elements.
What are the equipments that allow its transformations?
The various processes mentioned above therefore make it possible to convert different types of waste into energy. In the vast majority of cases, this waste must be prepared and sorted accordingly to allow it to be processed in an optimal way. For example, packaged food must be separated from its packaging, waste of a certain size must be reduced to a smaller size, and mixtures can also be made. In short, there are different types of equipment to allow you to prepare your waste with this in mind and we will introduce you to some of them.
In the current context of recycling frenzy, there seem to be a multitude of options available for waste disposal and recycling. This can make it difficult to keep a new one of the latest methods of clean waste disposal. Let us explain a number of reasons why slow-speed shredders are able to significantly and effectively improve the way we handle waste, and how and why it might be useful to you.
Protecting the environment
These slow-speed shredders are among the company’s most valuable resources and an important part of our recycling initiative. These are large, robust machines, renowned for their reliability and quality. What makes these slow-speed shredders particularly environmentally friendly is that they are specially designed for very low fuel consumption. This means that even when used all day, the carbon dioxide produced is remarkably low.
Slow-speed shredders have proven to be the preferred favorite of many customers due to their high performance and low operating costs.
Clean and efficient recycling of wood waste
Slow grinders are ideally suited to handle all types of wood, regardless of size or footprint, including pallet waste, construction and demolition waste, construction waste and MDFs or particle panels. The wood is first sorted and sorted, and the detritus is removed. It is then subjected to a careful double shredding system to ensure the removal of any metal contaminant. The newly shredded wood waste recycling product is then processed according to its final use. This can include the manufacture of panels, biomass, animal litter or composting.
The densimetric separator combines two physical rules – vibration and blowing effect – to properly separate heavy contaminants from wood particles. The material is introduced by the top of the machine by a special hopper on the densimetric table. The material is distributed throughout the surface of the table to obtain an appropriate and freely controllable air pressure in the deposited material, which generates a type of bubbling allowing effective densimetric separation. By applying a tilted screen oscillation, the heavy materials placed on the screen rise upwards and thus into the equipped contaminated waste hopper, while the lighter materials (wood) slide down the hopper that collects clean materials. Depending on the different types of materials to be treated and the degree of cleanliness to be obtained, 3 main parameters can be adjusted. These settings are easily adjustable by the operator using a programming keyboard and a screen on the machine’s electrical panel.
The densimetric table is made up of an aluminum frame with a mesh, easily removable for quick change and cleaning. The cleaning interval depends on the type of material being treated and the type of contaminants present. Thanks to the supply of air, the material does not pass through the screen. The size of the mesh is chosen according to the type of material treated. A fan is installed inside the machine to independently suck fresh air from the outside through a removable filter panel.
– Excellent disposal of heavy pollutants from recycling wood.
– Excellent removal of fine sand and dust
– Separation of heavy pollutants from dry materials, i.e. releases from SL and CL separators.
– Flexible setting for effective disposal of sand, stones, metals, plastic, rubber, glass, laminates, etc.
– No deposit in the combustion chambers thanks to clean dust
– Drastic reduction in fan wheels, hose elbows and cyclones.
– Drastic reduction in the silica content of the panels through the use of clean dust for combustion and clean SL and CL particles.
The extruding press separates organic waste sorted at source, packaged food superimposed, and kitchen and restoration waste into a solid, liquid phase. The bioavailable components are concentrated in the liquid phase and can be used as a biogas substrate in a wet fermenter. Waste is introduced into the mixing hopper by a wheel loader or other handling equipment. Two contrarotative mixing screws gently open the packaging by shearing without producing small pieces of plastic. The disintegrated waste is then taken care of by the pressing screw which carries the material against the hydraulically controlled pressing cone and thus increases the pressure in the treatment chamber. If the pressure exceeds the predefined value, the cone opens accordingly and more material is released. As the cone rotates with the screw shaft, the circumferential gap is always in motion and clogging is avoided. Thanks to careful decay and pressing, the liquid biogas substrate requires no additional treatment and already contains less than 0.5% contamination compared to dry matter before the fermenter. The solid phase consists mainly of packaging materials and other solids.
The result of the process
The purpose of the extruding press process is not to extract as much biogas as possible from the feed material, but rather to provide a clean biogas substrate with a single machine. Neither the pre-processing of the raw material nor the post-treatment of the biogas substrate are necessary. As a result, the residual moisture and organic matter available in the solid fraction may need to be reduced by biological post-treatment.
There is no need to add water to the entrance. But it reduces the viscosity of the liquid phase and thus ensures better drainage in the treatment chamber, resulting in a drier solid fraction.
The screw press is generously sized to ensure that kitchen waste and packaged food can be processed without pre-shredding or pre-sorting and to accept solid bodies with a maximum diameter of 80mm. The two mixing screws as well as the pressing screw are designed to avoid wrapping plastic film or fibrous material. The disintegration of the packaging in the hopper and the separation in the press are carried out in a gentle and non-destructive way. As a result, the filter is very untaminated, especially with regard to deformable plastics.
The machine is driven by an electric motor. The link between the engine and the planetary gearbox is automatically disconnected in case of excessive charge by a turbocoupleur with renewable fuses.
Maintenance doors: The walls of the 15m³ mixing room hopper are designed as hinged doors, allowing easy cleaning and replacement of wear parts.
Mixing screws: Three horizontal screws do the mixing work. Wear-resistant material segments are positioned at different angles of tilt and are easily replaceable.
Benefits at a glance With three sturdy blend screws and a capacity of 15m³, the blender masters the most demanding applications and ensures constant throughput for the next steps in the process.
– Variable mixing behaviour with interchangeable shovels on screws (smooth or toothed).
– Robust and non-sensitive process for heavy mixing tasks.
– Good accessibility of tools and treatment room thanks to large maintenance doors
– Possibility of continuous or batch operation
– Precise adjustment of operating parameters with a programmable automaton.
The result of the process The application of the mixer is the homogenization of organic waste or materials such as:
– Green waste and tree cutting
– Contaminated soil
– certain additives (e.g. lime or bark mulch)
The mixer introduces a strong mixing energy into the material to disintegrate the agglomerates by shearing strain. The continuous flow is about 100m³/h depending on the material. When operating in batches, the flow is lower depending on the mixing time and the loading speed.
The purpose of the process
– Immobilize moisture
– Add a structure for better ventilation
– Neutralize or adjust pH with additives
– Define the desired nutrient balance
– Homogeneous inoculation for biological treatment or soil remediation
The material follows a circular motion in the mixing chamber thanks to the counter-current mixing screws. In the case of a loader loader on wheels, an extension of the hopper can be installed as an option to prevent the material from spilling onto the sides of the machine. A hydraulically controlled, remote control lid can be opened for loading and closed to reduce dust and steam emissions from the mixing chamber. Other options are the water application system and the weighing system.