There is a general consensus surrounding the importance of developing renewables to ensure the long-term sustainability of humanity. Several reports have already focused not only on the impending doom of global warming, but also in the finite nature of fossil fuels. The greatness of solar panels and wind turbines comes from them creating non-polluting sources of energy, they do not seem to unilaterally solve the problem of global warming and pollution. Equally, geothermal and hydroelectric energy contains inherent risks which often harm their surroundings and living organisms around them.
This is perhaps where energy generated from waste seems to bridge the two problems of global warming and pollution through providing a unique solution – catered to the needs of both humans and mother earth. However, you may not have heard much about waste-to-energy plants as there is a large level of press surrounding wind and solar energy. This is particularly due to falling costs which attracts investment in renewable technologies. Despite the positive aspects of both types, there is a large dependency on weather and the initial prices of installation and maintenance remain fairly high whilst storing the energy they create remains a fundamental problem.
What is waste-to-energy?
Energy from waste is certainly not a new concept – with the first incinerator being built in Nottingham in 1874, the British initially led the way in this ground-breaking sector. There are several methods used to recover energy – likewise, each method is designed to take advantage of particular sources. The three main technologies/methods are Pyrolysis (also known as Gasification) or at lower temperatures, Torrefaction, Combustion and Anaerobic Digestion.
These technologies have been built in order to take advantage of various sources of energy. They likewise produce a variety of products which can be used for a variety of purposes. The principal similarity between them is that they all use waste and disregarded material. Whereas Pyrolysis and Combustion uses Municipal Solid Waste (MSW) and Commercial & Industrial Waste (C&I), Anaerobic Digestion processes food waste, agricultural residue and sewage sludge – for a full comparison, see table 1.
Table 1 – Energy from Waste comparisons
The primary differences between the technologies is the level of heat applied – whereas anaerobic uses low temperatures to breakdown the waste into biogas and biomethane, Pyrolysis and Combustion burns the feedstock to produce the energy. The key differences between these two technologies is the type of products produced and the level of heat applied. Although Combustion (incineration) has a long track record and is proven to work, the level of heat applied causes harmful greenhouse gases to be emitted. Equally, it produces bottom and fly ash, which if not treated properly can cause dust and harmful toxins.
Anaerobic Digestion has a diversified outlet for crops and is suitable for organic waste management. However, Anaerobic Digestion plants are complex in their technology and require a very good operating practice and detailed monitoring for their correct performance – particularly as it is necessary to pasteurize composted material to ensure all infectious agents are removed. The development of the technology may be costly as large tanks/vessels must be purchased. There are additional downsides in terms of the smell/fumes produced if it is run inefficiently.
Why Pyrolysis then?
Pyrolysis is not a new technology – but recent developments have created versions which outperforms its predecessors. Plants are now quicker to build by using very advanced technologies. The process is now much more renewable as the plants use little to none oxygen is used in the production of energy, which is a lot less if compared to mass-burn incineration (Combustion).
In terms of the products, there is a variety produced due to the different segments of the plant. Usually, Syngas, Torrefied Fuel and Pyrolysis Oils are produced directly by the plant – these as used for a variety of industries and houses (see table 1). The gas and oil produced can also be processed, stored and transported for later usage.
The plants have been developed to take advantage of all the products – even those which are often disregarded. For example, the char produced (a combination of bottom ash and fly ash) can be used as aggregates or road bed materials. Residue can also be passed to a gasifier and the char is used to produce additional Syngas.
In addition, all the energy produced may be eligible for ROCs, increasing the potential income from any power generated from an investors point of view.
There is no good, bad or ugly.
All renewable sources of energy should be welcomed at this point in history. The on growing pressures of finite fossil fuels, global warming and the feasibility and cost effectiveness of renewables is breaking through the energy sector.
Nonetheless, the development of new types of technologies should be kept up with. The recognition of waste-to-energy plants has previously been hampered by the bad press surrounding Combustion technologies. With new, innovative approaches, Pyrolysis is leading the way in waste-to-energy technologies and we truly believe in its success here at Amio Wealth Limited.
All sources have been referenced.
Author: Elizabeth Frumson
All rights © Amio Wealth Limited.